Oxford IB Diploma Programme: Biology Course Companion [2014 ed.] 0198392117, 9780198392118

Table of contents :
Contents
1 Cell Biology
1.1 Introduction to cells
1.2 Ultrastructure of cells
1.3 Membrane structure
1.4 Membrane transport
1.5 The origin of cells
1.6 Cell division
Questions
Answers
2 Molecular Biology
2.1 Molecules to metabolism
2.2 Water
2.3 Carbohydrates and lipids
2.4 Proteins
2.5 Enzymes
2.6 Structure of DNA and RNA
2.7 DNA replication, transcription and translation
2.8 Cell respiration
2.9 Photosynthesis
Questions
Answers
3 Genetics
3.1 Genes
3.2 Chromosomes
3.3 Meiosis
3.4 Inheritance
3.5 Genetic modification and biotechnology
Questions
Answers
4 Ecology
4.1 Species, communities and ecosystems
4.2 Energy flow
4.3 Carbon cycling
4.4 Climate change
Questions
Answers
5 Evolution and Biodiversity
5.1 Evidence for evolution
5.2 Natural selection
5.3 Classification of biodiversity
5.4 Cladistics
Questions
Answers
6 Human Physiology
6.1 Digestion and absorption
6.2 The blood system
6.3 Defence against infectious disease
6.4 Gas exchange
6.5 Neurons and synapses
6.6 Hormones, homeostasis and reproduction
Questions
Answers
7 Nucleic Acids (AHL)
7.1 DNA structure and replication
7.2 Transcription and gene expression
7.3 Translation
Questions
Answers
8 Metabolism, Cell Respiration and Photosysthesis (AHL)
8.1 Metabolism
8.2 Cell respiration
8.3 Photosysthesis
Questions
Answers
9 Plant Biology (AHL)
9.1 Transport in the xylem of plants
9.2 Transport in the phloem of plants
9.3 Growth in plants
9.4 Reproduction in plants
Questions
Answers
10 Genetics and Evolution (AHL)
10.1 Meiosis
10.2 Inheritance
10.3 Gene pools and speciation
Questions
Answers
11 Animal Physiology (AHL)
11.1 Antibody production and vaccination
11.2 Movement
11.3 The kidney and osmoregulation
11.4 Sexual reproduction
Questions
Answers
A Neurobiology and Behaviour
A.1 Neural development
A.2 The human brain
A.3 Perception of stimuli
A.4 Innate and learned behaviour (AHL)
A.5 Neuropharmacology (AHL)
A.6 Ethology (AHL)
Questions
Answers
B Biotechnology and Bioinformatics
B.1 Microbiology: organisms in industry
B.2 Biotechnology in agriculture
B.3 Environmental protection
B.4 Medicine (AHL)
B.5 Bioinformatics (AHL)
Questions
Answers
C Ecology and Conservation
C.1 Species and communities
C.2 Communities and ecosystems
C.3 Impacts of humans on ecosystems
C.4 Conservation and biodiversity
C.5 Population ecology (AHL)
C.6 The nitrogen and phosphorous cycles (AHL)
Questions
Answers
D Human Physiology
D.1 Human nutrition
D.2 Digestion
D.3 Functions of the liver
D.4 The heart
D.5 Hormones and metabolism (AHL)
D.6 Transport of respiratory gases (AHL)
Questions
Answers
Internal Assessment
Index

Citation preview

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Continued

on

back

page.

Contents

1

Cell Biology

Introduction

to

Ultrastructure

7

cells

of

1

cells

16

Membrane

structure

25

Membrane

transport

33

Nucleic acids (AHL)

DNA

structure

Environmental

and

replication

343

Transcription

and

Bioformatics

591

gene

expression

Ecology and conser vation

355

Species origin

of

cells

45

Translation

and

communities

division

603

362

Communities Cell

575

582

C

The

protection

Medicine

and

51

ecosystems

8

Impacts

2

613

Metabolism, cell

Molecular Biology

of

humans

on

respiration and ecosystems

Molecules

to

metabolism

625

photosynthesis (AHL)

61

Conservation Water

68

Metabolism

373

73

Cell

380

Population Carbohydrates

and

lipids

respiration

The Proteins

87

Enzymes

96

Photosynthesis

of

ecology

nitrogen

of

DNA

replication,

and

RNA

105

transcription

9

translation

111

cycles

649

Plant biology (AHL)

Transport

in

the

Human physiology

xylem

Human and

642

389

D DNA

of

plants

nutrition

659

403

Digestion Cell

respiration

122

Transport

in

the

phloem

671

of

Functions Photosynthesis

129

plants

of

in

plants

Genetics

liver

678

heart

684

422

Hormones Reproduction

in

plants

and

metabolism

694

429

Transport Genes

the

412

The Growth

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reproduction

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offspring

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genetic

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“Estimating the human mutation

rate using autozygosity in a founder

population.” Nature Genetics, 44:

1 277 1 281. doi: 10.1038/ng.24 18

145

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.

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and

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the

conditions

cells

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in

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normal

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hemoglobin

shape.

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bundles

changes

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Figure 4 Map (a) shows the frequency of

time

after

time,

as

the

red

blood

cells

circulate.

Both

the

hemoglobin

red

blood

and

the sickle cell allele and map

the

plasma

membrane

are

damaged

and

the

life

of

a

cell

can

be

cells

at

(b) shows malaria aected areas in

shortened

to

as

little

as

4

days.

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body

cannot

replace

red

blood

Africa and Western Asia

a

rapid

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for

a

enough

small

rate

change

individuals

that

and

to

a

anemia

gene

inherit

therefore

can

the

have

gene.

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develops.

very

is

harmful

not

consequences

known

how

often

this

S

mutation

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remarkably

have

two

copies

have

one

copy

These

... 146

occurred

common.

of

so

individuals

but

In

the

allele

make

only

in

some

parts

both

suffer

of

and

parts

East

of

Africa

develop

normal

mild

the

up

world

the

to

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5%

anemia.

hemoglobin

and

anemia.

Figure 5 Micrographs of sickle cells and normal red blood cells

Hb

allele

newborn

Another

the

mutant

is

babies

35 %

form.

3 . 1

G E N E s

Wha i a geome?

The genome is the whole of the genetic information of

an organism.

Among

genetic

DNA,

of

its

●

biologists

so

a

living

DNA

In

today

information

the

●

number

of

In

plant

species

in

the

means

Genetic

is

the

the

whole

information

entire

base

is

of

the

contained

sequence

of

in

each

in

consists

the

This

is

the

chromosomes

nucleus

the

plus

is

the

plus

pattern

in

usually

genome

the

of

nucleus

is

DNA

the

46

molecules

the

DNA

other

that

form

molecule

animals,

in

the

though

the

different.

DNA

molecules

molecules

in

the

of

chromosomes

mitochondrion

and

chloroplast.

The

in

genome

genome

genome

chromosomes

the

word

organism.

organism’s

mitochondrion.

●

the

an

molecules.

humans

the

of

genome

the

of

circular

prokaryotes

is

chromosome,

much

plus

smaller

any

and

plasmids

consists

that

are

of

the

DNA

present.

the Huma Geome Projec

The entire base sequence of human genes was

sequenced in the Human Genome Project.

The

Human

base

Genome

sequence

of

improvements

the

in

be

Project

entire

base

sequence

to

complete

sequence

sequencing

published

in

began

human

much

in

1990.

Its

genome.

techniques,

sooner

aim

This

than

was

to

project

which

nd

allowed

expected

in

the

drove

rapid

a

2000

draft

and

a

Actvt

2003.

Etc of genoe eeac Although

knowledge

immediate

what

can

and

be

total

of

entire

base

understanding

regarded

many

as

researchers

for

which

sequences

base

the

a

rich

years

are

to

of

mine

human

of

come.

sequence

data,

For

has

genetics,

which

example,

protein-coding

not

genes.

will

it

is

it

given

has

be

are

an

given

worked

possible

There

us

to

Ethical questions about

us

genome research are wor th

by

predict

discussing.

approximately

Is it ethical to take a DNA

23,000

of

these

in

the

human

genome.

Originally,

estimates

for

the

sample from ethnic groups

number

of

genes

were

much

higher.

around the world and

sequence it without their Another

discovery

was

that

most

of

the

genome

is

not

transcribed.

permission? Originally

that

called

within

expression

“junk

these

as

DNA,”

“junk”

well

as

it

is

regions,

highly

being

there

repetitive

increasingly

are

elements

sequences,

recognized

that

called

affect

gene

satellite

Is it ethical for a biotech

DNA.

company to patent the

base sequence of a gene to The

genome

that

was

sequenced

consists

of

one

set

of

chromosomes

–

it

prevent other companies is

a

human

genome

rather

than

the

human

genome.

Work

continues

from using it to conduct to

nd

variations

in

sequence

between

different

individuals.

The

vast

research freely? majority

unity,

of

but

base

there

contribute

to

sequences

are

also

human

are

many

shared

single

by

all

humans

nucleotide

giving

us

genetic

polymorphisms

which

Who should have access to

this genetic information?

diversity.

Should employers, Since

the

publication

other

species

of

the

human

genome,

the

base

sequence

of

many

insurance companies and has

been

determined.

Comparisons

between

these

genomes

law enforcement agencies reveal

aspects

of

the

evolutionary

history

of

living

organisms

that

were

know our genetic makeup? previously

of

biology

unknown.

in

the

21st

Research

into

genomes

will

be

a

developing

theme

century.

147

3

G e n e t i c s

techique ued for geome equecig

Developments in scientic research follow improvements in technology: gene

sequencers, essentially lasers and optical detectors, are used for the sequencing

of genes.

The

idea

seemed

of

sequencing

impossibly

improvements

in

the

entire

difcult

at

technology

human

one

time

towards

uorescent

genome

ending

but

the

end

20th

century

made

it

possible,

though

still

These

improvements

continued

The

samples

once

copies

was

underway

and

draft

sequences

Further

species

completed

advances

to

be

much

are

sooner

allowing

sequenced

at

an

than

the

ever

A

expected.

genomes

of

sequence

small

separately.

of

DNA,

using

a

lengths

genome,

of

To

DNA.

nd

the

it

base

single-stranded

DNA

is

rst

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polymerase,

of

increasing

broken

these

is

sequence

copies

but

of

the

it

of

up

a

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the

whole

base

sequence

has

putting

small

quantities

of

a

the

copies

in

and

one

all

lane

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of

of

a

gel

nucleotides.

along

the

lane

to

make

the

uoresce.

of

is

a

detector

is

used

uorescence

series

of

to

along

peaks

each

to

of

detect

the

the

lane.

uorescence,

number

of

nucleotides

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computer

deduces

the

base

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copied the

by

for

bases.

together

number

markers

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●

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separated

the

scans

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into

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is

laser

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made

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rate.

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are

are

are

to

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other

●

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used

were

●

therefore

is

the

the according

project

of

very DNA

ambitious.

marker

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of ●

the

in

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of

colours

of

uorescence

non-standard detected.

nucleotide

separately

each

of

of

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with

copy

of

varying

samples

of

the

sequence

bases

the

copy

tracks

bases

in

advance

sequencing

by

in

the

in

the

is

gel,

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technology

uorescent

mark

DNA

it

markers

copies.

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end

a

samples

; T G G C T C T G G C A A T G C T C T T C GC T A T T G G C CC J

80

100

110

each

number

in

'I

just

which

the

deduced.

that

90

each

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band

be

is

of

each

from

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produced,

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separated

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are

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length

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by

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length

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to

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148

with

the

one

copy.

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speeded

up

this:

are

different

used

to

colour

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Figure 6 Sequencing read from the DNA of Pinor Noir variety

of grape

3 . 2

C h r O m O s O m E s

3.2 Coooe

Uderadig Applicaio Prokaryotes have one chromosome consisting

➔

Cairns’s technique for measuring the length

➔

of a circular DNA molecule. of DNA molecules by autoradiography.

Some prokaryotes also have plasmids but

➔

Comparison of genome size in T2

➔

eukaryotes do not. phage, Escherichia coli, Drosophila

Eukaryote chromosomes are linear

➔

melanogaster, Homo sapiens and

DNA molecules associated with histone

Paris japonica.

proteins. Comparison of diploid chromosome numbers

➔

In a eukaryote species there are

➔

of Homo sapiens, Pan troglodytes, Canis

dierent chromosomes that carry dierent

familiaris, Oryza sativa, Parascaris equorum.

genes. Use of karyotypes to deduce sex and diagnose

➔

Homologous chromosomes carry the same

➔

Down syndrome in humans.

sequence of genes but not necessarily the

same alleles of those genes.

skill

Diploid nuclei have pairs of homologous

➔

chromosomes.

Use of online databases to identify the locus of

➔

a human gene and its protein product.

Haploid nuclei have one chromosome of

➔

each pair.

The number of chromosomes is a characteristic

➔

naure of ciece feature of members of a species.

Developments in scientic research follow

➔

A karyogram shows the chromosomes of

➔

improvements in techniques: autoradiography an organism in homologous pairs of

was used to establish the length of DNA decreasing length.

molecules in chromosomes. Sex is determined by sex chromosomes and

➔

autosomes are chromosomes that do not

determine sex.

Bacerial chromoome

Prokaryotes have one chromosome consisting

of a circular DNA molecule.

The

structure

most

molecule

of

of

prokaryotic

prokaryotes

the

there

containing

cell.

sometimes

The

DNA

described

all

in

as

is

cells

one

the

was

described

chromosome,

genes

bacteria

is

needed

not

in

sub-topic

consisting

for

the

associated

basic

with

of

a

life

1.2.

In

circular

DNA

processes

proteins,

so

is

naked.

149

3

G e n e t i c s

Because

is

only

usually

present

a

briey

preparation

are

one

only

moved

after

for

to

chromosome

single

cell

copy

the

of

present

The

poles

and

in

gene.

chromosome

division.

opposite

is

each

has

two

the

a

prokaryotic

Two

identical

been

replicated,

genetically

cell

then

identical

splits

in

cell,

there

copies

but

are

this

is

a

chromosomes

two.

Plamid

Some

do

prokaryotes

are

small

extra

prokaryotes

but

circular

and

naked,

but

those

not

antibiotic

when

an

a

antibiotic

are

not

of

formed

plas mids

cell

bu t

eukaryot es

of

spread

through

natural

a

present

or

in

a

life

the

the

cell

same

and

a

are

commonly

that

processes.

in

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may

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plasmids.

environment

replicated

at

genes

located

in

that

eukaryotes.

few

basic

cell

be

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dies

method

to

can

at

the

rate.

same

may

are

be

found

usually

useful

example,

These

but

as

there

not

be

not

the

may

to

in

small,

the

genes

genes

are

time

Hence

plasmid

transferred

population.

barrier.

biologists

is

its

often

always

plasmids

prokaryotic

for

are

a

in

are

at

cell

for

benecial

other

times.

chromosome

be

passed

multiple

to

both

cells

division.

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species

molecules

unusual

containing

cell

plasmids

by

DNA

very

needed

prokaryotic

copies

by

are

resistance

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the

have

not .

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of

also

of

is

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is

happens

absorbed

gene

transfer

transfer

genes

from

even

if

by

a

one

plasmid

a

cell

of

between

between

cell

possible

a

for

that

to

is

released

different

species.

species

another,

plasmids

to

cross

when

species.

Plasmids

allowing

are

It

is

also

a

a

used

articially.

Figure 1 (a) Circular DNA molecule from

a bacterium (b) Bacterium preparing

trimethoprim

to divide

genes to help the

resistance plasmid spread

penicillin family disinfectant resistance

resistance

streptomycin family

resistance

vancomycin

resistance

Figure 2 The pLW1043 plasmid

Uig auoradiography o meaure DnA molecule

Developments in scientic research follow improvements in techniques:

autoradiography was used to establish the length of DNA molecules in chromosomes.

Quantitative

the

hypothesis,

that

150

data

strongest

type

but

provide

in

the

is

usually

of

considered

evidence

biology

most

it

is

for

or

to

sometimes

convincing

be

against

Developments

a

images

evidence.

to

be

invisible.

but

in

produced

of

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sometimes

microscopy

structures

sometimes

also

change

have

that

allowed

were

conrm

our

images

previously

existing

ideas

understanding.

3 . 2

Autoradiography

the

1940s

substances

John

way

DNA

time

were

Cairns

in

the

was

used

not

used

to

the

biologists

in

where

cells

or

technique

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obtained

from

E.

clear

by

discover

located

1960s.

molecules

it

was

onwards

coli

in

a

of

At

than

Cairns

time.

whole

to

the

was

one,

a

but

answered

revealed

different

images

the

more

tissues.

bacteria.

whether

chromosome

from

specic

C h r O m O s O m E s

single

the

this

replication

Cairns’s

question.

forks

technique

investigate

the

DNA

molecule

images

in

structure

They

DNA

was

used

of

or

produced

by

also

for

the

by

rst

others

eukaryote

chromosomes.

bacterial

Meaurig he legh of DnA molecule

Cairns’s technique for measuring the length of DNA molecules by autoradiography.

John

from

Cairns

E.coli

produced

using

this

images

of

DNA

The

molecules

images

molecule ●

Cells

a

were

culture

grown

medium

thymidine.

linked

by

to

coli

DNA

make

a

replication

●

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cells

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the

were

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then

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of

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2

burst

surface

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the

some

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and

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end

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lm

release

dialysis

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with

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atomdecayed

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of

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in

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The

of

there

given

1,100

µm.

that

the

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length

of

is

the

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coli

to

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fruit

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Drosophila

12,000

total

µm

melanogaster

at

least

of

a

by

of

chromosome

of

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chromosome,

other

eukaryotic

melanogaster

long.

amount

D.

used

images

was

from

produced

corresponded

known

so

for

to

this

be

in

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molecule.

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contains

contrast

to

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very

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prokaryotes,

the

were

onto

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linear

rather

than

circular.

the

was

membrane

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tritium

energy

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,.

electrons,

lm.

and

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examined

point

position

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digested

emulsion

two-month

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circular

dialysis

were

DNA

the

high

the

showed

single

µm.

chromosomes.

contains

hydrogen,

months.

atoms

developed

microscope.

indicate

for

emitted

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a

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photographic

darkness

decayed

●

to

the

is

length

Autoradiography

used

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onto

only

molecule gently

by

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base

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it

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with

walls

lysozyme.

a

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in

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radioactive

radioactively

generations

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tritium,

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thymine

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for

produced

chromosome

technique:

where

dark

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with

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a

tritium

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DNA.

Figure 3

Eukaryoe chromoome

Eukaryote chromosomes are linear DNA molecules

associated with histone proteins.

Chromosomes

DNA

with

is

a

in

single

histone

eukaryotes

immensely

proteins.

are

long

Histones

composed

linear

are

of

DNA

globular

DNA

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molecule.

in

shape

protein.

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is

and

The

associated

are

wider

151

3

G e n e t i c s

than

the

DNA.

with

the

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chromosome

are

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in

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are

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with

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of

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stretches

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gives

during

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in

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of

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eukaryotic

in

molecule

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chromosome

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interphase.

Dierece bewee chromoome

In a eukaryote species there are dierent chromosomes

that carry dierent genes.

Eukaryote

chromosomes

microscope

during

chromosomes

Figure 4 In an electron micrograph the

visible

histones give a eukaryotic chromosome

of

the appearance of a string of beads during

if

become

stains

mitosis

the

chromatids,

are

that

much

bind

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narrow

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centromere

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held

an

different

position

together.

end

to

the

of

types

the

The

centromere

centre

of

the

chromosome.

OH

PH

There

are

at

least

two

different

types

in

every

eukaryote

but

in

most

phe 16S 7S DNA

val

species

there

are

more

than

that.

In

humans

for

example

there

are

23S

thr

23

types

of

chromosome.

cyt b leu

PL pro

Every

gene

in

eukaryotes

occupies

a

specic

position

on

one

type

of

N1

ile

chromosome,

called

the

locus

of

the

gene.

Each

chromosome

type

glu f-met

therefore

gln

N6

N2

DNA

carries

molecule.

a

In

specic

many

sequence

of

genes

chromosomes

this

arranged

sequence

along

the

contains

linear

over

a

ala

control loop

asn

ribosomal RNA

trp

N5

thousand

genes.

cys transfer RNAs OL

tyr

leu

protein coding gene

Crossing

experiments

were

done

in

the

past

to

discover

the

sequenceof

ser

his

genes

ser

on

chromosome

types

in

Drosophila

melanogasterand

other

species.

OX1

The

base

sequence

of

whole

chromosomes

can

now

be

found,

allowing

N4

asp

a

rg

more

accurate

and

complete

gene

sequences

to

be

deduced.

OX2 3 N gly

lys OX3

ATPase

Having

the

genes

chromosome

arranged

allows

parts

in

of

a

standard

sequence

chromosomes

to

be

along

a

swapped

type

of

during

meiosis.

Figure 5 Gene map of the human mitochondrial

chromosome. There are genes on both of the

two DNA strands. The chromosomes in the

Homologou chromoome nucleus are much longer, carry far more genes

and are linear rather than circular

Homologous chromosomes carry the same sequence of

genes but not necessarily the same alleles of those genes.

If

two

chromosomes

homologous.

each

are

If

of

other

because,

for

at

the

same

sequence

chromosomes

least

some

of

are

the

of

not

genes

genes

usually

on

they

are

identical

them,

the

to

alleles

different.

two

the

eukaryotes

are

chromosomes

chromosome

152

have

Homologous

in

the

members

in

one

other.

of

of

the

them

This

same

to

allows

be

species,

we

homologous

members

of

a

can

with

species

expect

at

to

each

least

one

interbreed.

3 . 2

C h r O m O s O m E s

:r·························· ..........................................................: r - - - - - - - - , ... ... ... ... ... ... ... .

and humans

Figure

6

shows

humans.

all

of

Numbers

chromosomes

that

the

and

are

types

of

colours

chromosome

are

used

homologous

to

to

in

mice

indicate

sections

of

and

in

sections

human

of

mouse

chromosomes.

Mouse and human genetic similarities

Mouse chromosomes

2

1

4

3

5

7

9

8

19

8 11

9

2 2

I I

4

11

11

4

19

16

7

1

16 3

12

20

4

11

10 1

13

12

13

14

15

11

16

3

22 6

6 11

10

1

10

19

3

15

1

2

7

16

16 2 1

8

14

~

6

22

3 6

8

2 1

19

22

14

19 1 7

18

2 1

13

5

12

2

12

2

10

3

11

12

10

18

5

18

Y

1 9

10

1

...

13

20

Y

X

11

5

6

14

7

15

8

mcocope nvetgaton of gac

coooe

1

16

X

2 1

22

X

Garlic has large chromosomes so is an

ideal choice for looking at chromosomes.

Cells in mitosis are needed. Garlic bulbs

grow roots if they are kept for 3 or 4 days

9

1 7

with their bases in water, at about 25°C.

Root tips with cells in mitosis are yellow

in colour, not white.

polystyrene

garlic bulb

18

~ I I Ia

19

r

19

4

III I I I I

18

16

7

6

5

22

1 7

5

10

7

2

10

15

4

15

2

3

18

1

11

19

7

3

.... ..... ... ....

Actvt

II ~ ~ ~ I I II

9

19

7

8

8

6

Human chromosomes

6

~ I~ I I~ I

10

:

... ...

Data-baed queton: Comparing the chromosomes of mice

disc with

hole cut

through

I

water at 25 °C

beaker

Y

I

2

Root tips are put in a mixture of a stain

that binds to the chromosomes and

acid, which loosens the connections

between the cell walls. A length of about

Figure 6 Chromosomes

5 mm is suitable. Ten parts of aceto-

3

orcein to one part of 1.0 mol dm

1

Deduce

the

number

of

types

of

chromosomes

in

mice

and

hydrochloric acid gives good results.

in

humans.

[2] stain–acid mix ture

5 mm long garlic

2

Identify

the

similarto

two

human

mouse

chromosome

types

that

are

root tip

most

chromosomes.

[2] watch glass

3

Identify

mouse

chromosomes

nothomologous

to

human

which

contain

sections

that

are

chromosomes.

[2]

3

4

Suggest

reasons

andhuman

for

the

many

similarities

between

the

The roots are heated in the stain–acid

mixture on a hot plate, to 80°C for

mouse

genomes.

5 minutes. One of the root tips is put

[2]

on a microscope slide, cut in half and 5

Deduce

how

chromosomes

have

mutated

during

the

evolution

......................................................................................! of

animals

such

as

mice

and

humans.

the 2.5 mm length fur thest from the

[2]

end of the root is discarded.

root tip

i Comparig he geome ize

Comparison of genome size in T2 phage, Escherichia

I 4

coli, Drosophila melanogaster, Homo sapiens and

f:e:w' t

watch glass

6t

hot plate

set at

80 °C

A drop of stain and a cover slip is added

and the root tip is squashed to spread

Paris japonica. out the cells to form a layer one cell

The

genomes

of

living

organisms

vary

by

a

huge

amount.

The

smallest

thick. The chromosomes can then be

genomes

are

those

of

viruses,

though

they

are

not

usually

regarded

as

examined and counted and the various

living

organisms.

The

table

on

the

next

page

gives

the

genome

size

of

phases of mitosis should also be visible.

one

virus

and

four

living

organisms. thumb pressing down to

squash root ti p

One

of

the

smallest

four

living

genome.

The

organisms

genome

is

size

a

prokaryote.

of

eukaryotes

It

has

much

depends

on

the

the

size

cover

and

number

of

chromosomes.

It

is

correlated

with

the

complexity

slip

of

the

organism,

reasons

genes

is

for

this.

very

but

The

is

not

directly

proportion

variable

and

also

of

the

proportional.

the

DNA

amount

that

of

There

acts

gene

as

are

microscope

slide

folded

lter paper

several

functional

duplication

varies.

153

3

G e n e t i c s

Ogan

Genoe ze

Decpton

(on bae pa)

T2 phage

0.18

Virus that attacks

Escherichia coli

Escherichia coli

5

Drosophila melanogaster

Gut bacterium

140

Fruit y

Homo sapiens

3,000

Humans

Paris japonica

150,000

Woodland plant

Fidig he loci of huma gee

Use of online databases to identify the locus of a human gene and its

protein product.

The

locus

of

homologous

be

used

to

a

gene

is

its

particular

chromosomes.

nd

the

locus

of

position

Online

human

on

databases

genes.

together

can

that

with

the

total

an

example

Mendelian

by

Johns

of

such

a

Inheritance

Hopkins

database

in

Man

in

the

of

gene

loci

on

There

Gene nae is

number

chromosome.

Decpton of gene

Online

website,

maintained

DRD4

A gene that codes for a dopamine

University.

receptor that is implicated in a variety of

neurological and psychiatric conditions. ●

Search

home

for

the

abbreviation

OMIM

to

open

the

page.

CF TR

A gene that codes for a chloride channel

protein. An allele of this gene causes ●

Choose

●

Enter

Search

Gene

Map.

cystic brosis.

the

name

of

a

gene

into

the

Search

HBB Gene

Map

box.

This

should

bring

up

a

gene,

including

The gene that codes for the beta-globin

table

subunit of hemoglobin. An allele of this with

information

about

the

its

gene causes sickle cell anemia. locus,

the

starting

gene

genes

is

are

with

located.

shown

the

chromosome

Suggestions

on

the

of

on

which

human

F8

The gene that codes for Factor VIII, one

right.

of the proteins needed for the clotting of

blood. The classic form of hemophilia is ●

An

alternative

to

entering

the

name

of

a

gene

caused by an allele of this gene. is

of

to

select

the

sex

sequence

a

chromosome

chromosomes

of

gene

loci

from

X

will

or

be

Y.

1–22

A

or

one

complete

TDF

Testis determining factor – the gene that

displayed,

causes a fetus to develop as a male.

Haploid uclei

Haploid nuclei have one chromosome of each pair.

A

haploid

set

of

the

humans

contain

Gametes

are

Gametes

have

contain

154

nucleus

has

one

chromosomes

23

the

23

chromosome

that

are

found

chromosomes

sex

cells

haploid

that

nuclei,

chromosomes.

fuse

so

for

of

in

each

its

It

has

one

Haploid

full

nuclei

in

example.

together

in

type.

species.

humans

during

both

sexual

egg

and

reproduction.

sperm

cells

3 . 2

C h r O m O s O m E s

Diploid uclei

Diploid nuclei have pairs of homologous chromosomes.

A

diploid

sets

of

humans

When

contain

with

cells

consist

a

46

two

gametes

with

gametes

are

fuse

found

for

is

nuclei

diploid

of

in

each

its

during

sexual

When

produced.

apart

type.

species.

It

has

two

Diploid

full

nuclei

in

example.

produced.

are

cells,

sexual

for

together

nucleus

diploid

of

chromosomes

that

chromosomes

diploid

entirely

produce

has

chromosomes

haploid

zygote

more

nucleus

the

from

Many

the

reproduction,

this

divides

animals

cells

that

by

and

they

a

mitosis,

plants

are

using

to

reproduction.

Figure 7 Mosses coat the trunks of the laurel

Diploid

nuclei

have

two

copies

of

every

gene,

apart

from

genes

on

the trees in this forest in the Canary Islands.

sex

chromosomes.

An

advantage

of

this

is

that

the

effects

of

harmful Mosses are unusual because their cells are

recessive

mutations

can

be

avoided

if

a

dominant

allele

is

also

present. haploid. In most eukaryotes the gametes are

Also,

organisms

are

often

more

vigorous

if

they

have

two

different

alleles haploid but not the parent that produces them

of

genes

reason

instead

for

of

strong

just

one.

growth

of

This

F

is

known

hybrid

as

crop

hybrid

vigour

and

is

the

plants.

1

Chromoome umber

The number of chromosomes is a characteristic feature

of members of a species.

One

of

are

a

of

the

unlikely

species

The

to

need

number

species.

if

most

fundamental

chromosomes.

splits

It

can

occur.

number

to

numbers

be

to

of

Organisms

able

decrease

There

to

if

are

same

so

all

number

can

change

these

are

unchanged

the

of

a

over

of

is

the

number

chromosomes

interbreeding

members

of

chromosomes.

during

that

rare

species

number

become

mechanisms

However,

of

different

chromosomes

also

remain

a

interbreed

the

chromosomes

double.

tend

to

have

characteristics

with

the

evolution

fused

can

events

millions

together

cause

and

of

the

of

a

or

increase

chromosome

Figure 8 Trillium luteum cell with a diploid

chromosome

years

of

number of 12 chromosomes. Two of each

evolution.

type of chromosome are present

Comparig chromoome umber

Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes,

Canis familiaris, Oryza sativa, Parascaris equorum

The

Oxford

large

of

English

volumes,

information

Dictionary

each

consists

containing

about

the

a

origins

large

and

of

twenty

and

amount

meanings

eukaryotes.

This

information

could

have

been

have

a

smaller

number

of

larger

volumes

or

in

a

of

smaller

volumes.

There

is

a

eukaryotes

the

numbers

and

sizes

of

small

large

chromosomes

ones.

have

so

the

at

least

diploid

two

different

chromosome

types

of

number

at

least

four.

In

some

cases

it

is

over

a

hundred.

parallel The

with

few

larger is

number

many

a

published chromosome,

in

have

of All

words.

others

Some

chromosomes

table

on

the

next

page

shows

the

diploid

in chromosome

number

of

selected

species.

155

3

G e n e t i c s

scentc nae

Eng

Dpod coooe

of pece

nae

nube

Parascaris

horse

equorum

threadworm

4

Oryza sativa

rice

24

Homo sapiens

humans

46

Pan troglodytes

chimpanzee

48

Canis familiaris

dog

78

Figure 9 Who has more chromosomes – a dog or its owner?

Data-baed queton: Dierences in chromosome number

Pant

Coooe nube

Ana

Haplopappus gracilis

4

Parascaris equorum (horse threadworm)

Luzula purpurea (woodrush)

6

Aedes aegypti (yellow fever mosquito)

Crepis capillaris

8

Drosophila melanogaster (fruity)

Vicia faba (eld bean)

12

Musca domestica (house y)

Brassica oleracea (cabbage)

18

Chor thippus parallelus (grasshopper)

Citrullus vulgaris (water melon)

22

Cricetulus griseus (Chinese hamster)

Lilium regale (royal lily)

24

Schistocerca gregaria (deser t locust)

Bromus texensis

28

Desmodus rotundus (vampire bat)

Camellia sinesis (Chinese tea)

30

Mustela vison (mink)

Magnolia virginiana (sweet bay)

38

Felis catus (domestic cat)

Arachis hypogaea (peanut)

40

Mus musculus (mouse)

Coea arabica (coee)

44

Mesocricetus auratus (golden hamster)

Stipa spar tea (porcupine grass)

46

Homo sapiens (modern humans)

Chrysoplenum alternifolium (saxifrage)

48

Pan troglodytes (chimpanzee)

Aster laevis (Michaelmas daisy)

54

Ovis aries (domestic sheep)

Glyceria canadensis (manna grass)

60

Capra hircus (goat)

Carya tomentosa (hickory)

64

Dasypus novemcinctus (armadillo)

Magnolia cordata

76

Ursus americanus (American black bear)

Rhododendron keysii

78

Canis familiaris (dog)

T able 1

1

There

are

in

table,

the

for

of

many

example,

the

different

but

5,

species

some

7,

has

11,

13

chromosome

numbers

13.

are

Explain

numbers

3

missing,

why

species

none

chromosomes.

of

Discuss,

using

hypothesis

organism

156

the

that

is,

the

data

the

in

more

more

the

table,

complex

why

the

cannot

size

be

of

the

deduced

genome

from

the

of

a

number

chromosomes.

[1]

[3] 4

2

Explain

the

in

an

chromosomes

it

Suggest,

occurred

has.

[4]

using

the

chromosome

during

data

in

structure

human

table

that

1,

a

may

evolution.

change

have

[2]

3 . 2

C h r O m O s O m E s

sex deermiaio

Sex is determined by sex chromosomes and autosomes

female

male

XX

XY

are chromosomes that do not determine sex.

are

two

chromosomes

in

humans

that

determine

sex: X

X

There

●

the

X

the

middle.

chromosome

the

Y

the

end.

is

relatively

large

and

has

its

centromere

near

X

●

Y

XX

chromosome

is

m uch

s ma ll e r

and

ha s

its

c e n t ro m e r e

XX

n e ar

XY

XY

Because

the

X

and

chromosomes.

All

affect

a

whether

Y

chromosomes

the

other

fetus

determine

chromosomes

develops

as

a

male

sex

are

or

they

are

autosomes

called

and

the

do

sex

not

female.

1 female : 1 male

The

X

chromosome

has

many

genes

that

are

essential

in

both

males

and

Figure 10 Determination of gender

females.

The

Y

Y

All

humans

chromosome

chromosome

has

chromosome,

but

are

on

not

found

must

only

the

the

the

therefore

has

a

same

small

on

at

least

number

sequence

genes

X

have

the

of

as

remainder

of

and

are

X

genes.

genes

chromosome

of

one

not

a

chromosome.

A

small

small

the

Y

part

part

of

of

the

the

X

chromosome

needed

for

female

development.

One

Y

male.

male

this

A

chromosome

This

called

features,

gene

fetus

have

a

the

Females

has

TDF

of

their

an

X

or

a

X

by

Y

particular

SRY

one

so

X

in

mother.

chromosome

X

two

fertilization

be

two

in

testes

X

ovaries

not

The

one

egg

chromosome

and

one

sons

Y

Y

fetus

the

no

Y

instead

to

develop

a

develops

testes

and

of

Because

chromosome

of

as

development

production.

chromosome

and

develop

cell,

gender

the

a

initiates

as

a

does

of

male.

not

female

sex

testosterone.

Females

so

of

a

chromosome

half

It

testosterone

chromosomes.

each

causes

TDF .

and

and

chromosome.

and

or

chromosomes

produced,

chromosomes

from

with

gene

are

have

gene

either

including

fetus

that

hormones

X

is

When

all

human

is

carried

in

sperm

his

Y

on

one

inherit

of

an

determined

are

chromosome.

inherit

pass

offspring

the

sperm.

formed,

Daughters

their

X

at

the

This

half

two

chromosome

moment

can

either

contain

inherit

their

the

X

father’s

chromosome.

Karyogram

A karyogram shows the chromosomes of an organism

in homologous pairs of decreasing length.

The

chromosomes

with

to

make

type

If

cells

a

in

the

burst

spread.

cells

by

Often

can

usually

can

be

an

organism

giving

chromosomes

distinctive

dividing

then

of

metaphase

are

they

on

the

are

visible

clearest

up.

in

cells

view.

Some

that

Stains

stains

give

are

have

each

in

to

mitosis,

be

used

chromosome

pattern.

and

the

overlap

found

of

show

stained

pressing

be

taken

banding

the

with

placed

cover

each

no

stained

on

slip,

other,

a

microscope

the

but

overlapping

slide

chromosomes

with

careful

and

are

become

searching

chromosomes.

A

a

cell

micrograph

chromosomes.

157

3

G e n e t i c s

Originally

analysis

involved

cutting

out

all

the

chromosomes

and

TOK arranging

them

chromosomes

manually

are

but

arranged

this

process

according

to

can

their

now

size

be

done

and

digitally.

structure.

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The

To wat ex tent  detenng gende position

of

the

centromere

and

the

pattern

of

banding

allow

chromosomes

fo po tng copetton a centc that

are

of

a

different

type

but

similar

size

to

be

distinguished.

queton?

As

most

cells

are

diploid,

the

chromosomes

are

usually

in

homologous

Gender testing was introduced at

pairs.

They

are

arranged

by

size,

starting

with

the

longest

pair

and

the 1968 Olympic games to address

,, . • I I! ' .. ,i

ending

concerns that women with ambiguous

physiological genders would have

an unfair advantage. This has proven

with

the

smallest.

.,

to be problematic for a number of

reasons. The chromosomal standard

is problematic as non-disjunction can

Ii

lead to situations where an individual

1

2

~

not dene herself in that way. People

with two X chromosomes can develop

hormonally as a male and people with

7

an X and a Y can develop hormonally

The practice of gender testing was

discontinued in 1996 in par t because

II

. ,~

19

20

right to self-expression and the right to

Rather than

being a scientic question, it is more

;_

.

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.

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17

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16

21

6

11

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15

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10

81

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•-1 9

13

of human rights issues including the

.

"

8

Ii ;i

as a female.

identify one's own gender.

3

. I i \I I

might technically be male, but might

• J1 a, "i t

p

~

.

~

18

11

22

X

fairly a social question.

Figure 11 Karyogram of a human female, with uorescent staining

Karyoype ad Dow ydrome

Use of karyotypes to deduce sex and diagnose Down

syndrome in humans.

A

karyogram

arranged

property

that

at

1

Figure 12 Child with trisomy 2 1 or

the

in

of

is

an

organism

deduce

and

2

To

one

Y

is

pregnancy.

sometimes

158

there

called

a

be

chromosomes

of

is

number

nuclei.

used

the

of

two

is

an

length.

and

Karyotypes

in

individual

type

are

organism,

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karyotype

of

is

a

chromosomes

studied

by

looking

ways:

male

individual

or

is

female.

female

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two

XX

whereas

one

X

male.

using

are

of

decreasing

the

syndrome

two,

of

other

cells

copies

the

21.

the

Mental

and

fetal

three

trisomy

features

disorders.

it

its

an

done

instead

the

present

Down

If

component

vision

in

indicate

usually

karyotype

are

of

pairs

–

can

whether

diagnose

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has

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chromosomes

Down syndrome

image

organism

karyograms.

To

an

homologous

child

of

growth

from

the

Down

21

in

syndrome.

individuals

are

abnormalities.

uterus

chromosome

has

While

syndrome

and

chromosome

taken

vary,

hearing

retardation

This

some

loss,

are

during

the

of

heart

also

is

the

and

common.

3 . 3

m E i O s i s

',

Data-based questions: A human karyotype

The

1

karyogram

State

shows

which

the

karyotype

chromosome

type

of

a

fetus.

2

longest

b)

shortest.

Distinguish

the

structure

3

human

b)

the

chromosome

human

Deduce

with

a

X

and

reason

Y

2

and

chromosome

7

sex

of

the

.i

[4]

fetus.

[2]

13 4

Explain

whether

the

karyotype

shows

any

9

8

10

11

12

'

~

17

18

12

chromosome.

the

:

of

6 a)

,.

•. .

[2]

between

5

4

3

2 a)

•

is

abnormalities.

14

[2]

19

20

'

• t,

16

15

21

• .. 22

X

•

y

Figure 13

3.3 meo

Uderadig Applicaio ➔

One diploid nucleus divides by meiosis to ➔

Non-disjunction can cause Down syndrome

produce four haploid nuclei. and other chromosome abnormalities. Studies

➔

The halving of the chromosome number allows

showing age of parents inuences chances of

a sexual life cycle with fusion of gametes.

➔

DNA is replicated before meiosis so that all

non-disjunction.

➔

chromosomes consist of two sister chromatids.

➔

Methods used to obtain cells for karyotype

analysis e.g. chorionic villus sampling and

amniocentesis and the associated risks.

The early stages of meiosis involve pairing of

homologous chromosomes and crossing over

followed by condensation.

➔

chromosomes prior to separation is random.

➔

skill

Orientation of pairs of homologous

➔

Drawing diagrams to show the stages of

meiosis resulting in the formation of four

Separation of pairs of homologous

haploid cells.

chromosomes in the rst division of meiosis

halves the chromosome number.

➔

Crossing over and random orientation promotes

naure of ciece genetic variation. ➔

➔

Making careful obser vations: meiosis was

Fusion of gametes from dierent parents discovered by microscope examination of

promotes genetic variation. dividing germ-line cells.

159

3

G e n e t i c s

the dicovery of meioi

Making careful observations: meiosis was discovered by microscope examination

of dividing germ-line cells.

When

in

the

cell

improved

19th

structures,

specically

revealed

microscopes

century

it

that

was

stained

been

detailed

discovered

the

thread-like

had

gave

nucleus

structures

that

of

in

some

the

chromosome

developed

images

cell.

observation

of

a

dyes

These

dividing

halves

dyes

nuclei

special

named

chromosomes.

From

the

1880s

the

group

of

German

biologists

carried

out

observations

how

mitosis

of

dividing

and

nuclei

meiosis

careful

that

can

these

that

biologists

they

slides

can

a

on

bud

or

the

we

The

must

the

be

microscope

or

the

images

of

the

process.

by

shapes

A

key

experts

as

during

the

the

observation

(Parascaris

in

it

was

egg

of

egg

animals

of

there

contains

The

must

generation

be

that

number.

unlike

during

mitosis

gamete

had

already

development

and

plants.

These

divisions

in

were

as

the

method

used

to

halve

the

Suitable

anthers

cells

in

enough

of

cells

from

begins

at

of

this

birth

out

the

between

advantage

of

by

0

and

were

of

28

is

occurs

in

careful

ovaries

species

and

they

events

named

meiosis

rabbits

days

that

of

( Oryctolagus

old.

in

slowly

was

observation

The

females

over

meiosis

many

days.

to

are

show

slides

understand

variety

worked

taken

and

squashed

meiosis

prepared

number

sequence

eventually

cuniculus)

tissue

inside

locust.

then

The

the

bizarre

meiosis.

in

are

the

two

sperm

four.

a

meiosis.

of

microscope

and

clear

to

every

there

gradually

observations

dissected

with

form

that

and

a

no

difcult

stages

equorum)

nuclei

fertilized

is

not

Even

chromosomes

of

stained

Often

are

the

developing

of

in

fertilization.

that

and

achievements

challenging.

testis

slide.

details

images

is

the

xed,

visible

made

repeat

preparation

from

from

to

by

occur.

considerable

try

meiosis

obtained

tissue

a

if

made.

showing

be

lily

The

appreciate

division

divisions

observed

chromosome

We

doubled

chromosome

identied revealed

is

hypothesis

onwards

both detailed

the

that

been a

to

nuclear

Nuclear were

number

led

horse

chromosomes

cells,

This

threadworm

whereas

indicated

the

that

the

Figure 1

▲

Meioi i oulie

one diploid cell 2n

One diploid nucleus divides by meiosis to produce four meiosis I

haploid nuclei.

two haploid cells

n

n

Meiosis

is

cell

divide.

can

one

of

the

The

two

ways

other

in

which

method

is

the

nucleus

mitosis,

of

a

eukaryotic

which

was

described

twice.

The

rst

in

meiosis II

sub-topic

four haploid cells

n

n

produces

nuclei.

1.6.

two

The

In

meiosis

nuclei,

two

the

each

divisions

nucleus

of

are

which

divides

divides

known

as

again

meiosis

I

to

give

and

a

division

total

meiosis

of

four

II.

Figure 2 Over view of meiosis

The

has

nucleus

two

known

by

known

The

the

160

as

undergoes

has

just

involves

as

cells

of

homologous

meiosis

Meiosis

that

chromosomes

a

a

of

the

by

rst

type.

division

chromosome

of

the

of

meiosis

Chromosomes

chromosomes.

halving

reduction

produced

halving

one

the

each

Each

of

of

each

the

type

chromosome

of

four

–

is

the

diploid

same

nuclei

they

number.

are

It

is

–

it

type

are

produced

haploid.

therefore

division.

meiosis

I

chromosome

have

one

number

chromosome

happens

in

of

the

each

rst

type,

so

division,

3 . 3

not

the

second

haploid

two

division.

number

of

chromatids.

four

nuclei

that

chromosome

The

two

nuclei

chromosomes,

These

have

but

chromatids

the

consisting

haploid

of

a

produced

each

separate

number

single

by

meiosis

chromosome

during

of

I

still

meiosis

the

consists

II,

chromosomes,

have

m E i O s i s

of

producing

with

each

chromatid.

Meioi ad exual life cycle

The halving of the chromosome number allows a sexual

life cycle with fusion of gametes.

The

life

life

cycles

cycle

the

genetically

of

living

offspring

identical.

organisms

have

In

of

In

organisms,

eukaryotic

from

two

different

chromosome

halved

at

number

Meiosis

it

some

can

happens

therefore

Meiosis

stage

happen

diploid

is

a

in

at

the

and

complex

What

is

and

the

it

be

sexual

cycle

there

so

reproduction

of

Fertilization

It

sex

cycle.

This

as

the

is

involves

cells,

or

an

the

the

the

are

cause

the

diversity.

process

number

of

so

genetic

number

halving

asexual

between

gametes,

therefore

if

In

parent

differences

there

doubles

would

generation,

life

asexual.

are

parents,

union

every

or

chromosomes

the

occurs.

the

during

during

developed.

time

number

happens

is

parents.

each

life

sexual

Fertilization

chromosomes

of

offspring

can

same

sexual

chromosomes

fertilization.

the

a

the

of

usually

of

a

doubling

was

not

also

chromosome

meiosis.

any

stage

process

have

two

process

clear

of

is

during

copies

and

that

a

creating

it

its

is

sexual

the

of

most

not

at

cycle,

but

Body

in

cells

animals

are

genes.

the

evolution

life

gametes.

moment

was

a

clear

critical

how

step

in

it

the Figure 4 Fledgling owls (bottom) produced by

origin

of

eukaryotes.

Without

meiosis

there

cannot

be

fusion

of

gametes a sexual life cycle have diploid body cells but

and

the

sexual

life

cycle

of

eukaryotes

could

not

occur. mosses (top) have haploid cells

Data-baed queton: Life cycles

Figure

3

mosses,

number

shows

with

of

n

the

life

being

cycle

used

chromosomes

of

to

humans

represent

and

2n

to

1

and

the

haploid

represent

the

number.

main

moss

Sporophytes

plant

and

of

mosses

consist

of

a

grow

stalk

ve

cycle

a

of

similarities

moss

and

of

a

between

in

which

spores

are

life

[5]

Distinguish

between

a

a

the

life

cycles

of

on

and

moss

and

human

by

giving

ve

a differences.

capsule

the

human.

the 2

diploid

Outline

[5]

produced.

egg

n

sperm sperm

egg

n

n

n

moss

human male

zygote

human female

2n

2n

2n

'-./'-./

plant

...

2n

\

Key

-+ -+ -+

zygote

n

mitosis

meiosis

... --

I

spore

sporophyte

n

2n

fer tilization

. . . . . . ................ . . . . . . . ..... ......................................................................................... Figure 3

161

3

G e n e t i c s

Replicaio of DnA before meioi

DNA is replicated before meiosis so that all chromosomes

2n interphase

consist of two sister chromatids.

During

by

the

early

supercoiling.

chromosome

stages

As

of

soon

consists

meiosis

as

of

they

two

the

chromosomes

become

visible

chromatids.

This

it

is

is

gradually

clear

because

that

all

shorten

each

DNA

in

2n homologous

the

nucleus

is

replicated

during

the

interphase

before

meiosis,

so

each

chromosomes

chromosome

Initially

the

genetically 2n

n

n

two

of

two

chromatids

identical.

This

sister

that

is

chromatids.

make

because

up

DNA

each

chromosome

replication

is

very

are

accurate

and

meiosis I

the

n

consists

n

number

of

mistakes

We

might

the

second

expect

the

chromosome

the

division

in

the

DNA

of

to

copying

be

meiosis,

of

the

replicated

but

it

does

DNA

again

not

is

extremely

between

happen.

the

This

small.

rst

and

explains

how

meiosis II

n

n

in

which

to

produce

one

each

number

is

halved

chromosome

four

haploid

during

consists

nuclei

in

of

meiosis.

two

which

One

diploid

chromatids,

nucleus,

divides

eachchromosome

twice

consists

of

chromatid.

Figure 5 Outline of meiosis

Bivale formaio ad croig over

The early stages of meiosis involve pairing of homologous

chromosomes and crossing over followed by condensation.

Some

I

of

while

a

most

of

two

pair

of

DNA

and

of

the

junction

is

at

Because

a

and

in

each

As

the

is

us

one

occurred,

A

bivalent

there

at

is

pair

with

and

a

there

mutual

are

each

at

the

called

the

in

up

the

can

the

be

with

each

with

other.

consists

associated

in

each

chromosomes

place.

of

the

is

is

The

very

molecular

important.

homologous

chromatid.

Crossing

chromosomes.

At

over

least

one

several.

same

exchange

homologous

meiosis

synapsis.

takes

be

of

seen

chromosome

outcome

each

start

cannot

molecules

other

along

pair

over

but

the

and

homologous

crossing

here,

precisely

chromatids

of

sometimes

anywhere

occurs

DNA

chromatid

rejoins

happen

elongated

four

called

concern

meiosis

chromosomes

are

process

where

of

very

already

there

process

involved,

chromatids.

has

positions

crossover

chromatids

Figure 6 A pair of homologous

a

not

breaks

occurs

still

chromosomes.

created

random

crossover

so

pairing

need

chromosomes

occurs

and

synapsis,

this

events

are

homologous

replication

homologous

after

details

Firstly

chromatids

bivalent

Soon

important

chromosomes

microscope.

Because

A

the

the

position

of

but

on

genes

not

the

two

between

identical,

the

some

chromosomes contains four

alleles

of

the

exchanged

genes

are

likely

to

be

different.

Chromatids

with

chromatids and is sometimes called

new

combinations

of

alleles

are

therefore

produced.

a tetrad. Five chiasmata are visible

in this tetrad, showing that crossing

over can occur more than once

Radom orieaio of bivale

Orientation of pairs of homologous chromosomes prior to

separation is random.

While

pairs

nucleus

growing

162

of

of

a

homologous

cell

from

in

the

the

chromosomes

early

poles

of

stages

the

cell.

of

are

condensing

meiosis,

After

the

spindle

nuclear

inside

the

microtubules

membrane

has

are

3 . 3

broken

the

down,

these

attachment

The

principles

●

Each

●

The

two

The

The

the

The

to

the

centromeres

of

spindle

microtubules

is

not

the

same

as

in

mitosis.

is

attached

to

one

chromosomes

pole

in

a

only,

not

bivalent

to

are

both.

attached

to

poles.

to

which

pair

of

of

each

of

orientation

section

bivalents

of

of

on

chromosome

chromosomes

attaching

consequences

the

the

orientation

chance

●

attach

these:

homologous

pole

way

of

are

chromosome

different

●

microtubules

chromosomes.

The

●

spindle

m E i O s i s

to

each

one

the

is

and

bivalent

is

attached

facing.

random,

pole,

random

genetic

is

This

so

each

not

orientation

later

in

of

affect

of

depends

called

the

being

other

which

has

pulled

an

to

are

equal

it.

bivalents.

bivalents

this

on

orientation.

chromosome

eventually

does

diversity

is

The

discussed

MITOSIS

in

topic.

Halvig he chromoome umber

Separation of pairs of homologous chromosomes in the

rst division of meiosis halves the chromosome number.

either

The

movement

of

chromosomes

is

not

the

same

in

the

rst

division

or

of

MEIOSIS

meiosis

as

in

chromatids

mitosis.

that

Whereas

make

up

a

in

mitosis

the

chromosome

centromere

move

to

divides

opposite

and

poles,

in

the

two

Figure 7 Comparison of attachment

meiosis

of chromosomes to spindle

the

centromere

does

not

divide

and

whole

chromosomes

move

to

the

poles.

microtubules in mitosis and meiosis

Initially

by

the

two

chiasmata,

then

the

The

of

one

is

cell

rst

the

of

halves

division

chromosome

formed

these

called

of

separation

the

the

to

but

chromosomes

chromosomes

moves

chromosomes

in

of

the

chromosome,

pairs

so

the

of

the

homologous

type

moves

division

they

are

is

of

the

the

to

are

held

separation

of

chromosomes

the

reduction

each

pole,

contain

to

to

cell.

both

of

of

each

the

bivalent

other

opposite

It

is

division.

one

and

homologous

from

chromosome

of

together

chromosomes

chromosome

number

meiosis

both

of

This

One

other

chromosome

that

bivalent

end

separate.

and

meiosis

each

rst

can

to

each

disjunction.

poles

the

of

slide

in

poles

therefore

Because

the

each

pole.

two

one

nuclei

type

of

haploid.

Obaiig cell from a feu

Methods used to obtain cells for karyotype analysis e.g. chorionic villus sampling

and amniocentesis and the associated risks.

Tw o

procedures

containing

producing

passing

wall,

The

a

the

a

needle

used

is

used

fluid

amniotic

sac.

obtaining

to

to

the

mother's

guide

withdraw

containing

fetal

the

a

cells

needed

Amniocentesis

through

ultrasound

amniotic

for

chromosomes

karyotype.

needle

using

are

fetal

The

A

second

procedure

sampling

used

abdomen

membranes

needle.

from

This

to

tool

involves

sample

cells

for

obtain

can

be

that

cells

from

done

of

amniocentesis,

the

with

which

earlier

but

it

is

chorionic

from

the

in

is

1%,

villus

through

the

the

chorion,

placenta

the

whereas

amniocentesis

sampling

is

enters

sampling.

vagina

one

the

risk

is

the

develops.

pregnancy

with

of

of

than

miscarriage

chorionic

villus

2%

163

3

G e n e t i c s

Diagram of he age of meioi

Drawing diagrams to show the stages of meiosis resulting in the formation of four

haploid cells.

In

mitosis

prophase,

Meiosis

each

four

can

stage

second

stage

also

be

are

in

twice:

meiosis

mitosis

usually

anaphase

divided

happens

time

in

stages

metaphase,

also

II.

into

in

happen

main

in

actual

telophase.

these

meiosis

The

Usually

recognized:

and

I

stages,

and

but

then

events

of

a

a

each

showing

prophase:

condensation

of

visible

even

metaphase:

attachment

of

spindle

microtubules;

is

why

rather ●

anaphase:

movement

of

often

is

worth

Permanent

in

then

meiosis

it

is

chromosomes

of

we

decondensation

than

draw

stages

to

slides!

of

chromosomes.

Cell has 2n chromosomes (double nuclear membrane

chromatid): n is haploid number of

chromosomes. spindle microtubules

and centriole ●

Homologous chromosomes pair (synapsis).

●

Crossing over occurs.

Prophase I

metapae i

Spindle microtubules move homologous pairs

to equator of cell.

bivalents aligned

on the equator

●

Orientation of paternal and maternal

chromosomes on either side of equator

is random and independent of other

Metaphase I

homologous pairs.

Anapae i

●

Homologous pairs are separated. One

homologous

chromosomes

chromosome of each pair moves to each being pulled to

opposite poles

pole.

Anaphase I

Teopae i

●

Chromosomes uncoil. During interphase

that follows, no replication occurs.

cell has divided

across the equator

●

Reduction of chromosome number from

diploid to haploid completed.

Telophase I ●

164

Cytokinesis occurs.

down

to

slides

but

usually

it

have

temporary

interpret

their

construct

Popae i

●

from

them

attempting

from

The rst division of meiosis

●

at

microscope

slides

than

thepoles;

telophase:

of

difcult

bivalents

usually

microscope

●

structures

looking

is

more

mounts,

the

chromosomes; structure

●

biological

Preparation

meiosis

challenging.

but ●

draw

microscope.

cells

meiosis:

we

specimens,

appearance.

diagrams

from

of

specimens

This

meiosis

on

3 . 3

m E i O s i s

The second division of meiosis

Popae ii

●

Chromosomes, which still consist of two

I) I)

chromatids, condense and become visible.

Prophase II

metapae ii

Metaphase II

Anapae ii

●

Centromeres separate and chromatids are

moved to opposite poles.

Anaphase II

Teopae ii

●

Chromatids reach opposite poles.

●

Nuclear envelope forms.

●

Cytokinesis occurs.

1)

1)

!_)

I)

Telophase II

Meioi ad geeic variaio

Crossing over and random orientation promotes genetic

variation.

When

two

parents

unpredictable

the

have

mixture

unpredictability

parent

has

genetic

Apart

there

of

the

each

will

parent.

new

child,

they

know

characteristics

due

to

meiosis.

combination

of

that

from

Every

alleles

–

it

will

each

of

gamete

meiosis

is

inherit

them.

an

Much

produced

a

source

by

of

of

a

endless

variation.

from

copies

a

is

a

of

be

genes

gene.

one

There

are

on

In

copy

the

some

of

likely

X

cases

that

to

be

and

Y

chromosomes,

the

allele

in

two

copies

every

thousands

of

are

gamete

genes

humans

in

the

have

same

produced

the

two

allele

by

parent’s

and

the

genome

165

3

G e n e t i c s

where

Actvt

the

chance

a

gene

of

two

alleles

being

with

the

are

passed

alleles

different.

on

A

in

and

a

Each

gamete.

a.

Half

of

of

Let

the

the

us

two

alleles

suppose

gametes

has

that

an

there

produced

by

equal

is

the

If g is the number of genes

parent

will

contain

A

and

half

will

contain

a.

in a genome with dierent

g

alleles, 2

is the number

of combinations of these

alleles that can be generated

by meiosis. If there were

Let

us

now

Again

can

aB

half

result

and

suppose

of

in

ab.

the

that

there

gametes

gametes

There

are

will

with

two

is

another

contain

different

processes

B

gene

and

with

half

b.

combinations

in

meiosis

the

of

that

alleles

However,

these

B

and

genes:

generate

b.

meiosis

this

AB,

Ab,

diversity.

just 69 genes with dierent

alleles (3 in each of the B

23 chromosome types in

a

B

A

b

a

50%

humans) there would be

probability b

590,295,810,358,705, A

700,000 combinations. B

b telophase I

Assuming that all humans

A

are genetically dierent, and

a

that there are 7,000,000 50%

humans, calculate the

a

a

b

A

B

probability prophase I

percentage of all possible

B

genomes that currently exist. A

metaphase I

▲

Figure 8 Random orientation in metaphase I

1. Random orientation of bivalents

In

of

metaphase

one

Random

the

orientation

does

not

orientation

variation

For

I

bivalent

every

among

genes

additional

combinations

in

of

a

bivalents

that

are

bivalent,

cell

of

bivalents

inuence

the

is

the

on

the

produced

is

process

different

number

by

random

orientation

that

and

any

the

of

possible

doubles.

orientation

the

generates

chromosome

of

meiosis

of

others.

genetic

types.

chromosome

For

a

haploid

number

n

of

n,

the

number

of

possible

combinations

is

2

.

For

humans

with

a

23

haploid

number

of

23

this

amounts

to

2

or

over

8

million

combinations.

2. Crossing over

Without

crossing

chromosomes

chromosome

these

genes

It

over

would

carried

combinations

to

be

increases

meiosis

so

in

be

the

to

number

much

that

it

I,

combinations

linked

combination

could

reshufed,

the

prophase

forever

occur

produce

of

is

in

allele

together.

CD

and

gametes.

new

alleles

another

carried

over

combinations

that

on

example,

Crossing

combinations

effectively

of

For

such

can

be

if

one

cd,

allows

as

Cd

only

linked

and

generated

cD.

by

innite.

Ferilizaio ad geeic variaio

Fusion of gametes from dierent parents promotes

genetic variation.

The

fusion

both

Figure 9

166

for

of

●

It

is

●

It

allows

the

new

gametes

individuals

start

of

alleles

individual.

to

and

the

produce

for

life

from

a

zygote

is

a

highly

signicant

event

species.

of

two

a

new

individual.

different

individuals

to

be

combined

in

one

3 . 3

●

The

●

Fusion

●

Genetic

combination

of

of

gametes

variation

alleles

is

therefore

is

unlikely

ever

promotes

essential

for

to

have

genetic

existed

variation

in

m E i O s i s

before.

a

species.

evolution.

no-dijucio ad Dow ydrome

Non-disjunction can cause Down syndrome and other chromosome abnormalities.

Meiosis

One

is

sometimes

example

of

chromosomes

is

termed

any

of

Both

pairs

the

to

gamete

that

the

decient

involved

be

an

47

to

of

in

other

separate

a

pole.

has

at

The

can

human

to

result

either

13.

with

pole

will

be

If

the

45

gamete

the

result

abnormal

born

of

babies

by

a

having

the

syndrome

or

is

in

humans

not

with

trisomy

can

sex

also

an

18

so

and

the

numbers

chromosomes

XXY.

only

are

trisomy

in

syndrome

having

serious

Babies

result

abnormal

by

are

survive.

Klinefelter’s

caused

chromosome,

is

do

with

chromosomes.

of

is

sex

caused

Turner’s

one

sex

X.

will

or

diploid parent cell with

chromosomes.

An

trisomies

offspring

Non-disjunction

birth

and

chromosome

fertilization,

with

one

other

the

sometimes

This

happen

chromosomes.

extra

chromosome.

individual

that

anaphase.

This

move

an

Most

errors.

homologous

homologous

either

in

to

when

chromosomes

neither

is

fail

subject

is

non-disjunction.

the

of

this

two chromosome 21

number

of

chromosomes non-disjunction

will

often

lead

syndrome,

signs

or

to

i.e.

a

a

person

collection

symptoms.

For

possessing

of

a

during meiosis

gamete with no

chromosome 21

physical

gamete with two

example

chromosome 21

trisomy

21,

also

known

as

Down

cell dies

syndrome,

event

that

is

due

leaves

to

a

the

non-disjunction

individual

with

fusion of

normal haploid ×

three

of

instead

some

chromosome

of

of

two.

the

number

While

21

individuals

component

features

gametes

gamete

vary,

of trisomy: zygote with

the

syndrome

include

hearing

loss, three chromosome 21

heart

and

vision

disorders.

Mental

and

Figure 10 How non-disjunction can give rise to Down syndrome

growth

retardation

are

also

common.

-+Pareal age ad o-dijucio

trisomy 2 1

all chromosomal

abnormalities

non-disjunction

The

data

maternal

presented

age

and

chromosomal

1

Outline

of

in

the

gure

11

shows

incidence

of

the

relationship

trisomy

21

and

of

between

other

abnormalities.

the

relationship

chromosomal

between

abnormalities

in

maternal

live

age

and

the

incidence

births.

)sht rib evil lla fo %( ecnedicni

Studies showing age of parents inuences chances of

14

12

10

8

6

4

[2]

2

2

a)

For

mothers

40

years

of

age,

a

child

determine

the

probability

that

0

they

will

give

birth

to

with

trisomy

21.

[1] 20

b)

Using

the

mother

of

data

40

chromosomal

in

gure

years

of

11,

age

calculate

will

abnormality

give

other

the

birth

than

probability

to

a

child

trisomy

21.

that

with

40

60

maternal age (years)

a

a

▲

[2]

Figure 11 The incidence of trisomy 2 1

and other chromosomal abnormalities

as a function of maternal age

167

3

G e n e t i c s

3

Only

are

a

small

ever

commonest.

4

Discuss

having

number

found

the

of

among

Suggest

risks

possible

live

reasons

parents

chromosomal

births,

face

for

and

these

when

trisomy

abnormalities

21

is

much

the

trends.

choosing

to

[3]

postpone

children.

[2]

3.4 inetance

Uderadig Applicaio ➔

Mendel discovered the principles of inheritance ➔

Inheritance of ABO blood groups.

➔

Red-green colour-blindness and hemophilia as

with experiments in which large numbers of

pea plants were crossed. examples of sex-linked inheritance.

➔

Gametes are haploid so contain one allele of ➔

Inheritance of cystic brosis and Huntington’s

each gene. disease.

➔

The two alleles of each gene separate into ➔

Consequences of radiation after nuclear

dierent haploid daughter nuclei during meiosis. bombing of Hiroshima and Nagasaki and the

➔

Fusion of gametes results in diploid zygotes nuclear accidents at Chernobyl. with two alleles of each gene that may be the

same allele or dierent alleles.

➔

alleles but co-dominant alleles have joint eects.

➔

Construction of Punnett grids for predicting the

outcomes of monohybrid genetic crosses.

➔

Comparison of predicted and actual outcomes

of genetic crosses using real data.

Some genetic diseases are sex-linked and some

are due to dominant or co-dominant alleles.

➔

➔

Many genetic diseases in humans are due to

recessive alleles of autosomal genes.

➔

skill

Dominant alleles mask the eects of recessive

➔

Analysis of pedigree char ts to deduce the

pattern of inheritance of genetic diseases.

The pattern of inheritance is dierent with

sex-linked genes due to their location on sex

chromosomes.

naure of ciece ➔

Many genetic diseases have been identied in

➔

Making quantitative measurements with

humans but most are very rare.

replicates to ensure reliability: Mendel’s genetic ➔

Radiation and mutagenic chemicals increase crosses with pea plants generated numerical data. the mutation rate and can cause genetic

disease and cancer.

168

3 . 4

i N h E r i T A N C E

Medel ad he priciple of iheriace

Mendel discovered the principles of inheritance

with experiments in which large numbers of pea

plants were crossed.

When

living

offspring.

also

blue

this,

whales

on.

However,

tails

of

We

in

acquired

their

parents.

of

it

the

was

not

Mendel’s

nd

out

many

of

pea

inheritance

In

1866

were

was

interest

in

biologists

done

same

pea

female

that

He

also

his

did

just

an

of

used

inheritance

Mendel’s

other

plants

explained

the

For

pea

in

of

the

theories,

and

early

earlier.

theories

characters

between

made

in

those

the

of

▲

in

Figure 1 Hair styles are acquired

characteristics and are for tunately not

rst

inherited by ospring

inheritance,

“Experiments

of

pea

grown

of

plant,

on

its

Plant

result

and

with

grew

the

of

Mendel

male

variety.

each

seven

each

own.

the

another

repeated

over

been

plants

that

They

with

basis

on

cosmetic

pollen

He

them

cross

to

with

different

pairs

principles

of

effect.

have

work.

and

a

be

resemble

blending

demonstrated

isolated

research.

the

transferring

experiment

reasons

experiments

as

can

available.

owers

Mendel

reliably

of

inherit

by

paper

when

in

seen

and

current

biologists

by

than

whale,

Hippocrates

varieties

formed

were.

this

his

Various

using

Scars

intermediate

was

together

were

of

explained

his

their

are

characteristics.

sometimes

Many

that

More

blue

to

to

young

inherited.

offspring

theory

parts

results

not

be

characters

of

published

with

time

parents.

published

were

be

children

a

attacks

According

which

not

of

parents’

whale

cannot

observations

could

the

the

species.

skin

inherited.

the

that

their

characters

pattern

theory

this.

these

alternative

the

ignored.

the

the

the

so

his

of

since

have

Mendel

rediscovered

experiments

Mendel’s

of

peas,

that

as

than

so

seeds

and

Mendel

such

observed

an

their

in

largely

factor

examples

be

killer

characters

to

pea

by

characteristics

same

the

inherit

cannot

caused

varieties

plants.

characters

offspring

on

reproduce,

the

and

that

variety

the

on

in

had

what

of

markings

century

crossed

collected

members

discussed

experiments

one

are

more

until

reliably

carefully

pass

inheritance,

Some

Hybridization”

which

are

been

parents

19th

blue

the

whales

blending

both

whales

the

Aristotle

from

from

that

grandparents

involved

half

as

characteristics

has

they

when

characteristics

blue

example,

reproduce,

they

humans

Inheritance

their

–

such

say

some

some

surgery

but

example,

variations,

passed

For

organisms

For

thirty

years

suggested

and

species.

quickly

animals.

there

In

These

inheritance

in

was

1900

did

his

for

ndings

this.

not

several

cross-breeding

conrmed

all

One

great

plants

that

and

animals.

Replicae ad reliabiliy i Medel’ experime

Making quantitative measurements with replicates to ensure reliability: Mendel's

genetic crosses with pea plants generated numerical data.

Gregor

the

Mendel

father

of

attributed

to

for

research

is

regarded

genetics.

being

into

His

the

by

most

success

rst

to

inheritance.

is

use

Peas

biologists

as

sometimes

pea

plants

have

clear

characteristics

that

to

can

the

easily

next.

hybrids

or

such

be

They

they

as

red

or

followed

can

can

also

be

white

from

be

ower

one

crossed

allowed

to

colour

generation

to

produce

self-pollinate.

169

3

G e n e t i c s

In

fact

Mendel

plants.

was

Thomas

horticulturalist,

Downton

18th

in

and

Philosophical

Knight

had

Castle

century

made

not

the

Andrew

rst

conducted

Transactions

in

the

results

the

important

pea

cross pollinating peas:

English

research

his

of

use

an

Herefordshire

published

some

to

Knight,

to the stigma here

at

late

in

Royal

pollen from another plant is dusted on

the

Society.

discoveries:

pollen is collected

●

male

the

●

and

female

parents

contribute

equally

to

from the anthers

offspring;

characters

that

such

apparently

reappear

in

inheritance

the

is

as

white

ower

disappear

next

in

colour

offspring

generation,

discrete

rather

can

showing

than

that

blending; – called the keel

●

one

character

can

show

“a

alternative

such

as

stronger

red

ower

tendency”

colour

than

self pollinating peas:

the

– if the ower is left untouched, the anthers

inside the keel pollinate the stigma

character.

▲

Although

Mendel

was

not

as

pioneering

in

Figure 2 Cross and self pollination

his

(a) Prediction based on

experiments

as

sometimes

thought,

he

deserves

blending inheritance

credit

for

was

pioneer

in

a

another

having

seven

Table

in

large

different

1

shows

aspect

of

obtaining

numbers

cross

the

his

research.

quantitative

of

replicates.

experiments,

results

of

his

Mendel

results

He

not

also

just

tall plants

and

3

dwarf plants

did

one.

monohybrid

crosses. pea plants with an

It

is

now

repeats

standard

in

practice

experiments

to

in

science

to

demonstrate

intermediate height

include

the (b) Actual results

reliability

of

results.

Repeats

can

be

compared

to tall plants

see

how

close

identied

tests

can

and

be

differences

they

are.

Anomalous

excluded

done

to

between

from

assess

results

analysis.

the

It

is

3

dwarf plants

be

Statistical

signicance

treatments.

can

also

of

standard pea plants as tall

practice

to

repeat

whole

experiments,

using

a as the tall parent

different

organism

or

different

treatments,

to

test ▲

a

hypothesis

in

different

ways.

Mendel

Figure 3 Example of a monohybrid cross experiment. All the

should hybrid plants produced by crossing two varieties together

therefore

be

regarded

as

one

of

the

fathers

of had the same character as one of the parents and the

genetics,

but

even

more

we

should

think

of

him character of the other parent was not seen. This is a clear

as

a

pioneer

of

research

methods

in

biology.

Paenta pant

Tall stem × dwarf stem

Round seed × wrinkled seed

Yellow cotyledons × green cotyledons

Purple owers × white owers

Full pods × constricted pods

Green unripe pods × yellow unripe pods

Flowers along stem × owers at stem tip

▲

170

T able 1

hbd pant

falsication of the theory of blending inheritance

Opng fo ef-ponatng te bd

rato

All tall

787 tall : 277 dwarf

2.84 : 1

All round

5474 round : 1850 wrinkled

2.96 : 1

All yellow

6022 yellow : 2001 green

3.01 : 1

All purple

705 purple : 224 white

3.15 : 1

All full

882 full : 299 constricted

2.95 : 1

All green

428 green : 152 yellow

2.82 : 1

All along stem

651 along stem : 207 at tip

3.14 : 1

3 . 4

i N h E r i T A N C E

Gamee

Gametes are haploid so contain one allele of each gene.

Gametes

are

start

new

of

a

produced

gametes

cells

when

are

than

gamete

moves

smaller

Parents

one

male

the

pass

and

less

in

or

genes

only

female

and

has

female

at

to

gametes,

It

all.

usually

In

cell

so

are

each

and

the

sex

fuse

The

able

humans,

in

a

its

gene.

The

This

is

parents

Male

is

the

to

of

make

the

female

sperm

to

has

the

a

egg.

contain

of

a

both

an

cell

female

generally

Gametes

true

the

and

swim

nucleus

is

single

whereas

tail

gametes.

that

the

gamete

move

example,

uses

cell

and

zygote.

male

to

haploid.

female

single

cells,

is

for

and

offspring

of

male

called

motility.

egg

type

allele

so

produce

gametes

is

the

their

each

one

and

one.

than

on

of

to

sometimes

size

not

volume

together

are

female

chromosome

therefore

fuse

They

different

smaller

much

that

life.

Figure 4 Pollen on the anthers of a ower

gamete

contains the male gamete of the plant. The

male

equal

male gametes contain one allele of each of

genetic

the plants

contribution

to

their

offspring,

despite

being

very

different

in

overall

size.

Zygoe

Fusion of gametes results in diploid zygotes with two

alleles of each gene that may be the same allele or

dierent alleles.

When

the

male

and

chromosomes

each

If

female

chromosome

of

each

The

type

so

fuse,

their

nucleus

is

of

diploid.

nuclei

the

It

join

zygote

contains

there

were

of

Aa

Some

also

two

either

and

alleles

allele

or

of

a

one

gene,

of

A

and

a,

each.

The

three

the

zygote

two

doubling

two

alleles

of

possible

contain

two

combinations

are

aa.

genes

blood

could

possible

have

more

than

two

alleles.

For

example,

A

ABO

together,

contains

gene.

copies

AA,

gametes

number.

groups

in

humans

combinations

of

has

three

alleles:

I

the

gene

for

B

,

I

and

i.

This

gives

six

alleles:

A ●

three

with

two

of

●

three

with

two

different

the

same

allele,

I

A

alleles,

I

A

I

B

I

B

,

I

B

I

and

A

,

I

i

ii

B

and

I

i.

segregaio of allele

The two alleles of each gene separate into dierent

haploid daughter nuclei during meiosis.

During

nuclei.

meiosis

The

haploid

●

●

If

nuclei

two

a

copies

will

alleles

were

two

of

different

receive

either

every

alleles

one

of

of

copy

a

of

gamete

were

the

twice

two

to

copies

produce

of

each

four

gene,

haploid

but

the

one.

allele

one

divides

contains

only

one

receive

PP ,

nucleus

nucleus

contain

nuclei

If

diploid

diploid

gene

were

this

allele.

will

receive

present,

alleles

present,

or

each

the

For

one

copy

haploid

other

each

of

example,

of

if

the

the

P .

nucleus

allele,

haploid

two

not

will

both.

For Figure 5 Most crop plants are pure-bred strains

example,

if

the

two

alleles

were

Pp,

50 %

of

the

haploid

nuclei

would with two of the same allele of each gene

receive

P

and

50%

would

receive

p.

171

3

G e n e t i c s

The

separation

of

alleles

into

different

nuclei

is

called

segregation.

It

TOK breaks

up

existing

combinations

to

combinations

form

in

the

of

alleles

in

a

parent

and

allows

new

offspring.

Dd mende ate  eut fo

pubcaton?

In 1936,

the English statistician

Domia, receive ad co-domia allele

R.A. Fisher published an analysis

Dominant alleles mask the eects of recessive alleles but of Mendel’s data. His conclusion

was that “the data of most, if not

all, of the experiments have been

falsied so as to agree closely with

Mendel’s expectations.” Doubts still

persist about Mendel's data

– a

recent estimate put the chance of

co-dominant alleles have joint eects.

In

each

plant,

the

of

all

other.

pea

plant,

the

Mendel’s

of

the

For

all

parents

example,

the

is

seven

offspring

crosses

showed

in

a

offspring

due

to

one

between

the

cross

were

gene

between

tall.

with

different

character

The

two

a

of

tall

varieties

one

pea

difference

of

the

plant

in

of

pea

parents,

and

height

a

not

dwarf

between

alleles:

getting seven ratios as close to 3:1 as ●

the

●

the

●

they

tall

parents

have

two

copies

of

an

allele

that

makes

them

tall,

TT

Mendel’s at 1 in 33,000.

1

dwarf

parents

have

two

copies

of

an

allele

that

makes

them

dwarf,

tt

To get ratios as close to 3:1 as

Mendel's would have required a

“miracle of chance”. What are the

of

each

each

pass

allele,

on

one

allele

to

the

offspring,

which

therefore

has

one

Tt

possible explanations apar t from a ●

when

the

two

alleles

are

combined

in

one

individual,

it

is

the

allele

miracle of chance? for

2

Many distinguished scientists,

is

tallness

that

determines

the

height

because

the

allele

for

tallness

dominant

including Louis Pasteur, are ●

the

other

allele,

that

does

not

have

an

effect

if

the

dominant

allele

is

known to have discarded results present,

is

recessive.

when they did not t a theory. Is it

acceptable to do this? How can we

In

distinguish between results that

was

are due to an error and results that

effect

falsify a theory? What standard do

well-known

you use as a student in rejecting

plant

each

of

Mendel’s

recessive.

when

is

crosses

However,

they

are

present

example

crossed

with

one

some

is

a

the

of

the

genes

together.

ower

alleles

have

They

colour

white-owered

was

pairs

are

of

dominant

of

alleles

called

Mirabilis

plant,

the

and

where

the

co-dominant

jalapa.

offspring

If

a

have

other

both

have

alleles.

an

A

red-owered

pink

owers.

anomalous data? R ●

there

is

an

allele

for

red

●

there

is

an

allele

for

white

●

these

alleles

owers,

C

W

owers,

C

R

The

a

usual

protein

allele

are

reason

that

codes

is

for

co-dominant

for

dominance

active

a

and

so

of

carries

non-functional

C

one

out

W

C

a

gives

allele

is

172

that

function,

protein.

Figure 6 There are co-dominant alleles of the gene for coat

colour in Icelandic horses.

pink

owers.

this

allele

whereas

the

codes

for

recessive

3 . 4

i N h E r i T A N C E

parents:

Pue grid

genotype

tt

TT

phenotype

dwarf stem

tall stem

j

Construction of Punnett grids for predicting the

outcomes of monohybrid genetic crosses.

Monohybrid

height

with

two

of

a

two

of

crosses

pea

only

plant,

so

pure-breeding

the

produces

same

just

allele,

one

involve

they

parents.

not

type

of

one

involve

two

character,

only

This

means

different

gamete,

one

for

that

alleles.

containing

example

gene.

Most

the

parents

Each

one

the

parent

copy

of

T

eggs or pollen

crosses

t

start

have

therefore

the

allele. F

hybrids genotype

Tt

1

Their

offspring

are

also

identical,

although

they

have

two

different

tall stem

phenotype

alleles.

The

offspring

obtained

by

crossing

the

parents

are

called

F 1

hybrids

or

the

F

generation.

different

alleles

of

the

gene,

so

they

can

each

g

two

1

s

g

have

T

hybrids

F

T

The

e

1

TT

produce

two

types

of

gamete.

If

two

F

hybrids

are

crossed

together,

1

or

if

an

F

plant

is

allowed

to

self-pollinate,

there

are

four

possible

1

outcomes.

after

the

cross

This

can

geneticist

between

two

be

shown

who

F

rst

plants

using

used

are

a

2

this

×

2

type

called

the

of

F

1

To

make

a

Punnett

table,

called

table.

The

a

Punnett

offspring

and

outcomes

overall

both

should

ratio

be

below

Tt

tall

of

a

tt

dwarf

generation. 2

grid

the

tT

tall

grid

as

clear

as

possible

the

gametes

should

be

▲

labeled

t

t

tall

alleles

and

shown

the

on

the

the

Punnett

character

grid.

It

is

of

the

also

four

useful

Figure 7 Explanation of Mendel’s 3:1 ratio

possible

to

give

an

grid. parents:

Figure

7

shows

Mendel’s

cross

between

tall

and

dwarf

plants.

It

R

genotype

explains

the

F

ratio

of

three

tall

to

one

dwarf

plant.

phenotype

C

W

R

W

C

C

C

white owers

red owers

2

shows

the

Mirabilis

results

jalapa.

of

It

a

cross

explains

between

the

red

ratio

F

and

of

white

one

red

l l

y

owered

to

two

pink

2

R

owered

R

Data-baed queton: Coat colour in the house mouse

F

hybrids genotype

C

1

phenotype

In

the

were

early

done

years

in

a

of

the

similar

20th

way

century,

to

those

many

of

crossing

Mendel.

The

W

C

experiments

French

geneticist

used

the

house

mouse,

Mus

musculus,

to

see

C

C

Cuénot

whether

R

C

principles

that

Mendel

had

discovered

also

operated

in

red

C

crossed

normal

grey-coloured

mice

with

albino

mice.

R

C

animals.

W

He

The

hybrid

C

R

W

C

C

pink

mice

that

were

produced

were

all

grey.

These

grey

hybrids

were W

together

and

produced

198

grey

and

72

albino

W

C

pink

C

crossed

C

pink owers

R

Lucien

the

W

C

plant.

e

white

C

one

R

to

g

8

of

g

plants

s

Figure

W

C

offspring. white

1

Calculate

your

2

3

ratio

between

grey

and

albino

offspring,

showing

working.

Deduce

two

the

the

colour

reasons

for

Choose

suitable

and

the

list

symbols,

[2]

of

your

together

of

that

is

due

to

a

recessive

allele,

for

the

[3]

alleles

combinations

with

alleles.

the

coat

Figure 8 A cross involving co-dominance

with

answer.

symbols

possible

combination

coat

▲

of

for

grey

alleles

colours

of

and

mice

associated

albino

using

with

coat

your

each

[3]

173

3

G e n e t i c s

4

typica

annulata

Using

5

a

Punnett

grid,

explain

how

and

albino

mice

was

produced.

The

albino

mice

had

red

eyes

the

observed

ratio

of

grey

[5]

in

addition

to

white

coats.

Suggest

• • * * :::::: : ::::::::::::: :::: :::::::::::::: ::::· ** * * ** * ** * how

▲

one

gene

can

determine

whether

the

mice

had

grey

fur

Figure 9

and

black

eyes

or

white

fur

and

red

eyes.

[2]

Data-baed queton: The two-spot ladybird

Adalia

▲

Figure 10 F

bipunctata

called

ladybugs.

There

is

a

rarer

is

a

species

The

of

ladybird.

commonest

form

called

form

annulata.

In

of

North

this

Both

America

species

forms

are

is

ladybirds

known

shown

as

in

are

typica.

gure

9.

hybrid ospring

1

1

Compare

2

The

the

differences

gene.

If

male

offspring

annulata

are

When

is

annulata

the

female

typica.

are

that

typica

and

between

and

forms

conclusions

3

typica

two

typica

Similarly,

mated

can

be

mated

forms

are

forms

are

the

all

of

Adalia

are

mated

due

bipunctata.

to

a

together,

offspring

annulata.

single

all

produced

Explain

[2]

the

when

the

drawn.

with

[2]

annulata,

the

hybrid

F

offspring

are

1

not

▲

Figure 11 F

identical

to

either

parent.

Examples

of

these

hybrid

F

1

ospring

2

offspring

are

shown

in

gure

10.

Distinguish

between

the

F

1

hybrid

offspring

and

the

typica

and

annulata

parents.

[3]

Actvt 4

If

hybrid

F

offspring

are

mated

with

each

other,

the

offspring

1

ABO bood goup include

It is possible for two parents to have

the

both

same

typica

wing

and

case

annulata

markings

as

forms,

the

and

also

hybrid

F

offspring

with

offspring.

1

an equal chance of having a child with a)

Use

a

genetic

b)

Predict

diagram

to

explain

this

pattern

of

inheritance.

[6]

blood group A, B, AB or O. What would

be the genotypes of the parents?

the

expected

ratio

of

phenotypes.

[2]

ABO blood group

Inheritance of ABO blood groups.

A

The

ABO

example

blood

of

nd

out

system

co-dominance.

importance:

to

group

before

the

blood

blood

It

is

in

is

humans

of

great

of

a

an

medical

transfused,

group

is

it

patient

is

vital

recessive

alleles

being

that

it

is

matched.

Unless

this

is

may

be

complications

due

to

being

I

B

and

I

.

co-dominant

recessive

are

as

The

and

reasons

the

for

other

two

allele

follows:

All

of

the

three

alleles

cause

the

production

of

done, a

there

both

and ●

ensure

to

glycoprotein

in

the

membrane

of

red

blood

coagulation cells.

of

red

blood

cells.

One

gene

determines

the

ABO

A A

blood

group

of

a

person.

The

genotype

B

blood

group

A

and

the

genotype

I

I

A

●

I

gives

gives

group

B

I

I

alters

the

glycoprotein

galactosamine.

This

by

altered

addition

of

acetyl-

glycoprotein

is

A A

B.

Neither

I

B

nor

I

is

dominant

over

the

A

allele

a

and

a

different

person

blood

with

group,

the

genotype

called

AB.

I

absent

other

B

I

so

has

There

is

a

allele

of

the

ABO

blood

group

gene,

exposed

i.

A

person

with

the

genotype

ii

is

I

alters

in

A

O.

The

genotypes

I

174

A

and

B

they

not

make

have

anti-A

the

allele

I

antibodies.

the

glycoprotein

This

altered

by

addition

glycoprotein

of

is

not

B

in

people

who

do

not

have

the

allele

I

B

i

and

I

i

give

blood so

groups

it

do

blood present

group

to

who

usually galactose.

called

people

B ●

third

if

from

respectively,

showing

that

i

is

if

exposed

to

it

they

make

anti-A

antibodies.

3 . 4

A ●

The

be

genotype

altered

by

I

B

i N h E r i T A N C E

A

I

causes

addition

of

the

glycoprotein

either

to

acetyl-galactosamine

the

of

the

I

B

or

glycoprotein

I

is

alleles

is

altered

also

by

present

addition

A

and

galactose.

anti-A

nor

As

a

anti-B

consequence

antibodies

neither

are

acetyl-galactosamine

produced.

therefore

give

the

or

same

galactose.

I

phenotype,

of

A

I

A

and

as

do

I

i

B

B

I

I

B

This

genotype

therefore

A

phenotype

to

I

A

gives

B

I

and

I

a

different

B

I

and

I

i

The

allele

A

so

the

alleles

I

and ●

i

is

recessive

because

it

does

not

B

I

are

co-dominant. A

cause

the

production

of

a

glycoprotein.

I

A

I

A ●

The

allele

i

is

recessive

because

it

and

causes

I

i

do

I

therefore

B

production

of

the

basic

glycoprotein:

if

so

B

I

give

I

same

phenotype

and

i

Group A

Group O

anti-A

anti-B

anti-A

anti-B

Group B

Group AB

anti-A

▲

the

B

and

anti-B

anti-A

anti-B

Figure 12 Blood group can easily be determined using test cards

teig predicio i cro-breedig experime

Comparison of predicted and actual outcomes of genetic crosses using real data.

It

is

in

the

principles

not

just

nature

that

to

of

science

explain

describe

to

natural

individual

try

to

nd

general

phenomena

examples

of

one

face

and

Mendel

discovered

showing

that

have

great

principles

predictive

can

still

use

them

to

predict

the

important

crosses.

Table

2

lists

outcomes

possible

predictions

actual

usually

outcomes

This

is

chance

involved

tossing

of

a

coin

of

genetic

exactly

because

in

is

the

a

crosses

with

there

the

is

coin

to

to

t,

either

the

element

of

analogy.

results,

genes.

We

of

The

due

land

50%

of

times

with

each

An

uppermost,

not

bi ol og y

of

an

is

d ecid ing

ex pe ri men t

pre d i cti o ns

the

resul ts

but

if

we

toss

it

1,000

expect

it

to

land

precisely

500

obvio us

difference

to

for

us

to

ar e

c l os e

a cc e pt

d iffe r ence s

a re

t ha t

too

or

the

p re di ct i on s

gr e at

must

the

less

chance

predictions

do

tr e nd

bet w e e n

lik e l y

and

no t

tha t

the

t

is

tha t

ob se r ve d

the

mor e

the

the

and

g re a ter

e xpe c t e d

di ffe re nc e

l ik el y

t ha t

is

the

r e sul ts .

expect

of

its

assess

objectively

times

times

whether

results

t

two statistical

tests

are

used.

For

genetic

we crosses

do

in

whethe r

predictions, faces

skil l

resul ts

the

or

false.

the

not

predicted

an

inheritance

simple

do

To the

the

crosses.

correspond

outcomes.

other

in

be

The

the

of

and monohybrid

with

power.

they genetic

times

of

enough We

500

showing.

whether inheritance

and

a An

phenomenon.

face

the

chi-squared

test

can

be

used.

This

test

with is

described

later

in

the

book

in

sub-topic

4.1.

175

3

G e n e t i c s

Co

Pedcted outcoe

Exape

Pure-breeding parents one with

All of the ospring will have the same

All ospring of a cross between pure-

dominant alleles and one with

character as the parent with dominant

breeding tall and dwarf pea plants

recessive alleles are crossed.

alleles.

will be tall.

Pure-breeding parents that have

All of the ospring will have the same

All ospring of a cross between red

dierent co-dominant alleles

character and the character will be

and white owered Mirabilis jalapa

are crossed.

dierent from either parent.

plants will have pink owers.

Two parents each with one

Three times as many ospring have

3:1 ratio of tall to dwarf pea plants

dominant and one recessive

the character of the parent with

from a cross between two parents

allele are crossed.

dominant alleles as have the character

that each have one allele for tall

of the parent with the recessive

height and one allele for dwarf

alleles.

height.

A parent with one dominant and

Equal propor tions of ospring with

1:1 ratio from a cross between a

one recessive allele is crossed

the character of an individual with a

dwarf pea plant and a tall plant with

with a parent with two recessive

dominant allele and the character of

one allele for tall height and one for

alleles.

an individual with recessive alleles.

dwarf height .

T able 2

Data-baed queton: Analysing genetic crosses

1

Charles

majus

pure

Darwin

plants,

breeding

symmetric.

cr o s s e d

which

pla nts

All

the

pure

hav e

w ith

F

bre e din g

b i l ate ra l ly

pe lo ri c

offspring

wil d- t ype

s ymm et ri c

o w e r s

produced

t h at

Antirrhinum

owe rs ,

a re

wit h

r a di al l y

b i l a ter a ll y

sy m m et r i c

1

owers.

Darwin

the n

cro ss e d

the

F

plants

together.

In

the

F

1

generation

owers

Figure 13 Antirrhinum owers –

there

and

37

were

with

88

p la nts

p e l or ic

2

wi t h

bi la t e ra ll y

s ym m et r i c

owe rs.

(a) wild type, (b) peloric

a)

Construct

between

a

Punnett

the

F

grid

to

predict

the

outcome

of

the

cross

plants.

[3]

1

b)

Discuss

whether

enough

c)

Peloric

to

There

are

called

light,

together,

three

only

buff

pheasants

a)

crossed

Discuss

enough

176

a

with

of

and

141

the

support

all

cross

close

[2]

feather

offspring

buff

there

rare

for

pheasants

produced.

the

are

extremely

reasons

with

light

with

[1]

bred

Similarly,

were

wild

coloration

were

were

in

this.

ring.

75

when

When

light

to

predict

the

outcome

of

pheasants.

actual

the

are

Suggest

were

the

buff.

grid

buff

of

outcome.

pheasant

ring,

Punnett

whether

plants

When

crossed

together

to

majus

species.

buff.

results

predicted

offspring

were

ring

Construct

breeding

b)

and

light

were

68

this

varieties

ring

ring

offspring,

of

actual

the

Antirrhinum

populations

2

the

support

results

predicted

[3]

of

the

cross

outcome.

are

close

[2]

3 . 4

3

Mary

and

character

of

the

are

Herschel

called

fungus

shown

Mitchell

poky

grow

in

the

more

table

mae paent

in

investigated

fungus

slowly

the

inheritance

Neurospora

than

the

crassa.

wild-type.

of

Poky

The

i N h E r i T A N C E

a

strains

results

3.

Feae paent

Wild type

Wild type

Poky

Nube of wd

Nube of pok

tpe opng

opng

9,691

90

Poky

0

10,591

Wild type

Poky

0

7,905

Poky

Wild type

4,816

43

T able 3

a)

Discuss

table

b)

1

whether

(page

Suggest

a

between

male

c)

data

ts

any

of

the

Mendelian

ratios

in

reason

wild

[2]

for

type

all

the

and

offspring

poky

strains

being

when

poky

a

in

wild

a

cross

type

is

the

parent.

Suggest

cross

is

the

170).

a

[2]

reason

between

the

female

for

wild

a

small

type

number

and

poky

of

poky

strains

offspring

when

a

in

wild

a

type

parent.

[1]

Figure 14 Feather coloration from a bu pheasant

Geeic dieae due o receive allele

Many genetic diseases in humans are due to recessive

alleles of autosomal genes.

A

genetic

diseases

only

usually

person

has

will

recessive

Genetic

in

as

this.

one

not

allele

they

do

illness

a

allele

to

they

for

that

have

the

by

a

parents

show

probability

of

of

do

a

the

have

gene.

the

of

disease

of

a

gene.

but

recessive

one

allele

the

a

can

are

pass

called

If

the

a

allele,

on

the

carriers.

Aa

must

they

child

of

allele.

appear

disease

disease,

having

therefore

allele

dominant

they

usually

the

genetic

disease

dominant

individuals

with

Most

The

the

and

disease,

child

parents

by

a

copies

These

symptoms

of

not

recessive

of

these

caused

two

offspring.

caused

Both

is

allele

genetic

symptoms

their

not

that

recessive

individuals

show

diseases

The

an

by

because

unexpectedly.

but

is

caused

develops

gene,

they

disease

are

are

with

be

unaware

the

Aa

carriers,

disease

of

is

25 a

per

cent

caused

(see

by

a

gure

15).

recessive

Cystic

allele.

It

brosis

is

is

an

described

example

later

in

of

this

a

genetic

A

disease

sub-topic.

Oher caue of geeic dieae AA

Aa

aA

aa

not carrier

Some genetic diseases are sex-linked and some are due

carrier

to dominant or co-dominant alleles.

A

small

It

is

not

proportion

possible

dominant

allele

to

of

genetic

be

then

a

diseases

carrier

they

of

are

these

themselves

caused

diseases.

will

do not develop the disease

by

If

develop

a

a

dominant

person

the

has

disease.

allele.

one

If

one

develops the genetic disease

▲

Figure 15 Genetic diseases caused

by a recessive allele

177

3

G e n e t i c s

Bb

parent

bb

is

50

has

per

genetic

b

the

cent

allele

(see

disease

for

the

gure

caused

disease,

16).

by

a

A

very

small

alleles.

An

disease

dominant

proportion

example

was

is

of

genetic

sickle-cell

is

bb

does not develop

Hb

a

It

is

child

is

an

inheriting

example

described

later

of

in

it

a

this

described

in

diseases

sub-topic

3.1.

possible

the

sickle

cell

combinations

allele

of

is

alleles

the disease

The

Hb

and

.

caused

by

molecular

normal

Figure

the

co-dominant

basis

allele

that

characteristics

have

as

one

those

for

of

this

hemoglobin

shows

the

three

that

result.

S

Hb

who

17

characteristics

A

Figure 16 Genetic diseases caused

are

The

S

and

Individuals

▲

of

disease

allele.

anemia.

A

Bb

disease

chance

sub-topic.

b

develops the

the

Huntington’s

and

have

one

two

Hb

allele

copies

of

do

not

either

have

allele,

the

so

same

the

by a dominant allele

alleles

Most

some

This

are

co-dominant.

genetic

show

is

diseases

a

called

red-green

affect

different

sex

males

pattern

linkage.

The

colour-blindness

of

and

inheritance

causes

and

females

of

sex

in

in

the

males

linkage

hemophilia,

same

are

and

and

way

but

females.

two

described

examples,

later

in

this

sub-topic.

A

A

alleles : Hb

A

Hb

alleles : Hb

s

Hb S

alleles : Hb

S

Hb

characteristics :

characteristics :

characteristics :

- susceptible to

- increased resistance

- susceptible to malaria

malaria

- severe anemia

to malaria

- not anemic

- mild anemia

normal red blood

sickle-cell shape

cell shape

A

Figure 1 7 Eects of Hb

▲

S

and Hb

alleles

Cyic broi ad Huigo’ dieae

Inheritance of cystic brosis and Huntington’s disease.

Cystic

brosis

in

parts

of

the

of

CFTR

channel

mucus

the

gene.

chromosome

ion

is

Europe.

and

7

is

This

and

that

commonest

It

is

the

due

to

gene

digestive

is

gene

involved

a

genetic

located

product

in

disease

recessive

allele

a

secretion

mucus

and

on

is

secretions,

chloride

of

sweat,

recessive

chloride

alleles

channels

function

properly.

up

pancreatic

enzymes

reach

the

them

in

the

very

lungs

duct

is

usually

secreted

small

viscous.

causing

by

the

Sticky

infections

blocked

of

of

this

being

gene

result

produced

Sweat

sodium

do

intestine.

that

containing

do

some

have

in

not

excessive

is

an

parts

recessive,

have

of

allele

any

a

Europe

for

cystic

single

effects.

one

copy

The

in

twenty

brosis.

of

the

chance

of

As

people

the

allele

two

allele

does

chloride

is

produced,

but

both

being

a

carrier

of

the

allele

not

parents

1 __

amounts

so

pancreas

juices. In

The

the

digestive

not

making

builds

is

1 __

× 20

, 20

1 ___

digestive

juices

and

mucus

are

secreted

with

which

is

.

The

chance

of

such

parents

having

400

insufcient

enough

178

sodium

water

chloride.

moves

by

As

a

osmosis

result

into

not

the

a

child

with

Punnett

cystic

grid.

brosis

can

be

found

using

a

3 . 4

Because

father

Cc

with

of

late

Huntington’s

children.

A

symptoms

C

the

i N h E r i T A N C E

onset,

many

disease

have

genetic

would

test

can

develop

people

diagnosed

already

show

had

before

whether

a

young

c

person

at

risk

has

the

choose

dominant

not

to

allele,

have

the

but

most

people

test.

Cc CC C

About

normal

one

in

10,000

people

have

a

copy

of

normal (carrier)

the

mother Cc

for

cC

c

cc

Huntington’s

two

can

normal

cystic

(carrier)

brosis

one

parents

both

nonetheless

of

their

allele,

to

so

is

have

develop

parents

it

has

the

the

a

very

unlikely

copy.

disease

allele

A

if

person

only

because

it

is

dominant.

ratio 3 normal : 1 cystic brosis

father

Hh

Huntington’s

allele

of

the

HTT

chromosome

named

still

disease

4

gene.

and

huntingtin.

being

is

due

This

the

to

dominant

gene

gene

The

a

is

located

product

function

of

is

a

on

protein

huntingtin

H

h

is

researched.

Hh hh h

The

dominant

allele

of

HTT

causes

Huntington’s normal

degenerative disease

changes

in

the

brain.

Symptoms

usually

start mother hh

when

a

person

is

between

30

and

50

years

old. Hh hh

Changes

to

behaviour,

thinking

and

emotions h

Huntington’s normal

become

the

increasingly

start

of

severe.

symptoms

is

Life

about

expectancy

20

years.

A

after

disease

person ratio 1 normal : 1 Huntington’s disease

with

and

or

the

disease

usually

some

eventually

succumbs

other

to

infectious

needs

heart

full

nursing

failure,

care

pneumonia

disease.

sex-liked gee

The pattern of inheritance is dierent with

sex-linked genes due to their location on sex

chromosomes.

Plants

such

female

which

same

●

pea

were

in

When

plants

the

the

are

in

same

female

hermaphrodite

Thomas

the

late

Andrew

18th

whichever

gamete.

–

For

they

can

Knight

century,

character

example,

he

was

produce

did

crossing

discovered

in

these

both

the

two

the

gamete

crosses

and

experiments

that

male

male

gave

and

the

results:

pollen

plant

●

peas

gametes.

between

results

as

with

pollen

plant

from

plant

purple

from

with

a

a

green

stems

placed

onto

on

the

stigma

of

a

stems;

plant

green

with

with

purple

stems

placed

onto

on

the

stigma

of

a

stems.

179

3

G e n e t i c s

Plants

white eye

r

X

red eye

r

are

always

carried

give

out,

the

but

same

in

results

animals

the

when

reciprocal

results

are

crosses

sometimes

such

as

different.

these

An

R

X

X

Y

inheritance

X

r

X

One r

X

sex

pattern

where

the

ratios

are

different

in

males

and

females

is

linkage

R

called

of

the

rst

examples

of

sex

linkage

was

discovered

by

Thomas

R

X

Morgan

the

fruit

y,

Drosophila.

This

small

insect

is

about

4

mm

long

X

Y

r

red

in

r r

X

R

X

X

and

Y

completes

its

life

cycle

in

two

weeks,

allowing

crossing

experiments

white

red

to

be

done

quickly

with

large

numbers

of

ies.

Most

crosses

in

Drosophila

r

Y

X

do

not

show

sex

linkage.

For

example,

these

reciprocal

crosses

give

the

white

same

red eye

R

X

white eye

R

results:

●

normal-winged

●

vestigial-winged

males

×

males

vestigial-winged

×

females;

normal-winged

females.

r

X

X

Y

These

gave

different

●

red-eyed

●

white-eyed

males

white-eyed

males.

males

×

results:

white-eyed

females

gave

only

red-eyed

×

females

gave

red-eyed

offspring;

r

R

X

crosses

X R

X

R

X

red-eyed

females

and

X

Y

R

red

R

X

r

R

X

X

red

Y

red

Geneticists

had

obs e r v e d

tha t

the

inhe ri t a n c e

of

g e n es

an d

of

R

X

Y

chromosomes

sho we d

cle a r

pa r a ll el s

and

so

g en e s

wer e

l ik e ly

to

be

red

located

have

on

two

chromo s o me s .

copies

of

a

It

wa s

a l so

chro mos ome

kn o wn

c a l le d

X

t ha t

an d

fe m a l e

m al e s

Drosophila

on l y

h ave

one

Key

copy.

R

X

Morgan

ded uce d

that

se x

li nka g e

of

eye

c o lo u r

cou ld

t h e r efor e

X chromosome with allele

be

for red eye (dominant)

due

to

the

eye

co l o ur

g e ne

b ei n g

lo c a t ed

on

the

X

ch r om o so m e .

r

X

X chromosome with allele

Male

Drosophila

also

have

a

Y

chro mo s ome ,

but

th i s

do es

not

ca r ry

for white eye (recessive)

the

Y

eye-colour

Y chromosome

Figure ▲

ge ne .

18

explains

the

inheritance

of

eye

colour

in

Drosophila.

In

crosses

Figure 18 Reciprocal sex-linkage

involving

sex

linkage,

the

alleles

should

always

be

shown

as

a

superscript

crosses

letter

on

should

a

letter

also

be

X

to

represent

shown

though

it

the

X

does

chromosome.

not

carry

an

The

allele

Y

of

chromosome

the

gene.

Red-gree colour-blide ad hemophilia

Red-green colour-blindness and hemophilia as examples of sex-linked inheritance.

Many

examples

discovered

to

genes

are

very

X

of

few

of

genes

recessive

cone

specic

They

the

on

X

the

allele

cells

of

a

the

wavelength

all

Y

as

chromosome.

described

due

to

here:

due

there

Two

genes

on

red-green

hemophilia.

gene

proteins.

in

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distinguish between the colours of the owers and the leaves

180

3 . 4

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Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.

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3

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c::::::J c::::::J

182

although

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Figure 2 1 Pedigree of a family with cases of vitamin D-resistant rickets

in

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ts

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X

3 . 4

i N h E r i T A N C E

Data-baed queton: Deducing genotypes from pedigree char ts

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gure22

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3

4

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3

4

5

6

7

9

8

10

11

12

13

14

15

evidence III

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6

7

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Figure 22 Example of a pedigree char t

unaected female

aected male

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allele;

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3

and

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allele;

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in

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[2]

dominant 4

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two

examples

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[3] would

t

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[2]

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Many genetic diseases have been identied in humans

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genetic

including

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(PKU),

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research

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genetic

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small

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than

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between

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chance

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already

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human

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human

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together when they have a child. There is a

small chance that two recessive alleles will

come together and cause a genetic disease

due

the

to

one

same

of

rare

these

recessive

alleles

if

the

other

parent

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allele.

183

3

G e n e t i c s

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185

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estimate

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Hiroshima

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1990

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cell.

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nuclear

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from

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cell

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a

1986

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1945.

in

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radioactive

people”

Party

30,000

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deaths

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tonnes

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Radiation

and

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Effects

Foundation.

radaton

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Leukemia

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Figure 27 Humans have been excluded from

a large zone near the Chernobyl reactor. Some

>1

Cancer

plants and animals have shown deformities

0.005–0.2 that may be due to mutations

>1

1

Calculate

due

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you

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186

in

and

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to

of

Sv

of

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to

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radiation

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groups

Sv

radiation.

or

table,

cancer

(a)

over

chart

to

[4]

represent

including

should

be

the

two

two

what

the

y-axes,

for

deaths

in

the

deaths.

on

data

percentages

[4]

due

to

leukemia

cancer.

reasons,

the

deaths

exposed

of

of

the

excess

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calculated.

Compare

Discuss,

(b)

column

deaths

deaths

of

people

suitable

leukemia

and

4

a

in

radiation

right-hand

that

3

of

Construct

the

percentage

leukemia

(sieverts)

2

the

[3]

level

environment.

of

radiation

might

be

[4]

3 . 5

G E N E T i C

m O D i F i C A T i O N

A N D

B i O T E C h N O l O G y

3.5 Genetc odcaton and botecnoog 

Uderadig Applicaio ➔

Gel electrophoresis is used to separate proteins Use of DNA proling in paternity and forensic

➔

or fragments of DNA according to size. investigations.

➔

PCR can be used to amplify small amounts of DNA.

➔

DNA proling involves comparison of DNA .

➔

Genetic modication is carried out by gene

Gene transfer to bacteria with plasmids using

➔

restriction endonucleases and DNA ligase.

Assessment of the potential risks and benets

➔

transfer between species.

➔

associated with genetic modication of crops.

Clones are groups of genetically identical

Production of cloned embryos by somatic-cell

➔

organisms, derived from a single original

nuclear transfer.

parent cell.

➔

Many plant species and some animal species

skill

have natural methods of cloning.

➔

Design of an experiment to assess one factor

➔

Animals can be cloned at the embryo stage by

aecting the rooting of stem-cuttings.

breaking up the embryo into more than one

➔

group of cells.

➔

Analysis of examples of DNA proles.

Methods have been developed for cloning adult

➔

Analysis of data on risks to monarch butteries

animals using dierentiated cells.

of Bt crops.

naure of ciece

➔

Assessing risks associated with scientic research: scientists attempt to assess the risks associated

with genetically modied crops or livestock .

DNA samples

Gel elecrophorei negative electrode

Gel electrophoresis is used to separate proteins or

sample well

fragments of DNA according to size.

Gel

electrophoresis

eld,

in

is

a

according

gel.

The

applied.

to

gel

is

involves

their

size

separating

and

immersed

Molecules

in

the

in

charged

charge.

a

gel

conducting

sample

that

molecules

Samples

are

are

uid

and

charged

in

placed

an

will

an

in

electric

wells

electric

move

cast

eld

through 1

the

gel.

Molecules

directions.

with

Proteins

negative

may

be

and

positive

positively

or

charges

negatively

move

in

opposite

charged

so

can

positive electrode

be large fragments

separated

according

to

their

charge.

direction of

The

gel

resists

used

the

in

gel

electrophoresis

movement

of

molecules

consists

in

a

of

a

sample.

mesh

DNA

of

laments

molecules

that

migration

from

small fragments

eukaryotes

are

too

long

to

move

through

the

gel,

so

they

must

be

• 1

broken

charges

up

so

into

smaller

move

in

the

fragments.

same

All

DNA

direction

molecules

during

gel

carry

negative

electrophoresis,

but

not

▲

Figure 1 Procedure for gel electrophoresis

187

3

G e n e t i c s

at

the

move

to

same

rate.

further

separate

in

Small

a

fragments

given

fragments

time.

of

move

Gel

DNA

faster

than

electrophoresis

according

to

large

can

ones

so

therefore

they

be

used

size.

DnA amplicaio by PCR

PCR can be used to amplify small amounts of DNA .

The

polymerase

of

of

technique

this

amount

a ▲

DNA.

chain

copies

of

single

It

DNA

is

are

is

reaction

almost

described

needed

molecule.

is

Within

used

always

at

in

the

an

to

make

simply

sub-topic

start

hour

or

of

large

called

2.7.

the

two,

numbers

PCR.

The

Only

a

process

millions

–

of

very

in

of

details

small

theory

copies

just

can

Figure 2 Small samples of DNA being

be

made.

This

makes

it

possible

to

study

the

DNA

further

without

ex tracted from fossil bones of a Neander thal

the

risk

of

using

up

a

limited

sample.

For

example,

DNA

extracted

for amplication by PCR

from

fossils

from

blood,

can

be

amplied

semen

or

hairs

using

can

PCR.

also

be

Very

small

amplied

amounts

for

use

in

of

DNA

forensic

investigations.

PCR

is

such

the

not

as

used

blood

person

sperm

PCR

from

cells

is

in

used

copying

by

a

to

primer

The

selectivity

a

presence

primer

is

of

that

amplied

whom

a

of

by

to

blood

semen

DNA

that

set

blood

allows

or

to

greater

but

if

a

man’s

is

A

in

and

entire

of

a

sample

chromosomes

the

together

genome.

sequence

start

is

Instead

selected

desired

of

the

for

sequence.

pairing.

desired

mixture

in

modied

there

all

example,

the

ingredients

genetically

PCR,

for

base

molecules

contain

sequences.

particular

even

DNA

contain

binds

modied

the

of

cells

came,

complementary

genetically

the

of

primer

PCR

binds

entire

White

specic

genome

by

the

the

sample

copy

binds

whole

copy

semen.

using

The

from

to

or

none

sequences

of

DNA.

foods

DNA.

be

the

such

PCR

copied

test

involves

Any

present

to

One

for

the

use

DNA

has

the

of

no

effect.

Data-based questions: PCR and Neander thals

The

be

evolution

studied

DNA.

species

time.

If

a

in

species

base

The

number

Samples

of

fossil

of

living

the

base

separates

sequence

accumulate

“evolutionary

from

groups

into

two

over

differences

the

long

can

be

Neanderthal

can

sequences

between

gradually

of

organisms

groups,

two

periods

used

as

of

an

clock”.

DNA

were

bones

neanderthalensis).

of

a

recently

obtained

Neanderthal

They

were

( Homo

amplied

using

and

between

the

humans

and

the

chimpanzees.

of

fo ycneuqerf

differences

of

comparing

% / secnereid fo rebmun

their

by

25

human–Neander thal 20

human–human

15

human–chimp

10

PCR.

5

A

section

was

of

the

sequenced

Neanderthal

and

mitochondrial

compared

with

DNA

sequences

0

from

994

humans

and

16

chimpanzees. 0

The

bar

chart

sequence

sample

188

of

in

gure

differences

humans,

3

shows

were

how

found

between

the

many

within

▲

the

humans

and

the

5

10

15

20

25

30

35

40

45

50

55

60

65

number of dierences in base sequence

base-

Figure3 Number of dierences in base sequences

between humans, chimps and Neander thals

a

present

3 . 5

1

State

in

2

the

base

most

Humans

in

the

common

sequence

and

genus

classied

in

number

between

pairs

Neanderthals

Homo

the

and

genus

are

G E N E T i C

of

of

differences

humans.

both

Discuss

this

[1]

the

classied

chimpanzees

Pan.

m O D i F i C A T i O N

3

A N D

classication

bar

a

supported

by

the

data

in

[3]

limitation

conclusion

whether

is

chart.

Suggest

are

B i O T E C h N O l O G y

from

to

the

drawing

any

human–Neanderthal

comparison.

[1]

DnA prolig

DNA proling involves comparison of DNA .

DNA

●

proling

A

sample

from

●

involves

of

Sequences

are

DNA

another

in

selected

these

is

obtained,

source

the

and

●

The

copied

●

The

fragments

●

This

produces

is

are

a

such

DNA

are

DNA

stages:

as

that

copied

split

vary

from

or

a

a

known

crime

considerably

individual

or

scene.

between

individuals

PCR.

fragments

separated

of

fossil

by

into

pattern

either

a

using

bands

using

gel

that

restriction

endonucleases.

electrophoresis.

is

always

the

same

with

DNA

▲

taken

from

one

individual.

This

is

the

individual's

DNA

Figure 4 DNA proles are often referred to as

prole. DNA ngerprints as they are used in a similar

●

The

proles

bands

are

of

the

different

same

individuals

and

which

are

can

be

compared

to

see

which

way to real ngerprints to distinguish one

individual from all others

different.

Paeriy ad foreic iveigaio

Use of DNA proling in paternity and forensic investigations.

DNA

proling

is

used

in

forensic

DNA

investigations.

proling

is

investigations. ●

Blood

stains

on

a

suspect’s

clothing

could

to

come

from

the

Blood

from

stains

the

at

the

victim

crime

could

scene

be

that

shown

to

are

not

come

a

A

single

come

each

the

of

a

hair

to

at

the

come

from

from

scene

sample

If

of

the

a

crime

from

sexual

the

example

crime

victim.

Men

the

highly

scene

could

be

the

is

crime

could

be

shown

to

DNA

a

prole

compared

taken

pattern

of

with

from

bands

that

the

two

the

same

father

to

of

a

nd

out

child.

paternity

There

investigations

are

being

person.

who

of

material

the

the

DNA

suspect

matches

samples

This

can

committed

from

●

prole

or

the

exactly

claim

now

of

DNA

have

many

the

databases

criminal

to

raise

to

that

avoid

they

are

the

having

to

not

pay

the

the

child.

A

provide

crime.

of

DNA

cases

to

who

wish

to

have

ha d

identi f y

mul ti ple

the

pa rtn e r s

bio lo gi cal

fa th e r

of

child

may

man

was

they

are

wish

their

their

to

prove

father

in

that

order

a

to

deceased

show

that

heir.

proles

of

the

mother,

the

child

and

the

are

very

are

needed.

DNA

proles

of

each

of

patterns

of

the

strong are

prepared

and

the

bands

Some

proles,

be

compared.

If

any

bands

in

the

child’s

prole

which do

allowed

child

it

are countries

a

child.

samples of

of

Women

may

suspect.

DNA

likely

evidence

have

for

sometimes

mother

man from

the

suspect.

DNA is

is

requested.

●

Semen

In

paternity

suspect.

shown

●

man

reasons

father

●

in

done

from ●

the

are

victim. various

●

used

be whether

shown

also

These

not

occur

in

the

prole

of

the

mother

or

solved. man,

another

person

must

be

the

father.

189

3

G e n e t i c s

Aalyi of DnA prole

Analysis of examples of DNA proles.

Analysis

two

if

of

DNA

the

DNA

proles

samples

pattern

of

are

in

very

bands

on

forensic

likely

the

to

investigations

have

prole

is

come

the

is

from

the

same

person

same.

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I

II Ill

11111111 11

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victim

specimen

111111 I 11 I I I II I 11111 II I I I I I Ill I II Ill 1•1 ■ I Ill I ▲

straightforward:

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1

2

suspects

3

Figure 5 Which of the three suspects’ DNA ngerprints matches the

specimen recovered from the crime scene?

Analysis

Each

in

of

the

of

DNA

the

biological

prole

must

prole

or

more

proles

bands

be

in

do

prole

paternity

child’s

mother

not,

in

the

checked

the

bands

in

or

to

of

DNA

father’s

make

the

another

investigations

prole

prole.

sure

man

man

that

must

Every

it

have

to

more

the

band

occurs

presumed

must

is

be

be

been

in

the

either

the

the

complicated.

same

in

as

a

band

child’s

the

father.

If

mother’s

one

biological

or

father.

Geeic modicaio

Genetic modication is carried out by gene transfer

between species.

Molecular

be

to

transferred

another

genetic

the

code

amino

is

Genetic

to

milk

crop

the

was

daodil plants to rice, to make the rice

produce

be

These

genes

involved

transfer

genes

from

that

the

from

so

of

from

are

that

allow

genes

It

is

from

possible

transferred

them

is

genes

one

to

species

because

between

unchanged

–

the

species,

the

same

of

been

silk

has

gene

large

used

protein.

to

for

bacteria.

making

quantities

also

been

as

purple

of

it

been

of

One

of

human

this

the

insulin

hormone

to

can

silk

used

have

is

new

characteristics

produced

that

immensely

secrete

strong,

but

commercially.

to

produce

genetically

rather

three

introduce

have

Spider

produce

known

transfer

to

goats

snapdragons

are

the

to

diabetics.

used

are

eukaryotes

that

example,

spider

not

fruits

when

transfer

has

For

modication

example

The

modication.

translated

done

treating

species.

plant.

Figure 6 Genes have been transferred from

rice

for

could

Genetic

of

was

This

containing

spiders

so

transferred

modication

animal

species.

techniques

produced.

examples

produced

developed

genetic

sequence

been

bacterium.

as

universal,

Genes

be

190

between

acid

have

have

known

is

a

produce a yellow pigment in its seeds

is

polypeptide

early

▲

biologists

been

than

genes,

many

modied

or

transferred

red.

two

The

from

new

GM

to

tomatoes

production

daffodil

varieties

crops.

of

plants

For

to

golden

and

3 . 5

one

in

from

the

a

rice

bacterium,

so

that

the

G E N E T i C

yellow

m O D i F i C A T i O N

pigment

β-carotene

is

A N D

B i O T E C h N O l O G y

produced

grains.

Actvt

Scientists have an obligation to consider the ethical implications of their

research. Discuss the ethics of the development of golden rice. β-carotene is

a precursor to vitamin A. The development of golden rice was intended as a

solution to the problem of vitamin A deciency, which is a signicant cause of

blindness among children globally.

techique for gee rafer o baceria

Gene transfer to bacteria with plasmids using restriction

y

endonucleases and DNA ligase.

Genes

of

can

be

transferred

techniques.

engineering.

Together

Gene

from

these

transfer

one

species

techniques

to

bacteria

to

another

are

known

usually

by

as

involves

a

variety

genetic

plasmids,

Bacterial cell

Plasmid

mRNA extracted from

restriction

enzymes

and

DNA

ligase.

-

human pa ncreat ic cells ●

A

plasmid

have

is

about

1,000

small

1,000

kbp.

plasmids

a

They

are

cytoplasm

are

therefore

pathogenic

advantage

base

and

on

they

can

viruses

but

than

a

over

most

their

bacterium

plasmids

have

The

encourage

favours

rather

smallest

bacteria.

one

with

The

but

in

that

selection

bacterium

DNA.

kbp),

from

parallels

natural

a

genes

transfer

some

(1

of

commonly

with

and

circle

pairs

occur

those

the

extra

to

replication

plasmids

plasmids

are

that

disadvantage.

in

There

cDNA

confer

an

plasmids

to

exchange

genes,

so

naturally

absorb

them

them

into

their

main

circular

DNA

molecule.

enzyme

with reverse

Plasmid and

cDNA fused

and to make

incorporate

cut with

mRNA treated

transcriptase

use

0

Plasmid

restriction

not

Bacteria

from bacteria

mRNA

abundant

another.

Plasmid obtained

Plasmids

using DNA ligase

complementary Recombinant

are

very

useful

in

genetic

DNA (cDNA)

engineering.

plasmid

introduced into ●

Restriction

enzymes,

also

known

as

endonucleases,

are

enzymes host cells

that

cut

used

to

DNA

cut

molecules

open

at

plasmids

specic

and

base

also

to

sequences.

cut

out

They

desired

can

genes

be

from

Bacteria

larger

DNA

molecules.

Some

restriction

enzymes

have

the

useful multiply in

property

of

cutting

the

two

strands

of

a

DNA

molecule

at

different a fermenter

points.

sticky

This

ends

leaves

single-stranded

created

complementary

by

base

any

one

sections

particular

sequences

so

can

be

called

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enzyme

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enzyme example of gene transfer. It has been used

that

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used to create genetically modied E. coli bacteria

to

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messenger

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for use in treating diabetes

191

3

G e n e t i c s

Aeig he rik of geeic modicaio

Assessing risks associated with scientic research:

scientists attempt to assess the risks associated with

genetically modied crops or livestock .

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of

when

Paul

Figure 8 The biohazard symbol indicates any

the

rst

many

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going

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Figure 9 GM corn (maize) is widely grown in

harmful

would

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that

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192

have

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Figure 10 Wild plants growing nex t to a crop of GM maize

of

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B i O T E C h N O l O G y

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193

3

G e n e t i c s

toxic

or

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livestock

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reactions

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developed.

Aalyig rik o moarch buerie of

B cor

Analysis of data on risks to monarch butteries of Bt crops.

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protein.

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194

is

cob.

insect.

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toxin.

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mays.

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buttery

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nubilalis.

corn

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of

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corn

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investigated

available

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3 . 5

G E N E T i C

m O D i F i C A T i O N

A N D

B i O T E C h N O l O G y

.

Data-baed queton: Transgenic pollen and monarch lar vae

To

investigate

monarch

collected

spatula

old

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by

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the

of

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was

leaves

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lightly

the

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to

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each

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days.

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were

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deposit

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.

of

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leaves

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)%( eavral hcranom fo lavivruS

...................................................................................... .. ..

a

A

ne

three-day-

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100

75

50

25

0

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1

2

3

4

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larvae

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days.

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the

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ve

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leaves

not

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leaves

dusted

●

days.

fael evitalumuC

of

four

four

leaves

dusted

with

with

dusted

with

pollen

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pollen

(blue)

pollen

from

Bt

(yellow)

corn

avral rep noitpmusnoc

Three

over

after

1.5

1

0.5

(red)

0

The

results

are

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the

table,

bar

chart

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graph

on

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1

right.

2

3

4

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1

a)

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the

variables

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Source: Losey JE, Rayor LS, Carter ME (May 1999).

experiment.

[3] “Transgenic pollen harms monarch larvae”.

2

b)

Explain

the

a)

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need

the

to

total

keep

these

number

of

variables

larvae

constant.

used

in

[2]

the

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experiment.

b)

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the

Nature 399 (6733): 214.

need

for

replicates

in

experiments.

[2]

Mean mass of

surviving larvae (g)

[2]

Leaves not dusted

0.38

with pollen

3

The

bar

Explain

chart

how

and

the

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graph

bars

help

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the

results

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and

and

error

bars.

Leaves duste d wit h

evaluation

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non-GM pollen

of

4

data.

[2]

Explain

the

conclusions

that

can

be

drawn

from

Leaves dusted wit h

the

0.16

pollen from Bt corn

percentage

5

Suggest

survival

reasons

between

the

for

three

of

larvae

the

in

the

differences

three

in

treatments.

leaf

[2]

consumption

treatments.

[3]

Actvt

6

Predict

with

the

mean

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mass

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fed

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leaves

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Etatng te ze of a cone

pollen.

[2]

A total of 130,000 hectares of Russet

7

Outline

this

differences

experiment

might

by

any

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affect

and

between

processes

whether

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that

monarch

procedures

occur

larvae

are

in

used

nature,

actually

Burbank potatoes were planted in

in

Idaho in 2011. The mean density

which

of planting of potato tubers was

harmed

pollen.

[2]

50,000 per hectare. Estimate the size

of the clone at the time of planting and

at the time of harvest.

Cloe

Clones are groups of genetically identical organisms,

derived from a single original parent cell.

A

zygote,

the

rst

sexual

and

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cell

of

a

by

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develops

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the

fusion

organism.

they

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adult

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male

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all

and

genetically

organism.

If

female

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it

are

gamete,

produced

different.

reproduces

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zygote

sexually,

is

by

grows

its

195

3

G e n e t i c s

offspring

Actvt

also

identical

The

a

will

different.

When

they

In

some

do

this,

species

they

organisms

produce

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genetically

organisms.

of

Although

identical

of

genetically

genetically

we

do

twins

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develop

genetically

asexually.

production

group

the

be

reproduce

of

a

into

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usually

the

identical

identical

think

smallest

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zygote

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organisms

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clone

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in

can

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called

them

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dividing

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cloning

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clone.

way,

exist.

embryo

called

a

a

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cells,

pair

are

which

splitting

into

of

either

each

two

How many potato clones are there in

parts

which

each

develop

into

a

separate

individual.

Identical

twins

this photo?

are

not

identical

different

rarely

in

all

ngerprints.

identical

their

A

triplets,

characteristics

better

term

for

quadruplets

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them

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is

even

for

example,

monozygotic.

quintuplets

More

have

beenproduced.

Sometimes

For

a

clon e

example,

Large

but

clones

even

so

ca n

cons i st

com me r c ia ll y

are

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fo r me d

the

of

ve ry

gr own

by

cloning

o r g a ni sms

la rg e

pot a t o

ma y

n u m be r s

v a ri e t ie s

h ap pe n in g

be

t r ac ed

a g a in

back

of

a re

to

o rg a n is m s .

hu g e

and

one

c l on e s.

a ga i n,

or ig i n al

parentcell.

naural mehod of cloig

Many plant species and some animal species have

natural methods of cloning.

Although

identical

the

produced

▲

Figure 11 Identical twins are an example

of cloning

twig.

by

●

by

Many

plants

Two

plants

very

examples

A

a

single

A

at

they

garlic

of

are

a

end.

or

the

growing

Natural

are

bulb,

●

and

can

for

in

It

any

the

comes

method

involve

group

early

from

of

of

20th

the

cloning.

stems,

genetically

century

Greek

The

roots,

for

plants

word

for

methods

leaves

or

used

bulbs.

here:

planted,

produce

plant

the

uses

enough

bulbs

g r o ws

in

l ong

p l a ntl e ts

us i ng

plan t.

genetical l y

the

its

food

food

by

group

stores

to

grow

photosynthesis

are

genetically

to

grow

identical

A

hor i zon t a l

g r ow

the i r

roo t s

le a ve s,

he a lthy

i d e ntica l

so

can

s tr awbe r ry

ne w

st e m s

i nt o

p la nt s

th e

with

s oi l

b e c om e

p la nt

in

t h is

p la n t le t s

and

in d ep en d en t

c an

way

pr oduc e

du r in g

t en

a

season.

do

of

cloning

are

less

common

in

animals

but

some

species

it.

Hydra

clones

gure

1,

Female ▲

to

natural

when

All

These

methods

able

used

used

clone.

parent

more

a

given

photosynthesize

of

now

rst

reproduction.

varied

bulbs.

is

was

leaves

strawberry

the

it

have

are

These

group

so

clone

asexual

are

leaves.

●

word

organisms,

itself

page

aphids

by

a

process

called

budding

(sub-topic

1.6,

51).

can

give

birth

to

offspring

that

have

been

produced

Figure 12 One bulb of garlic clones itself to

produce a group of bulbs by the end of the

growing season

196

entirely

meiosis.

from

The

diploid

egg

offspring

cells

are

that

were

therefore

produced

clones

of

their

by

mitosis

mother.

rather

than

3 . 5

G E N E T i C

m O D i F i C A T i O N

A N D

B i O T E C h N O l O G y

Iveigaig facor aecig he rooig of em-cuig

Design of an experiment to assess one factor aecting the rooting of

stem-cuttings.

Stem-cuttings

used

to

from

clone

the

stem,

independent

1

are

Many

the

new

plants

Ocimum

short

plants

lengths

articially.

cutting

can

of

If

stem

roots

that

●

are

develop

become

whether

the

cutting

is

placed

in

water

or

compost

an ●

what

●

how

●

whether

type

of

compost

is

used

plant.

can

be

basilicum

cloned

roots

from

warm

the

cuttings

are

kept

cuttings.

particularly

easily.

a

plastic

bag

is

placed

over

the

cuttings 2

Nodes

are

positions

on

the

stem

where

leaves

●

are

attached.

below

3

a

Leaves

the

4

The

most

species

the

stem

is

cut

whether

holes

are

cut

in

the

plastic

bag.

node.

are

stem.

upper

With

removed

If

half

there

they

lowest

from

are

can

third

of

the

many

also

the

be

lower

large

half

leaves

of

in

You

should

you

design

or

water.

about

these

questions

when

experiment:

the 1

What

2

How

is

your

independent

variable?

reduced.

cutting

is

inserted

Compost

should

be

will

you

measure

the

amount

into of

compost

think

your

root

formation,

which

is

your

dependent

sterile variable?

and

contain

plenty

of

both

air

and

water.

3

5

A

clear

plastic

bag

with

a

few

holes

cut

in

Which

variables

should

you

keep

it constant?

prevents

excessive

water

loss

from

cuttings

4 inserted

in

How

you

6

Rooting

normally

takes

a

few

weeks.

new

different

types

of

plant

should

leaves

usually

indicates

that

use?

Growth

5 of

many

compost.

the

How

many

cuttings

should

you

use

for

each

cutting

treatment? has

Not

to

all

developed

gardeners

clone

plants

gardeners

ngers”

the

carry

have

using

sometimes

for

an

success

root

biologist

their

about

cuttings

out

factors

your

a

evidence

whether

the

are

but

reason

give

roots.

success.

root

the

list

to

or

have

“green

this

that

You

or

can

determine

can

design

investigate

below,

as

Experiments

not.

to

trying

Successful

reject

factors

experiment

on

said

would

the

when

cuttings.

one

another

and

of

factor

of

own.

Possible

factors

●

whether

●

how

●

whether

the

long

callus

to

stem

the

the

investigate:

is

cut

cutting

end

of

above

or

below

a

node

is

the

stem

is

left

in

the

air

to

over

●

how

●

whether

many

a

leaves

are

hormone

left

on

rooting

the

cutting

powder

is

used

197

3

G e n e t i c s

Cloig aimal embryo

Animals can be cloned at the embryo stage by breaking

up the embryo into more than one group of cells.

At

an

early

stage

pluripotent

theoretically

and

each

This

cells

one

is

embryo

most

separated

Only

a

certain

an

into

a

or

in

all

to

an

animal

types

divide

separate

by

presumably

of

two

individual

up

this

It

or

with

Coral

breaking

because

embryo

tissue).

into

fragmentation.

themselves

cells,

are

up

egg

still

can

has

been

could

not

into

be

of

are

is

therefore

more

all

embryos

into

parts

body

smaller

increases

parts.

have

groups

the

of

chance

of

little

stage

interest

it

is

not

vitro

can

be

and

be

this

and

in

allowed

separated

into

obtained

cells

successful

method

possible

cloning

by

naturally.

articially

embryo

most

in

as

this

transplanted

can

the

do

splitting,

However,

some

cases

it

the

embryos.

in

cells

and

clones

usually

to

embryos

fertilized

divisions

is

regarded

multiple

pluripotent

of

be

appear

Individual

number

embryos

embryo

do

animal

develop

number

at

twins

species

embryo.

There

the

clone

break

parts

of

embryo

splitting

identical

limited

.. \,

.

. ) ~ .,,/ ~ ,., '. ir' .~ ... iv' '

.

,

•

•

.

,.

'f

\

• • ,.. .,\If ~ r... . -,I

•

•

'

.. '\.,

..,

Splitting

▲

to

they

a

the

cells

into

surviving.

multicellular

while

to

all

developing

for

called

single

of

livestock,

of

develop

animal

possible

In

is

even

Formation

but

to

observed

or

development

possible

part

process

been

of

(capable

to

at

of

assess

develop

the

surrogate

this

are

to

from

way,

no

the

articial

stage.

cloning

a

after

pluripotent.

eight-cell

whether

a

mothers.

because

longer

into

embryo

new

because

individual

Figure 13 Sea urchin embryo (a) 4-cell stage

produced

by

sexual

reproduction

has

desirable

characteristics.

(b) blastula stage consisting of a hollow ball

of cells

Cloig adul aimal uig diereiaed cell

Methods have been developed for cloning adult animals

using dierentiated cells.

It

is

relatively

is

impossible

easy

to

characteristics.

assess

This

are

their

is

the

undifferentiated

biologist

nuclei

cells

the

as

from

from

nuclei

carried

tissues

Prize

of

for

Figure 14 Xenopus tadpoles

198

body

cell

there

cells

the

using

Xenopus

or

had

interest

in

out

in

the

frog.

cells

for

an

it

to

is

easy

clone

adult

new

during

and

to

them.

animal

animal

as

and

his

on

cloning

the

body

The

though

egg

they

differentiation

Gurdon

was

pioneering

proved

mammal

to

was

uses

therapeutic

be

them

cells

were

to

the

He

frog

removed

into

into

zygotes.

form

awarded

all

egg

which

They

the

the

Nobel

research.

much

Dolly

of

in

1950s.

transplanted

removed.

reproductive

it

of

a

it

desirable

adults

difcult

experiments

2012

for

stage

needed.

tadpoles

In

in

that

have

into

body

Oxford

been

at

will

more

tissues

developed

cloned

obvious

are

growth

Medicine

first

up

but

grown

much

the

cells

differentiated

The

is

all

Xenopus

cell

embryos

have

make

carried

transplanted

the

also

of

it

student

nucleus

division,

normal

from

is

Gurdon

Physiology

mammals.

Apart

▲

a

that

pluripotent

John

were

but

embryos,

the

embryos

produce

postgraduate

which

out

Cloning

in

a

cells

To

animal

whether

the

characteristics,

because

Xenopus

clone

know

Once

differentiated.

The

to

this

reasons.

more

the

type

If

difficult

sheep

of

this

in

1996.

cloning,

procedure

3 . 5

was

done

stem

with

cells,

Because

adult

the

from

rejection

humans,

which

cells

could

the

be

would

whom

the

embryo

used

be

to

would

was

m O D i F i C A T i O N

consist

regenerate

genetically

nucleus

G E N E T i C

identical

obtained

of

tissues

to

they

A N D

B i O T E C h N O l O G y

pluripotent

for

those

would

the

of

adult.

the

not

cause

problems.

Mehod ued o produce Dolly

Production of cloned embryos by somatic-cell nuclear transfer.

The

production

development

was

used

somatic

a

is

The

Adult

a

normal

were

Dorset

laboratory,

the

cells

●

of

a

a

of

was

cell

method

the

were

that

with

that

transfer.

a

A

diploid

stages:

medium

so

The

nuclear

nutrients.

eggs

Scottish

pioneering

from

and

inactive

Unfertilized

a

these

taken

using

differentiation

body

has

ewe

concentration

in

was

cloning.

somatic-cell

method

cells

Finn

Dolly

animal

called

cell

nucleus.

●

is

of

in

udder

grown

of

in

the

containing

This

the

made

a

low

genes

pattern

of

lost.

were

taken

Blackface

ewe.

from

The

the

ovaries

nuclei

were ▲

removed

cells

to

from

each

around

of

gel.

cause

10%

into

from

egg

the

A

an

Finn

cell,

egg,

small

the

of

the

two

the

these

eggs.

Dorset

inside

the

which

electric

cells

fused

One

to

cells

is

a

was

the

cultured

placed

zona

pellucida

was

the team that produced her

●

coating

used

together.

developed

to

a

The

embryos

seven

could

About

like

Figure 15 Dolly with Dr Ian Wilmut, the embryologist who led

next

protective

pulse

fuse

of

zygote

embryo.

in

the

days

act

as

same

embryos

through

were

old

then

into

injected

uteri

of

surrogate

mothers.

way

IVF .

as

implanted

a

the

normal

in

when

other

This

about

ewes

was

that

done

Only

one

of

successfully

and

developed

gestation.

This

was

the

29

Dolly.

egg without a

nucleus fused

with donor cell

using a pulse of

electricity

cell taken from udder of

donor adult and cultured

embryo resulting from

in laboratory for six days

fusion of udder cell and

egg transfered to the

(J

surrogate mother uterus of a third sheep gives birth to lamb. which acts as the Dolly is genetically surrogate mother identical with the

sheep that donated

the udder cell

unfertilized egg taken from another

(the donor)

sheep. Nucleus removed from the egg

▲

Figure 16 A method for cloning an adult sheep using dierentiated cells

199

3

G e n e t i c s

Queio

1

Human

while

somatic

our

chimpanzee,

have

the

48

the

primate

human

12

and

have

primate

the

gorilla

chromosomes.

human

from

cells

closest

of

ancestor.

two

The

chromosome

13

and

from

the

orangutan

number

2

2

below

compared

is

was

chromosomes

in

Compare

the

formed

part

a

from

chromosome

the

two

study

gene

this

19

The

(Felis

of

chromosomes,

is

repeats

If

the

predict

region

of

an

endangered

and

variation

out.

samples

analysed

In

were

for

with

samples

Gel

the

East

of

the

one

taken

the

electrophoresis.

compared

blood

sylvestris).

used

to

separate

called

gel

as

in

which

protein

The

electrophoresis

from

19

domestic

electrophoresis

proteins

using

the

can

same

DNA

proling.

the

fusion

what

the

of

same

be

chromosome

hypothesized

to

short

hypothesis

would

have

represent

forms

The

of

bands

the

on

protein

telomeres, transferrin

true,

gel

of

carried

blood

is

South

[3]

many

sequence.

using

level

was

and

in

chromosomes

17).

ends

have

the

pool

jubatus)

found

2

the

b)

of

study,

for

principles (gure

cat

cheetahs

were

patterns

chromosome

chimpanzee

of

results

be with

A

(Acinonyx

large

transferrin

chimpanzee.

human

of

cheetah

that

cats a)

cheetah

Africa.

all

shows

to

The

species

the

hypothesis

image

3

chromosomes,

the

One

chromosome

fusion

46

relatives,

indicated.

were

found

where

are

DNA

in

the

the

fusion

occurred.

[2]

transferrin

C H ▲

Figure 1 7

origin

.......

-------------------

1

2

3

4

5

6

7

8

9

10 11 12

13

14 15 16

1 7 18 19

cheetahs

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pedigree

groups

I

II

III

▲

of

in

three

gure

18

shows

generations

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a

the

ABO

--■---·•--·-·

family.

•·--

:·i11·iii;i11l1-~1-=

AB

B

O

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1

2

3

4

B

A

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O

1

2

3

4

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?

1

2

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4

5

[1111111111•1111 =------------------I•

O

J

transferrin

5

t

Figure 18 origin

~

lillilliiiiilliiiii

-------------------

1

2

3

4

5

6

7

8

9

10 11 12

13

14 15 16

1 7 18 19

domestic cats

a)

Deduce

the

genotype

of

each

person

in

the

family.

b)

Deduce

[4]

the

individual

of

possible

III

5,

blood

with

the

groups

▲

of

percentage

chance

each.

Using

Deduce

the

percentage

(i)

of

of

is

200

possible

chance

children

partner

(ii)

gure

19,

deduce

with

reasons:

[2] a)

c)

Figure 19

who

children

in

of

blood

of

groups

each

blood

individual

is

of

blood

also

III

group

2

in

her

the

and

for

his

group

partner

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the

b)

[2]

who

[2]

number

number

group:

1

blood

and

AB.

III

and

the

in

c)

domestic

transferrin

gene

number

the

of

cheetahs

number

the

the

in

the

of

gene

of

of

of

the

heterozygous

of

of

[2]

the

transferrin

domestic

alleles

pool

and

were

gene;

alleles

pool

cats

that

of

the

cats;

transferrin

cheetahs.

gene

[2]

gene

[1]

W I T H I N TO P I C Q U E S T I O N S

Topic 3 - data-based questions Page 145 1. (Non-smokers without the cancer are controls in this study as they do not have the risk factor of smoking, or the cancer.) A is more common; as the percentage with A and G or A and A is much higher than the percentage with G and G (the Hardy Weinberg equation could be used to predict the base frequencies: ___________ frequency of G is √ ​ 0.126    = 0.355 ​; frequency of A is 1 - 0.355 = 0.645); 2. a) patients with cancer = 43.7 + 9.8 = 54%; without cancer = 35.6 + 9.4 = 45%;

b) a higher percentage of those with the cancer were smokers than those who did not have the cancer, suggesting that smoking increases the risk of the cancer / gastric adenocarcinoma; 3. the base A is associated with a higher risk; 19.3% GG total for those with the cancer versus 22.0% for those without the cancer; 83.7% AG plus AA total for those with cancer versus 78% for those without cancer; 4. increased more in smokers who have the A allele; proportion of smokers with AG or AA is 43.7   ​ = 0.82; proportion of non-smokers with AG or AA is __ 35.6   ​ = 0.79; __ ​     ​     (43.7 + 9.8) (35.6 + 9.4) Page 153 1. 20 in mice (or 21 if the X and Y chromosomes are considered to be separate types); 23 in humans (or 24 if the X and Y chromosomes are considered to be separate types); 2. X, 1, 14; 3. 1 and 13; 4. common evolutionary history / common mammal ancestor; evolutionary divergence was relatively recent; rate of mutation / change is low; conserved function / roles of genes; 5. duplication of some chromosomes; fission of some chromosomes; fusion of some chromosomes; translocation of parts of chromosomes to a different chromosome; Page 156 1. such an organism would be sterile; meiosis requires synapsis/chromosome splitting; odd number means meiosis; 2. not supported when considering plants; meaning of complex needs to be established as all are multicellular; no difference in complexity of cat and dog yet dog has more chromosomes etc; threadworm is least complex so possible; would need to see chromosome number of prokaryotes etc; 3. some chromosomes may be long/fused; 4. chimpanzee and human have different chromosome numbers (48 versus 46); chimpanzee and human have a common ancestor so either chimp number increased by fission / duplication or human number decreased by fusion of chromosomes; Page 159 1. a) chromosome 1; b) chromosome 21; 2. a) chromosome 2 is longer; chromosome 2 has the centromere nearer the middle of the chromosome; banding pattern is different suggesting differences in structure; b) the X chromosome is significantly longer; the banding pattern differs; the centromere of the X chromosome is nearer to the middle of the chromosome and is toward one end in the Y chromosome; 3. male; has an X and Y chromosome; 4. it has three chromosomes #21; the child will have Down’s syndrome;

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1 11/28/14 10:48 AM

W I T H I N TO P I C Q U E S T I O N S

Page 161 1. similarities between the life cycle of a moss and of a human include: both have haploid sperm and egg; both have an ‘n’ stage; both have a ‘2n’ stage; both have mitosis, meiosis and fertilization; both have a zygote stage; 2. in humans the zygote gives rise to either male or female in individuals but in moss, the zygote gives rise to sporophyte; in moss sporophyte gives rise to spores whereas diploid human gives rise to gametes; eggs and sperm created by mitosis in moss but meiosis in humans; moss plant can give rise to male or female, but separate genders create gametes in humans; in moss, there is a gametophyte and a sporophyte, but we don’t have this in humans; meiosis gives rise to gametes in humans, but to spores in moss; Page 167 1. limited change in incidence until mid-30s; exponential increase after mid-30s; 2. a) 1% +/- 0.5%; b) 1.7-1.0; 0.7%; 3. chromosome 21 is one of the smallest of the human chromosomes; trisomies of other chromosomes have more serious effects; causing death of the zygote / embryo / fetus before birth; missing chromosomes / chromosome mutations also too harmful for the individual to survive; 4. data doesn’t discuss risk of advanced age of father; before age of 40, risk of non-disjunction is still relatively small; other possible complications besides chromosomal abnormalities; risk might be balanced by other benefits of postponed parenthood; Page 173–174 1. 198 grey: 72 albino; 2.75 grey: 1 albino; 2. albino is recessive; the presence of the albino is masked by the grey allele; in a cross of heterozygotes, approximately 25% are albino; 3. GG / homozygous dominant is grey; Gg / heterozygous is grey; gg / homozygous recessive is albino; 4. the parental phenotypes are grey and albino; the parental genotypes are GG and gg; the alleles in the gametes are G and g; the hybrid phenotype is grey; the hybrid genotype is Gg; the alleles in the gametes are G and g;

G g



G GG Gg

g Gg gg

5. white fur and red eyes due to lack of the same pigment / melanin; due to a single mutation in gene for an enzyme needed to make the pigment; Page 174 1. both typical and annulata have black and red colouration; both have spots; annulata has more black pigmentation; 2. in both cases, they are pure breeding strains; homozygous for the gene influencing coloration; 3. larger black spots than typica; black in more parts of the wing cases than typica; less black than annulata; do not have the rear black strip crossing from left to right side that annulata has; 4. a)  key to alleles with AT as allele for typical and AA as allele for annulata (or other suitable symbols); F1 genotypes are ATAA ; gametes produced by F1 are AT and AA ; F2 genotypes are ATAT, ATAA , AAAT, AAAA; corresponding phenotypes are typical, hybrid, hybrid, annulata; Punnett grid used as the genetic diagram; b) 1: 2: 1; typical: hybrid: annulata;

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W I T H I N TO P I C Q U E S T I O N S

Page 176 1. a) Bb × Bb;

B B



B BB Bb

b Bb Bb

prediction is: 3 bilateral: 1 radial; observed is: 2.38 bilateral: 1 radial; b) fewer bilateral than expected, but close enough to support the prediction; c) lack of success in pollination/attracting pollinators; reducing the number of recessive alleles;

2. a) LL’ × LL’;

L L’



L LL LL’

L’ LL’ L’L’

b) predict ratio of 1 light: 2 bluff: 1 ringed; actual observed 1.1: 2.1: 1.0; within sampling error, these results are close to predicted results; 3. a)  do not fit Mendelian ratio; different results from wild type × poky crosses are different depending on which the female parent is; wild type × wild type gives some poky offspring, but not 3 : 1 ratio; b) due to a mutation in a mitochondrial gene; mitochondria are inherited from female parent; c) mutations to produce the poky allele of the mitochondrial gene; Page 183 1. it is recessive as unaffected parents in generation I produce affected children; 2. a) 100% that they will be homozygous recessive; b) 0%; c) 0%; 3. a) Dd; the mother is dd; b) Dd or DD; most likely DD as condition is rare and person is marrying into family with history of disease; 4. cystic fibrosis; sickle cell anemia; other example of autosomal genetic disease caused by a recessive allele; Page 186 1. a) 10/70*100% = 14.3% b) 47/56*100% = 83.9%

>1

ce 00 r 5– 0 0. .2 2– 0. 5 0. 5– 1 0.

Ca n

>1

90 80 70 60 50 40 30 20 10 0

Le uk e 0. mia 00 5– 0 0. .2 2– 0. 5 0. 5– 1

% of deaths attirbutable

2.

radiation dose range [Sv]

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W I T H I N TO P I C Q U E S T I O N S

3. higher doses increase deaths in both cases; more deaths due to leukemia than cancer; nearly quadruple at 0.5–1/double at >1; 4. less than 0.0005 Sv; as this level gives 14% increase in leukemia; and 2% increase in cancer; which is unacceptably high; Page 188–189 1. 7; 2. data suggests Neanderthals more closely related to humans; because of the fewer differences in bases between humans and Neanderthals; minimum difference in human-Neanderthal exceeds maximum human-human difference, therefore humans and Neanderthals not the same species; 3. based on the bones of a single Neanderthal/limited support; Page 195 1. a) type of leaf; equal misting; all in same type of tube; same method of applying pollen; same number of larvae on each leaf; same length of time of monitoring; time at which larvae were weighed; b) to ensure that the only variable was genetic modification; so the effects of this variable could be isolated from other variables; 2. a) 5 larvae per leaf x 5 replicates x 3 treatment groups = 75 larvae; b) to be able to identify anomalous results; to assess the reliability / variability of the results; to ensure that differences are not due to sampling error / variability between larvae; 3. error bars provide an indication of variability of data; if error bars overlap, likely to be no difference if difference in means exist; 4. mortality is only seen in group where leaves were dusted with GMO pollen; difference is significant suggesting an effect of GM pollen; 5. larvae may find leaves dusted with pollen unpalatable; pollen may provide nutrients and reduce the need for consumption of leaves; consumption of pollen/GM pollen may affect the health of larvae and reduce appetite; 6. 0.26 (g) / mid-way between other treatment groups; because leaf consumption is mid-way between them; 7. whether the larvae would consume leaves dusted in pollen; leaves still connected to plants in wild; density of caterpillars on one leaf affecting how much of one leaf they eat; whether mortality rates in the wild are normally this high.

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E N D O F TO P I C Q U E S T I O N S

Topic 3 - end of topic questions 1. a) the long arm of the chimp chromosome #12 and the short arm of the human chromosome appear to be identical; the entire length of the chimp chromosome #13 appears to be found on the long arm of the human chromosome; the final band on the end of the short arm of chimp chromosome #13 does not appear in the human chromosome; the human chromosome is longer than either of the chimp chromosomes; b) near the centromere on the long arm of the human chromosome, you would find a number of repeats that were more characteristic of telomeres than sequences normally found near the centromere; 2. a) AB individuals are all IAIB; O individuals are ii; A individuals are all IAi; B individuals are all IBi except II 1 which may be IBIB; b) A or B or O or AB; 25% chance of each; c) (i) 100% blood group O; (ii) 50% group A, 25% AB and 25% B; 3. a) zero cheetahs; thirteen domestic cats; b) one allele in cheetahs; three alleles in domestic cats; c) three alleles.

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4

E c o l o g y

Intrdutin

Ecosystems

energy

to

energy

lost

of

carbon

require

fuel

as

and

ecosystems

life

a

continuous

processes

heat.

and

Continued

other

depends

chemical

on

supply

to

availability

elements

cycles.

of

replace

The

in

future

survival

depends

of

living

on

Concentrations

signicant

Earth’s

organisms

sustainable

of

effects

gases

on

including

ecological

in

the

climates

humans

communities.

atmosphere

experienced

have

at

the

surface.

4.1 Sps, s   sss

Understandin Skis ➔

Species are groups of organisms that can ➔

Classifying species as autotrophs, consumers,

potentially interbreed to produce fer tile ospring. detritivores or saprotrophs from a knowledge of

➔

Members of a species may be reproductively their mode of nutrition.

isolated in separate populations. ➔

➔

Testing for association between two species

Species have either an autotrophic or using the chi-squared test with data obtained

heterotrophic method of nutrition (a few by quadrat sampling.

species have both methods). ➔

➔

Recognizing and interpreting statistical

Consumers are heterotrophs that feed on living signicance.

organisms by ingestion. ➔

➔

Setting up sealed mesocosms to try to

Detritivores are heterotrophs that obtain organic establish sustainability. (Practical 5)

nutrients from detritus by internal digestion.

➔

Saprotrophs are heterotrophs that obtain

Nature f siene

organic nutrients from dead organic matter by

external digestion.

➔

A community is formed by populations

of dierent species living together and

➔

Looking for patterns, trends and discrepancies:

plants and algae are mostly autotrophic but

some are not.

interacting with each other.

➔

A community forms an ecosystem by its

interactions with the abiotic environment.

➔

Autotrophs and heterotrophs obtain inorganic

nutrients from the abiotic environment.

➔

The supply of inorganic nutrients is maintained

by nutrient cycling.

➔

Ecosystems have the potential to be

sustainable over long periods of time.

201

-

4

E c o l o g y

Speies

Species are groups of organisms that can potentially

interbreed to produce fer tile ospring.

Birds

of

paradise

islands.

In

courtship

to

the

dances,

display

their

that

they

reason

is

show

to

Papua

season

repeatedly

exotic

female

the

are

New

the

carrying

plumage.

t

that

and

One

would

they

Guinea

males

are

out

a

a

series

for

type

of

this

suitable

same

other

elaborate

reason

be

the

and

do

Australasian

and

is

to

show

partner.

of

distinctive

movements

bird

of

to

a

Another

paradise

as

female.

There

these

are

each

forty-one

usually

between

of

the

the

characters

types

▲

inhabit

breeding

of

only

different

different

forty-one

that

are

organism

types

reproduces

types

types

are

of

different

such

as

of

with

of

paradise.

of

its

rarely

bird

to

bird

others

of

those

these

type

produced.

paradise

of

other

species .

For

Each

and

this

remains

types.

Although

of

hybrids

reason

distinct,

Biologists

few

with

call

species

have

Figure 1 A bird of paradise in Papua

as

elaborate

courtship

rituals

as

birds

of

paradise,

most

species

have

New Guinea

some

method

members

When

they

two

are

of

trying

their

members

This

paradise.

is

However,

are

species

becoming

The

almost

reproductive

species

being

distinguish

summary,

fertile

of

called

species

a

it

a

to

ensure

that

they

reproduce

with

other

species.

the

interbreeding.

together.

of

of

same

species

Occasionally

cross-breeding.

the

always

offspring

infertile,

mate

and

members

It

of

happens

produced

which

by

produce

different

offspring

species

occasionally

cross-breeding

prevents

the

genes

breed

with

of

birds

between

two

mixed.

separation

recognizable

from

even

species

is

a

the

between

type

of

most

group

of

species

is

organism

closely

the

with

related

organisms

that

reason

for

characters

other

each

that

species.

interbreed

to

In

produce

offspring.

Pps

Members of a species may be reproductively isolated in

separate populations.

A

population

same

area

at

a

the

group

same

they

are

unlikely

they

are

different

still

If

members

two

of

to

they

and

difcult

decide

to

biologists

different

time.

same

of

a

in

are

interbreed

If

If

two

species

each

same

species

live

other.

potentially

never

in

This

could

interbreed

characters.

considered

fertile

whether

sometimes

the

populations

with

they

of

who

live

different

does

not

interbreed,

in

the

areas

mean

they

that

are

species.

their

produce

species.

organisms

interbreed

the

differences

differences,

of

species.

populations

develop

202

is

be

the

offspring.

two

disagree

to

Even

same

In

populations

about

if

then

there

species

practice

have

whether

they

are

it

may

gradually

recognizable

until

can

reached

populations

they

be

this

are

cannot

very

point

the

and

same

or

4 . 1

S P e c i e S ,

c o m m u n i t i e S

a n d

e c o S y S t e m S

aph  hph  av

Species have either an autotrophic or heterotrophic Gápgs  ss

method of nutrition (a few species have both methods). The tor toises that live on

All

organisms

amino

acids.

obtaining

need

They

these

a

supply

are

of

needed

carbon

organic

for

nutrients,

growth

compounds

can

and

be

such

as

glucose

reproduction.

divided

into

two

and

Methods

the Galápagos islands are

of

types:

the largest in the world.

They have sometimes been

grouped together into one some

●

organisms

make

their

own

carbon

compounds

from

carbon

species, Chelinoidis nigra, dioxide

and

other

simple

substances

–

they

are

autotrophic,

which

but more recently have been means

self-feeding;

split into separate species.

some

●

organisms

obtain

their

carbon

compounds

from

other

Discuss whether each organisms

–

they

are

heterotrophic,

which

means

feeding

on

others.

of these observations

Some

unicellular

gracilis

there

by

for

is

organisms

example

sufcient

endocytosis.

has

light,

use

both

methods

chloroplasts

and

but

feed

Organisms

can

that

also

are

not

of

carries

on

nutrition.

out

photosynthesis

detritus

exclusively

Euglena

or

smaller

autotrophic

indicates that populations

when

organisms

on the various islands are

separate species:

or ●

heterotrophic

are

The Galápagos tor toises

mixotrophic.

are poor swimmers and

cannot travel from one

island to another so

they do not naturally

interbreed.

●

Tor toises from

dierent islands have

recognizable dierences

in their characters,

including shell size and

shape.

●

▲

Figure 3 Arabidopsis

▲

Figure 4 Humming birds

▲

Tor toises from dierent

Figure 5 Euglena – an

islands have been

mated in zoos and

thaliana –the autotroph

are heterotrophic; the plants

unusual organism

that molecular biologists

from which they obtain

as it can feed both

use as a model plant

nectar are autotrophic

autotrophically and

hybrid ospring have

been produced but they

heterotrophically

have lower fer tility and

higher mor tality than

the ospring of tor toises

ts  p  g  from the same island.

Looking for patterns, trends and discrepancies: plants

and algae are mostly autotrophic but some are not.

Almost

all

complex

plants

organic

substances.

algae

is

A

obtain

therefore

and

supply

by

algae

are

compounds

of

autotrophic

using

energy

absorbing

light.

photosynthesis

is

carbon

needed

Their

and

they

–

they

to

do

method

carry

make

dioxide

it

and

this,

of

out

their

other

which

plants

autotrophic

in

own

simple

and

nutrition

chloroplasts. ▲

This

by

trend

for

plants

photosynthesis

However

the

there

trend,

in

are

because

and

algae

to

chloroplasts

small

make

is

numbers

although

they

their

followed

of

are

both

own

by

carbon

the

plants

majority

and

recognizably

algae

plants

Figure 2 Galápagos tor toise

compounds

of

that

or

species.

do

algae,

not

t

they

203

4

-

E c o l o g y

do

not

These

them

To

contain

species

and

cause

decide

algae

and

are

whether

groups

are

The

and

It

is

1%

almost

alga

were

them.

all

they

different

of

this

autotrophs,

plant

can

the

and

out

from

parasitic.

theory

whether

to

photosynthesis.

compounds

that

they

consider

plants

are

how

and

just

many

minor

species

the

easily

parasitic

This

is

relatively

ancestral

parasitic

be

lost

species

pattern

from

species

species

from

are

suggests

photosynthetic

ecologists

number

algae

of

small

–

only

species.

original

that

quite

Also,

families.

small

the

or

need

algal

and

repeatedly

a

falsify

we

carry

carbon

therefore

species

plants

and

that

evidence,

with

not

evolved.

developed.

evolved

do

obtain

are

plants

parasitic

Chloroplasts

many

Because

They

autotrophic

certain

be

have

harm.

autotrophic

easily

they

plants,

discrepancies

of

of

and

other

parasitic

of

how

number

about

●

on

them

insignicant

there

●

chloroplasts

grow

regard

plants

exceptional

of

cells,

diverse

that

plant

evolved

but

and

from

cannot

and

occur

parasitic

species.

and

algae

species

as

that

groups

are

of

parasitic.

d-bs qss: Unexpected diets

Although

animals

and

to9

do

we

to

not

show

usually

be

expect

consumers,

always

four

conform

organisms

plants

living

to

our

with

to

be

autotrophs

organisms

are

very

expectations.

diets

that

are

and

varied

Figures

6

unexpected.

1

Which

of

the

organisms

is

autotrophic?

[4]

2

Which

of

the

organisms

is

heterotrophic?

[4]

3

Of

organisms

the

consumer,

which

that

a

are

heterotrophic,

detritivore

and

deduce

which

a

which

saprotroph.

is

a

[4]

▲

Figure 6 Venus y trap: grows in

swamps, with green leaves that

carry out photosynthesis and also

catch and digest insects, to provide

a supply of nitrogen

▲

204

Figure 7 Ghost orchid: grows

▲

Figure 8 Euglena: unicell

underground in woodland, feeding

that lives in ponds, using its

o dead organic matter, occasionally

chloroplasts for photosynthesis,

growing a stem with owers above

but also ingesting dead organic

ground

matter by endocytosis

▲

Figure 9 Dodder: grows parasitically

on gorse bushes, using small root-like

structures to obtain sugars, amino acids

and other substances it requires, from

the gorse

in

plants

4 . 1

S P e c i e S ,

c o m m u n i t i e S

a n d

e c o S y S t e m S

css

Consumers are heterotrophs that feed on living organisms

by ingestion.

Heterotrophs

source

them

of

in.

are

divided

organic

One

Consumers

group

feed

into

molecules

off

of

groups

that

heterotrophs

other

by

they

is

organisms.

ecologists

use

and

called

These

the

according

method

to

of

the

taking

consumers.

other

organisms

are

either ▲

still

alive

or

have

only

been

dead

for

a

relatively

short

time.

A

feeds

on

Figure 10 Red kite (Milvus milvus) is a

mosquito consumer that feeds on live prey but also

sucking

blood

from

a

larger

animal

is

a

consumer

that

an on dead animal remains (carrion)

organism

a

that

is

still

alive.

A

lion

feeding

off

a

gazelle

that

it

has

killed

is

consumer.

Consumers

material

ingest

from

digestion.

lions

Consumers

to

and

take

what

are

other

autotrophs;

In

practice,

because

inside

their

sometimes

secondary

their

it

into

organisms

most

that

digest

such

as

up

into

do

feed

not

t

material

they

and

by

on

a

undigested

the

take

into

variety

in

of

by

such

it.

according

feed

consumers

of

food

consumers

groups

any

products

the

consumers

primary

neatly

in

swallowing

trophic

Primary

from

take

absorb

Multicellular

system

consume.

consumers

it

Paramecium

vacuoles.

divided

includes

means

They

digestive

they

consumers

diet

This

consumers

digest

food

food.

organisms.

Unicellular

endocytosis

as

their

other

one

of

trophic

on

and

so

these

on.

▲

groups

Figure 11 Yellow-necked mouse (Apodemus

avicollis) is a consumer that feeds mostly on

living plant matter, especially seeds, but also

groups.

on living inver tebrates

dvs

Spphs

Detritivores are heterotrophs that obtain

Saprotrophs are heterotrophs that obtain

organic nutrients from detritus by

organic nutrients from dead

internal digestion.

organic matter by external digestion.

Organisms

discard

matter,

example:

for

large

quantities

of

organic

Saprotrophs

organic

absorb ●

dead

leaves

and

other

parts

of

the

feathers,

hairs

and

other

dead

parts

of

animal

bodies

●

feces

This

from

dead

ecosystems

of

nutrition

digest

it

ingest

Large

earthworms

Unicellular

The

larvae

is

groups

dead

and

known

the

organisms

rolled

and

as

fungi

are

digestion.

into

the

They

Many

saprotrophic.

decomposers

carbon

compounds

release

elements

so

they

as

a

dead

then

types

in

such

because

dead

as

They

they

organic

nitrogen

are

of

break

matter

into

the

also

down

and

ecosystem

dung

into

that

can

be

used

again

by

other

organisms.

source

heterotroph

–

organic

absorb

dead

ingest

beetles

matter

the

and

products

detritivores

matter

it

into

feed

by

into

food

then

of

such

their

as

gut.

vacuoles.

ingestion

of ▲

feces

of

enzymes

externally.

accumulates

used

of

multicellular

ingest

of

products

it

saprotrophs.

internally

digestion.

rarely

instead

two

and

Detritivores

matter

and

by

detritivores

digestive

digest

animals.

organic

in

and

plants bacteria

●

secrete

matter

a

ball

by

their

Figure 12 Saprotrophic fungi growing over the surfaces of dead

parent. leaves and decomposing them by secreting digestive enzymes

205

-

4

E c o l o g y

- -_-

_- _-

_- _ -

_ - -

TOK

Identifin mdes f nutritin

t h x   h ss

Classifying species as autotrophs, consumers, detritivores sss (bs  gs) 

or saprotrophs from a knowledge of their mode of nutrition. s s s  h  pv?

By

answering

a

series

of

simple

questions

about

an

organism’s

mode

of

There are innite ways to divide up

nutrition

it

is

usually

possible

to

deduce

what

trophic

group

it

is

in.

These

our observations. Organisms can be

questions

are

presented

here

as

a

dichotomous

key,

which

consists

of

a

organized in a number of ways by

series

of

pairs

of

choices.

The

key

works

for

unicellular

and

multicellular

scientists: by morphology (physical

organisms

but

does

not

work

for

parasites

such

as

tapeworms

or

similarity to other organisms),

fungi

that

cause

diseases

in

plants.

All

multicellular

autotrophs

are

phylogeny (evolutionary history) and

photosynthetic

and

have

chloroplasts

containing

chlorophyll.

niche (ecological role). In everyday

language, we classify organisms such

),

Feeds on living or recently

Feeds on dead organic

as domesticated or wild; dangerous or

.

I

killed organisms = CONSUMERS

harmless; edible or toxic.

matter = DETRITIVORES

Either ingests organic matter by endocytosis (no cell walls) or by taking it into its gut.

START HERE

av

cg

Cell walls present. No ingestion of organic matter. No gut.

Secretes enzymes into

Enzymes not secreted.

its environment to digest

Only requires simple

dead

I

organic matter

II(

.

ions and compounds

such as CO

= SAPROTROPHS

2

▲

Figure 14

= AUTOTROPHS

In a classic essay written in 1972, the

physicist Philip Anderson stated this:

The ability to reduce everything to

simple fundamental laws does not

cs imply the ability to start from those

laws and reconstruct the universe. At

A community is formed by populations of dierent

each level of complexity entirely new

species living together and interacting with each other. properties appear.

An

important

part

of

ecology

is

research

into

relationships

between

Clearcutting is the most common organisms.

These

relationships

are

complex

and

varied.

In

some

cases

and economically protable form of the

interaction

between

two

species

is

of

benet

to

one

species

and

logging. It involves clearing every tree harms

the

other,

for

example

the

relationship

between

a

parasite

and

its

in an area so that no canopy remains. host.

In

other

cases

both

species

benet,

as

when

a

hummingbird

feeds

With reference to the concept of on

nectar

from

a

ower

and

helps

the

plant

by

pollinating

it.

emergent proper ties, suggest why the

ecological community often fails to

recover after clearcutting.

206

All

species

are

dependent

long-term

survival.

never

in

live

For

isolation.

on

this

relationships

reason

Groups

of

a

with

other

population

populations

of

live

species

one

for

species

together.

A

their

can

group

4 . 1

of

is

populations

known

in

hundreds

▲

living

ecology

or

even

together

as

a

in

an

area

community.

thousands

of

S P e c i e S ,

and

interacting

Typical

species

c o m m u n i t i e S

with

communities

living

together

in

each

consist

an

a n d

e c o S y S t e m S

other

of

area.

Figure 13 A coral reef is a complex community with many interactions between the

populations. Most corals have photosynthetic unicellular algae called zooxanthellae living

inside their cells

Fied wrk – assiatins between speies

Testing for association between two species using the chi-squared test with data

obtained by quadrat sampling.

Quadrats

out

are

using

involves

a

square

quadrat

repeatedly

sample

frame.

areas,

usually

Quadrat

placing

a

marked

●

sampling

positions

in

a

quadrat

habitat

and

frame

The

usual

quadrats

●

of

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procedure

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base

●

the

way

table

is

using

Random

a

present

for

each

randomly

placed

the

precisely

two

at

random

the

distances

numbers.

this

procedure

is

followed

correctly,

with

a

large

the number

of

replicates,

reliable

estimates

of

time.

positioning

this:

line

habitat

all

organisms

is

by

at

recording

enough numbers

quadrat

determined

If random

The

marked

a

along

the

numbers

or

a

out

along

measuring

edge

are

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tape.

of

the

obtained

number

the

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edge

must

of

the

extend

habitat.

using

either

generator

on

a

calculator.

●

A

a

●

rst

random

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number

along

the

distances

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random

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must

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the

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must

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distances

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used

number

across

All

is

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likely.

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be

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equally

used

habitat

across

determine

tape.

to

at

the

likely.

determine

right

angles

habitat

▲

Figure 15 Quadrat sampling of seaweed populations on a

rocky shore

207

-

4

E c o l o g y

population

suitable

not

--------------

sizes

for

are

plants

motile.

obtained.

and

Quadrat

populations

of

other

sampling

most

The

method

organisms

animals,

is

not

for

is

that

suitable

obvious

only

2

are

Calculate

the

expected

fre quenci es ,

assuming

independent

dis tr ibut ion,

each

for

of

Each

reasons.

the

presence

or

absence

of

more

than

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ex pected

values If

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on

the

species

for

combinations.

frequency

is

contingency

calcula ted

table

usi ng

from

this

one equation:

species

is

recorded

sampling

of

a

in

every

habitat,

it

is

quadrat

possible

during

to

test

for

row total × column total ___

an

expected

often

frequency

=

association

unevenly

between

species.

distributed

Populations

because

some

are

parts

of

3 habitat

are

more

suitable

for

a

species

than

two

they

This

species

will

is

occur

tend

to

be

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a

in

the

same

found

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positive

parts

the

of

same

a

Calculate

be

negative

or

the

degrees

There

species

can

be

of

degrees

of

freedom

of

freedom

=

(m

1)(n

1)

can

distribution

m

and

n

are

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two

number

equation.

habitat,

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association.

associations,

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this

where

also

total

others. using

If

grand

the

number

of

columns

in

the

contingency

independent. table.

There

are

two

possible

hypotheses: 4

H

:

two

species

are

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Find

the

table

independently

of

critical

region

chi-squared

for

chi-squared

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using

the

from

a

degrees

0

(the

null

of

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freedom

that

signicance :

H

two

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negatively

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can

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in

value

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hypotheses

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–

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(5 %).

and

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a

critical

of

chi-squared

larger

than

table.

Calculate

chi-squared

chi-squared

using

this

equation:

statistical

(f procedure

calculated

0.05

apart).

5 We

of

so the

they

have

(p)

positively

1

so

you

level

test.

f o

e

_

2

X

)2

=

Σ f e

The

chi-squared

expected

sample

test

is

frequencies

was

taken

at

only

are

5

valid

or

random

if

all

larger

from

the

and

the

where

the

f

is

the

observed

frequency

o

population. is

f

the

expected

frequency

and

e

Method for chi-squared test Σ

1

Draw

up

a

contingency

table

of

6 frequencies,

which

are

the

numbers

of

or

not

containing

the

sum

of.

Compare

the

two

the

calculated

value

of

chi-squared

quadrats with

containing

is

observed

the

critical

region.

species.

●

Species A

Species A

Row

present

absent

totals

If

the

calculated

region,

for

We

an

there

is

value

reject

in

evidence

association

can

is

at

between

the

the

critical

the

5%

the

hypothesis

level

two

species.

H

Species B present

0

●

If

the

calculated

value

is

not

in

the

critical

Species B absent

region,

because

it

is

equal

or

below

the

Column totals value

obtained

squared Calculate

the

row

and

column

totals.

row

the

same

totals

or

Adding

the

column

totals

should

no

evidence

208

total

in

the

lower

right

is

the

table

not

of

chi-

rejected.

at

the

5%

level

for

There

an

give association

grand

H 0

is the

from

values,

cell.

between

the

two

species.

4 . 1

S P e c i e S ,

c o m m u n i t i e S

a n d

e c o S y S t e m S

d-bs qss: Chi-squared testing

Figure

16

Caradoc,

The

hill

shows

a

area

hill

is

an

in

grazed

walkers

area

on

the

Shropshire,

cross

by

it

sheep

on

summit

of

Caer

3

Calculate

4

Find

in

grassy

summer

paths.

There

hummocks

growing

in

suggested

of

moss

with

them.

that

A

heather

visual

in

heather

this

(Calluna

survey

Rhytidiadelphus

growing

these

with

area,

of

of

the

hummocks.

heather

and

this

6

site

a

State

a

sample

of

100

the

quadrats,

presence

moss

was

,

the

and

of

freedom.

[2]

positioned

region

level

of

for

chi-squared

at

a

5%.

[2]

chi-squared.

[4]

two

alternative

evaluate

them

hypotheses,

using

the

H

and

calculated

1

value

for

chi-squared.

[4]

or Suggest

ecological

reasons

for

an

association

recorded the

heather

and

the

moss.

[4]

randomly.

8

Explain

used

Results

area

Sps

degrees

0

H

species

associated

The

critical

Calculate

between

in

of

are

7

absence

number

vulgaris)

squarrosus,

was

the

signicance

and

5 raised

the

England.

to

of

the

methods

position

that

should

quadrats

have

randomly

in

been

the

study.

[3]

Fq

Heather only

9

Moss only

7

Both species

57

Neither species

27

Questions

1

Construct

a

contingency

table

of

observed

values.

2

[4]

Calculate

the

association

expected

between

values,

the

assuming

no

species.

[4]

▲

Figure 16 Caer Caradoc, Shropshire

Statistia siniane

Recognizing and interpreting statistical signicance.

Biologists

often

signicant”

experiment.

a

statistical

alternative

use

when

This

the

refers

hypothesis

types

phrase

discussing

of

to

the

test.

“statistically

results

of

outcome

There

are

that

an

a

of

H

is

the

null

and

is

the

belief

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of

critical

hypothesis:

hypothesis

is

the

of

region.

two

to ●

it

results

If

A

possible

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the

and

is

is

a nd

v a l ues

calcul a te d

region,

false

s ta ti s ti c

rese a r ch

nul l

ca l cul a te d

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sta ti stic

the

cr it i c a l

is

r e je cte d,

th e

wi t h

ex c ee d s

hyp othes i s

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u si n g

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con si de r ed

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that

0

we there

is

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cannot

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thi s

ha s

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means

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correlation

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is

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a

biologist

statistically ●

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signicant

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between

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usual

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probability

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would

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) 0

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tes t

the

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is

cut-off

null

209

-

4

E c o l o g y

hypothesis

5%

is

one

when

often

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-------------in

chosen,

twenty.

signicance

That

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than

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the

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Esstems

A community forms an ecosystem by its interactions

with the abiotic environment.

A

community

organisms

living

is

composed

could

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surroundings

surroundings

as

In

the

some

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organisms.

specialized

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the

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and

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wave

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ecosystems

of

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up

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Ecologists

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to

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Ecologists

between

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the

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grow

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be

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deposited.

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environment

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Autotrophs and heterotrophs obtain inorganic nutrients

from the abiotic environment.

●

▲

organisms

Carbon,

need

hydrogen

a

supply

and

of

oxygen

chemical

are

elements:

needed

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make

carbohydrates,

Figure 1 7 Grasses in an area of developing

sand dunes

210

lipids

and

other

carbon

compounds

on

which

life

is

are

interacting

ig s

Living

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only

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Sand

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coasts

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the

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of

4 . 1

Nitrogen

●

and

phosphorus

are

also

S P e c i e S ,

needed

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c o m m u n i t i e S

make

many

of

a n d

e c o S y S t e m S

these

compounds.

Approximately

●

organisms.

are

fteen

Some

nonetheless

Autotrophs

nutrients

obtain

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Heterotrophs

several

however

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environment,

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the

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the

as

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elements

are

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needed

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all

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on

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the

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carbon

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sodium,

they

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these

two

compounds

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potassium

as

and

elements

in

their

nutrients

and

inorganic

carbon

nitrogen.

and

food.

from

They

the

do

abiotic

calcium.

n s

Reserves of an

living

they

are

limited

organisms

have

endlessly

have

run

to

Earth

using

This

is

the

from

the

of

the

chemical

supplies

because

Organisms

nutrients

them

on

been

out.

recycled.

inorganic

return

not

supplies

absorb

abiotic

environment

elements.

for

chemical

the

three

with

elements

the

billion

elements

environment,

atoms

that

use

Although

can

they

them

years,

be

require

and

as

then

unchanged.

~

nutrient cycling.

There

=~ =

The supply of inorganic nutrients is maintained by

element in the

abiotic environment

Element forming

part of a living

organism

Recycling

diagram

before

vary

of

and

it

is

from

nitrogen

often

element

cycle

nutrient

in

this

for

carbon

it

element

back

to

the

into

The

is

is

rarely

passed

The

described

an

as

from

in

shown

organism

cycle

refer

is

as

environment.

to

often

element

an

cycle

simple

carbon

nutrient

means

as

abiotic

Ecologists

word

nitrogen

is

the

element.

simply

cycle

and

elements

example.

cycles.

context

topic4.2

an

released

as

The

chemical

of

an

a

details

from

schemes

ambiguous

in

the

collectively

biology

organism

nutrient

this

organism

The

different

these

that

example

Option

is

to

in

but

needs.

cycle

in

sub-

C.

Ssb f sss

Ecosystems have the potential to be sustainable over

long periods of time.

The

it

is

concept

clear

that

Something

fossil

fuels

carry

fuels

are

on

Natural

that

our

of

is

is

sustainability

some

current

sustainable

an

nite,

example

are

not

if

risen

human

it

of

has

can

an

to

uses

prominence

of

continue

resources

being

are

indenitely.

unsustainable

currently

recently

activity.

renewed

and

because

unsustainable.

Human

Supplies

cannot

use

of

of

fossil

therefore

indenitely.

ecosystems

children

requirements

for

●

nutrient

●

detoxication

●

energy

can

and

teach

us

how

grandchildren

sustainability

in

to

can

live

live

in

as

a

sustainable

we

do.

There

way,

are

so

three

ecosystems:

availability

of

waste

products

▲

Figure 18 Living organisms have been recycling

for billions of years

availability.

211

4

-

E c o l o g y

-------------Nutrients

not

be

a

products

species.

Energy

▲

Figure 19 Sunlight supplies energy to a forest

ecosystem and nutrients are recycled

recycled

the

one

and

species

used

Dust

does

supply

light

the

it

not

from

be

to

in

the

energy

an

recycled,

sun.

The

of

toxic

as

released

source

but

by

is

done

life

a

is

resource

by

because

there

based.

should

The

by

of

the

waste

another

decomposers

Nitrosomonas

sustainability

Most

reduced

only

energy

eruption

causing

was

to

this

which

exploited

ions

importance

the

atmosphere

supplies

so

ecosystems.

the

This

energy

if

on

are

bacteria

action

in

of

the

these

accumulate.

afterwards,

starvation.

usually

potentially

consequences

months

are

and

elements

ammonium

for

is

indenitely

chemical

example,

cannot

energy

by

be

of

Ammonium

bacteria

as

of

For

absorbed

soil.

can

lack

a

the

crop

of

in

is

supply

Mount

intensity

the

on

supplied

this

failures

temporary

ecosystems

of

depends

and

phenomenon,

of

ecosystems

be

in

sunlight

globally

form

to

can

Tambora

of

continued

illustrated

1815.

for

some

deaths

due

however,

sunlight

will

to

and

continue

av for

billions

of

years.

cv sss

Organisms have been found

living in total darkness in

Messms caves, including eyeless

sh. Discuss whether

Setting up sealed mesocosms to try to establish

ecosystems in dark caves

sustainability. (Practical 5) are sustainable. Mesocosms

are

sma ll

experimental

areas

t hat

are

set

up

as

Figure 20 shows a ecological

exp erime nts.

Fe nce d-off

enclos ures

in

grasslan d

or

small ecosystem with forest

could

be

used

as

terrestrial

mesoc osms;

tanks

s et

up

in

photosynthesizing plants the

laboratory

can

be

used

as

aquatic

mesocosm s.

Ecological

near ar ticial lighting in a experiments

can

be

done

in

r eplicate

mesocosm s,

to

nd

out

the

cave that is open to visitors effects

of

varying

one

or

mor e

conditions .

For

example,

t anks

could

in Cheddar Gorge. Discuss be

set

up

with

and

without

sh,

to

inv estigate

th e

effects

of

sh

on

whether this is more or aquatic

ecosystems.

less sustainable than

Another

possible

use

of

mesocosms

is

to

test

what

types

of

ecosystems

ecosystems in dark caves.

are

sustainable.

together

You

or

●

with

should

also

soil

or

these

sealing

water

up

a

inside

questions

community

a

of

organisms

container.

before

setting

up

either

aquatic

mesocosms:

glass

be

involves

and

consider

terrestrial

Large

This

air

jars

used.

are

ideal

Should

the

but

transparent

sides

of

the

plastic

container

containers

be

could

transparent

or

opaque?

●

Which

a

of

these

sustainable

groups

of

community:

organisms

must

autotrophs,

be

included

consumers,

to

make

saprotrophs

up

and

detritivores?

●

How

can

we

organisms

will

●

be

How

▲

Figure 20

212

able

can

placed

in

in

ensure

the

to

we

the

that

the

mesocosm

oxygen

as

once

supply

it

is

is

sufcient

sealed,

no

for

more

all

the

oxygen

enter.

prevent

any

mesocosm?

organisms

suffering

as

a

result

of

being

4 . 2

e n e r G y

F l o w

4.2 eg  

Understandin Skis ➔

Most ecosystems rely on a supply of energy Quantitative representations of energy ow

➔

from sunlight. using pyramids of energy.

➔

Light energy is conver ted to chemical energy in

carbon compounds by photosynthesis.

➔

Nature f siene

Chemical energy in carbon compounds ows

through food chains by means of feeding.

➔

Use theories to explain natural phenomena:

➔

the concept of energy ow explains the limited

Energy released by respiration is used in living

length of food chains.

organisms and conver ted to heat.

➔

Living organisms cannot conver t heat to other

forms of energy.

➔

Heat is lost from ecosystems.

➔

Energy losses between trophic levels restrict

the length of food chains and the biomass of

higher trophic levels.

Suniht and esstems

Most ecosystems rely on a supply of energy from

sunlight.

For

most

sunlight.

Three

biological

Living

groups

eukaryotic

organisms

can

autotroph

carry

of

algae

cyanobacteria.

communities,

including

These

the

initial

harvest

out

are

energy

of

by

photosynthesis:

seaweeds

organisms

this

source

that

grow

often

on

referred

energy

is

photosynthesis.

plants,

rocky

to

by

shores,

and

ecologists

asproducers.

Heterotrophs

dependent

on

consumers,

almost

harvested

The

the

and

in

all

by

amount

world.

for

becomes

their

light

are

food

in

as

the

of

The

energy

percentage

example,

the

redwood

in

the

Sahara

to

the

a

producers

in

of

are

to

this

other

they

are

indirectly

heterotroph

in

of

carbon

them

energy.

compounds

ecosystems

energy

that

organisms

of

In

use

most

will

the

energy

in

is

also

sunlight

because

California

more

of

of

All

but

ecosystems:

ecosystems

originally

have

all

been

producers.

intensity

of

much

groups

source

carbon

organisms

forests

but

to

directly,

detritivores.

supplied

available

available

energy

several

and

photosynthesis

In

because

use

There

energy

therefore

Desert,

it.

not

saprotrophs

compounds

or

do

is

there

varies

harvested

varies.

very

are

intensity

becomes

sunlight

high

very

of

In

by

Sahara

but

to

little

of

it

producers.

sunlight

available

producers

the

few

around

is

less

than

organisms

abundant.

213

4

-

E c o l o g y

d-bs qss: Insolation av Insolation

is

a

measure

of

solar

radiation

The

two

maps

in

gure

2

cb  vs show

Cyanobacteria are

annual

(upper

map)

mean

and

insolation

at

the

at

Earth’s

the

top

surface

of

the

(lower

Earth’s

atmosphere

map).

photosynthetic bacteria that

are often very abundant

Questions

in marine and freshwater 1

State

the

relationship

between

distance

from

the

equator

and

ecosystems. Figure 1 insolation

at

the

top

of

the

Earth’s

atmosphere.

[1]

shows an area of green

2

State

the

mean

annual

insolation

in

Watts

per

square

metre

cyanobacteria on an area

for

the

most

northerly

part

of

Australia

of wall in a cave that is

illuminated by articial light.

a)

at

the

top

of

the

b)

at

the

Earth’s

atmosphere

[1]

The surrounding areas are surface.

[1]

normally dark. If the articial 3

Suggest

reasons

for

differences

in

insolation

at

the

Earth’s

light was not present, what surfacebetween

places

that

are

at

the

same

distance

from

other energy sources could theequator.

[2]

be used by bacteria in caves?

4

Tropical

rainforests

continents.

Evaluate

They

the

insolation.

are

have

found

very

hypothesis

Include

equatorial

high

that

named

in

rates

this

parts

is

of

of

due

the

regions

of

all

photosynthesis.

to

very

world

in

high

your

answer.

▲

Figure 1

[5]

-

•

-

-

2

0

▲

214

40

Figure 2

80

120

160

200

240

280

320

360

400 w/m

4 . 2

e n e r G y

F l o w

Ener nversin av

Light energy is conver ted to chemical energy in carbon Bsh  fs s

compounds by photosynthesis.

Producers

absorb

pigments.

This

make

carbohydrates,

Producers

can

respiration

is

sunlight

converts

eventually

lipids

release

and

then

lost

to

using

the

and

energy

use

the

chlorophyll

light

it

energy

all

the

from

for

cell

to

other

their

and

carbon

carbon

activities.

environment

as

other

chemical

photosynthetic

energy,

compounds

compounds

Energy

waste

which

to

cell

in

However,

used

producers.

by

released

heat.

in

is

this

only

way

some ▲

of

the

carbon

compounds

in

producers

are

used

in

this

way

and

Figure 3

the

Figure 3 shows a bush re in largest

part

remains

in

the

cells

and

tissues

of

producers.

The

energy

in

Australia. these

carbon

compounds

is

available

to

heterotrophs.

What energy conversion is

happening in a bush re?

Ener in fd hains Bush and forest res

Chemical energy in carbon compounds ows through food

occur naturally in some

ecosystems.

chains by means of feeding.

Suggest two reasons for this A

food

chain

is

a

sequence

of

organisms,

each

of

which

feeds

on

the

previous

hypothesis: There are fewer one.

There

are

usually

between

two

and

ve

organisms

in

a

food

chain.

It

is

heterotrophs in ecosystems rare

for

there

to

be

more

organisms

in

the

chain.

As

they

do

not

obtain

food

where res are common from

other

organisms,

producers

are

always

the

rst

organisms

in

a

food

compared to ecosystems chain.

The

subsequent

organisms

are

consumers.

Primary

consumers

feed

where res are not common. on

producers;

consumers

the

last

feed

therefore

falls

▲

in

on

organism

compounds

Figure

secondary

4

in

is

an

secondary

in

the

indicate

a

food

on

direction

of

a

feed

on

consumers,

chain.

organisms

the

example

northern

consumers

primary

and

Consumers

which

of

they

energy

food

chain

so

on.

obtain

feed.

consumers;

No

consumers

energy

The

tertiary

from

arrows

in

feed

the

a

on

carbon

food

chain

ow.

from

the

forests

around

Iguazu

Argentina.

Figure 4

Respiratin and ener reease

Energy released by respiration is used in living organisms

and conver ted to heat.

Living

organisms

●

Synthesizing

●

Pumping

●

Moving

or

ATP

in

need

large

things

or

around

cells

energy

for

molecules

molecules

muscle

supplies

energy

the

for

ions

like

inside

the

activities

DNA,

across

protein

these

cell

RNA

such

that

activities.

as

cause

Every

as

and

membranes

cell,

bres

such

by

these:

proteins.

active

transport.

chromosomes

muscle

cell

or

vesicles,

contraction.

produces

its

own

ATPsupply.

215

4

-

E c o l o g y

All

cells

can

produce

compounds

oxidation

in

reason

such

as

The

are

ATP

second

never

in

Energy

have

is

law

not

of

is

cell

be

molecules

respiration.

and

make

and

the

and

other

for

in

cell

to

may

heat.

reside

such

eventually

of

states

the

Some

warm

for

as

a

digested

is

time

the

is

in

carbon

cell,

but

large

energy

is

the

ATP .

The

chemical

transformations

the

to

oxidation

ATP .

but

for

as

ATP

is

example.

when

when

released

The

when

contract

molecules

proteins,

to

compounds

produced

they

used

activities.

energy

from

also

when

and

in

transferred

heat

up

DNA

the

that

is

transfers

compounds

different

energy

carbon

These

released

respiration

energy

by

process

oxidized.

energy

cell

many

respiration

Muscles

synthesized,

all

this

are

carbon

usable

directly

Not

the

So

chemical

immediately

used

In

lipids

ATP .

thermodynamics

activities.

are

to

efcient.

ATP

cell

exothermic

that

converted

from

been

by

glucose

is

compounds

remainder

used

this

can

100%

carbon

are

from

doing

glucose

in

ATP

carbohydrates

reactions

energy

for

energy

as

reactions

endothermic

chemical

of

such

they

these

heat.

d-bs qss 20

Figure

shows

the

res ul ts

yellow-billed

of

mag pies

an

experiment

(Pica

nuttalli)

in

were 1

be

in

a

cage

in

contr olled.

was

The

measured

from

30 ° C

10 ° C

the

which

at

to

birds’

s even

+ 40 ° C.

magpie s

temperature,

the

but

temperature

rate

of

temperatures ,

Between

maintained

above

30 ° C

could

respiration

different

10 ° C

cons tant

body

15

g Wm( etar noitaripser

put

)

which

5

and

body

tempera ture

10

5

increased.

a)

Describe

the

temperature

relationship

and

between

respiration

rate

external

in

0

yellow-

0

10

billed

b)

magpies.

Explain

the

10

[3]

change

in

respiration

rate

20

30

40

50

temperature (°C)

▲

as

Figure 5 Cell respiration rates at dierent temperatures in

yellow-billed magpies

temperature

c)

Suggest

a

drops

reason

respirationrate

from

30 °C

to

from

for

as

the

+10 °C

to

change

temperature

10 °C.

[3]

in

d)

increased

40 °C.

Suggest

two

respiration

[2]

reasons

rate

for

the

between

variation

the

birds

at

in

each

temperature.

[2]

Heat ener in esstems

Living organisms cannot conver t heat to other forms

of energy.

Living

energy

can

chemical

various

Light

●

Chemical

energy

to

kinetic

●

Chemical

energy

to

electrical

●

Chemical

energy

to

heat

cannot

to

perform

●

They

216

organisms

convert

heat

energy

in

energy

in

into

conversions:

photosynthesis.

in

energy

energy

energy

energy

muscle

in

contraction.

nerve

cells.

heat-generating

any

other

form

adipose

of

tissue.

energy.

4 . 2

e n e r G y

F l o w

Heat sses frm esstems av

Heat is lost from ecosystems. thkg b g

Heat

This

resulting

heat

can

from

be

cell

useful

respiration

in

making

makes

living

cold-blooded

organisms

animals

warmer.

more

hgs

active.

What energy conversions Birds

and

mammals

increase

their

rate

of

heat

generation

if

necessary

to

are required to shoot a maintain

their

constant

body

temperatures.

basketball?

According

to

the

laws

of

thermodynamics

in

physics,

heat

passes

from

What is the nal form of the

hotter

to

cooler

lost

the

bodies,

so

heat

produced

in

living

organisms

is

all

eventually

energy?

a

to

while,

abiotic

but

ultimately

atmosphere.

in

cell

environment.

Ecologists

activities

will

is

lost,

The

for

assume

ultimately

heat

may

example

that

be

all

lost

remain

when

energy

from

heat

in

is

released

an

the

ecosystem

radiated

by

into

respiration

for

the

for

use

ecosystem.

expg h gh f f hs

Use theories to explain natural phenomena: the

concept of energy ow explains the limited length

of food chains.

If

we

consider

chain,

we

leading

that

can

up

fed

to

on

in

the

There

are

might

expect

branches

the

that

occur

how

which

carnivore

many

if

fed

than

chains

innitum.

science,

of

of

top

example,

more

length

a

an

on

that

stages

osprey

is

at

there

the

are

feeds

on

phytoplankton,

end

in

the

sh

of

food

food

such

there

a

are

chain

as

salmon

four

chain.

food

concept

of

out

For

food

ad

of

restricted

is

work

it.

rarely

another

diet

shrimps,

stages

by

the

we

energy

between

to

be

This

try

food

four

stages

limitless,

not

explain

chains

trophic

ve

does

to

ow

or

using

along

levels

with

in

one

happen.

natural

that

chain.

species

In

and

provide

the

an

We

being

ecology,

theories.

chains

can

food

phenomena

scientic

food

a

as

eaten

in

such

In

this

all

as

the

case

energy

it

losses

explanation.

▲

Figure 6 An infrared camera image of an

Ener sses and esstems African grey parrot (Psittacus erithacus)

shows how much heat is being released to the

Energy losses between trophic levels restrict the length environment by dierent par ts of its body

of food chains and the biomass of higher trophic levels.

Biomass

tissues

is

of

the

those

compounds

energy,

added

the

be

per

energy

year

The

they

has

by

per

added

square

Most

of

for

the

organisms

a

of

of

the

is

by

each

in

loss

food

trophic

to

of

is

the

measure

their

so

how

that

by

and

other

much

level

carbon

energy

is

are

trophic

is

and

chemical

results

always

is

cells

levels

found:

less.

always

In

less

per

consumers.

between

digested

the

have

The

energy

primary

released

is

trophic

of

of

different

trend

amount

in

and

biomass.

same

energy

is

consists

compounds

successive

than

that

level

can

the

It

carbohydrates

carbon

ecosystem

ecosystem

is

the

done,

example,

trend

organisms.

Because

organisms

this

for

of

Ecologists

biomass

energy

in

of

metre

metre

this

group

including

energy.

When

to

a

contain.

consumers,

reason

of

groups

square

compared.

secondary

●

year

mass

organisms,

that

biomass

per

calculated

can

total

trophic

levels.

absorbed

them

in

by

respiration

▲

for

Figure 7 The osprey (Pandion halietus) is a

sh-eating top carnivore

217

-

4

E c o l o g y

-------------use

in

cell

available

av

activities.

to

It

is

organisms

carbohydrates

and

therefore

in

the

other

next

carbon

lost

as

heat.

trophic

The

level

compounds

is

that

only

energy

chemical

have

not

energy

been

in

used

S  s

up

in

cell

respiration.

Most salmon eaten by

The

●

humans is produced in sh

by

farms. The salmon have

organisms

organisms

sometimes

traditionally been fed on

parts

sh meal, mostly based on

the

anchovies harvested o the

of

bodies

trophic

next

of

their

in

all

plants

passes

organisms

have become scarce and

a

the

consume

some

material

coast of South America. These

in

in

to

the

level

the

are

prey

such

in

usually

For

an

bones

or

or

entirely

example,

area

Predators

as

trophic

not

level.

plants

eaten.

saprotrophs

next

are

trophic

but

more

may

not

hair.

Energy

detritivores

eat

rather

consumed

locusts

usually

material

in

only

from

uneaten

than

passing

to

level.

expensive. Feeds based on Not

●

all

parts

of

food

ingested

by

the

organisms

in

a

trophic

level

are

plant products such as soy digested

and

absorbed.

in

Energy

Some

material

is

indigestible

not

on

and

is

egested

beans are increasingly being feces.

in

feces

does

pass

along

the

food

chain

and

used. In terms of energy ow, instead

passes

to

saprotrophs

or

detritivores.

which of these human diets is

Because

of

these

losses,

only

a

small

proportion

of

the

energy

in

most and least ecient?

1

thebiomass

of

organisms

in

one

thebiomass

of

organisms

in

the

trophic

level

will

ever

become

part

of

Salmon fed on sh meal

2

Salmon fed on soy beans

3

Soy beans.

often

quoted,

variable.

less

As

energy

stages

in

enough

trophic

a

to

but

the

the

losses

available

food

in

food

measured

to

carbon

food

of

of

chain

higher

levels.

of

trophic

level

the

in

is

or

levels

all,

of

trophic

is

of

in

a

energy

The

chain,

level.

this

of

10 %is

levels

there

After

remaining

For

gure

trophic

food

trophic

level.

only

would

reasonthe

is

is

lessand

a

few

not

be

number

of

restricted.

also

diminishes

water

from

therefore

a

level.

between

stage

undigested

is

than

each

loss

successive

and

generally

of

at

grams,

uneaten

trophic

energy

amount

chains

dioxide

trophic

There

each

another

Biomass,

loss

of

occur

to

chain

support

levels

level

next

higher

any

parts

of

usually

biomass

other

along

food

respiration

trophic

loss

organisms.

smaller

of

chains,

and

The

than

producers,

the

biomass

that

the

due

from

of

lower

lowest

level.

secondary consumer decomposers

2

(200 kJ m 2

(16,000 kJ m

Pramids f ener

1

yr

)

1

yr

)

Quantitative representations of energy ow using

primary consumer

2

(2,500 kJ m

1

yr

)

pyramids of energy.

plankton

The 2

of

energy

converted

to

new

biomass

by

each

trophic

level

in

)

an

▲

amount

1

yr

(150,000 kJ m

ecological

Figure 8 An energy pyramid for an aquatic

This

ecosystem (not to scale)

The

is

a

type

community

can

of

with

amounts

bar

of

chart

energy

be

a

should

represented

horizontal

be

per

unit

with

bar

a

for

area

pyramid

each

per

are

kilojoules

should

lowest

be

per

metre

stepped,

bar.

The

not

bars

squared

per

triangular,

should

be

year

(kJ

starting

labelled

m

with

Often

energy.

level.

the

units

1

yr

the

producer,

trophic

year.

2

of

).

The

pyramid

producers

rst

in

consumer,

the

second

secondary consumer

2

(3,000 MJ m

consumer

1

yr

and

so

on.

If

a

suitable

scale

is

chosen,

the

length

of

each

bar

)

can

be

proportional

to

the

amount

of

energy

that

it

shows.

primary consumer

2

(7,000 MJ m

1

yr

)

Figure

8

shows

ecosystem.

To

an

be

example

more

of

a

pyramid

accurate,

the

bars

of

energy

should

be

for

an

aquatic

drawn

with

relative

producers

2

(50,000 MJ m

1

yr

widths

Figure 9 Pyramid of energy for grassland

218

match

the

relative

energy

content

at

each

trophic

level.

Figure

)

9

▲

that

shows

a

pyramid

of

energy

for

grassland,

with

the

bars

correctly

to

scale.

4 . 2

e n e r G y

F l o w

d-bs qss: a simple food web

A

sinkhole

cavern

a

sinkhole

due

in

is

a

surface

collapses.

lled

part

to

feature

Montezuma

with

the

water.

which

Well

It

extremely

is

an

high

forms

in

the

when

an

Sonoran

aquatic

underground

desert

ecosystem

concentrations

of

in

that

Arizona

lacks

dissolved

is

sh,

CO

.

The

2

dominant

grow

to

Figure

1

top

70 mm

10

Compare

3

4

Deduce

7

a

using

P

b)

what

is

the

a

bakeri,

a

giant

water

of

that

can

for

Montezuma

Belostoma

bakeri

Well.

and

Ranatra

montezuma

[2]

which

organism

occupies

more

level.

[2]

values:

be

the

most

preferred

pyramid

the

of

common

prey

of

energy

B.

for

food

chain

in

this

web

[2]

bakeri?

the

rst

[1]

and

second

the

trophic

levels.

Outline

energy

lost

between

the

rst

and

[2]

of

classifying

organisms

into

[2]

additional

the

of

levels.

difculties

the

complete

[3]

percentage

trophic

Discuss

pyramid

information

of

energy

that

for

would

the

third

be

and

required

to

fourth

level.

[1]

Ranatra montezuma

235,000 kJ ha

-

1

2

P = 1.0 gm

insect

levels.

Calculate

trophic

web

reason,

would

Construct

Belostoma

web.

trophic

what

second

6

roles

a)

trophic

5

food

food

with

one

is

length.

a

the

the

Deduce,

than

in

shows

within

2

predator

yr

-

Belostoma bakeri

1

1

.,..____

yr

1

588,000 kJ ha

2

P = 2.8 gm

1

yr

1

yr

Telebasis salva

1

1,587,900 kJ ha

2

P = 7.9 gm

1

yr

1

yr

Hyalella montezuma

1

30,960,000 kJ ha

2

P = 215 gm

phytoplankton - Metaphyton

1

234,342,702 kJ ha

2

P = 602 g C m

▲

1

yr

1

yr

piphyton

1

yr

1

427,078,320 kJ ha

1

yr

1

yr

2

P = 1,096 g C m

1

yr

Figure 10 A food web for Montezuma Well. P values represent the biomass stored

in the population of that organism each year. Energy values represent the energy

equivalent of that biomass. Arrows indicate trophic linkages and arrow thickness

indicates the relative amount of energy transferred between trophic levels

219

4

-

E c o l o g y

-------------

4.3 cb g

Understandin Appiatins ➔

Autotrophs conver t carbon dioxide into ➔

Estimation of carbon uxes due to processes in

carbohydrates and other carbon compounds. the carbon cycle.

➔

In aquatic habitats carbon dioxide is present as ➔

Analysis of data from atmosphere monitoring

a dissolved gas and hydrogen carbonate ions. stations showing annual uctuations.

➔

Carbon dioxide diuses from the atmosphere or

water into autotrophs.

➔

Skis

Carbon dioxide is produced by respiration and

diuses out of organisms into water or the

➔

Construct a diagram of the carbon cycle.

atmosphere.

➔

Methane is produced from organic matter

Nature f siene

in anaerobic conditions by methanogenic

archaeans and some diuses into the ➔

atmosphere.

➔

➔

Making accurate, quantitative measurements:

it is impor tant to obtain reliable data on the

Methane is oxidized to carbon dioxide and

concentration of carbon dioxide and methane

water in the atmosphere.

in the atmosphere.

Peat forms when organic matter is not fully

decomposed because of anaerobic conditions

in waterlogged soils.

➔

Par tially decomposed organic matter from past

geological eras was conver ted into oil and gas

in porous rocks or into coal.

➔

Carbon dioxide is produced by the combustion

of biomass and fossilized organic matter.

➔

Animals such as reef-building corals and molluscs

have hard parts that are composed of calcium

carbonate and can become fossilized in limestone.

carbn xatin

Autotrophs conver t carbon dioxide into carbohydrates

and other carbon compounds.

Autotrophs

it

into

that

absorb

carbon

carbohydrates,

they

require.

This

the

dioxide

lipids

has

concentration

of

atmosphere

currently

and

the

all

from

the

effect

atmosphere.

of

The

the

atmosphere

other

carbon

reducing

mean

the

and

convert

compounds

carbon

dioxide

concentration

CO

of

the

2

mole

is

(µmol/mol)

photosynthesis

220

but

rates

it

approximately

is

have

lower

been

above

high.

0.039 %

parts

of

or

the

390

micromoles

Earth’s

surface

per

where

4 . 3

c a r B o n

c y c l i n G

d-bs qss: Carbon dioxide concentration

The

by

two

maps

NASA.

in

They

concentration

above

the

gure

show

of

the

surface

of

1

were

the

atmosphere

the

4

produced

carbon

Earth,

a)

Deduce

lowest

eight

between

in

kilometres

May

part

mean

May

State

whether

fall(autumn)

2

a)

October

in

Distinguish

the

in

the

Suggest

a)

Distinguish

dioxide

the

in

in

spring

and

Earth

dioxide

October

that

had

the

concentration

2011.

[1]

Suggest

reasons

for

hemisphere.

carbon

May

and

for

the

between

the

concentrations

and

the

being

the

carbon

lowest

in

dioxide

this

area.

[2]

or

[1]

dioxide

October

hemisphere.

reasons

northern

the

southern

northern

b)

is

between

concentrations

3

the

2011. concentration

1

of

carbon

and b)

October

the

dioxide

[1]

difference.

[2]

carbon

in

May

between

southern

Carbon Dioxide 2011 Mole Fraction (µmol/mol) hemisphere.

[1]

388 b)

Suggest

reasons

for

the

difference.

389

390

391

392

393

39d

395

Figure 1

[2]

carbn dixide in sutin

In aquatic habitats carbon dioxide is present as a

dissolved gas and hydrogen carbonate ions.

Carbon

dioxide

is

soluble

in

water.

It

can

either

remain

in

water

as

av a

dissolved

gas

or

it

can

combine

with

water

to

form

carbonic

acid

pH hgs  k ps (H

CO 2

).

Carbonic

acid

can

dissociate

to

form

hydrogen

and

hydrogen

3

+

carbonate

ions

and

(H

HCO

).

This

explains

how

carbon

dioxide

can

Ecologists have monitored

3

reduce

the

pH

of

pH in rock pools on sea

water.

shores that contain animals Both

dissolved

carbon

dioxide

and

hydrogen

carbonate

ions

are

absorbed

and also photosynthesizing by

aquatic

plants

and

other

autotrophs

that

live

in

water.

They

use

them

algae. The pH of the to

make

carbohydrates

and

other

carbon

compounds.

water rises and falls in

a 24-hour cycle, due to

changes in carbon dioxide

Absrptin f arbn dixide

concentration in the water.

Carbon dioxide diuses from the atmosphere or water

The lowest values of about

pH 7 have been found during

into autotrophs.

the night, and the highest Autotrophs

use

carbon

dioxide

in

the

production

of

carbon

compounds

values of about pH 10 have by

photosynthesis

or

other

processes.

This

reduces

the

concentration

been found when there was of

carbon

dioxide

inside

autotrophs

and

sets

up

a

concentration

bright sunlight during the gradient

between

cells

in

autotrophs

and

the

air

or

water

around.

day. What are the reasons for Carbon

dioxide

therefore

diffuses

from

the

atmosphere

or

water

into

these maxima and minima? autotrophs.

The pH in natural pools or

In

land

plants

stomata

surface

so

in

of

with

the

the

diffusion

leaves

underside

leaves

can

be

and

this

of

diffusion

the

stems

through

leaves.

is

any

usually

In

usually

part

of

happens

aquatic

plants

permeable

these

parts

to

of

through

the

entire

carbon

the

dioxide,

ar ticial aquatic mesocosms

could be monitored using

data loggers.

plant.

221

-

4

E c o l o g y

Reease f arbn dixide frm e respiratin

Carbon dioxide is produced by respiration and diuses out

of organisms into water or the atmosphere.

Carbon

dioxide

produced

grouped

in

all

is

a

waste

cells

according

that

to

trophic

●

non-photosynthetic

●

animal

●

saprotrophs

Carbon

into

cells

of

out

level

in

aerobic

aerobic

of

the

cell

cell

respiration.

respiration.

It

is

These

can

be

organism:

producers

for

example

root

cells

in

plants

cells

dioxide

the

product

carry

such

as

fungi

produced

atmosphere

or

by

that

decompose

respiration

water

that

dead

diffuses

surrounds

organic

out

these

of

cells

matter.

and

passes

organisms.

d-bs qss: Data-logging pH in an aquarium

Figure

2

shows

the

pH

and

light

intensity pH sensor (pH)

in

an

aquarium

containing

a

varied

7.50

100

light intensity

community

of

organisms

including

90 pH

newts

and

other

animals. 7.45

The

data

was

obtained

by

stinu yrartibra/ ytisnetni thgil

pondweeds,

data

80

logging 70

using

a

pH

electrode

and

a

light

meter. 7.40

The

aquarium

was

illuminated

60

articially 50

to

give

a

24-hour

cycle

of

light

and

dark

7.35

using

a

lamp

controlled

by

a

40

timer.

30

1

Explain

the

changes

in

light 7.30

intensity

during

the

experiment.

20

[2] 10

2

Determine

how

many

days

the 0

7.25

data

logging

covers.

[2]

0.14:02:31

0.23:13:11

06 February 2013

3

a)

Deduce

the

trend

in

pH

3.08:23:50

4.17:34:30

6.02:45:09

absolute time (d.hh:mm:ss)

14:02:31

in Figure 2

the

light.

[1]

4

b)

Explain

this

trend.

a)

Deduce

the

b)

Explain

trend

in

pH

in

darkness.

[1]

[2]

this

trend.

[2]

Methanenesis

Methane is produced from organic matter in anaerobic

conditions by methanogenic archaeans and some

diuses into the atmosphere.

In

a

1776

reed

was

on

this

it

is

a

Three

name.

waste

Bacteria

Volta

He

product

had

is

of

groups

that

collected

margins

Methane

different

alcohol,

222

the

inammable.

it

1

Alessandro

bed

hydrogen

Lake

of

bubbles

discovered

type

of

anaerobic

and

in

and

though

anaerobic

from

found

Volta

mud

that

did

not

in

it

give

environments,

as

respiration.

into

dioxide.

emerging

Italy,

prokaryotes

matter

carbon

gas

in

methane,

widely

anaerobic

organic

of

Maggiore

produced

a

convert

of

a

are

involved.

mixture

of

organic

acids,

4 . 3

2

Bacteria

carbon

3

that

use

dioxide

Archaeans

acetate.

that

They

CO

+

CH

organic

this

→

CH

out

→

in

CH

this

Mud

along

●

Swamps,

peat

the

+

mires,

●

Guts

of

●

Landll

sites

from

chemical

2H

to

produce

acetate,

carbon

dioxide,

hydrogen

and

reactions:

O

CO

group

in

are

many

and

in

mangrove

are

termites

alcohol

2

third

shores

deposits

and

2

methanogenesis

●

or

+

4

archaeans

carry

two

4

3

The

methane

by

2

COOH

acids

c y c l i n G

hydrogen.

produce

do

4H

2

the

and

c a r B o n

therefore

anaerobic

the

bed

forests

of

and

methanogenic.

They

environments:

lakes.

other

wetlands

where

the

soil

waterlogged.

and

where

of

ruminant

organic

mammals

matter

is

in

such

wastes

as

that

cattle

and

have

sheep.

been

buried.

Some

of

the

methane

environments

in

the

atmosphere

Methane

produced

diffuses

is

produced

into

the

between

from

by

archaeans

atmosphere.

1.7

organic

and

1.85

waste

in

in

these

anaerobic

Currently

the

micromoles

anaerobic

concentration

per

mole.

digesters

is

Figure 3 Waterlogged woodland–a typical

not

habitat for methanogenic prokaryotes

allowed

to

escape

and

instead

is

burned

as

a

fuel.

oxidatin f methane

Methane is oxidized to carbon dioxide and water

in the atmosphere.

Molecules

on

of

average

the

methane

for

only

stratosphere.

released

12

years,

Monatomic

into

the

because

oxygen

atmosphere

it

is

(O)

naturally

and

persist

there

oxidized

highly

in

reactive

•

hydroxyl

explains

amounts

human

radicals

why

of

(OH

)

are

atmospheric

production

of

involved

in

methane

concentrations

methane

by

are

both

oxidation.

not

high,

natural

This

despite

processes

large

and

activities.

Peat frmatin

Peat forms when organic matter is not fully decomposed

because of anaerobic conditions in waterlogged soils.

In

many

soils

eventually

obtain

the

in

the

of

soils

cannot

In

thrive

saprotrophs

in

and

matter

such

saprotrophic

they

need

these

conditions

also

dead

so

tend

methanogens

leaves

and

respiration

water

waterlogged

conditions

as

bacteria

for

environments

become

Acidic

m a t t e r.

by

that

some

they

decomposed.

organic

organic

oxygen

soil.

so

all

digested

and

is

to

organic

develop,

that

from

unable

to

anaerobic.

dead

might

from

fungi.

plants

is

Saprotrophs

air

spaces

drain

out

Saprotrophs

matter

further

break

is

not

fully

inhibiting

down

the

Figure 4 Peat deposits form a blanket on a

boggy hill top at Bwlch Groes in Nor th Wales

223

4

-

E c o l o g y

d-bs qss: Release of carbon from tundra soils

Soils

in

tundra

amounts

of

carbon

accumulates

of

dead

ecosystems

plant

this,

from

of

in

Alaska.

the

of

organic

investigate

areas

in

because

form

low

matter

ecologists

tussock

Some

of

typically

of

rates

by

peat.

of

areas

and

This

samples

Toolik

been

and

To

of

the

soil

nitrogen

and

phosphorus

every

or

15°C.

others

the

Some

were

carbon

amount

5

shows

of

the

eight

years

(TF)

and

some

soils

were

incubated

for

had

100-day

were

with

the

kept

water

soils

was

dioxide

monitored.

moist

(W).

The

measured

given

The

(M)

bar

off

during

chart

in

results.

fertilized

year

for

a)

State

the

effect

not

of

increasing

the

the of

the

soils

on

the

rate

(TC). of

The

of

carbon

was

temperature previous

samples

saturated

content

experiment

gure

Lake

1 with

7

initial

decomposition

near

had

either

large

saprotrophs.

collected

vegetation

the

contain

periods

release

of

carbon.

[2]

at

b)

Explain

the

a)

Compare

reasons

for

this

effect.

[2]

40

C laitini fo egatnecrep

□ □

30

2

the

rates

of

release

of

carbon

in

TC

moist

soils

with

those

in

soils

saturated

TF

with

b)

water.

Suggest

[2]

reasons

for

the

differences.

[2]

20

3

Outline

release

the

of

effects

carbon

of

fertilizers

from

the

on

rates

of

soils.

[2]

10

4

Discuss

whether

amount

of

differences

water

in

the

in

soil

or

temperature,

amount

of

0

7M

7W

15M

fertilizer

15W

treatment group

release

have

of

the

greatest

impact

on

the

carbon.

[2]

Figure 5

Large

quantities

of

partially

accumulated

in

brown

material

is

acidic

covered

the

total

by

some

peat

called

and

quantities

of

decomposed

ecosystems

as

peat.

the

this

and

organic

become

About

depth

material

is

3%

ten

are

matter

have

compressed

of

the

metres

to

Earth’s

or

more

form

land

in

a

dark

surface

some

places,

immense.

Fssiized rani matter

Par tially decomposed organic matter from past geological

eras was conver ted into oil and gas in porous rocks or

into coal.

Carbon

can

and

remain

are

large

the

result

in

●

deposits

Coal

is

compounds

of

that

coal.

coal

Large

coastal

buried

left

a

the

of

from

were

Carboniferous.

formed

level

coal.

past

chemically

of

of

very

millions

geological

of

peat

compressed

deposits

the

are

hundreds

eras.

organic

of

These

matter

stable

years.

and

There

deposits

and

its

are

burial

rock.

deposits

is

swamps

when

seam

peat

carbon

for

decomposition

when

The

of

rocks

carbon

became

formed

of

in

incomplete

sediments.

falls;

224

of

sediments

period

Figure 6 Coal at a power station

some

unchanged

rose

are

and

formed

There

buried

heated,

during

was

a

as

the

level

and

the

sea

the

cycle

fell

under

turning

Pennsylvanian

of

and

spread

other

gradually

sea

level

were

inland.

rises

and

destroyed

Each

into

sub-

cycle

and

has

4 . 3

Oil

●

and

lakes.

natural

incomplete.

As

decomposed

which

We

largest

these

part

that

above

more

formed

of

other

or

compressed

mixtures

crude

gas.

them

the

mud

mud

is

natural

below

the

anaerobic

complex

hold

in

usually

mixtures

can

and

are

are

matter

produce

call

rocks

gas

Conditions

oil

of

porous

rocks

are

are

gas.

found

that

and

of

seas

deposited

Chemical

carbon

natural

shales

bottom

decomposition

heated.

liquid

and

as

the

so

sediments

and

Deposits

such

at

and

prevent

the

compounds

the

and

partially

there

are

deposit’s

occur,

or

forms

impervious

c y c l i n G

often

changes

Methane

where

also

is

c a r B o n

gases.

the

porous

rocks

escape.

cmbustin

Carbon dioxide is produced by the combustion of biomass

and fossilized organic matter.

If

organic

of

matter

oxygen

it

is

will

heated

set

light

to

its

and

ignition

burn.

The

temperature

oxidation

in

the

reactions

presence

that

occur Figure 7 Carbon dioxide is released by

are

called

dioxide

In

and

some

forests

the

combustion.

biomass

rapidly

In

other

are

Coal,

in

are

areas

rainforest

leaves

of

complete

combustion

are

carbon

combustion of the leaves of sugar cane

the

the

world

forest

often

it

Carbon

or

well

is

natural

dioxide

is

grassland.

adapted

to

for

there

released

In

these

res

and

to

be

from

periodic

the

areas

the

res

in

combustion

trees

communities

and

of

other

regenerate

afterwards.

sometimes

cane

of

grassland.

organisms

products

water.

parts

or

The

for

due

them

planting

traditionally

burn

oil

res

cause

off,

and

to

to

oil

palms

burned

leaving

natural

natural

occur.

the

gas

causes

Fire

or

is

for

shortly

cattle

before

harvestable

are

are

used

different

very

to

unusual,

clear

areas

ranching.

they

are

but

of

humans

tropical

Crops

of

sugar

harvested.

The

dry

stems.

forms

of

fossilized

organic

Figure 8 Kodonophyllum–a Silurian coral, in

matter.

They

are

all

burned

as

fuels.

The

carbon

atoms

in

the

carbon limestone from Wenlock Edge. The calcium

dioxide

released

may

have

been

removed

from

the

atmosphere

by carbonate skeletons of the coral are clearly

photosynthesizing

plants

hundreds

of

millions

of

years

ago. visible embedded in more calcium carbonate

that precipitated 420 million years ago in

shallow tropical seas

limestne

Animals such as reef-building corals and molluscs have

hard par ts that are composed of calcium carbonate and

can become fossilized in limestone.

Some

animals

(CaCO

have

hard

body

parts

composed

of

calcium

carbonate

): 3

●

mollusc

●

hard

corals

calcium

When

shells

contain

that

build

calcium

reefs

carbonate;

produce

their

exoskeletons

by

secreting

carbonate.

these

animals

die,

their

soft

parts

are

usually

Fig u r e

decomposed

9

E ng la nd.

quickly.

In

acid

conditions

the

calcium

carbonate

dissolves

away

but

or

alkaline

conditions

it

is

stable

and

deposits

of

it

from

parts

can

form

on

the

sea

bed.

In

shallow

tropical

seas

cl i f f s

is

a

on

the

f or m

of

sou th

coast

l i mestone

of

that

a l most

enti r ely

of

90 - m i l l ion- yea r-

hard old

animal

Cha l k

in

cons i sts

neutral

Cha l k

s hel l s

of

ti ny

u n icel l u la r

a n i ma l s

ca l led

calcium fo r a m i n i fe r a

225

-

4

E c o l o g y

carbonate

is

limestone

rock,

visible

as

also

of

carbon

the

by

precipitation

deposited

hard

in

the

parts

water.

of

The

animals

result

are

is

often

fossils.

Approximately

12%

deposited

where

the

are

10%

mass

of

locked

of

the

up

all

sedimentary

calcium

in

rock

carbonate

limestone

rock

on

is

on

Earth

carbon,

is

so

limestone.

huge

About

amounts

of

Earth.

carbn e diarams

Construct a diagram of the carbon cycle.

Ecologists

recycling

studying

of

other

the

carbon

elements

cycle

use

the

and

Diagrams

the

terms

pool

cycle.

and

arrows

ux.

for

diagram A

●

pool

is

a

reserve

of

the

element.

It

can

or

inorganic.

dioxide

in

the

of

carbon.

ecosystem

The

is

For

example

atmosphere

biomass

an

of

organic

is

an

the

ux

one

ux

is

pool

is

the

to

the

transfer

another.

of

in

be

An

absorption

of

element

example

carbon

of

the

atmosphere

and

its

to

plant

to

be

represent

used

Figure

can

be

10

for

shows

converted

shows

ecosystems.

a

for

combined

the

A

labeled

diagram

diagram

cycle

separate

marine

or

of

for

all

for

diagram

aquatic

and

reserve

of

aquatic

could

ecosystems,

ecosystems.

ecosystems,

the

In

inorganic

carbon carbon

conversion

hydrogen

is

dissolved

carbonate,

carbon

which

is

dioxide

and

by

various

means

biomass. the

water.

in

cell respiration

in saprotrophs

and detritivores

u

le

s f

cell respiration

li

carbon in

s

organic

f

o

s

in consumers

compounds

fo

in producers

it

n o

o

m

b

u

s c

death

feeding

egestion

carbon in dead

organic matter

incomplete

decomposition

and fossilization

of organic matter

and

absorbed

by

by

2

226

a

and

illustrated

dioxide

CO

Figure 10 Carbon cycle

an

to

carbon

atmosphere

oil

carbon

arrows.

only

marine

into

coal

the

pools

from

producers photosynthesis

and

constructed

and from

10

terrestrial

an

pool.

the

can

uxes.

which

boxes

Figure

pool

or A

●

used

carbon

inorganic

producers

be

boxes

be text

organic

can

Text

gas

is

released

back

4 . 3

c a r B o n

c y c l i n G

carbn uxes

Estimation of carbon uxes due to processes in the carbon cycle.

The

carbon

cycle

diagram

in

gure

10

shows

F x/ggs Pss

processes

another

uxes.

uxes

but

It

is

it

transfer

does

not

them.

not

but

scientists

Estimates

individual

carbon

show

possible

precisely

interest,

in

that

as

global

quantities

on

or

1

to

of



these

are

of

120

Cell respiration

119.6

great

Ocean uptake

92.8

Ocean loss

90.0

for

measurements

in

Photosynthesis

carbon

estimates

many

ecosystems

pool

quantities

produced

based

natural

the

one

measure

these

have

are

to

from

mesocosms.

Deforestation and land use

1.6

changes Global

carbon

estimates

are

gigatonne

based

on

is

uxes

in

1,015

Ocean

are

extremely

gigatonnes

grams.

large

(petagrams).

Table

Biogeochemical

1

shows

Dynamics,

so

Burial in marine sediments

0.2

Combustion of fossil fuels

6.4

One

estimates

Sarmiento T able 1

and

Gruber,

2006,

Princeton

University

Press.

d-bs qss: Oak woodland and carbon dioxide concentrations

Carbon

uxes

deciduous

in

England.

robur

and

have

been

woodland

The

at

trees

Quercus

measured

Alice

are

Holt

mainly

petraea,

with

since

1998

Research

oaks,

some

in

1

on

Quercus

ash,

They

were

planted

in

1935

and

are

20

metres

more

Deduce

dioxide

times

a

concentrations

are

net

is

second.

ecosystem

the

net

From

these

forest

indicate

the

an

forest

decrease

and

production

ux

of

the

can

carbon

be

dioxide

atmosphere.

increase

and

due

in

the

negative

to

shows

net

the

the

months

in

Explain

for

net

year.

[1]

the

in

which

forest

was

the

carbon

pool

highest

of

Positive

carbon

values

loss

daily

pool

indicate

carbon

average

the

reasons

net

pool

of

several

years

ecosystem

for

and

biomass

increases

in

the

in

the

forest

part

of

the

year

and

decreases

in

between parts.

[4]

values

4

of

the

annual

carbon

ux

to

or

from

forest.

a

dioxide.

State

the

[2]

The Suggest

a

reason

based

on

the

data

for

ecosystem

also

the

planting

of

more

the oak

cumulative

the

[2]

encouraging

production

in

decreases

deduced.

5

graph

or

measurements

other the

the

pool

lowest.

during This

in

carbon

increases

measured

carbon the

the

forest

tall.

3 20

days

biomass

and

Carbon

the

now of

nearly

whether

of

Fraxinus 2

excelsior.

Calculate

biomass

Forest

forests.

[1]

production.

20

25

1

) 20

1

1

)

h

15

15 ah

ah 10

5

5

0 0 0

50

100

150

200

250

300

530

−5

OC t( PEN evitalumuc

2

OC gk( PEN egareva yliad

2

10

−5 −10

−10

−15

day of year

227

-

4

E c o l o g y

Envirnmenta mnitrin

Making accurate, quantitative measurements: it is important to obtain reliable data

on the concentration of carbon dioxide and methane in the atmosphere.

Carbon

in

the

dioxide

and

atmosphere

effects.

Carbon

methane

have

dioxide

photosynthesis

rates

the

pH

of

above

affect

seawater.

inuence

global

temperatures

and

as

a

600

extent

of

ice

sheets

at

the

poles.

therefore

affect

sea

levels

and

data

lines.

Through

their

effects

the

on

position

heat

the

energy

affect

in

ocean

the

oceans

currents,

and

the

and

extreme

also

the

weather

the

such

and

as

these

hypotheses

and

The

carbon

dioxide

atmosphere

time

in

the

is

severity

past

twenty

over

can

Human

activities

dioxide

and

have

Data

on

higher

million

of

than

the

prerequisite

predictions

methane

long

of

by

a

the

period

past

human

the

at

any

Research

now

years.

of

Organization,

for

of

such

concentration

as

possible

and

possible

future

of

gases

in

the

Atmosphere

atmosphere

Watch

increased

the

the

on

World

agency

in

Meteorological

of

the

various

atmosphere,

Hawaii

has

United

parts

of

but

Nations.

the

world

Mauna

records

from

carbon

concentrations

in

period.

Carbon

dioxide

concentrations

the been

measured

activity

will

cause

atmospheric

records

from

are

of

1984.

from

1959

These

immense

and

onwards

value

other

and

to

reliable

scientists.

Analysis of data from atmosphere

monitoring stations showing

annual uctuations.

freely

it.

atmosphere

available

There

are

uctuations

data

and

stations

are

in

monitoring

allowing

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in

Observatory

of

the

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Hawaii

data

any

long-term

from

available

The

person

trends

for

and

to

and

Mauna

produces

this

stations

analyse

annual

Loa

vast

other

is

amounts

monitoring

analysis.

Figure 11 Hawaii from space. Mauna Loa is near the

centre of the largest island

228

Loa

the

Trends in atmspheri arbn dixide

from

are

before

atmosphere.

Human

Data

as

atmospheric

activity.

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the

an

stations

monitor

methane

●

level

century.

predictions:

have Earth’s

and

concentrations

collected

longest methane

and

as

evaluate

Observatory ●

from

a

of

hurricanes.

concentration

currently

essential

measurements

dioxide

programme

●

the

to

of

is Consider

rise

atmosphere

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frequency

events

an

hypotheses

consequences rainfall

of

to

2014

amount

we they

end

in

of

needed of

are

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carbon coast

the

mole

Indirectly these.

they

by

per

result evaluating

the

concentrations

Both Reliable

gases

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397micromoles

important

concentrations

and

carbon

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very

4 . 4

c l i m a t e

c H a n G e

4.4 c hg

Understandin Appiatins Carbon dioxide and water vapour are the most

➔

Correlations between global temperatures and

➔

signicant greenhouse gases. carbon dioxide concentrations on Ear th.

Other gases including methane and nitrogen

➔

Evaluating claims that human activities are not

➔

oxides have less impact. causing climate change.

The impact of a gas depends on its ability to

➔

Threats to coral reefs from increasing

➔

absorb long-wave radiation as well as on its concentrations of dissolved carbon dioxide. concentration in the atmosphere.

The warmed Ear th emits longer-wave radiation

➔

(heat).

Nature f siene

Longer-wave radiation is reabsorbed by

➔

Assessing claims: assessment of the claims

➔

greenhouse gases which retains the heat in the

that human activities are not causing climate

atmosphere.

change.

Global temperatures and climate patterns are

➔

inuenced by concentrations of greenhouse

gases.

There is a correlation between rising atmospheric

➔

concentrations of carbon dioxide since the star t

of the industrial revolution two hundred years ago

and average global temperatures.

Recent increases in atmospheric carbon

➔

dioxide are largely due to increases in the

combustion of fossilized organic matter.

greenhuse ases

Carbon dioxide and water vapour are the most signicant

greenhouse gases.

The

in

Earth

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is

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would

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the

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combustion

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cell

biomass

respiration

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fossil

229

4

-

E c o l o g y

-------------fuels.

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is

removed

dissolving

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●

in

the

vapour

transpiration

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liquid

back

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the

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evaporation

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the

the

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much

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other reenhuse ases

Other gases including methane and nitrogen oxides have

less impact.

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carbon

dioxide

and

water

vapour

are

the

most

signicant

Figure 1 Satellite image of Hurricane Andrew in

greenhouse

gases

there

are

others

that

have

a

smaller

but

nonetheless

the Gulf of Mexico. Hurricanes are increasing in

frequency and intensity as a result of increases

signicant

effect.

in heat retention by greenhouse gases

Methane

●

from

sites

is

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extraction

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●

vehicle

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than

1%

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fuels

bacteria

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have

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waterlogged

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habitats

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emitted

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of

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the

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the

gases

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the

in

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as

gases

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atmosphere,

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together

oxygen

absorb

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therefore

make

up

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atmosphere.

Assessin the impat f reenhuse ases

The impact of a gas depends on its ability to absorb

long-wave radiation as well as on its concentration in the

atmosphere.

Two

factors

●

how

●

the

For

readily

carbon

atmosphere

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the

its

water

there

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for

as

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nine

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the

much

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average,

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molecule

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the

methane

dioxide

for

released

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immensely

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carbon

per

concentration

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atmosphere

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much

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impact

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warming

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gas

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the

the

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at

together

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rapid,

rate

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it

in

4 . 4

c l i m a t e

ln-waveenth emissins frm Earth

c H a n G e

TOK

The warmed Ear th emits longer-wave radiation. Qss xs b h 

The

warmed

sun

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Figure

2

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pass

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much

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Most

the

f s ph. wh

the

sqs gh hs hv f h

nm.

pb pp  sg

f s?

surface

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nm.

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energy

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much

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the

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emitted

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warm

Earth

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involves entities and concepts beyond

that

blue

bodies

Much of what science investigates

(red)

everyday experience of the world,

curves

of

such as the nature and behaviour

the

of electromagnetic radiation or the

sun.

build-up of invisible gases in the

atmosphere. This makes it dicult

for scientists to convince the general ytisnetni lartceps

public that such phenomenon

actually exist – par ticularly when

the consequences of accepting their

existance might run counter to value

systems or entrenched beliefs.

UV

Visible

Infrared

1

0.2

10

70

wavelength (µm)

Figure 2

greenhuse ases

Longer-wave radiation is reabsorbed by greenhouse gases which retains

the heat in the atmosphere.

25–30%

the

is

sun

of

the

that

absorbed

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radiation

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short-wavelength

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absorbed

therefore

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radiation

the

the

atmosphere

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absorbed

ozone.

the

to

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ultraviolet

70–75 %

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of

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70%

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Key

) short-wave radiation

from the sun

long-wave radiation

from earth

Figure 3 The greenhouse eect

231

-

4

E c o l o g y

Greenhouse

only

absorb

Figure

of

4

gases

the

in

energy

below

radiation

shows

-------------the

in

shows

by

the

bands

Earth’s

specic

total

percentage

atmosphere.

of

individual

atmosphere

the

wavebands.

The

wavelengths

carbon

absorption

graph

absorbed

Earth

is

by

a

some

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wavelengths

between

dioxide,

absorb

also

gases.

are

of

5

and

methane

these

greenhouse

re-emitted

70nm.

and

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nitrous

wavelengths,

oxide

so

by

vapour,

each

all

of

them

gas.

100

tnecrep

75

Total absorption 50 and scattering

25

0

0.2

1

10

70

Water vapour stnenopmoc rojam

Carbon dioxide

•I

Oxygen and ozone

.

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I

I

I

I

I

I

0.2

I

j

I

,,

l. ' '~'

.,

1

. .. I

Nitrous oxide

I

...

I

10

70

wavelength (µm)

Figure 4

gba temperatures and arbn dixide nentratins

Correlations between global temperatures and carbon dioxide concentrations

on Ear th.

If

the

in

concentration

the

size

atmosphere

of

its

change

can

contribution

and

test

this

global

To

is

drilled

trapped

to

in

in

nd

the

greenhouse

can

expect

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using

to

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than

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the

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carbon

fall.

to

We

dioxide

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past,

ice

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isotopes

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concentration.

from

ratios

5

shows

results

for

an

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the

present.

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were

year

obtained

carbon

–

when

the

ice

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232

by

drilled

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in

Dome

European

C

on

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the

for

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the

to

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the

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higher

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striking

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of

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800,000

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in

the

ice

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carbon

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type

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prove

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periods

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much

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the

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800,000

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of

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dioxide

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Antarctica.

there

the

effect

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near

carbon

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hydrogen

the

of

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older

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the

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temperatures

the

carbon

temperatures

over

of

of

considerably.

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any

hypothesis

concentration

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of

changes,

Coring

in

falls

in

atmospheric

carbon

dioxide

4 . 4

c l i m a t e

c H a n G e

300

vmpp/

250

OC

2

200

erutarepmet(

-380 warm )yxorp

9°C

-410

%/Dδ

° -440

cold

800,000

600,000

400,000

200,000

0

age (years before present)

Figure 5 Data from the European Project for Ice Coring in the Antarctic Dome C ice core

d-bs qss: CO

concentrations and global temperatures

2

Figure

6

shows

atmospheric

measurements

The

points

ice

at

show

concentrations

polar

The

red

line

Mauna

carbon

carbon

shows

Loa

0.6

dioxide

direct

)C°( ylamona erutarepmet

concentrations.

Observatory.

dioxide

measured

from

trapped

air

in

cores.

380

Annual average

0.4 Five year average

0.2

0

-0.2

emulov yb noillim rep strap

Direct measurments 360 Ice core measurments

-0.4 340

1880

1900

1920

1940

1960

1980

2000

320

Figure 7

300

2

Compare

the

trends

in

carbon

280

dioxide

260

concentration

temperatures

1750

1800

1850

1900

1950

and

between

global

1880

and

2008.

[2]

2000

3

Estimate

the

change

in

global

average

Figure 6

temperature

Figure

7

shows

temperatures

Institute

annual

for

a

Space

averages

ve-year

from

1961

1990.

1

Discuss

carbon

ice

global

the

average

NASA

The

red

are

is

a)

1900

and

2000

[1]

b)

1905

and

2005

[1]

Goddard

green

curve

values

mean

points

a

given

temperature

are

rolling

as

4

a)

the

Suggest

the

between

measurements

concentration

consistent

measurements

at

with

Mauna

years

of

b)

from

during

trend

Discuss

indicate

direct

Loa.

reasons

temperatures

overall

whether

are

the

The

the

dioxide

cores

of

by

Studies.

and

average.

deviation

and

record

compiled

between

a

global

for

rising

whether

that

global

period

of

does

average

few

an

temperatures.

[2]

falls

dioxide

not

temperatures.

a

with

these

carbon

concentration

[2]

for

falling

inuence

[2]

233

-

4

E c o l o g y

-------------

greenhuse ases and imate patterns

evaporation

of

water

from

the

oceans

and

Global temperatures and climate therefore

patterns are inuenced by

frequent

bursts surface

of

the

Earth

is

warmer

than

and

delivered

concentrations of greenhouse gases.

The

is

be

with

no

greenhouse

gases

in

Mean

temperatures

are

estimated

32°C

higher.

greenhouse

and

we

If

the

gases

should

concentration

rises,

expect

more

an

heat

increase

of

will

in

any

be

of

global

average

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not

all

mean

that

global

likely

are

gas

directly

inuence,

orbit

and

proportional

Other

Milankovitch

variation

in

increases

in

greenhouse

and

to

also

Global

of

cause

higher

more

global

frequent

cycles

sunspot

gas

temperatures

climate.

Higher

very

and

more

of

rain

other

intense

signicantly.

temperatures

cause

In

tropical

to

be

faster

more

wind

frequent

and

speeds.

of

any

rise

unlikely

become

to

in

be

global

evenly

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Scotland

might

The

average

spread.

west

become

Not

coast

colder

in

activity.

heat

other

temperatures

Atlantic

Current

brought

less

if

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from

the

Gulf

distribution

of

Stream

rainfall

to

north-west

would

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be

Europe.

likely

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the with

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areas

becoming

more

prone

Even droughts

and

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areas

to

intense

periods

of

will and

ooding.

Predictions

about

changes

to

temperatures

intense

inuence

amount

have

concentrations

average

and

with

are

and

North

rainfall tend

be

to

factors

to so,

ocean

hurricanes

would

change, Earth’s

increase

to

average

concentrations.

including

and

powerful,

areas

The an

to

consequences

water greenhouse

The

thunderstorms

higher

Ireland

the temperatures

during

temperature

of does

protracted.

likely

the

retained

temperatures.

This

are

to more

be

rain

the storms

atmosphere.

of

it addition,

would

periods

weather

patterns

that

a

are

very

uncertain,

but

it

is

clear

waves.

aspects

increase

just

profound

few

degrees

changes

to

of

the

warming

Earth’s

would

cause

very

climatepatterns.

the

d-bs qss: Phenology

Phenologists

of

seasonal

the

are

biologists

activities

opening

of

tree

in

who

animals

leaves

and

study

and

the

the

laying

temperature

timing

plants,

of

such

as

35

of

birds.

Data

climate

The

date

such

as

changes,

in

the

these

can

including

spring

when

provide

global

new

was

been

chestnut

recorded

Figure

year’s

8

trees

in

shows

date

of

Germany

the

leaf

(Aesculus

warming.

leaves

open

hippocastaneum)

every

difference

opening

year

since

between

and

the

Identify

the

a)

the

opening

between

1970

and

indicate

earlier

than

that

b)

mean

1951.

2

Use

the

mean.

date

The

of

leaf

graph

date

between

each

year’s

mean

March

the

and

for

April

these

and

two

the

the

in

and

~

1

2

lJ

L

,

I ~

leaves

on

whether

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to

deduce

the

between

and

the

temperatures

date

of

in

opening

horse

chestnut

trees.

[1]

there

is

evidence

towards

the

end

of

global

of

the

century.

[2]

for

◄

Figure 8 The relationship

between temperature and 10

-,..

I

I

(1 J

ILt( Ji r Iii"

f

5

0

5

15

4

1980

......................................... 234

[1]

mean

data

3

-

and

temperature

10

1970

graph

April

1990

- ~~~~

2000

syad / gninepo fael

I

March

lowest.

the

fo etad ni ecnereid

C° / erutarepmet

naem ni ecnereid

0

Il

their

the

15

2

1

at

relationship

4

3

in

[1]

was

shows

overall

months.

earliest

temperatures

data

20th temperature

opened

were

warming during

which:

of

b) difference

in

Negative

opening

also

of

following:

of

the

year

leaves

March

values

records

has

each

mean

2000.

the

on

a)

leaf

from

stations.

evidence

April horse

obtained

climate

eggs 1

by

German

horse chestnut leaf opening

in Germany since 1951

Key:

■ □

temperature

leaf opening

............................................................................

4 . 4

c l i m a t e

c H a n G e

Industriaizatin and imate hane

There is a correlation between rising atmospheric

concentrations of carbon dioxide since the star t of the

industrial revolution two hundred years ago and average

global temperatures.

The

graph

800,000

of

uctuations.

180

parts

rose

as

atmospheric

years

During

per

high

shown

300

carbon

gure

5

glaciations

million

as

in

by

the

volume.

ppm.

The

dioxide

concentrations

indicates

there

concentration

During

rise

that

warm

during

over

have

dropped

to

interglacial

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237

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238

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do

Suggest

why

areas

Mauna

it

year.

drought

and

The

graphs

index,

a

gure

combination

precipitation,

destroyed

in

and

the

15

of

area

show

Loa,

have

Baring

chosen

Head

such

and

the

locations

for

monitoring

Alert

stations.

[1]

the

temperatures

of

as

in as

one

scientists

life

spruce

b)

Compare

the

trends

illustrated

in

both

graphs.

trees

[2]

annually. c)

Explain

why

patterns.

the

graphs

show

different

[3]

239

4

-

e c o l o G y

5

Figure

17

shows

the

concentration

of

CO

in

the

tundra

above

taiga

2

root

ground

atmosphere,

In

a

forest,

measured

in

parts

concentrations

of

per

CO

million

change

(ppm).

over

above

the

2

ground

course

top

of

of

the

the

day

forest

and

is

change

referred

to

with

as

height.

the

The

root

canopy.

soil

soil

m/thgieh

310 ppm

30

320

Top forest canopy

grasslands

deciduous forest

20 above

above

ground

ground

305

330

10

root root 340

soil

soil

350 350

0

0

6

12

18

24

time of day / hours savannah

equatorial forest

Figure 1 7

a)

(i)

State

the

highest

concentration

of

above

above

ground

ground

CO 2

reached

in

the

canopy.

[1] soil

(ii)

Determine

found

in

the

the

range

of

concentration

canopy.

soil

root

root

[2]

Figure 18 The distribution of nitrogen in the three organic

b)

(i)

State

the

time

of

day

(or

night) matters compar tments for each of six major biomes

when

the

highest

levels

of

CO

are 2

detected.

[1]

a)

Deduce

what

the

compartment (ii)

The

highest

levels

of

CO

are

“above

consists

of

ground”

in

an

ecosystem.

[1]

detected

2

just

above

reasons

c)

Give

an

the

why

ground.

this

example

of

is

an

Deduce

the

two

b)

case.

hour

[2]

when

CO

State

which

ground”

c)

Explain

biome

has

the

largest

“above

compartment.

why

it

is

difcult

[1]

to

grow

crops

in

2

concentrations

the

full

range

are

of

reasonably

uniform

over

heights.

an

[1]

cleared

d)

State

by 6

Within

an

ecosystem,

nitrogen

can

be

area

where

of

the

one

above

Figure

in

the

of

three

ground,

18

organic

in

shows

three

roots

the

organic

matter

and

in

matter

the

soil.

of

of

six

major

has

been

of

the

and

[2]

process

detritus

carried

feeders

out

that

stored

CO

e)

nitrogen

compartments

into

the

atmosphere.

[1]

2

Suggest

tundra

why

most

ecosystem

of

is

the

in

nitrogen

the

in

a

soil.

[1]

for f)

each

name

compartments:

distribution

forest

vegetation.

decomposers

releases in

its

equatorial

Explain

why

warming

due

to

climate

biomes. change

might

cause

a

release

of

CO

from 2

tundra

240

soil.

[2]

W I T H I N TO P I C Q U E S T I O N S

Topic 4 - data-based questions Page 204 1. venus fly trap is autotrophic; Euglena is autotrophic; both fix carbon compounds by photosynthesis; though both also feed on other organisms; 2. ghost orchid is heterotrophic; ghost orchid does not carry out photosynthesis despite being a plant; dodder is heterotrophic; feeds parasitically on autotrophs; 3. ghost orchid is saprotrophic; feeds on dead organic matter underground; dodder isn’t a detritivore or a saprotroph as it feeds on living plants; dodder is a parasite / not a typical consumer / does not ingest living organisms; Page 209 1. observed values:



Moss Present Moss Absent Column Total

Heather Present 57 9 66

Heather Absent 7 27 34

Row Total 64 36 100

2. expected values: based on the row totals, moss should be present 64% of the time and absent 36% of the time; this should hold in all four cell; based on the column totals, heather should be present 66% of the time and absent 34% of the time;



Moss Present Moss Absent Column Total

Heather Present (64 × 66)/100 = 42.2 (36 × 66)/100 = 23.8 66

Heather Absent (64 × 34)/100 = 21.8 (36 × 34)/100 = 12.2 34

Row Total 64 36 100

3. degrees of freedom = (m - 1)(n - 1) = (2 - 1)(2 - 1); degrees of freedom = 1; 4. the critical region (obtained from a table of chi-squared values) is 3.83 or larger; 5. (57 - 42.2)2 / 42.2 + (7 - 21.8)2 / 21.8 + (9 - 23.8)2 / 23.8 + (27 - 12.2)2 / 12.2 = 5.1905 + 10.0477 + 9.2034 + 17.9541 = 42.3957; 6. the calculated value of chi-squared is in the critical region, so there is evidence at the 5% level for an association between the two species; we can reject the null hypothesis H0; 7. mosses are mostly confined to damp habitats; on this Shropshire hilltop, the moss Rhytidiadelphus squarrosus is associated with the heather because the heather provides shade, humidity and shelter from drying winds; neither species can tolerate trampling on the paths created by hill walkers on this site; in the photo, the heather appears purple-brown in colour and the paths are green; 8. a measuring tape was laid down along one edge of the area; random numbers were used to determine a distance along the tape and then another random number was used to determine a distance at right angles to the tape, where the quadrat was positioned; this procedure was repeated one hundred times; Page 214 1. insolation decreases with increasing distance from the equator / inverse relationship; 2. a) 400 W/m2 b) 240-260 W/m2 3. different levels of cloud cover / variations in the composition of the upper atmosphere that absorbs sunlight; 4. tropical rainforests are near equator so supported; rainforests in areas with high insolation, but not the highest in all areas; some high insolation areas are desert, such as Sahara/Atacama deserts; some tropical rainforests in areas of low insolation, like South East Asia; © Oxford University Press 2014: this may be reproduced for class use solely for the purchaser’s institute

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W I T H I N TO P I C Q U E S T I O N S

Page 216 a) respiration rate increases with decreasing temperature below 12 °C; temperature changes between 12 °C and 33 °C have no effect on respiration rate; as temperature climbs above 33 °C respiration rate begins to increase (sharply); b) bird is trying on maintain temperature; homeostasis; respiration generates waste heat; rise in metabolic rate undertaken to preserve core temperature; bird may increase motion as well to preserve core temperature; c) increase in metabolic rate linked to activities designed to keep cool; such as evaporative cooling through increased ventilation rate; becoming hyperthermic / body temperature higher than normal; faster metabolism / enzyme-catalysed reactions including cell respiration; d) random/expermental error; variation in surface area of birds effects temperature homeostasis; variation in muscle contractions / some birds more physically active than others; Page 219 1. both are top predators; both occupy more than one trophic level; both can be predator/prey of the other; belastoma has higher productivity; 2. Ranatra and Belostama both can be considered as secondary, tertiary and quartenary consumer; 3. a) Metaphyton → Hyalella → Telebasis → Belostoma; b) telebasis; 4. first rung is sum of metaphyton and epiphyton energy values; first rung labelled as producers or with species name; Second rung is labelled primary consumers; second rung shown 5% as wide as first rung; final-initial 5. ​ __  ​    × 100% = -95.3%; initial 6. same organisms can occupy more than one trophic level at the same time; some organisms can occupy different trophic levels at different points in their life cycle; easier to define trophic level in a food chain rather than a food web; 7. determine the fraction of each organism’s diet coming from each specific trophic level; Page 221 1. it is in the spring; 2. a) higher in May than in October; b) photosynthesis in Northern Hemisphere forests; depletes carbon dioxide in summer leading to lower concentrations in autumn; 3. a) much higher in Northern Hemisphere; b) Southern Hemisphere at the end of summer, but Northern Hemisphere at beginning; photosynthesis reduces carbon dioxide concentrations in summer; greater burning of fossil in Northern Hemisphere (during Northern winter than in Southern summer); more ocean in Southern Hemisphere where carbon dioxide can dissolve; colder water in Southern Hemisphere so more carbon dioxide dissolves; more land area in Northern Hemisphere so higher total respiration rates; 4. a) the Equator; b) less fluctuations due to absence of seasons; presence of tropical rainforests to absorb carbon dioxide;

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W I T H I N TO P I C Q U E S T I O N S

Page 222 1. sharp rises and falls are due to artificial light being switched on and off by a timer; fluctuations when artificial light is on are due to variation in natural light / cloudy or sunny conditions; 2. six days; 3. a) pH rises in the light; becomes more alkaline / basic; b) absorption of carbon dioxide (which is acidic) from the water; by photosynthesis; 4. a) pH falls in darkness (mostly) / becomes more acidic; b) more cell respiration than photosynthesis; carbon dioxide released into the water; Page 224 1. a) increasing the temperature increases the release of carbon; the effect is more significant in moist soils than waterlogged soils; b) higher temperature means higher rates of chemical reactions, including respiration which releases CO2; 2. a) in both cases, carbon release increases with temperature; an increase in carbon release is much higher in moist rather than water logged soils; b) in water-logged soils, more anaerobic respiration in bacteria and fungus; only some have alcoholic fermentation; anaerobic respiration releases adding fertiliser increases release of carbon dioxide; in moist soils, but not in soils saturated with water; adding fertilizer impacts carbon release – in moist soils only; 3. amount of water in the soil has the greatest impact; differences between M and W greater than differences between 7 and 15 or TC and TF; Page 227 1. approximately 210 days of decreasing versus approximately 160 days of increasing; 2. lowest on day 135 which is in April; highest on day 290 which is in October; 3. high rates of photosynthesis in summer due to high insolation and warm temperatures leads to high net ecosystem photosynthesis (NEP); low rates of photosynthesis with cellular respiration 4. annual carbon flux is 17.5 t CO2 ha-1 because this is the value reached at the end of the cumulative curve; 5. they could capture more carbon dioxide and reduce the concentration in the atmosphere / reduce the greenhouse effect; Page 233 1. direct and indirect measurements are very similar in the years when both data is available; 2. both rise between 1880 and 2008; both rise most steeply from 1970/80 onwards; temperature fluctuates more than carbon dioxide concentration; 3. 0.22 - (-0.19) = > 2000 - 1900 = 0.41 C  0.41 -(-0.21) = > 2005 - 1905 = 0.62 C 4. a) some possible explanations: natural variability / solar variability / variations in fossil fuel use; local conditions at monitoring stations vary; feedback systems from the earth triggered by warming; b) they suggest that CO2 is not the only variable influencing temperature; strong correlation both in figure 5 and in the figure 6 + 7; Page 234 1. a) 1990; b) 1970; 2. a) the higher the temperature, the earlier the opening of the chestnut leaves; b) over the final 10 year period, highest average temperatures occurred; pervious pattern appeared to be cyclical; supports claim of global worming; © Oxford University Press 2014: this may be reproduced for class use solely for the purchaser’s institute

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W I T H I N TO P I C Q U E S T I O N S

Page 236 1. greater affluence in the US leading to more transportation; more use of air conditioning in the US; no winter so no heating use in Brazil; greater industrial activity in the US; 2. rapid growth in fossil fuel use in the four named countries; cheap oil in countries that produce it; large use of fossil fuel for air conditioning / water purification / construction / oil production; 3. forest fires; to clear land for farming; combustion releases carbon dioxide; 4. farming activities / cattle / sheep / ruminants release methane; Page 237 1. AIFI; 2. minimum 1.1 °C; maximum 5.9 °C; 3. 1.8 °C;

4. 2.1 °C in the Arctic versus 1.8 °C global average; Arctic temperature rise is higher than global average; 5. whether positive feedback cycles will exacerbate the problem; such as melting of polar ice caps; or permafrost melting; or increase in cloud cover; 6. depends on whether data used by centres is the same or independently gathered; more centres means more validity; similar logic applies to positive impact of sample size on certainty in IA experiments; 7. according to precautionary principle strong action called for because consequences of inaction are potentially catastrophic; costs of mitigation should be borne equally; developing nations need assess to carbon production to achieve higher standard of living; will require greater reductions in developed world; 8. forces acting in support of avoiding economic risk are more powerful; some shifts in economic activity possible; local versus global economies; shift to greater degree of subsistence activities; fossil fuel shortage may aid shift.

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E N D O F TO P I C Q U E S T I O N S

Topic 4 - end of topic questions 1. a) respiration loss = gross production - net production = 1 × 102 kJ m-2 y-1 b) answer presumes a student draws a pyramid of net production: base of pyramid is 50 units wide; second tier is 6 units wide; third tier is 0.6 units wide; (accept equivalent ratios) tiers labeled as producers, primary consumers, secondary consumers (accept equivalent terms); 2. a) greater fraction of incident light energy lost in desert; deserts are less productive/less vegetation to fix energy; b) large amounts of energy pass to decomposers in dead plant matter; large amounts of energy accumulated in forests in wood; 3. a) the late 1960s and the 1990s; b) (i) the number of years with an infestation is a longer stretch in the 1990s; the number of affected hectares is much higher in the 1990s; (ii) increase in the number of cycles in one season; population explosion with limited predation due to global warming; c) data suggests increased destruction of spruce trees in future; warmer temperatures will reduce life cycle to one year / increase reproduction rates; rates of destruction may remain stable / decrease; if there is an increase in predation of the spruce beetle; 4. a) all are in remote areas/areas uncontaminated by local pollution; b) both increase over time; greater annual fluctuations at Alert than at Baring Head; c) smaller annual fluctuations at Baring Head because it is in the southern hemisphere; less land mass / more ocean; so less photosynthesis and respiration / more storage and release of carbon dioxide in seawater; 5. a) (i) between 330 and 340 ppm; (ii) 310 to 330 ppm; b) (i) 0–7 hours; (ii) carbon dioxide produced by cell respiration in the soil; furthest from leaves that reduce the carbon dioxide concentration by photosynthesis in the day; lower speeds of wind that cause mixing of air; carbon dioxide is a dense gas so it sinks; c) 8.00 hours; 6. a)  all organisms living above the surface of the soil (including plant shoots and animals); b) equatorial forest; c) little nitrogen stored in the soil; growth of crop plants will be limited by lack of nitrogen/ mineral nutrients in the soil; high rainfall leaches nitrogen/mineral nutrients out of the soil; d) cell respiration; e) low biomass of plants above ground / small maximum plant size / organic matter accumulates in the soil due to slow rates of decomposition; f) melting of permafrost allowing diffusion of gases / carbon dioxide; faster rates of cell respiration in saprotrophs / bacteria / fungi; faster metabolism / enzyme activity.

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5

Ev O Lu t I O n

a n d

B I O d I v E r s I t Y

Iocio

There

that

is

the

overwhelming

diversity

continues

ancestry

to

of

of

evolve

groups

evidence

life

by

of

has

for

the

evolved,

natural

species

selection.

can

be

theory

and

comparing

Species

The

deduced

are

their

base

named

internationally

or

and

agreed

amino

acid

classied

sequences.

using

an

system.

by

5.1 Edee  e

ueig applicio ➔

Evolution ours when heritale harateristis ➔

Comparison of the pentadatyl lim of

of a speies hange. mammals, irds, amphiians and reptiles

➔

The fossil reord provides evidene for

with dierent methods of loomotion.

evolution. ➔

➔

Seletive reeding of domestiated

Development of melanisti insets in

polluted areas.

animals shows that ar tiial seletion

an ause evolution.

➔

radiation explains similarities in struture when

there are dierenes in funtion.

➔

➔

ne of ciece

Evolution of homologous strutures y adaptive

➔

Looking for patterns, trends and disrepanies:

there are ommon features in the one

Populations of a speies an gradually diverge

struture of ver terate lims despite their

into separate speies y evolution.

varied use.

Continuous variation aross the geographial

range of related populations mathes the

onept of gradual divergene.

241

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

Eolio i mmy

Evolution ours when heritale harateristis

of a speies hange.

There

time.

is

strong

scientic

should

the

evidence

Biologists

this

for

be

drawn

of

from

of

between

an

characteristics

process

understanding

lifetime

passed

call

the

parent

to

natural

acquired

individual

of

evolution.

and

offspring.

It

species

lies

world.

at

An

heart

important

characteristics

heritable

changing

the

that

only

a

distinction

develop

characteristics

Evolution

over

of

that

concerns

during

are

heritable

characteristics.

The ▲

mechanism

of

evolution

is

now

well

understood

–

it

is

natural

Figure 1 Fossils of dinosaurs show there were

selection.

Despite

the

selection,

there

still

robustness

of

evidence

for

evolution

by

natural

animals on Ear th in the past that had dierent

is

widespread

disbelief

among

some

religious

characteristics from those alive today

groups.

evolve

There

than

evolution.

are

to

It

stronger

the

is

logic

objections

of

therefore

the

to

the

mechanism

important

to

concept

that

look

at

that

species

inevitably

the

can

causes

evidence

for

evolution.

Eiece fom foil

The fossil reord provides evidene for evolution.

In

the

or

strata

eras

rst

were

various

20th

ages

of

●

layers

the

The

ago

and

would

and

It

of

has

of

that

was

out

the

a

fossils

us

in

in

which

and

fossils

strong

is

of

dating

them.

which

the

the

fossils.

has

branch

evidence

in

In

revealed

There

the

layers

geological

found

sequence

radioisotope

fossils,

given

sequence

worked

there

the

into

Many

that

been

of

the

the

a

science

evolution

on

back

very

ts

land,

and

worms

bony

matches

with

later

sh

mya,

110

in

appear

evolve,

340

appearing

sequences

with

over

60

similar

of

the

bacteria

and

land

appeared

reptiles

sequence

and

vertebrates

about

320

420

mya,

in

simple

later

million

birds

which

algae

250

still.

years

mya

mya.

with

before

plants

fossils

their

members

rhinoceroses

now totally ex tinct

and

mammals

also

to

the

ecology

animal,

suitable

of

plants

for

the

on

insect

groups,

land

with

before

pollination

before

pollinators.

zebras,

hundreds of millions of years but the group is

fungi

amphibians

fossils

organisms

and

fossils

vertebrates,

sequence

insect

which

expected

rst,

placental

The

in

be

the

(mya),

animals

242

–

methods

research

the

was

obvious

different

strata

of

sequence

plant

Figure 2 Many trilobite species evolved over

were

century,

became

palaeontology.

Among

▲

It

reliable

rock

appearing

●

19th

deposited

occurred.

they

●

the

were

named.

amount

called

of

rock

century,

huge

has

half

of

and

a

likely

known,

ancestors.

of

the

genus

tapirs.

An

extensive

million

to

are

years,

links

rhinoceros.

which

For

Equus,

link

example,

are

most

sequence

them

to

together

of

existing

horses,

closely

fossils,

Hyracotherium,

asses

related

to

extending

an

animal

5 . 1

E v i D E n c E

f o r

E v o l u t i o n

Daa-baed qe: Missing links

An

objection

been

for

gaps

in

example

to

fossil

the

a

evidence

record,

link

called

between

for

evolution

missing

reptiles

has

The

links,

and

Calculate

~~~

-

(b)

of

fossils

exciting

that

for

ll

in

these

gaps

is

biologists.

birds. 1

(a)

discovery

particularly

from

its

the

length

head

to

the

of

tip

Dilong

of

its

paradoxus,

tail.

[2]

(g)

(c)

~

(d)

2

Deduce

three

paradoxus

Earth

=

similarities

and

reptiles

between

that

live

Dilong

on

today.

[3]

(i)

(h)

3

Suggest

a

function

for

the

protofeathers

of

100 mm

'

Dilong

paradoxus.

[1]

(j)

(e)

▲

(f)

4

Suggest

would

Figure 3 Drawings of fossils recently found in Western

two

have

features

had

capable

of

Explain

why

to

which

evolve

Dilong

to

paradoxus

become

ight.

[2]

China. They show Dilong paradoxus, a 130-million-year-old

5

it

is

not

possible

to

be

certain

tyrannosauroid dinosaur with protofeathers. a–d: bones of

whether

the

protofeathers

of

Dilong

paradoxus

skull; e–f: teeth; g: tail ver tebrae with protofeathers; h–j:

are

homologous

with

the

feathers

of

birds.

[2]

limb bones

Eiece fom elecie beeig

Seletive reeding of domestiated animals shows that

ar tiial seletion an ause evolution.

Humans

have

thousands

the

wild

of

species

Consider

the

junglefowl

of

Western

other

It

is

clear

The

that

that

very

have

to

cause

in

Asia,

by

of

articial

but

naturally,

with

it

or

to

does

that

breeds

have

for

process

selection

is

is

prove

Blue

and

that

by

over

It

the

in

the

that

of

has

is

been

selection.

time

changes

that

selection

species

evolution

and

individuals

considerable

of

aurochs

their

change

periods

shows

the

cattle

breeds.

articial

evolution

for

and

existed

the

breeding

called

time.

mechanism

that

huge.

the

sheep,

between

for

with

often

and

cattle

of

always

is

shown

animals

geological

not

not

are

hens

breeds

variation

species

compared

differences

Belgian

selecting

animal

are

egg-laying

explanation

This

the

the

different

much

domesticated

comparison

particular

livestock

between

repeatedly

in

of

modern

many

credible

uses.

used

resemble,

or

also

livestock,

human

evolution,

occurred

most

are

only

and

breeds

between

domesticated

The

occurred

short,

they

There

simply

suited

bred

modern

Southern

Asia.

effectiveness

that

▲

of

form.

achieved

If

differences

domesticated

current

most

deliberately

years.

has

natural

are

can

actually

selection.

Figure 4 Over the last 15,000 years many breeds of dog have been developed by ar ticial

selection from domesticated wolves

243

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

Daa-baed qe: Domestication of corn

Homology  A

eolio

wild

grass

probably

is

grown

called

the

as

teosinte

ancestor

a

crop,

it

of

that

grows

cultivated

gives

yields

in

corn,

of

Central

Zea

about

America

mays.

150

kg

When

per

was

teosinte

hectare.

This

Looking for patterns, trends compares

and disrepanies: there are

at

the

Corn

with

start

was

of

a

world

the

21st

average

century.

domesticated

at

yield

Table

least

7,000

of

1

corn

gives

years

of

4,100

the

kg

lengths

per

of

hectare

some

cobs.

ago.

ommon features in the one

struture of ver terate lims

1

Calculate

and

the

Silver

percentage

difference

in

length

between

teosinte

Queen.

[2]

despite their varied use.

2 Vertebrate

limbs

are

used

Calculate

and many

different

walking,

running,

swimming,

These

ways,

varied

uses

such

and

world

percentage

average

yields

difference

of

in

yield

between

teosinte

corn.

[2]

as

jumping,

grasping

the

in

ying,

3

Suggest

factors

4

Explain

why

apart

from

cob

length,

selected

for

by

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[3]

digging.

require

joints

improvement

slows

down

over

generations

of

that selection.

articulate

velocities

different

be

in

different

of

movement

amounts

reasonable

have

but

very

there

features

found

in

Patterns

are

all

the

As

a

common

vertebrate

piece

of

Teosinte – wild relative of orn

14

Early primitive orn from Colomia

45

Peruvian anient orn from 500 bc

65

Imriado – primitive orn from Colomia

90

common

only

far

legh  b (mm)

to

that

are

Silver Queen – modern sweetorn

limbs.

require

The

so

c aey ad g

would

structure,

structure

this

also

It

them

bone

fact

evolution

ancestor.

expect

[3]

different

and

force.

vertebrate

like

explanation

is

in

bone

explanation.

case

to

of

different

of

ways,

T able 1

▲

Figure 5 Corn cobs

reasonable

proposed

from

▲

170

a

in

this

common

consequence,

bone

limbs

structure

has

evidence

for

become

of

a

classic

evolution.

Eiece fom homologo ce

Evolution of homologous strutures y adaptive

radiation explains similarities in struture when there are

dierenes in funtion.

Darwin

pointed

structure

dugong

those

between

and

244

a

very

in

the

When

or

tail

we

different.

The

Origin

organisms

whale,

between

structures.

are

out

ns

study

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are

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supercial,

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whales

them

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closely

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some

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shes

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similarities

example

sh.

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nd

interpretation

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Similarities

known

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as

a

like

analogous

structures

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5 . 1

different

same

or

origins

a

Homologous

may

look

which

of

what

could

in

the

digit

that

be

limb,

same

are

that

many

the

without

Darwin

called

function.

of

These

of

and

have

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an

teeth

the

of

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easily

that

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–

of

so

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the

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the

bat

that

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they

pentadactyl

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asked

the

surface

is

that

but

example

and

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structures.

have

or

they

but

they

ve-

perform

thigh

bone

the

are

are

found

gradually

that

as

reveal

to

serve

of

the

in

that

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despite

in

prove

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structures

examples

appendix

not

do

difcult

the

whales,

evolution

do

and

structures

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course

They

ancestry

organs

by

E v o l u t i o n

radiation.

reduced

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the

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embryo

explained

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He

explanation

common

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They

they

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different

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that

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snakes,

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nd

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homologous

called

small

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called

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than

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called

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the

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relative

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Darwin

of

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the

and

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E v i D E n c E

are

adults

body

wall

humans.

structures

that

no

lost.

Pecyl limb

Comparison of the pentadatyl lim of mammals, irds, amphiians and reptiles

with dierent methods of loomotion.

The

pentadactyl

limb

consists

of

these

structures:

classes

birds

Be e

femb

that

and

have

a mp hib ia ns,

Ea ch

of

the m

r e pti le s ,

h as

Hdmb pentadactyl

single one in the

l i mb s :

mamma l s .

humerus

limbs :

femur

●

crocodiles

walk

or

crawl

on

land

and

use

their

proximal par t

webbed

two ones in the

radius and ulna

hind

limbs

for

swimming

tiia and ula

●

penguins

use

their

hind

limbs

for

walking

and

distal par t

their

group of wrist/

arpals

forelimbs

●

ankle ones

echidnas

also

series of ones in

metaarpals and

metatarsals

eah of ve digits

phalanges

and phalanges

●

use

frogs

use

pattern

present

in

mammals,

of

all

bones

or

a

modication

amphibians,

whatever

the

reptiles,

function

of

birds

of

it

use

photos

in

one

example

gur e

of

ea ch

6

s how

of

ippers

for

swimming

all

the

the

four

four

four

for

limbs

forelimbs

limbs

for

for

walking

and

digging

for

walking

the

relative

and

their

jumping.

is Differences

can

thicknesses

of

be

seen

in

lengths

and

and

their

the

bones.

Some

metacarpals

and

limbs. phalanges

The

all

their

hindlimbs

The

as

tarsals

s ke le t o ns

of

the

have

penguin’s

been

lost

during

the

evolution

of

forelimb.

v ert ebr at e s

245

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

Ay

Peaday mb 

mamma

mole

horse

▲

Figure 6

porpoise

speciio

Populations of a speies an gradually diverge into

separate speies y evolution.

If

two

not

populations

interbreed

of

and

a

species

natural

become

selection

separated

then

acts

so

that

they

differently

on

do

the

two

bat

populations,

human

the

two

will

populations

recognizably ▲

they

evolve

will

different.

If

in

different

gradually

the

ways.

diverge.

populations

The

After

a

characteristics

time

subsequently

they

will

merge

of

be

and

have

Figure 7 Pentadactyl limbs

(not to scale)

the

chance

clear

that

of

interbreeding,

they

have

evolved

but

do

into

not

actually

separate

interbreed,

species.

This

it

would

process

is

be

called

Choose a olour ode for speciation.

the types of one in a

pentadatyl lim and olour

Speciation

the diagrams in gure 7 to

by

often

show the type of eah one.

species

on

How is eah lim used?

certain

geographical

What features of the ones

are

in eah lim make them well

of

adapted to the use?

different

migrating

an

the

occurs

an

islands.

example

of

archipelago.

species,

divergence.

246

to

after

island.

An

population

explains

endemic

area.

this.

On

a

This

The

One

six

formed

species

lava

species

smaller

by

is

of

to

species

the

is

found

of

is

all

a

island

the

and

by

range

in

a

Islands

main

closely

its

endemic

only

Galápagos

on

there

extends

numbers

that

the

present

islands

migration

a

large

one

lizards

is

of

the

islands

related

but

subsequent

5 . 1

E v i D E n c E

f o r

E v o l u t i o n

Eiece fom pe of iio

Pinta

0

Continuous variation aross the geographial

()

Genovesa

Marchena

range of related populations mathes the Santiago

onept of gradual divergene.

If

populations

gradually

diverge

over

time

to

become

separate Santa Cruz

Fernandina

species,

to

nd

then

at

any

examples

of

one

all

moment

stages

of

we

would

expect

divergence.

This

is

to

be

San Cristóbal

able

indeed Santa Fe

what

we

nd

in

nature,

as

Charles

Darwin

describes

in Isabela

Chapter

II

of

The

Origin

of

Species.

He

wrote:

(J a Español

Santa Maria

Many

years

ago,

when

comparing,

and

seeing

others

compare,

key

the

birds

both

from

one

with

mainland,

is

the

the

I

separate

another ,

was

distinction

islands

and

much

with

struck

between

of

those

how

species

the

Galápagos

from

entirely

and

the

Archipelago, T.albemarlensis

T.delanonis

T.habelii

T.duncanensis

T.pacicus

T.bivittatus

American

vague

and

□

T.grayii

arbitrary

varieties.

▲

Figure 8 Distribution of lava lizards in the

Galápagos Islands

Darwin

gave

different,

species.

but

One

ptarmigan

species

Because

there

is

being

split

The

to

his

two

for

can

sudden

separate

into

They

therefore

species

are

species

and

as

have

gradually

be

origin

of

variation

were

new

the

clearly

it

been

classied

provides

of

separate

This

is

a

organisms.

time

one

populations

and

species

to

together

or

arbitrary.

distinct

their

as

willow

lagopus.

of

populations

as

the

living

periods

lump

rather

and

Lagopus

classify

long

between

by

separate

Britain

populations

to

created

species

of

and

over

two

across

recognizably

species

name

remains

Instead

of

are

grouse

decision

constant

unchanging.

are

sometimes

being

species

in

they

diverge

the

species

that

red

who

from

species,

that

that

the

varieties

switch

should

the

is

biologists

range

belief

populations

extent

separate

continuous

the

the

Norway.

species

no

of

examples

sometimes

problem

them

either

and

not

of

of

and

common

examples

does

types

geographic

evidence

for

of

not

range

the

match

organism

or

TOK

that

evolution

of

t wha ex e a mpe mde

be ed  e hee?

evolution.

The usefulness of a theory is

the degree to whih it explains

Iil melim

phenomenon and the degree to

whih it allows preditions to e

Development of melanisti insets in polluted areas. made. One way to test the theory

Dark

varieties

of

typically

light-coloured

insects

are

called

melanistic.

of evolution y natural seletion is

The

most

famous

example

of

an

insect

with

a

melanistic

variety

through the use of omputer models.

is

Biston

betularia,

the

peppered

moth.

It

has

been

widely

used

as

The Blind Watchmaker omputer

an

example

of

natural

selection,

as

the

melanistic

variety

became

model is used to demonstrate how

commoner

in

polluted

industrial

areas

where

it

is

better

camouaged

omplexity an evolve from simple

than

the

pale

peppered

variety.

A

simple

explanation

of

industrial

forms through ar tiial seletion. The

melanism

is

this:

Weasel omputer model is used to

●

Adult

and

Biston

betularia

moths

y

at

night

to

try

to

nd

a

demonstrate how ar tiial seletion

mate

an inrease the pae of evolution

reproduce.

over random events. What features ●

During

●

Birds

the

day

they

roost

on

the

branches

of

trees.

would a omputer model have to

they

and

nd

other

them.

animals

that

hunt

in

daylight

predate

moths

if

inlude for it to simulate evolution y

natural seletion realistially?

247

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

●

In

unpolluted

lichens

●

and

Sulphur

dioxide

blackens

●

●

tree

moths

polluted

areas.

In

polluted

▲

kills

are

well

covered

in

pale-coloured

camouaged

lichens.

are

well

the

camouaged

melanic

variety

over

a

Soot

from

against

variety

of

relatively

▲

Figure 9 Museum specimen of the

against

coal

them.

burning

dark

Biston

short

tree

branches

betularia

time,

but

in

replaced

not

in

non-

Figure 10 The ladybug Adalia bipunctata

peppered form of Biston betularia

has a melanic form which has become

mounted on tree bark with lichens

common in polluted areas. A melanic male

from an unpolluted area

is mating with a normal female here

have

evolution

by

ndings

been

into

criticized

and

selection

ever

Michael

book

in

pale

been

and

used

careful

in

to

a

The

predation

cast

classic

of

example

this,

design

of

doubt

evaluation

Biston

Naturalist

His

nding

melanism

factors

attacked.

and

as

because

the

of

some

moths

over

of

research

early

has

whether

been

natural

occurs.

a

New

2002).

though

of

has

gives

causing

Perhaps

repeatedly

melanism

the

melanism

selection.

actually

of

HarperCollins

pollution

industrial

camouage

this

Majerus

development

strong,

used

natural

have

experiments

rates

are

areas.

Biologists

his

branches

moths

pollution

areas

peppered

polluted

tree

branches.

Melanic

the

in

areas

peppered

other

melanic

in

series

is

that

Biston

than

of

betularia

evidence

and

(Moths,

the

other

camouage

the

of

Michael

evidence

betularia

about

species

and

can

for

other

also

moth

Majerus,

industrial

species

of

inuence

moth

is

survival

varieties.

Daa-baed qe: Predation rates in Biston betularia

One

into

of

the

moths

trunks

roost.

were

and

The

suitable

of

placed

that

1980s

the

moths

is

but

the

original

betularia

exposed

not

were

some

tested

were

in

this

moths

on

the

of

Biston

positions

persisted

248

criticisms

predation

able

even

to

so

effect

placed.

that

positions

normally

websites.

the

experiments

was

move

the

on

where

to

Experiments

of

the

position

Peppered

and

tree

they

have

done

in

in

which

melanic

(fty

in

and

two

the

in

the

a

of

oak

woods,

polluted

Midlands.

in

area

The

percentage

a

trunk.

Forest

of

of

Biston

positions

below

tree

New

each)

exposed

millimetres

at

more

criticisms

forms

placed

the

joint

This

one

near

procedure

in

an

were

trunks

a

major

was

in

eaten

gure

and

11

in

50

branch

area

and

out

of

another

the

show

moths

and

carried

unpolluted

England

Stoke-on-Trent

plots

moths

tree

between

southern

box

betularia

on

the

surviving.

5 . 2

1

a)

Deduce,

with

a

reason

from

the

n A t u r A l

data, peppered

whether

the

moths

were

more

s E l E c t i o n

likely

to

Stoke on Trent and New Forest

be

New Forest/melanic/BJ

eaten

if

trunk

or

branch

they

were

below

and

the

placed

the

on

the

junction

of

a

60

main

trunk.

New Forest/melanic/ET

38

62

[2] New Forest/peppered/BJ

b)

Suggest

a

a)

Compare

reason

for

the

difference.

74

and

contrast

the

68

in

b)

of

the

peppered

New

Explain

rate

and

melanic

the

the

Stoke/melanic/ET

[3]

difference

two

in

Stoke/peppered/BJ

survival

varieties

in

Forest.

Distinguish

between

New

woodlands

rates

Forest

of

peppered

the

and

Stoke-on-Trent

Pollution

in

relative

melanic

survival

moths.

due

near

to

50

50

industry

has

Stoke-on-Trent

0%

42

20%

58

40%

60%

80%

100%

key

not eaten

[2]

■

eaten

BJ = branch junction

decreased

▲

greatly

40

and

ET = exposed trunk

4

60

[3]

melanic

3

28

the Stoke/peppered/ET

New

72

moths

Forest.

between

32

survival Stoke/melanic/BJ

rates

26

[1] New Forest/peppered/ET

2

40

exposed

since

the

Figure 11

1980s.

Source: Howlett and Majerus (1987) The Understanding of

Predict

the

consequences

of

this

change

for industrial melanism in the peppered moth (Biston betularia)

Biston

betularia.

[4] Biol. J.Linn.Soc. 30, 31–44

5.2 naa ee

ueig applicio ➔

Natural seletion an only our if there is ➔

Changes in eaks of nhes on Daphne Major.

➔

Evolution of antiioti resistane in ateria.

variation amongst memers of the same speies.

➔

Mutation, meiosis and sexual reprodution

ause variation etween individuals in a speies.

➔

Adaptations are harateristis that make an

ne of ciece

individual suited to its environment and way of life. ➔

➔

Speies tend to produe more ospring than

the environment an suppor t.

➔

Individuals that are etter adapted tend to survive

Use theories to explain natural phenomena:

the theory of evolution y natural seletion

an explain the development of antiioti

resistane in ateria.

and produe more ospring while the less well

adapted tend to die or produe fewer ospring.

➔

Individuals that reprodue pass on

harateristis to their ospring.

➔

Natural seletion inreases the frequeny of

harateristis that make individuals etter

adapted and dereases the frequeny of other

harateristis leading to hanges within the

speies.

249

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

viio

Natural seletion an only our if there is variation

amongst memers of the same speies.

Charles

causes

his

voyage

the

to

Figure 1 Populations of bluebells (Hyacinthoides

of

of

theory

and

20

to

in

the

understanding

years,

world

on

selection

for

1859.

presents

30

his

many

evidence

Species,

previous

over

natural

accumulate

his

developed

around

theory

Origin

▲

Darwin

evolution

it.

In

HMS

in

the

book

Beagle.

the

He

1830s,

published

of

evidence

of

returning

late

Darwin

this

the

after

nearly

for

it

England

probably

but

his

500

that

mechanism

to

he

then

great

developed

worked

work,

pages,

had

that

from

he

found

The

explains

over

the

years.

non-scripta) mostly have blue owers but

One

of

the

observations

on

which

Darwin

based

the

theory

of

evolution

white-owered plants sometimes occur

by

natural

respects.

blood

may

it

is

all

selection

Variation

group

not

be

there.

and

so

in

variation.

human

many

other

immediately

Natural

individuals

some

is

in

a

individuals

populations

populations

features.

obvious

selection

were

favoured

is

obvious

With

but

depends

population

being

Typical

other

careful

on

than

–

in

many

height,

species

the

observation

variation

identical,

more

vary

within

there

skin

colour,

variation

shows

that

populations

would

be

no

–

way

if

of

others.

soce of iio

Mutation, meiosis and sexual reprodution ause

variation etween individuals in a speies.

The

1

causes

of

Mutation

by

2

gene

Meiosis

an

Sexual

The

a

▲

the

in

new

is

usually

combination

of

in

a

over

reproduction

of

are

diploid

to

carry

and

the

involves

come

alleles

from

New

alleles

Every

different

fusion

of

different

two

understood:

pool

by

cell

alleles

of

a

are

breaking

produced

male

and

individuals.

by

the

the

meiosis

alleles,

of

bivalents.

female

so

This

up

of

orientation

parents,

produced

population.

combination

independent

the

from

well

gene

of

cell.

a

the

now

variation.

enlarges

combinations

likely

crossing

gametes

source

which

combination

of

populations

original

individual

because

3

is

mutation,

produces

existing

in

variation

gametes.

offspring

allows

has

mutations

Figure 2 Dandelions (Taraxacum ocinale)

that

occurred

in

different

individuals

to

be

brought

together.

appear to be reproducing sexually when they

disperse their seed but the embryos in the

In

seeds have been produced asexually so are

of

genetically identical

species

that

variation

not

is

generate

survival

do

not

carry

mutation.

enough

during

times

It

out

is

variation

of

sexual

generally

to

be

reproduction

assumed

able

environmental

to

that

evolve

the

only

such

source

species

quickly

will

enough

for

change.

apio

Adaptations are harateristis that make an individual

suited to its environment and way of life.

One

of

the

structure

correlated

250

recurring

and

themes

function.

with

its

diet

For

and

in

biology

example,

method

is

the

of

the

close

structure

feeding.

The

relationship

of

a

bird’s

thick

coat

between

beak

of

a

is

musk

5 . 2

ox

is

obviously

habitats.

The

infrequent

correlated

water

rainfall

with

storage

in

the

tissue

desert

low

in

temperatures

the

habitats.

In

stem

of

a

biology

in

its

cactus

n A t u r A l

s E l E c t i o n

northerly

is

related

characteristics

Ay

to

such

as

Adapa  bd’ beak

these

that

make

an

individual

suited

to

its

environment

or

way

of

life

The four photographs of are

called

adaptations.

irds show the eaks of a

The

term

and

thus

this

process.

natural

suited

one

adaptation

that

species

its

as

acquired

not

to

that

It

the

important

direct

They

Characteristics

acquired

is

characteristics

evolutionary

with

environment.

individual.

known

evolve.

According

selection,

to

implies

do

that

characteristics

characteristics

cannot

do

theory

of

develop

a

to

over

imply

making

during

during

widely

an

woodpeker. To what diet

by

individual

lifetime

lifetime

accepted

heron, maaw, hawk and

in

develop

the

a

time

purpose

adaptations

develop

and

be

not

purpose

not

develop

and method of feeding is

eah adapted?

of

are

theory

is

that

inherited.

Oepocio of opig

Speies tend to produe more ospring than the

environment an suppor t.

Living

An

organisms

example

southern

every

other

so

in

of

three

their

species

nucifera

in

which

on

do

have

a

a

bacteria,

there

It

can

number

with

a

and

However

pair

faster

could

the

be

as

needs

a

rate.

breeding

as

7

For

20

raises

for

of

60

the

in

within

living

out

a

a

be

a

the

at

as

least

70

two

years

offspring.

coconut

per

in

the

giant

palm,

year.

fungus

puffball

be

variation

there

is

an

produced

can

that

for

population.

for

for

will

will

the

Darwin

tend

to

existence

There

resources

individual

more

than

support.

this

in

overall

organisms

struggle

competition

every

may

is

edgling

(7,000,000,000,000).

environment

pointed

the

huge

to

of

long

twenty

rate,

offspring

to

as

called

spores

breeding

lead

rate

one

coconuts

all

body

Despite

trend

It

example,

rate

trillion

produce.

breeding

raise

and

fruiting

they

cooperation

live

theoretically

huge

many

slow

the

can

between

fastest

produces

offspring

leadbeateri .

they

breeding

produces

of

relatively

Bucorvus

average

this.

usually

gigantea.

the

hornbill,

lifetime

Cocos

from

to

in

species

years

Most

Calvatia

a

ground

adults

Apart

vary

will

and

obtain

be

not

enough ▲

to

allow

them

to

survive

Figure 3

and

reproduce.

▲

Figure 4 The breeding rate of pairs of

southern ground hornbills, Bucorvus

leadbeateri, is as low as 0.3 young per year

251

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

dieeil il  epocio Ay

Individuals that are etter adapted tend to survive and sma  aa

ee

●

Make ten or more

produe more ospring while the less well adapted tend

to die or produe fewer ospring.

ar tiial sh using Chance

plays

a

part

in

deciding

which

individuals

survive

and

reproduce

modelling lay, or some and

which

do

not,

but

the

characteristics

of

an

individual

also

have

an

other malleale material. inuence.

In

the

struggle

for

existence

the

less

well-adapted

individuals

Drop eah of them into tend

to

die

or

fail

to

reproduce

and

the

best

adapted

tend

to

survive

and

a measuring ylinder of produce

many

offspring.

This

is

natural

selection.

water and time how long

An

example

that

is

often

quoted

is

that

of

the

giraffe.

It

can

graze

on

eah takes to reah the

grass

and

herbs

but

is

more

adapted

to

browse

on

tree

leaves.

In

the

wet

ottom.

season ●

its

food

is

abundant

but

in

the

dry

season

there

can

be

periods

Disard the half of of

food

shortage

when

the

only

remaining

tree

leaves

are

on

high

the models that were branches.

Giraffes

with

longer

necks

are

better

adapted

to

reaching

slowest. Pair up the these

leaves

and

surviving

periods

of

food

shortage

than

those

with

fastest models and shorter

necks.

make intermediate

shapes, to represent

their ospring. Random

Iheice

new shapes an also e

introdued to simulate

mutation.

●

Test the new generation

and repeat the

elimination of the

slowest and the reeding

of the fastest. Does

one shape gradually

emerge? Desrie its

features.

Individuals that reprodue pass on harateristis

to their ospring.

Much

of

the

offspring

of

their

–

is

blackcap

some

Spain

Not

all

of

the

broken

of

an

tusk

person

atricapilla

are

signicant

in

and

not

the

of

children

of

skin

on

are

to

not

skin

evolution

with

colour

a

to

Those

broken

from

to

to

skin

colour

north

behaviour

sites

differences

in

in

can

the

their

Germany

genes,

to

Britain.

acquired

inherited.

through

Acquired

of

Due

offspring.

in

overwintering

southwestwards

usually

on

dark

Variation

northwestwards

calves

inherited.

to

passed

the

light-skinned

colour.

example.

others

be

inherit

migration

an

have

darker

not

and

light

can

children

migrate

passed

individual

does

is

a

is

species

winter

develops

skin

example

inherit

individuals

Maasai

direction

this

features

lifetime

darker

The

Sylvia

birds

for

for

parents

heritable.

between

heritable.

parents

European

be

variation

it

An

tusks

for

exposure

characteristics

during

elephant

example.

to

are

the

with

If

sunlight,

therefore

a

a

the

not

species.

Pogeie chge

Natural seletion inreases the frequeny of

harateristis that make individuals etter adapted and

dereases the frequeny of other harateristis leading

to hanges within the speies.

Because

pass

on

adapted

leads

252

to

better-adapted

characteristics

have

an

lower

increase

individuals

to

their

survival

in

the

survive,

offspring.

rates

and

proportion

less

of

they

can

Individuals

reproduce

that

reproductive

individuals

in

a

are

and

less

success.

well

This

population

with

5 . 2

characteristics

that

characteristics

of

natural

make

the

them

well

population

adapted.

gradually

Over

change

the

–

n A t u r A l

generations,

this

is

s E l E c t i o n

the

evolution

by

Ay

selection.

The impulse to reprodue and pass

Major

and

evolutionary

many

them

colours

air.

this

generations,

during

signicant

in

Two

our

that

has

examples

of

are

we

but

there

been

beaks

antibiotic

of

to

occur

not

are

are

in

many

resistance

on

in

to

the

long

be

in

time

able

examples

The

industrial

described

nches

over

expect

observed.

observed

evolution

to

likely

should

have

been

of

changes

development

so

lifetime,

changes

moths

book:

changes

to

of

the

of

with

next

Galapagos

but

dark

wing

Islands

pattern have evolved in lions and

with two or more males so their litters

of

and

infantiide. How ould this ehaviour

other speies? Female heetahs mate

polluted

sections

on harateristis an e very strong.

It an ause adult males to arry out

observe

smaller

evolution

areas

periods

the

have multiple paternity. How does this

protet the young against infantiide?

bacteria.

Daa-baed qe: Evolution in rice plants

The

bar

charts

evolution

in

in

rice

gure

6

plants.

show

F

the

hybrid

results

plants

of

an

were

investigation

bred

by

of

crossing

together

1

two

in

rice

varieties.

Japan.

collected

Each

from

These

year

the

the

hybrids

date

plants,

of

for

were

then

owering

re-sowing

F

grown

was

at

ve

recorded

that

site

F

3

at

in

different

and

the

seed

following

F

4

sites

was

year.

F

5



▲

Figure 5 A female cheetah’s cubs inherit

Sapporo

characteristics from her and from one of

43° N

the several males with whom she mated

Fujisaa

40° N

onasu

36° N

iratsua

singe

35° N

origina

popuation

panted

iugo

out at

33° N

iyaai

31° N

56

70

84

98 112 126

68

82

96

110 124 138

54

68

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96 110124 138

51

65

79

93

10712 1 135

days to owering

▲

1

Figure 6

Why

was

single

2

the

investigation

pure-bred

Describe

the

done

using

hybrids

rather

than

a

variety?

changes,

[2]

shown

in

the

chart,

between

the

F

and 3

F

generations

of

rice

plants

grown

at

Miyazaki.

[2]

6

3

a)

State

in

the

the

F

relationship

between

owering

time

and

latitude

generation.

[1]

6

4

b)

Suggest

a)

Predict

until

a

reason

the

the

for

results

F

if

this

the

relationship.

investigation

[1]

had

been

carried

on

generation.

[1]

10

b)

Predict

the

results

of

collecting

seeds

from

F

plants

grown

at

10

Sapporo

and

from

F

plants

grown

at

Miyazaki

and

sowing

10

them

together

at

Hiratsuka.

[3]

253

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

Glápgo che

Changes in eaks of nhes on Daphne Major.

0

Pinta (5)

0

Rabida (8)

()

Genovesa (4)

Marchena (4)

Santiago (10)

Daphne Major (2/3)

Santa Cruz

Fernandina

San Cristóbal

(9)

(9)

(7) (a)

G. fortis (large beak)

(b)

G. fortis (small beak)

(c)

G. magnirostris

Santa Fe

(5) Isabela (10)

() Española (3) Santa Maria (8)

▲

Figure 7 The Galápagos archipelago with the number

of species of nch found on each island

Darwin

and

were

14

species

diet.

and

(see

of

in

From

Galápagos

has

since

particular,

that

related

and

also.

particular

Grant’s

small

ground

called

Both

G.

fortis

can

of

competition

G.

fortis

is

Daphne

Major

of

Peter

a

in

than

birds

“one

of

might

birds

taken

and

Major.

feed

G.

on

Grant

diet

the

are

this

small

seeds.

fuliginosa

size

other

(c) G. magnirostris

does

of

a

is

the

for

the

small

island,

seeds,

In

and

(a) G. for tis (large beak). (b) G. for tis (small beak).

on

fuliginosa,

the

almost

though

absence

small

beak

Figure 8 Variation in beak shape in Galápagos nches.

have

Rosemary

fortis,

▲

closely

other

and

On

on

body

nches.

population

Geospiza

larger

from

smaller

the

and

their

into

Darwin’s

and

Geospiza

eat

research

as

Rosemary

been

nch,

species

also

been

did

islands

paucity

had

changes,

focus

nch,

absent.

intense

one

Daphne

ground

species

and

has

between

that

are

sizes

as

Galapagos

original

characters

when

research

medium

island

beak

the

varied,

hypothesized

an

known

Peter

shown

that

There

ends”.

been

become

the

1835

which

nches.

similarities

one

different

as

in

birds,

nches

over

from

Islands

small

observed

the

Darwin

that

for

have

A

of

overall

archipelago,

modied

what

7),

fancy

There

Darwin

beaks

the

of

identied

distribution

gure

this

all.

the

their

really

In

the

specimens

subsequently

shapes

in

visited

collected

seeds,

size

on

islands.

among

there

months

supply

seeds.

1977,

a

drought

on

Daphne

Major

of

of

G.

of

254

larger,

small

harder

seeds,

individuals

are

population

died

seeds,

so

G.

fortis

able

in

to

which

crack

that

year,

the

fed

open.

with

small,

with

El

soft

bred

small

that

seeds,

year,

and

only

they

and

seeds

breeding

37

per

were

in

population.

In

fewer

With

of

G.

1982–83

a

to

fortis

hard

the

return

until

those

eight

increased

large,

reduced

random

1987,

an

response

stopped

a

In

causing

result

greatly

cent

not

a

and

availability.

and

beaks.

event,

as

rapidly,

conditions

of

food

shorter

Niño

rain

in

to

1987.

alive

in

sample

had

dry

supplies

In

1983

of

the

longer

and

a beaks

than

the

1983

averages,

correlating

instead with

on

heavy

fortis

narrower shortage

severe

weather

bred

caused

a

increase

1983 In

individuals

was

the

reduction

in

supply

of

small

seeds.

larger-beaked

Most

of

highest

the

mortality

Variation

gure

8)

in

is

the

shape

mostly

due

and

to

size

of

genes,

the

beaks

though

the

(see

5 . 2

environment

the

has

variation

Using

and

the

data

breed,

The

the

between

predictions.

by

beak

µm

1983

10

and

µm

and

beak

1987

and

were

to

by

even

was

predicted

6

decrease

120

by

expect

the

by

the

observed

and

increased

of

to

µm.

selection

natural

actually

huge

if

it

had

linked

to

theory

to

have

It

have

followed

1859,

but

have

of

evolution

signicant

selection

changes

natural

the

that

occurring.

been

in

to

is

changes

published

signicant

s E l E c t i o n

objections

natural

caused

to

predicted.

to

was

predicted

decreased

by

width

survived

length

length

One

of

heritability.

close

actually

was

proportion

length

had

very

beak

actually

The

called

that

mean

and

width

is

beak

are

Average

Average

of

in

results

increase

effect.

genes

birds

changes

observed

130

to

heritability

about

the

width

some

due

n A t u r A l

not

is

changes

been

unreasonable

occurred

since

in

the

in

a

Darwin’s

case

occurred

of

that

theory

G.

are

to

species,

fortis,

clearly

selection.

by

µm.

Daa-baed qe: Galápagos nches

When

Peter

nches

there

on

and

the

were

Rosemary

island

breeding

of

Grant

Daphne

began

Major

populations

of

to

in

two

study

the

1973,

G.

fortis

and

Geospiza

scandens.

established

a

breeding

Daphne

Geospiza

island

in

1982,

initially

with

population

just

two

Major

is

100

three

males.

Figure

9

shows

the

m.

G.

magnirostris

and

G.

fortis

on

1997

and

has

an

area

and

of

1

0.34

km

hectare

is

.

100

the

maximum

×

and

females population

densities

of

G.

fortis

numbers

Daphne

1997–2006.

[4]

Major

Table between

[3]

hectares

Calculate

during

of

of

on

minimum

and

population

2

km

100

the

the

2

1

magnirostris

in

species, 2

Geospiza

changes

magnirostris.

2

shows

the

percentages

of

three

types

of

2006.

seed

in

the

Daphne

1500

diets

Major.

of

the

Small

three

seeds

nch

are

species

produced

on

by

22

G. for tis

plant

G. magnirostris

species,

srebmun

echios,

1000

and

Tribulus

medium

large

seeds

seeds,

by

which

the

are

cactus

very

Opuntia

hard,

by

cistoides.

500

3

a)

Outline

the

of

on

nch

diet

of

each

Daphne

of

the

species

Major.

[3]

0

1996

1998

2000

2002

2004

b)

2006

There

was

a

very

severe

drought

on

year

Daphne

▲

Figure 9 Changes in numbers of G. for tis and G. magnirostris

Deduce

between 1996 and 2006

a)

Describe

of

G.

and

the

changes

magnirostris

in

the

between

1997

4

2006.

Compare

the

[2]

changes

in

Figure

G.

population

fortis

between

spee

▲

1997

and

2006

10

fortis

the

during

in

the

2003

diet

the

and

of

the

2004.

nches

drought,

using

table.

[3]

shows

from

an

1973

assigned

the

index

to

of

2006,

value

beak

with

zero

size

the

and

of

adult

size

the

in

sizes

in

of

other G.

data

in

population

1973 b)

how

changed

the 1

Major

years

shown

in

comparison

to

this.

with

Geospiza fortis

Geospiza magnirostris

Geospiza scandens

Yea

1977

1985

1989

2004

1985

1989

2004

1977

1985

1989

2004

sma

75

80

77

80

18

5.9

4.5

85

77

23

17

Medm

10

0.0

5.1

11

0.0

12

26

15

22

70

83

lage

17

19

16

8.2

82

82

69

0.0

0.0

0.0

0.0

T able 2

255

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

c)

1

In

the

beak

0.5

rst

size

severe

of

G.

second

drought,

data

this

in

xedni ezis kaeb

selection

drought,

fortis

it

decreased.

question,

could

the

increased,

cause

in

Using

explain

these

mean

but

how

the

the

natural

changes

in

0

beak

5

The

size

in

intensity

of

the

two

droughts.

natural

selection

[3]

on

Daphne

0.5

Major

was

droughts.

calculated

The

during

calculated

the

values

two

are

called

1

selection

for

beak

differentials.

length

They

during

the

range

second

from

–1.08

drought,

1.5

to 1975

1980

1985

1990

1995

2000

with

year

▲

+0.88

for

beak

length

in

the

rst

drought,

2005

similar

width

and

These

are

selection

depth

and

differentials

overall

beak

for

beak

size.

Figure 10 Relative beak size in G. for tis between

very

large

selection

differentials,

1973 and 2006

compared

The

graph

change

in

shows

mean

correspond

two

beak

with

periods

size,

droughts

of

both

on

very

of

rapid

Suggest

Major.

beak

on a)

State

in

b)

two

mean

Suggest

beak

two

changing

a

periods

size

of

of

reasons

most

most

G.

[2]

mean

when

reasons

size

the

of

of

G.

island

in

other

evolution.

for

natural

fortis

of

calculated

being

Daphne

selection

unusually

on

the

intense

Major.

[2]

change

fortis.

for

rapidly

rapid

values

investigations

which

Daphne

to

beak

there

6

Discuss

of

size

for

is

drought.

few

being

[2]

the

advantages

evolution

over

long

long-term

of

investigations

periods

and

the

reasons

investigations

done.

[3]

nl elecio  ibioic eice

Use theories to explain natural phenomena: the theory of evolution y natural

seletion an explain the development of antiioti resistane in ateria.

Antibiotics

medicine

rst

in

the

a

it

but

antibiotic

of

have

resistance

trends

great

of

been

in

triumphs

When

expected

method

there

following

the

century.

was

permanent

diseases,

The

one

20th

introduced,

offer

of

were

they

that

they

were

would

controlling

bacterial

increasing

problems

pathogenic

have

development

of

become

an

of

the

of

develops

what

established:

is

antibiotic

evolution.

theory

understanding

of

bacteria.

example

terms

of

of

very

should

of

It

can

natural

how

useful

be

resistance

be

done

it

to

therefore

explained

selection.

antibiotic

as

is

A

in

scientic

resistance

gives

an

reduce

understanding

the

problem.

16

14 ●

After

an

antibiotic

patients,

●

a

bacteria

few

Resistance

and

more

to

introduced

showing

and

resistance

used

on

12

appear tnatsiser %

within

is

years.

the

antibiotic

species

of

spreads

pathogenic

to

more

bacteria.

10

8

6

4

●

In

each

species

the

proportion

of

infections

2

that

are

caused

by

a

resistant

strain

increases.

bacteria.

▲

The

Figure 11 Percentage resistance to ciprooxacin between

1990 and 2004

4002

3002

2002

there

antibiotic

of

1002

populations

0002

the

9991

of

diseases

in

8991

properties

bacterial

changes

7991

treat

6991

cumulative

5991

used

been

antibiotics

4991

been

have

which

3991

to

over

2991

time

have

resistance

256

the

1991

during

0991

0

So,

5 . 2

n A t u r A l

s E l E c t i o n

aibioic eice

Evolution of antiioti resistane in ateria.

Antibiotic

resistance

is

due

to

genes

in

bacteria

population with no

and

antibiotic-resistant bacteria

so

it

can

be

antibiotic

inherited.

resistance

The

to

mechanism

become

more

that

causes

prevalent

or antibiotic resistance

to

diminish

The

is

summarized

evolution

of

multiple

in

gure

antibiotic resistance

12.

antibiotic

gene received from a

gene formed by

bacterium in another

mutation in one

resistance population

has

occurred

evolution

is

in

just

due

to

a

few

the

decades.

following

This

bacterium

rapid

causes: population with some

antibiotic-resistant bacteria ●

There

has

been

antibiotics,

very

both

for

widespread

treating

use

of

diseases

and

in antibiotic is used therefore

animal

feeds

used

on

farms.

there is strong natural

selection for resistance

●

Bacteria

can

generation

reproduce

time

of

very

less

than

rapidly,

an

with

a

population with more

hour.

antibiotic-resistant bacteria

●

Populations

increasing

of

the

bacteria

chance

are

of

a

often

gene

huge,

for

antibiotic is not used therefore

antibiotic

there is natural selection

resistance

being

formed

by

mutation. (weak) against resistance

●

Bacteria

can

pass

genes

on

to

other

bacteria

in population with slightly

several

ways,

including

using

plasmids,

fewer

which antibiotic-resistant bacteria

allow

one

resistance

species

genes

of

bacteria

from

to

another

gain

antibiotic

species.

▲

Figure 12 Evolution of antibiotic resistance

Daa-baed qe: Chlor tetracycline resistance in soil bacteria

Bacteria

were

distances

collected

from

a

site

on

from

a

soil

pig

at

farm

different

in

3.0

Minnesota 2.5

from

feed

manure

an

had

animal

given

to

pen

the

subtherapeutic

out

rates.

what

and

pigs

low

chlortetracycline,

growth

been

on

this

of

order

of

farm

the

to

bacteria

percentage

to

overow

accumulate.

doses

in

The

allowed

The

contained

antibiotic

promote

were

them

)%( ecnatsised

where

faster

tested

was

to

nd

resistant

2.0

1.5

1.0

0.5

to 0.0

this

antibiotic.

chart.

The

The

yellow

chlortetracycline

results

bars

are

show

resistant

shown

the

in

the

percentage

bacteria

that

bar

5 m

of

grew

20 m

100 m

distance from animal pen

on Source: " The eects of subtherapeutic antibiotic use in farm animals

nutrient-rich

the

medium

percentage

on

a

and

the

orange

nutrient-poor

bars

show

medium

that

on the proliferation and persistence of antibiotic resistance among soil

bacteria", Sudeshna Ghosh and Timothy M LaPara, The International

Society for Microbial cology Journal (2007) 1, 191–203

encouraged

1

a)

different

State

the

types

of

relationship

bacteria

to

between

grow.

percentage 2

antibiotic

resistance

and

distance

from

Predict

whether

resistance animal

pen.

Explain

the

difference

in

between

the

pen

populations

of

and

far

been

antibiotic

lower

from

the

than

at

100

at

200

metres

metres.

[3]

Discuss

the

pen.

use

of

subtherapeutic

doses

of

bacteria antibiotics

near

percentage

have

antibiotic 3

resistance

would

[1] from

b)

the

the

in

animal

feeds.

[2]

[4]

257

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

5.3 caa  bd ey

ueig applicio The inomial system of names for speies is

➔

➔

Classiation of one plant and one animal

universal among iologists and has een agreed speies from domain to speies level. and developed at a series of ongresses. ➔

External reognition features of ryophytes,

When speies are disovered they are given

➔

liinophytes, oniferophytes and sienti names using the inomial system. angiospermophytes.

Taxonomists lassify speies using a hierarhy

➔

➔

Reognition features of porifera, nidaria,

of taxa. platyhelminthes, annelida, mollusa and

➔

All organisms are lassied into three domains.

➔

The prinipal taxa for lassifying eukaryotes are

ar thropoda, hordata.

➔

kingdom, phylum, lass, order, family, genus

Reognition of features of irds, mammals,

amphiians, reptiles and sh.

and speies.

@

In a natural lassiation the genus and

➔

aompanying higher taxa onsist of all the

speies that have evolved from one ommon

➔

anestral speies.

Constrution of dihotomous keys for use in

identifying speimens.

II @

Taxonomists sometimes relassify groups

➔

skill

of speies when new evidene shows that a

previous taxon ontains speies that have

➔

evolved from dierent anestral speies.

ne of ciece

Cooperation and ollaoration etween groups

of sientists: sientists use the inomial Natural lassiations help in identiation

➔

system to identify a speies rather than the of speies and allow the predition of

many dierent loal names. harateristis shared y speies within

a group.

@

Ieiol coopeio  clicio

Cooperation and ollaoration etween groups of sientists: sientists use the

inomial system to identify a speies rather than the many dierent loal names.

Recognizable

biologists

many

as

differ ent

language.

of

plant

has

cows

jack

and

French

258

For

local

to

ca lled

in

bulls,

is

organisms

same

names,

in

even

as

willy

also

a

devils

li ly

and

va riety

known

can

within

England

scientists

pulpit,

are

species

the

Arum

lo rds-and-ladies,

the

there

of

The

ex ample,

known

been

pint,

groups

specie s.

one

species

maculatum

chandel le,

la

Sainte-Vierge,

Spanish

species

de

del

a ngels,

snake’s

meat .

of

name s:

local

la

In

le

there

of

plant

are

de

pilette

e ven

these

other

le

la

de

manteau

vachotte .

names

j ust

vela

name

in

or

more

are

barba

fuego ,

T he

maculatum

in

la

alcatrax,

hoja s

quemado.

Arum

pie d- de-veau,

which

culebra,

menor,

cuckoo-

a nd

to

have

a

arón,

del

for

few:

languages.

but

for

this

one

comida

dragontia

diablo

primaveras

Spanish

de

In

a

is

and

yerba

u sed

for

different

5 . 3

Local

names

culture

of

venture

may

an

so

be

area,

a

valuable

but

scientic

science

names

understood

throughout

system

has

that

cooperation

The

credit

naming

for

is

Linnaeus

who

part

names

the

genius

is

a

still

in

style

many

there

each

was

the

use

of

(used

groups

to

in

anagallis

for

In

the

of

group

το

name,

λενκον

(used

by

of

as

in

and

of

a

was

to

jambu

bol

different

and

by

Fuchs),

(used

jambu

species

of

by

chilli

Eugenia).

of

that

in

that

name

specic

for

name

Ancient

anagallis

Pliny),

Malayan

Malays

(used

mynte

of

used

αδιαυτου

Latin

by

water

mirroring

the

the

and

Seeblumen

and

two-

system

so

Turner)

geel

mynte

of

recognizes

species,

wild

B i o D i v E r s i t Y

scientists.

stroke

been

style

consists

Threophrastus),

This

and

English

(applied

o f

biologist

system

had

The

example

Swedish

a

are

binomial

system

binomial

that

that

The

good

Linnaeus

similar

group

femina

the

the

fact

needed

modern

Seeblumen

the

international

between

century.

before.

a

αδιαυτου

by

18th

today.

species

Greek

to

nomenclature

are

a

introduced

basis

languages

attached

our

given

Carl

in

is

of

an

world.

collaboration

devising

species

are

the

developed

and

part

is

c l A s s i f i c A t i o n

το

μεαυ

mas

German

and

Figure 1 Arum maculatum

▲

weiss

deelopme of he biomil yem

The inomial system of names for speies is universal

among iologists and has een agreed and developed

at a series of ongresses.

To

ensure

that

organisms,

held

for

at

and

International

late

1753

19th

be

plants

150

avec

Botanical

as

fungi

the

to

Linné,

the

as

by

There

same

system

delegates

are

separate

then

the

Species

The

Congresses

The

IBC

starting

this

book

19

vasculaires.”

the

attended

intervals.

century.

kingdom

votes

use

of

from

names

around

congresses

for

the

for

living

world

animals

are

and

fungi.

taken

and

Plantarum,

plant

biologists

congresses

regular

plants

the

all

was

that

gave

that

IBC

(IBC)

in

both

when

consistent

“La

IBC

of

held

in

genera

binomials

Vienna

be

1753)

in

every

1892

in

pour

year

proposed

and

Linnaeus

nomenclature

(ann.

will

were

Genoa

for

year

The

Plantarum

19th

point

the

known.

rule

held

species

published

for

all

1905

Shenzhen,

of

Species

accepted

in

of

the

by

commence

groupes

China,

that

species

botanique

les

during

de

plantes

▲

Figure 2 Linnaea borealis. Binomials

are often chosen to honour a biologist,

or to describe a feature of the

organism. Linnaea borealis is named

2017.

in honour of Carl Linnaeus, the Swedish

The

rst

International

Zoological

Congress

was

held

in

Paris

in

1889. biologist who introduced the binomial

It

was

recognized

classifying

and

subsequent

valid

names

Systema

The

4th

animal

of

Natura

current

edition

scientists

that

internationally

species

congresses.

animal

in

he

rene

there

the

will

needed

1758

species

which

International

and

were

as

gave

Code

no

methods

accepted

was

this

and

doubt

that

for

Zoological

be

they

as

when

binomials

for

these

chosen

was

rules

more

use

for

were

the

agreed

starting

Linnaeus

all

species

in

naming

and

at

date

this

system of nomenclature and named

many plants and animals using it

for

published

known

Nomenclature

editions

for

naming

the

is

then.

the

future

as

species.

259

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

the biomil yem

When speies are disovered they are given sienti

names using the inomial system.

The

the

system

Linnaea

a

borealis

group

is

that

biologists

international

the

of

name

(gure

species

species

or

use

of

a

2).

that

The

share

specic

is

called

species

rst

name

certain

name.

binomial

consists

of

is

nomenclature,

two

the

words.

genus

characteristics.

There

are

various

An

name.

The

rules

because

example

A

genus

second

about

is

is

name

binomial

nomenclature:

●

The

genus

species

●

In

●

After

name

name

typed

a

or

●

The

binomial

to

or

for

text,

a

used

letter

example:

for

an

upper-case

(small)

binomial

been

initial

published

1758

with

lower-case

has

the

name,

earliest

plants

a

printed

abbreviated

species

begins

with

L.

name

animals,

once

of

shown

in

the

letter

and

the

a

in

piece

genus

italics.

of

text,

name

it

with

can

the

be

full

borealis

for

is

is

(capital)

letter.

a

the

species,

correct

from

1753

onwards

for

one.

ALLIGATORIDAE

the hiechy of x

Alligator

-{

mississippiensis

Taxonomists lassify speies using a hierarhy of taxa.

sinensis

The

word

taxa.

Caiman

i

crocodilus

is

of

In

taxon

biology,

classied

the

into

genera

is

Greek

species

a

and

are

genus.

and

means

Genera

species

a

arranged

in

a

are

group

or

of

grouped

family

is

something.

classied

into

into

shown

in

The

taxa.

families.

gure

3.

plural

Every

An

is

species

example

Families

are

latirostris

grouped

yacare

kingdom

taxa

and

Melano-

into

or

from

orders,

domain.

the

larger

orders

level

The

taxa

below.

numbers

of

into

classes

form

Going

species,

a

up

and

on

hierarchy,

the

which

so

up

as

fewer

the

each

hierarchy,

share

to

the

and

level

taxon

taxa

of

includes

include

fewer

larger

features.

niger suchus

Paleo-

suchus

-{

palpebrosus

the hee omi

All organisms are lassied into three domains. trigonatus

Traditional ▲

classication

systems

have

recognized

two

major

categories

Figure 3 Classication of the alligator family

of

organisms

based

classication

have

been

sequence

there

are

of

two

Members

of

the

but

so

the

eukaryotes.

biologists

very

as

eukaryotes

was

groups

of

and

inappropriate

diverse.

RNA

systems

Eubacteria,

of

types:

In

prokaryotes.

because

particular,

determined,

prokaryotes.

it

the

when

became

They

This

prokaryotes

the

base

apparent

were

given

that

the

names

Archaea.

domains,

some

be

distinct

and

organism,

shows

260

to

cell

regarded

ribosomal

classication

called

and

now

found

of

Eubacteria

Most

is

on

all

therefore

Archaea

organisms

features

that

domains

are

Bacteria

and

archaeans

are

now

and

are

can

Eukaryota.

classied

be

usually

used

less

are

well

three

These

into

to

referred

eukaryotes

often

recognize

three

major

categories

domains.

distinguish

to

as

known.

are

Table

between

bacteria,

relatively

categories

archaeans

familiar

to

1

them.

most

5 . 3

c l A s s i f i c A t i o n

feae

o f

B i o D i v E r s i t Y

Dma

Baea

Histones assoiated

Ahaea

Asent

Ekaya

Proteins similar to histones

with DNA

Present

ound to DNA

Presene of introns

Rare or asent

Struture of ell walls

Present in some genes

Made of hemial alled

Not made of peptidoglyan

peptidoglyan

Frequent

Not made of peptidoglyan;

not always present

Cell memrane

Glyerol-ester lipids;

Glyerol-ether lipids;

Glyerol-ester lipids;

dierenes

unranhed side hains;

unranhed side hains; l-form

unranhed side hains;

d-form of glyerol

of glyerol

d-form of glyerol

▲

T able 1

Archaeans

deep

are

ocean

Earth.

with

They

very

are

high

methanogens

of

their

of

termites

Viruses

have

found

in

sediments

also

salt

are

are

range

even

in

oil

responsible

classied

coding

for

in

for

any

proteins

habitats

fairly

or

anaerobes

Methanogens

of

deposits

some

concentrations

obligate

are

not

genes

broad

found

metabolism.

and

a

and

such

below

extreme

the

give

in

the

off

the

close

intestines

three

the

the

of

such

to

of

surface,

of

as

a

The

waste

cattle

and

gas”

in

Although

genetic

code

the

water

boiling.

as

“marsh

domains.

same

ocean

surface

methane

production

using

as

the

habitats

temperatures

and

live

of

far

as

product

the

guts

marshes.

they

living

Ay organisms

they

have

too

few

of

the

characteristics

of

life

to

be

regarded

ideyg a kgdm as

living

organisms.

This is a denition of the

Bacteria

Archaea

Eukaryota

harateristis of organisms in

Green lamentous

one of the kingdoms. Can you Slime

bacteria molds

Spirochetes

dedue whih kingdom it is?

Animals

Gram Methanobacterium Proteobacteria

positives

Fungi

Halophiles

Multicellular; cells typically Methanococcus

Plants

Cyanobacteria

held together by intercellular

Ciliates

junctions; extracellular

Flagellates

matrix with fibrous proteins,

typically collagens, between

two dissimilar epithelia;

sexual with production of an

egg cell that is fer tilized by a

▲

Figure 4 Tree diagram showing relationships between living organisms based on base

smaller, often monociliated,

sequences of ribosomal RNA

sperm cell; phagotrophic and

osmotrophic; without cell wall.

Ekyoe clicio

The prinipal taxa for lassifying eukaryotes are kingdom,

phylum, lass, order, family, genus and speies.

Eukaryotes

into

phyla,

genera.

are

The

phylum,

classied

which

are

hierarchy

class,

order,

into

kingdoms.

divided

of

taxa

family,

into

for

Each

classes,

classifying

genus

and

kingdom

then

orders,

is

divided

families

eukaryotes

is

thus

up

and

kingdom,

species. ▲

Most

biologists

recognize

four

kingdoms

of

eukaryote:

of

the

plants,

animals,

Figure 5 Brown seaweeds have

been classied in the kingdom

Protoctista

fungi

as

and

protoctista.

protoctists

kingdoms.

At

are

very

present

The

last

diverse

there

is

these

and

no

is

should

be

consensus

most

controversial

divided

on

how

up

into

this

more

should

be

done.

261

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

Exmple of clicio

Classiation of one plant and one animal speies from

domain to speies level.

Animals

shows

and

the

kingdom

plants

are

classication

down

to

kingdoms

of

one

of

plant

the

domain

and

one

Eukaryota.

animal

Table

species

2

from

species.

tax

Gey w

Dae pam

Kingdom

Animalia

Plantae

Phylum

Chordata

Angiospermophyta

Class

Mammalia

Monootyledoneae

Order

Carnivora

Palmales

Family

Canidae

Areaeae

Genus

Canis

Phoenix

Speies

lupus

dactylifera

▲

T able 2

Daa-baed qe: Classifying car tilaginous sh

All

the

sh

shown

Chondrichthyes.

found

sh

in

in

gure

They

this

class

are

in

6

are

the

in

most

the

class

1

State

frequently

north-west

in

the

gure

kingdom

6

to

which

all

of

the

species

belong.

[1]

Europe. 2

a)

Four

the

of

the

same

sh

in

genus.

gure

Deduce

6

are

classied

which

these

are.

b)

c)

[1]

Deduce

with

sh

in:

are

whether

these

four

same

or

different

species

[2]

(ii)

the

same

or

different

families.

[2]

State

The

sh

two

that

characteristics

are

of

possessed

these

by

the

four

other

[2]

four

sh

Deduce,

are

not

sh.

other

orders.

Figure 6 Car tilaginous sh in seas in nor th-west Europe

reason

the

four

▲

a

(i)

sh

3

in

sh

split

are

with

into

a

two

classied

reason,

into

how

two

the

four

orders.

[2]

nl clicio

In a natural lassiation, the genus and aompanying higher taxa onsist of all the

speies that have evolved from one ommon anestral speies.

Scientic

that

evolved.

of

a

closely

of

the

of

a

or

is

common

natural

to

this

higher

This

is

follows

Following

genus

ancestor.

262

consensus

most

the

a

in

should

natural

ancestry

to

species

way

convention,

taxon

called

group

classify

we

share

can

in

a

which

all

have

way

species

members

a

common

classication.

expect

many

the

Because

members

characteristics.

An

example

classication

and

all

insects

y.

and

as

differ

to

in

unnatural

be

one

grouped

evolved

do

many

classify

an

would

are

Flight

they

of

not

them

separately

It

articial

which

together,

share

ways.

or

in

a

together

in

these

common

would

not

other

birds,

because

groups

ancestor

be

than

bats

they

they

appropriate

to

place

them

5 . 3

all

in

in

the

the

one

time

they

an

animal

phylum

classied

have

It

cell

articial

separately

are

is

no

share

can

a

be

and

do

classication

to

clear

common

move,

cell

which

other

so

of

natural

Convergent

but

this

walls

than

distantly

bats

were

at

because

shows

groups

and

fungi

presumably

their

each

birds

and

research

ancestor,

problematic.

both

not

as

molecular

similar

always

and

Plants

together,

walls

and

more

not

kingdom

Chordata.

c l A s s i f i c A t i o n

to

organisms

adaptive

visible

of

some

in

sub-topic

was

have

signicant

groups.

More

can

supercially

make

different.

In

attempted

characteristics

methods

caused

appear

radiation

appear

classication

many

have

animals.

species

related

molecular

they

B i o D i v E r s i t Y

organisms

and

as

evolved

that

related

similar

natural

is

o f

been

as

by

possible,

of

to

the

this

past,

looking

introduced

changes

details

closely

the

but

and

at

new

these

classication

are

given

later,

do 5.4.

classication

evolution

can

make

TOK

Wha a ee he deepme  a e e?

Carl Linnaeus’s 1753 ook Species Plantarum introdued

genera and speies. This was inorporated in the Amerian

onsistent two-part names (inomials) for all speies of

“Rohester Code” of 1883 and in the ode used at the Berlin

the vegetale kingdom then known. Thus the inomial

Botanihes Museum and supported y British Museum of

Physalis angulata replaed the osolete phrase-name,

Natural History, Harvard University otanists and a group

Physalis annua ramosissima, ramis angulosis glabris,

of Swiss and Belgian otanists. The International Botanial

foliis dentato-serratis. Linnaeus rought the sienti

Congress of Vienna in 1905 aepted y 150 votes to 19

nomenlature of plants ak to the simpliity and revity

the rule that “La nomenlature otanique ommene ave

of the vernaular nomenlature out of whih it had grown.

Linné, Speies Plantarum (ann. 1753) pour les groupes de

Folk-names for speies rarely exeed three words. In

plantes vasulaires.”

groups of speies alike enough to have a vernaular 1

Why was Linnaeus’s system for naming plants adopted

group-name, the speies are often distinguished y a as the international system, rather than any other

single name attahed to the group-name, as in the Anient system?

Greek αδιαυτου το λενκον and αδιαυτου το µεαυ

2

Why do the international rules of nomenlature state

(used y Threophrastus), Latin anagallis mas and anagallis

that genus and speies names must e in Anient femina (used y Pliny), German weiss Seelumen and geel

Greek or Latin? Seelumen (used y Fuhs), English wild mynte and water

3

mynte (used y Turner) and Malayan jamu ol and jamu

Making deisions y voting is rather unusual in siene.

Why is it done at International Botanial Congresses?

hilli (applied y Malays to dierent speies of Eugenia).

What knowledge issues are assoiated with this The International Botanial Congress held in Genoa in 1892

method of deision making? proposed that 1753 e taken as the starting point for oth

reiewig clicio

Taxonomists sometimes relassify groups of speies

when new evidene shows that a previous taxon ontains

speies that have evolved from dierent anestral speies.

Sometimes

common

closely

from

The

one

related,

genus

species.

assigned

been

to

much

family.

so

species

to

classication

other

this

evidence

ancestor,

Conversely

be

new

so

two

or

another

of

in

all

should

taxa

the

of

a

up

are

more

group

into

if

any,

of

the

great

apes

were

two

or

not

or

species

share

more

found

are

a

taxa.

to

moved

taxa.

controversy

procedures,

family

do

sometimes

united,

higher

caused

and

split

taxa

are

taxonomic

which,

the

be

between

Primates

Originally

members

different

has

standard

about

that

more

or

humans

order

debate

group

classied

Using

the

the

shows

humans

Hominidae.

great

placed

than

apes

in

any

are

There

to

has

include

another

in

family,

263

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

the

Pongidae,

are

closer

same

if

research

This

also

classication

that

and

be

in

is

than

would

suggests

humans

should

but

humans

family.

evidence

so

to

has

to

just

shown

leave

separate

shown

in

are

FAMILY

are

so

closer

placed

genus.

gure

chimpanzees

and

orang-utans

chimpanzees

chimpanzees

a

that

orang-utans

A

in

should

in

the

than

of

gorillas

in

the

Pongidae.

gorillas

different

summary

and

be

to

genera,

this

Most

humans,

gorillas

scheme

for

human

7.

Hominidae

Pongidae

LJ GENUS AND

SPECIES

▲

Gorilla

Homo

Pan

Pan

Pongo

gorilla

sapiens

troglodytes

paniscus

pygmaeus

(gorilla)

(human)

(chimpanzee)

(bonobo)

(orang-utan)

Figure 7 Classication of humans

age of l clicio

Natural lassiations help in identiation of speies

and allow the predition of harateristis shared y

speies within a group.

There

is

great

of

biologists

to

nd

new

out

1

in

are

identied ▲

species

Identication

and

the

it

into

of

is

by

moment

areas

are

sometimes

research

found

at

surveying

what

species

helpful

interest

are

present.

species

is

Even

assigning

it

It

If

what

rst

to

biodiversity

research

in

a

the

specic

specimen

it

is,

kingdom,

world.

been

done

parts

classication

two

species

its

of

has

well-known

Natural

has

easier.

obvious

the

little

discovered.

biodiversity.

not

in

where

of

of

Groups

before,

the

world

species

is

very

advantages.

of

the

an

organism

specimen

then

the

is

can

phylum

be

within

Figure 8 Members of the Hominidae

the

kingdom,

class

within

the

phylum

and

so

on

down

to

species

and Pongidae

level.

Dichotomous

process

Ay

would

example,

colour

cg pa bgh

was

if

not

keys

work

owering

and

a

can

so

be

used

to

well

with

an

plants

were

white-owered

discovered,

it

would

not

with

articial

classied

bluebell

be

help

this

This

classication.

according

Hyacinthoides

identied

process.

to

For

ower

non-scripta

correctly

as

the

species

Phytophthora infestans, the normally

has

blue

owers.

organism that auses the disease

potato light, has hyphae and

was lassied as a fungus, ut

moleular iology has shown that it

is not a true fungus and should e

lassied in a dierent kingdom,

possily the Prototista. Potato

light has proved to e a diult

disease to ontrol using fungiides.

Disuss reasons for this.

2

Because

have

of

the

within

is

a

found

to

be

was

in

mammary

bats

For

mammalian

were

a

a

that

if

in

a

features.

in

this

related

a

is

of

these

with

all

useful

the

bat

about

heart

predictions

other

ying

a

species

drug

are

species

will

similar

of

as

chemicals

new

predictions

correct:

inherit

characteristics

that

If

classication

they

four-chambered

None

articially

or

natural

the

genus.

many

are

a

of

a

species,

chemical

the

make

they

placenta,

classied

group

genus,

species

could

certainty

glands,

in

a

ancestral

prediction

example,

plant

we

of

common

allows

other

discovered,

reasonable

if

one

in

a

This

group.

found

members

from

characteristics.

other

264

all

evolved

it

of

with

have

and

likely

bat

hair,

many

could

be

made

organisms.

5 . 3

c l A s s i f i c A t i o n

o f

B i o D i v E r s i t Y

dichoomo key

Constrution of dihotomous keys for use in identifying speimens

Dichotomous

keys

are

often

constructed

to

use

for

1

identifying

species

within

a

group.

A

Fore and hind lims visile, an emerge on land

Only fore lims visile, annot live on land is

a

division

into

two;

a

dichotomous

key

a

of

these

the

numbered

series

should

other

of

clearly

should

pairs

of

match

clearly

be

descriptions.

the

species

wrong.

The

the

designer

of

the

key

chooses

to

Fore and hind lims have paws

..................................... 3

One

and

Fore and hind lims have ippers

................................. 4

features

3

that

use

in

Fur is dark ............................................................

visible.

should

Each

of

to

another

of

in

the

or

key,

the

the

to

therefore

pair

of

reliable

descriptions

numbered

an

be

pairs

of

and

leads

example

of

a

polar ears

easily

4

either

descriptions

External ear ap visile ...........

No external ear ap

sea lions and fur seals

........................................................... 5

identication.

5

An

key

is

shown

in

table

3.

We

Two long tusks

.....................................................

it

to

identify

the

species

in

gure

9.

In

the

of

visible.

6

of

has

key,

They

the

a

the

key.

are

We

blowhole.

we

must

not,

so

must

It

decide

we

now

does

are

if

directed

decide

not,

so

hind

it

if

is

a

limbs

to

the

Mouth reathing, no lowhole

...

dugongs and manatees

are

Breathing through lowholes

stage

species

dugong

true seals

rst

6 stage

walruses

can

No tusks ...............................................................

use

sea otters

the

Fur is white ........................................................ descriptions

................ 6

consists

2 of

..... 2

dichotomy

or

7

......................................... 7

Two lowholes, no teeth .........................

aleen whales

a

One lowhole, teeth ........ dolphins, porpoises and whales manatee.

to

A

separate

fuller

key

dugongs

would

and

have

another

stage

▲

manatees.

T able 3 Key to groups of marine mammals

Ay

cg dhm key

Keys are usually designed for use in a par tiular area. All the groups or speies

that are found in that area an e identied using the key. There may e a

group of organisms in your area for whih a key has never een designed.

●

You ould design a key to the trees in the loal forest or on your shool

ampus, using leaf desriptions or ark desriptions.

●

You ould design a key to irds that visit ird-feeding stations in your area.

●

You ould design a key to the inver terates that are assoiated with one

par tiular plant speies.

●

You ould design a key to the footprints of mammals and irds (gure 10). ▲

Figure 9 Manatee

They are all right front footprints and are not shown to sale.

~ ~ 0 ~ bear

wolf

Y O duck

▲

rabbit / hare

fox

t

squirrel

cat

Q dog

~~ t deer

heron

Figure 10 Footprints of mammals and birds

265

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

Pl

External reognition features of ryophytes, liinophytes, oniferophytes

and angiospermophytes.

All

In

plants

the

life

gametes

formed

which

of

classied

cycle

are

of

it

The

and

into

embryo

is.

together

every

formed

develops

this

plant

into

are

plant,

fuse

an

in

different

The

depends

types

of

example

kingdom.

and

together.

embryo.

develops

one

male

The

way

on

main

female

one

phyla

of

the

smaller

phyla.

The

four

are:

●

Bryophyta

●

Filicinophyta

●

Coniferophyta

●

Angiospermophyta

–

mosses,

liverworts

and

hornworts

in

type

are

–

ferns

put –

conifers

phyla.

Most

plants

are

in

one

of

four

phyla,

but

other

smaller

phyla.

The

Ginkgo

–

owering

plants.

there

The are

in

zygote

the

plants

is

plant

biloba

tree

are

Byphya

Vegetative organs – par ts

Rhizoids ut no

of the plant onerned

true roots. Some

with growth rather than

with simple stems

reprodution

and leaves; others

external

recognition

features

of

these

phyla

for

shown

fphya

in

table

4.

cephya

Agpemphya

Roots, stems and leaves are usually present

have only a thallus

Vasular tissue – tissues

No xylem or

with tuular strutures used

phloem

Xylem and phloem are oth present

for transpor t within the plant

Camium – ells etween

No amium; no true trees and

Present in onifers and most angiosperms,

xylem and phloem that

shrus

allowing seondary thikening of stems and

an produe more of these

roots and development of plants into trees

tissues

and shrus

Pollen – small strutures

Pollen is not produed

ontaining male gametes

Pollen is produed

Pollen is produed

in male ones

y anthers in

that are dispersed

Ovules – ontains a female

owers

No ovaries or ovules

gamete and develops into a

seed after fer tilization

Seeds – dispersile unit

Ovules are produed

Ovules are enlosed

in female ones

inside ovaries in

owers

No seeds

Seeds are produed and dispersed

onsisting of an emryo

plant and food reserves,

inside a seed oat

Fruits – seeds together with

No fruits

Fruits produed for

a fruit wall developed from

dispersal of seeds

the ovary wall

y mehanial, wind

or animal methods

▲

266

T able 4

5 . 3

c l A s s i f i c A t i o n

o f

B i o D i v E r s i t Y

aiml phyl

Reognition features of porifera, nidaria, platyhelminthes, annelida, mollusa and

ar thropoda, hordata.

Animals

table

5.

are

Two

divided

up

examples

into

of

over

each

Phym

30

are

phyla,

shown

Mh/a

based

in

on

gure

their

characteristics.

Six

phyla

are

featured

in

11.

symmey

skee

ohe ex ea

eg eae

Porifera – fan sponges,

No mouth or

up sponges, tue

anus

None

Internal spiules

Many pores over the surfae

(sketetal needles)

through whih water is drawn

sponges, glass sponges

in for lter feeding. Very varied

shapes

Soft, ut hard

Tentales arranged in rings

jellysh, orals, sea

orals serete

around the mouth, with stinging

anemones

CaCO

ells. Polyps or medusae

Cnidaria – hydras,

Mouth only

Radial

3

(jellysh)

Platyhelminthes –

Mouth only

Bilateral

atworms, ukes,

Soft, with no

Flat and thin odies in the shape

skeleton

of a rion. No lood system or

tapeworms

system for gas exhange

Mollusa – ivalves,

Mouth and

gastropods, snails,

anus

Bilateral

Most have shell

A fold in the ody wall alled

made of CaCO

the mantle seretes the shell. A

3

hard rasping radula is used for

hitons, squid, otopus

feeding

Annelida – marine

Mouth and

ristleworms,

anus

Bilateral

oligohaetes, leehes

Internal avity

Bodies made up of many ring-

with uid under

shaped segments, often with

pressure

ristles. Blood vessels often

visile

Ar thropoda – insets,

Mouth and

arahnids, rustaeans,

anus

Bilateral

myriapods

▲

1

Segmented odies and legs or

other appendages with joints

hitin

etween the setions

T able 5 Characteristics of six animal phyla

Study

and

2

External skeleton

made of plates of

List

the

organisms

assign

the

each

one

organisms

a)

bilaterally

b)

radially

shown

to

that

its

in

gure

11

phylum.

3

List

the

organisms

not

symmetric

symmetric

symmetrical

in

have:

a)

jointed

b)

stinging

appendages

c)

bristles.

are:

4

List

the

their

structure.

tentacles

[3]

organisms

pumping c)

that

[7]

water

that

lter

through

feed

tubes

by

inside

[3]

their

bodies.

[2]

267

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

veebe

Reognition of features of irds, mammals, amphiians,

reptiles and sh.

Most

Adocia cinerea

species

of

chordate

belong

to

one

of

ve

major

classes,

each

of

Alcyonium glomeratum

which

are

not

are

about

5,700

bony

ve

Nymphon gracilis

Pycnogonum littorale

contains

are

certain

more

and

10,000

mammals.

sh,

with

largest

vertebrates,

(

new

bird

All

of

a

species

these

than

because

are

9,000

30,000

they

are

species.

still

classes

chordate

T By ay-

thousand

species,

of

more

classes

than

sometimes

reptiles,

are

species.

a

repe

r

numbers

amphibians

by

the

recognition

table

backbone

1 Amphba

6,000

The

in

the

discovered,

outnumbered

shown

have

Although

6.

All

of

composed

there

and

ray-nned

features

the

of

of

the

organisms

vertebrae.

l

I Bd

Mamma

ed h

-Lepidonotus clara

Corynactis viridis

Sales whih

Soft moist

Impermeale

Skin with

Skin has

are ony

skin

skin overed

feathers made

folliles with

plates in the

permeale

in sales of

of keratin

hair made of

skin

to water and

keratin

keratin

gases

-

~

Polymastia mammiliaris

Cyanea capillata

Gills overed

Simple lungs

Lungs with

Lungs with

Lungs with

y an

with small

extensive

para-ronhial

alveoli,

operulum,

folds and

folding to

tues,

ventilated

with one gill

moist skin for

inrease the

ventilated

using

slit

gas exhange

surfae area

using air sas

ris and a

-

diaphragm

' No lims

Tetrapods with pentadatyl lims

'-Fins

Four legs

suppor ted y

when adult

I

Four legs (in

I

Two legs and

I

Four legs in

Procerodes littoralis

most speies)

two wings

rays

most (or two

legs and two

wings/arms)

I Loligo forbesii

MIIIJ?frsu . . . / Arenicola marina

Eggs and sperm released for

Sperm passed into the female for internal

external fer tilization

fer tilization

Remain

Larval stage

Female lays

Female lays

Most give

in water

that lives in

eggs with soft

eggs with hard

ir th to live

throughout

water and

shells

shells

young and

their life yle

adult that

all feed

usually lives

young with

on land

milk from

~

mammary

Prostheceraeus vittatus

~

glands ~

Swim ladder

Eggs oated

Teeth all of

Beak ut no

Teeth of

ontaining gas

in protetive

one type, with

teeth

dierent

for uoyany

jelly

no living par ts

Caprella linearis

types with a

living ore

Do not maintain onstant ody temperature

Gammarus locusta

▲

Figure 11 Inver tebrate diversity

268

I

' ▲

Maintain onstant ody

T able 6

temperature

_I

5 . 4

c l A D i s t i c s

5.4 cad

ueig applicio ➔

A lade is a group of organisms that have Cladograms inluding humans and other

➔

evolved from a ommon anestor. primates.

➔

Evidene for whih speies are par t of a lade Relassiation of the gwor t family using

➔

an e otained from the ase sequenes evidene from ladistis. of a gene or the orresponding amino aid

sequene of a protein.

➔

skill

Sequene dierenes aumulate gradually

so there is a positive orrelation etween the

Analysis of ladograms to dedue evolutionary

➔

numer of dierenes etween two speies

relationships.

and the time sine they diverged from a

ommon anestor.

ne of ciece ➔

Traits an e analogous or homologous.

➔

Cladograms are tree diagrams that show the

Falsiation of theories with one theory eing

➔

superseded y another: plant families have most proale sequene of divergene in

een relassied as a result of evidene from lades.

ladistis. ➔

Evidene from ladistis has shown that

lassiations of some groups ased

on struture did not orrespond with the

evolutionary origins of a group of speies.

Cle

A lade is a group of organisms that have evolved from

a ommon anestor.

Species

can

happened

there

are

ancestor.

evolve

now

a

Clades

very

include

a

They

ten

member

can

with

the

and

be

just

thousand

common

been

group

all

species

small

about

of

and

some

groups

groups

A

time

with

of

split

species

species

of

to

highly

can

organisms

form

new

successful

all

be

derived

from

identied

evolved

species.

species,

by

from

a

a

This

so

has

that

common

looking

for

common

shared

ancestor

is

clade.

ancestral

extinct.

large

These

characteristics.

called

over

repeatedly

of

other

ancestral

a

clade

species

species

any

very

a

large

few.

living

For

that

and

The

clade

together

evolved

include

example,

evolved

this

today,

that

species

species.

in

alive

species

all

270

are

form

they

Ginkgo

about

but

it

million

now

of

one

have

biloba

the

and

thousands

birds

because

tree

with

from

is

all

became

species,

large

only

ago.

or

clade

evolved

the

years

common

then

with

from

living

There

have

extinct.

269

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

Ay

the EDGE  Exee pje

The aim of this projet is to identify animal speies

threatened or have lose relatives. In some ases speies

that have few or no lose relatives and are therefore

are the last memers of a lade that has existed for tens

memers of very small lades. The onservation status

or hundreds of millions of years and it would e tragi for

of these speies is then assessed. Lists are prepared of

them to eome extint as a result of human ativities.

speies that are oth Evolutionarily Distint and Gloally What speies on EDGE lists are in your par t of the world

Endangered, hene the name of the projet. Speies and what an you do to help onserve them?

on these lists an then e targeted for more intense

http://www.edgeofexistene.org/speies/ onservation eor ts than other speies that are either not

▲

Figure 1 Two species on the EDGE list: Loris tardigradus tardigradus (Hor ton Plains slender loris) from Sri Lanka and Bradypus

pygmaeus (Pygmy three-toed sloth) from Isla Escudo de Veraguas, a small island o the coast of Panama

Ieifyig membe of  cle

Evidene for whih speies are par t of a lade an e

otained from the ase sequenes of a gene or the

orresponding amino aid sequene of a protein.

It

is

not

always

ancestor

The

and

most

amino

objective

acid

ancestor

270

to

evidence

from

have

of

expected

Conversely,

diverged

likely

be

which

therefore

sequences

can

sequence.

but

obvious

should

a

many

species

be

comes

proteins.

to

have

species

common

have

included

from

sequences

that

look

tens

of

from

a

common

clade.

have

differences

might

ancestor

differences.

a

base

Species

few

that

evolved

in

in

a

of

base

similar

genes

recent

in

millions

or

amino

certain

of

or

common

years

acid

respects

ago

are

5 . 4

c l A D i s t i c s

Molecl clock

Sequene dierenes aumulate gradually so there is

a positive orrelation etween the numer of dierenes

etween two speies and the time sine they diverged

from a ommon anestor.

Differences

acid

gradually

occur

clock.

long

For

in

the

sequence

at

over

a

long

species

four

sequence

are

periods

of

split

a

mitochondrial

related

primates

DNA

result

time.

rate

so

differences

from

of

the

of

constant

number

example,

and

base

proteins

roughly

The

ago

of

DNA

evidence

be

used

can

the

that

as

be

in

They

a

amino

accumulate

mutations

molecular

used

to

deduce

how

ancestor.

from

been

is

can

sequence

common

has

therefore

mutations.

There

they

in

and

of

three

humans

European

completely

Japanese

sequenced.

From

hypothetical

in

gure

2.

the

ancestry

Using

differences

has

been

differences

in

base

sequence,

constructed.

in

base

It

is

sequence

a

shown

as

African

a

Common chimpanzee

molecular

between

clock,

groups

●

70,000

●

140,000

●

5,000,000

these

have

years

ago,

years

been

dates

for

splits

deduced:

Pygmy chimpanzee (bonobo)

European–Japanese

ago,

years

approximate

split

Gorilla

African–European/Japanese

ago,

human–chimpanzee

split

split

▲

Figure 2

alogo  homologo i

Traits an e analogous or homologous.

Similarities

between

Homologous

●

example

the

Analogous

●

human

Problems

in

structures

For

this

and

but

reason

rarely

base

or

the

they

are

wing,

are

are

used

amino

acid

similar

eye

led

to

identifying

sequences

arm

homologous

of

and

because

of

similar

other

because

they

(form

and

trusted

in

in

and

a

clade

for

forelimbs.

evolution.

structure

The

and

independently.

analogous

classication

structure)

of

analogous.

ancestry;

evolved

homologous

mistakes

or

pentadactyl

convergent

similarities

members

is

be

because

show

between

morphology

for

either

human

analogous

sometimes

the

can

similar

octopus

distinguishing

have

now

structures

chicken

structures

eye

function

organisms

of

and

in

the

past.

organisms

evidence

is

from

more.

cornea

iris

lens

retina

photoreceptors

optic nerve

▲

Figure 3 The human eye (left) and the octopus eye (right) are analogous because they are

quite similar yet evolved independently

271

5

E v o l u t i o n

a n d

b i o d i v E r s i t y

sruasonid

sdrib

naiva-non

sdrazil

sekans

seltrut

selidocorc

Clogm

Cladograms are tree diagrams that show the most

proale sequene of divergene in lades.

ancestral species A

A

cladogram

is

a

tree

diagram

based

on

similarities

and

differences

between

ancestral species B

the

or

species

amino

in

a

acid

clade.

Cladograms

sequences.

are

Computer

almost

always

programs

have

now

based

been

on

base

developed

that

ancestral species C

calculate

number ▲

how

of

species

changes

in

of

a

clade

base

or

could

amino

have

acid

evolved

with

sequence.

the

This

is

smallest

known

as

the

Figure 4 A cladogram showing the

principle

of

parsimony

and

although

it

does

not

prove

how

a

clade

actually

hypothesized relationship between birds and

evolved,

it

can

indicate

the

most

probable

sequence

of

divergence

in

clades.

the traditional taxonomic group “the reptiles”

The

branching

branch

off

at

points

a

node

on

but

cladograms

sometimes

are

called

there

are

nodes.

three

or

Usually

more.

two

The

clades

node

Ay represents

Figure 5 shows an ar tist’s impression

species.

of two pterosaurs, whih were the rst

base

a

hypothetical

Option

B

sequences

ancestral

includes

using

species

instructions

computer

for

that

split

to

form

constructing

two

or

cladograms

more

from

software.

hordates to develop powered ight. Figure

4

is

an

example

of

a

cladogram

for

birds

and

reptiles.

It

has

been

They were neither irds nor dinosaurs. based

on

morphology,

so

that

extinct

groups

can

be

included.

Where might pterosaurs have tted

into the ladogram shown in gure 4?

●

●

Birds,

non-avian

called

dinosauria.

Birds,

non-avian

part

a

Lizards,

●

This

or

clade

reptiles

are

and

either

be

closely

ancestral

crocodiles

species

and

A

form

ancestral

a

clade

species

B

species

that

divided

related

birds

into

to

C

should

two

birds

form

or

than

a

clade

be

more

to

called

regarded

groups,

other

squamates.

as

as

reptiles

some

reptiles.

Figure 5 Two pterosaurs in ight

Pime clogm

Cladograms inluding humans and 45,000

4.5 Myr ago

other primates.

The

closest

and

bonobos.

species

has

evidence

(gure

relatives

been

for

6).

estimates

The

the

The

of

of

humans

entire

sequenced

population

splits

occurred.

clock

with

These

on

sizes

are

of

the

a

these

very

cladogram

dates

on

a

Figure

7

is

mutation

rate

a

cladogram

for

of

10

are

when

27,000

molecular

–9

a

three

strong

cladogram

and

based

chimpanzees

of

giving

construction

numbers

are

genome

1 Myr ago

–1

yr

primates

and

the

most 12,000

closely

are

for

an

related

order

climbing

gibbons

272

and

other

of

groups

mammals

trees.

that

Humans,

lemurs

are

of

mammal.

have

primates.

Primates

adaptations

monkeys,

baboons,

are

archosaurs.

ancestral

suggests

should

more

and

dinosaurs,

called

snakes

cladogram

that

reptiles

▲

of

dinosaurs

Bonobo

▲

Figure 6

Chimpanzee

Human

5 . 4

c l A D i s t i c s

Cavies and Coypu

alyi of clogm

Porcupines

Mice and Rats

Analysis of ladograms to dedue evolutionary Beavers

relationships. Chipmunks

The

pattern

of

branching

in

a

cladogram

is

assumed

to

match

the Rabbits

evolutionary

origins

of

each

species.

The

sequence

of

splits

at

nodes

is Primates

therefore

a

diverged.

If

hypothetical

sequence

in

which

ancestors

of

existing

clades Treeshrews

two

clades

on

a

cladogram

are

linked

at

a

node,

they

are

Figure 7

▲

relatively

of

nodes,

Some

in

related.

are

cladograms

base

are

closely

they

or

amino

assumed

to

less

If

include

acid

occur

two

closely

species

numbers

sequence

at

a

are

only

connected

via

a

series

related.

or

to

in

relatively

indicate

genes.

numbers

Because

constant

rate,

of

genetic

these

Ay

differences

changes

numbers

A adgam  he gea ape

can

The great apes are a family of be

used

to

estimate

how

long

ago

two

clades

diverged.

This

method

primates. The taxonomi name is of

estimating

times

is

called

a

molecular

clock.

Some

cladograms

Hominidae. There are ve speies are

drawn

to

scale

according

to

estimates

of

how

long

ago

each

split

on Ear th today, all of whih are occurred.

dereasing in numer apar t from

Although

cladograms

history

a

of

group,

constructed

of

on

mutations

sequence

and

using

the

to

of

be

different

cannot

to

were

in

versions

the

for

for

proof.

smallest

base

or

is

convoluted.

of

cladograms

been

the

produced

humans. Figure 6 is a ladogram

evolutionary

Cladograms

possible

assumption

more

have

as

current

this

analysis

that

evidence

regarded

that

account

evolution

strong

be

Sometimes

cautious

several

provide

assumption

occurred

pathways

compare

they

differences.

important

can

for three of the speies. Use

are

this information to expand the

number

amino

ladogram to inlude all the great

acid

apes: the split etween humans

incorrect

It

is

and

and gorillas ourred aout

therefore

where

10 million years ago and the split

possible

etween humans and orang-

independently

utans aout 15 million years ago.

genes.

Daa-baed qe: Origins of tur tles and lizards

Cladograms

based

on

morphology

the

suggest

short-tailed

opossum

or

to

the

duck-billed

platypus. that

this

turtles

and

hypothesis,

compared

for

lizards

are

not

microRNA

nine

species

a

clade.

genes

of

To

have

been

chordate.

2

Calculate

found

The

but results

were

gure8.

which

used

The

to

construct

numbers

microRNA

on

genes

the

are

the

cladogram

cladogram

shared

by

a

clade

example,

humans

but

not

there

and

members

are

six

short-tailed

of

other

show

3

microRNA

opossums

genes

but

not

Discuss

other

chordates

on

the

the

Deduce,

whether

using

evidence

humans

are

microRNA

clade

on

genes

the

are

cladogram

clades.

the

supports

any

in

of

4

Evaluate

tetrapod

are

not

the

evidence

the

a

[2]

in

the

hypothesis

that

turtles

clade.

traditional

chordates

[3]

and

into

mammals

classication

amphibians,

using

evidence

of

reptiles,

from

the

cladogram.

cladogram.

1

other

whether

lizards

birds the

in

many

mammal

For

found

in

not

how

the

cladogram

members

clades.

in

in

and of

[2]

test

from

more

the

[3]

cladogram,

closely

related

to

273

5

E v o l u t i o n

a n d

African clawed frog

b i o d i v E r s i t y

fE 043

176

167

588

Human

Short-tailed opossum

681

095

378

3

15 2 1

79 3 1

6

Duck-billed platypus

1971

1541

0641

7641

9551

7651

1461

9661

9271

3471

4471

6571

9571

1871

4871

9871

3081

1312

1

4592

4692

094

7931

19

Zebra nch

Chicken

Alligator

7761

1

Painted turtle

▲

0935

1935

2935

3935

4

Lizard

Figure 8

Clogm  eclicio

Evidene from ladistis has shown that lassiations of

some groups ased on struture did not orrespond with

the evolutionary origins of a group of speies.

The

construction

only

the

became

sequence

been

data

developed

identication

Cladistics

has

classication.

classication

evolutionary

been

of

group

and

to

truly

to

274

is

is

from

groups

groups

cases

and

The

as

of

and

20th

amino

acid

century.

computer

of

sequences

Before

software

construction

in

plant

cladograms

does

not

species.

have

species

base

the

had

that

not

cladograms

and

cladistics.

morphology

of

of

revolutions

clear

Some

some

analysis.

known

on

end

available

some

on

origins

of

groups

disruptive

natural

have

some

be

the

now

classications

They

not

based

the

have

animal

traditional

always

As

been

and

that

a

merged,

been

match

result

some

others

transferred

the

groups

have

from

have

been

one

another.

potentially

also

do

based

in

towards

clades

caused

It

Reclassication

new

cladograms

was

to

reclassied.

divided

a

of

possible

based

of

some

signicant

organisms

biologists,

on

classication

revealed

similar.

for

cladistics

so

their

unnoticed

differences

is

but

it

are

time-consuming

is

certainly

likely

predictive

be

value

similarities

between

to

much

will

between

species

and

worthwhile.

be

closer

higher.

groups

previously

The

to

and

assumed

5 . 4

c l A D i s t i c s

Clogm  flicio

Falsiation of theories with one theory eing

superseded y another: plant families have een

relassied as a result of evidene from ladistis.

The

is

a

reclassication

good

theories

and

theories.

on

their

Laurent

revised

example

of

The

of

of

on

replacement

Jussieu

repeatedly

was

in

the

important

classication

morphology

de

plants

an

of

of

Genera

of

theories

discoveries

in

science:

found

to

be

angiospermophytes

begun

during

basis

process

by

the

French

plantarum ,

the

19th

false

into

in

cladistics

testing

with

of

new

families

botanist

published

in

the

based

Antoine

1789

and

century.

Clicio of he gwo fmily

Relassiation of the gwor t family using evidene from ladistis.

There

Until

are

more

recently

than

the

Scrophulariaceae,

gwort

family.

proposed

by

It

de

400

eighth

commonly

was

one

Jussieu

in

name

Scrophulariae

and

based

on

in

more

until

similarities

plants

there

5,000

were

were

families

largest

of

1789.

275

as

He

the

gave

families

it

sixteen

family

with

using

the

morphology.

genera,

Taxonomists

evolutionary

the

original

included

their

angiosperms.

known

the

discovered,

over

of

was

the

compared

the

genes

large

in

a

traditionally

As

genera

that

grew

than

in

and

One

base

in

into

the

sequences

to

related

the

of

one

of

three

in

project

chloroplast

genera

Scrophulariaceae

families.

clades

family

research

species

the

gwort

ve

the

gwort

important

assigned

that

investigated

of

number

closely

species

clade

combined

species.

origins

cladistics.

genera,

more

recently

family

had

It

was

were

and

found

not

incorrectly

a

true

been

family.

Two small families were merged

with the gwort family:

the buddleja family, Buddlejaceae

and the myoporum family, Myoporaceae

Two genera were moved to

Nearly fty genera have

a newly-created family,

been moved to the The gwort

the calceolaria family,

plantain family, family

Calceolariaceae

Plantaginaceae Scrophulariaceae

Thirteen genera have

▲

been

About twelve genera of

transferred to a newly-created

parasitic plants have been

family, the lindernia family,

moved to the broomrape

Linderniaceae

family, Orobanchaceae

Figure 9

275

5

E v o l u t i o n

A

major

Less

in

▲

half

family,

largest

b i o d i v E r s i t y

reclassication

than

the

a n d

of

the

which

among

the

has

species

is

now

now

only

angiosperms.

carried

been

the

A

out.

retained

thirty-sixth

summary

of

the

Figure 10 Antirrhinum majus has been transferred from the

gwor t family to the plantain family

276

been

have

changes

has

before

of

is

been

that

species

▲

shown

in

welcomed

the

gure

as

it

9.

was

This

Scrophulariaceae

rather

than

a

reclassication

widely

natural

appreciated

had

been

a

rag-bag

group.

Figure 11 Scrophularia peregrina has remained in the

gwor t family

Q u E s t i o n s

Qeio

The

bar

three

at

charts

in

gure

populations

different

came

from

Rhosneigr

copper

an

in

undersides

of

the

The

that

growth

Ectocarpus

concentrations.

ships

copper-containing

show

alga,

unpolluted

Wales.

of

12

an

One

environment

other

had

two

been

anti-fouling

4

of

siliculosus,

Which

of

copper

tolerance

the

following

to

~

emulov lagla ni esaercni %

0

in

a

are

required

for

population?

population (i)

variation

in

(ii)

inheritance

(iii)

failure

copper

tolerance

at

came

from

painted

the

with

of

copper

tolerance

a of

algae

with

lower

copper

paint. tolerance

500

processes

develop

Rhosneigr

I

I

tITo

a)

i)

only

b)

i)

and

ii)

c)

i)

and

iii)

d)

i),

to

survive

or

reproduce.

only

only

M.V. San Nicholas

500

0

fu

M.V. Amama

500

0

0.0

0.01

0.05

5

In

ii)

gure

species.

the

0.5

1.0

5.0

13,

The

diagram

The

0.1

and

circles

iii).

each

number

closer

the

that

more

represent

represents

two

numbers

similar

the

taxonomic

a

are

two

on

species.

groups.

For

10.0

example,

the

diagram

shows

that

2,

3,

4

and

-3

concentration of copper (mg dm

)

5

are

in

the

same

genus.

Figure 12

1

How

much

higher

concentration

was

the

tolerated

by

maximum

the

algae

copper

from

34 2 3

1

ships

than

the

algae

from

an

unpolluted

6 7 4 5

environment?

a)

0.09

times

higher

b)

0.11

times

higher

8

9 10

c)

1.0

times

higher

d)

10

times

11

higher.

12 13

19

24

14 20

25

15

2 1

16

22

1 7

26

27

28

18

29 23 30

2

What

is

the

reason

for

results

lower

than

zero 31

on

the

bar

32

charts?

33

a)

The

volume

b)

The

algae

c)

Increases

d)

Results

of

all

in

algae

decreased.

died.

Figure 13

volume

were

less

than

100 %

a)

State

with were

too

small

to

b)

State

with

c) What

was

the

reason

for

the

difference

tolerance

between

the

The

algae

on

the

ships

the

The

algae

can

develop

absorbed

it

on

to

their

State

The

d)

The

copper

in

copper

tolerance

selection

in

the

for

that

are

in

a

family

species

[2]

that

are

in

an

order

families.

[2]

State

the

species

that

are

in

a

class

with

orders.

[2]

Deduce

whether

species

8

is

more

closely

offspring.

the

the

[1]

and

paint

caused

paint

higher

caused

levels

of

to

species

16

or

species

6.

mutations. f)

copper

genus

genera.

two

related

c)

a

copper.

e) pass

in

species.

species

two

three

b)

is

algae?

d) a)

other

that

in with

copper

no

species

measure

accurately.

3

one

natural

copper

tolerance.

Explain

been

why

drawn

diagram.

three

concentric

around

species

circles

34

on

have

the

[2]

277

5

E v o l u t i o n

6

The

map

in

in

the

in

Britain

a n d

gure

1950s

of

and

b i o d i v E r s i t y

14

two

shows

forms

Ireland.

the

of

distribution

Biston

Biston

betularia

betularia

is

a

D Key

species

of

moth

that

ies

at

night.

It

spends

Non-melanic

the

daytime

roosting

on

the

bark

of

trees.

The

Melanic

non-melanic

with

black

wings.

the

a)

spots.

Before

melanic

wind

form

form

is

white

wings,

melanic

industrial

was

very

from

has

revolution,

rare.

the

form

peppered

The

black

the

•

prevailing

Atlantic

Ocean,

to

west.

State

the

maximum

percentages

b)

The

the

direction

has

of

Outline

the

the

forms

in

two

gure

the

trends

of

and

in

the

Biston

1Ip>0.5)

so

we

hypothesis.

D-bd q: Using the chi-squared test

Warren

and

Hutt

heterozygote

one

for

the

for

(1936)

two

presence

test-crossed

pairs

(Cr)

of

or

alleles

a

in

absence

double

1

(cr)

crest

and

one

for

white

(I)

or

a

contingency

table

of

[4]

of 2

a

Construct

observedvalues.

hens:

non-white

Calculate

the

expected

values,

assuming

(i) independent

assortment.

[4]

plumage.

3 For

their

F

cross,

there

was

a

total

of

Determine

the

number

of

degrees

of

754

2

freedom.

[2]

offspring.

4 337

were

white,

Find

the

critical

signicance

337

were

region

for

chi-squared

at

a

crested;

non-white,

were

non-white

46

were

white,

of

5%.

[2]

non-crested; 5

34

level

crested;

Calculate

chi-squared.

[4]

and 6

State

the

two

alternative

hypotheses,

H 0

non-crested.

andH

and

evaluate

them

using

the

calculated

1

value

454

for

chi-squared.

[4]

10 . 3

G e n e

P o o l s

a n D

s P e c i a t i o n

10.3 G p d p

Unrsning appiins A gene pool consists of all the genes and their

➔

Identifying examples of directional, stabilizing

➔

dierent alleles, present in an interbreeding and disruptive. population. Speciation in the genus Allium by polyploidy.

➔

Evolution requires that allele frequencies

➔

change with time in populations.

Skis

Reproductive isolation of populations can be

➔

temporal, behavioural or geographic.

Comparison of allele frequencies of

➔

Speciation due to divergence of isolated

➔

geographically isolated populations.

populations can be gradual.

Speciation can occur abruptly.

➔

Nur f sin

Looking for patterns, trends and discrepancies:

➔

patterns of chromosome number in some genera

can be explained by speciation due to polyploidy.

Gn ps

A gene pool consists of all the genes and their dierent

alleles, present in an interbreeding population.

The

most

species

commonly

concept.

interbreeding

to

exist

are

for

the

generation.

an

denes

isolated

same

that

equal

denition

species

a

of

as

a

species.

so

it

is

a

species

group

common

other

isolated

gene

of

is

pool

Some

the

biological

potentially

that

is

populations

possible

for

of

multiple

the

gene

same

pools

species.

reproduce

Genetic

a

with

from

geographically

Individuals

have

accepted

populations,

reproductively

species

This

contribute

equilibrium

chance

of

to

exists

contributing

the

gene

when

to

the

all

pool

of

members

future

gene

the

of

next

a

population

pool.

a frquny n uin

Evolution requires that allele frequencies change with

time in populations.

Evolution

of

a

dened

population

such

the

is

as

over

mutations

reproduction

emerging

events

also

the

time.

cumulative

Evolution

introducing

of

between

can

as

some

varieties

different

have

a

new

change

can

over

effect

If

on

the

due

a

and

heritable

to

selection

others

populations.

signicant

occur

alleles,

in

a

number

pressures

barriers

population

allele

characteristics

is

to

of

reasons

favouring

gene

small,

ow

random

frequency.

455

10

G e n e t i c s

a n d

e v o l u t i o n

( a H l )

ay

Prns f nur sin

In the cross depicted in gure 1,

Identifying examples of directional, stabilizing and the frequency of ower colour

disruptive selection.

phenotypes in Japanese four

o’clocks is shown over three

Fitness

R

found

yields red owers, the genotype

W

in

a

genotype

factors

the

that

next

or

phenotype

act

generation.

is

the

selectively

on

Selection

likelihood

certain

pressures

that

phenotypes

are

it

will

be

environmental

resulting

in

natural

W

C

C

of

R

C

generations. The genotype C

yields white owers

and because the alleles are

R

co-dominant, the genotype C

selection.

There

selection,

disruptive

are

three

patterns

selection,

of

and

natural

selection:

directional

stabilizing

selection.

W

C In

stabilizing

selection,

selection

pressures

act

to

remove

extreme

yields pink owers:

●

varieties.

For

example,

favoured

over

average

birth

weights

of

human

babies

are

in the rst generation, 50% of low

birth

weight

or

high

birth

weight.

A

clutch

is

the

the population is red and 50% number

of

eggs

a

female

lays

in

a

particular

reproductive

event.

Small

is white clutch

●

next

in the second generation,

as

100% of the owers are pink

may

mean

generation.

the

may ●

sizes

parent

impact

Very

cannot

their

that

none

large

clutch

provide

own

of

the

sizes

adequate

survival

to

offspring

the

may

mean

nutrition

next

survive

into

higher

and

season.

the

mortality

resources

This

means

and

that

a

in the third generation, there medium

clutch

size

is

favoured.

are 50% pink , 25% white and

25% red.

In

disruptive

intermediate

natural

selection,

varieties,

selection

favouring

the

pressures

extremes.

act

One

to

remove

example

is

in

the

Show that the allele frequency is

R

50% C

red

W

and 50% C

crossbill

Loxia

curvirostra.

The

asymmetric

lower

part

of

the

bill

in each of the

of

red

crossbills

is

an

adaptation

to

extract

seeds

from

conifer

cones.

three generations. While phenotype

An

ancestor

with

a

“straight”

bill

could

have

experienced

disruptive

frequencies can change between

selection,

given

that

a

lower

part

of

the

bill

crossed

to

either

side

generations, it is possible that allele

enables

a

more

efcient

exploitation

of

conifer

cones.

Both

left

over

frequency is not changing. This

right

and

right

over

left

individuals

exist

within

the

same

population

population is not evolving because

allowing

them

to

access

seeds

from

cones

hanging

in

different

positions.

allele frequencies are not changing.

In

directional

selection,

the

population

changes

as

one

extreme

of

a

eggs

range

R

C

is

better

adapted.

R

R

C

F

R

C

R

C

W

C

D-bd q: Stabilizing selection

generation

A

1 R

all C

population

of

bighorn

sheep

( Ovis

canadensis)

on

Ram

Mountain

W

C

in W

variation

C

sperm

C

of

W

C

R

C

W

C

W

C

Alberta,

has

been

monitored

since

the

1970s.

Hunters

W

C

can F

Canada,

buy

a

licence

to

shoot

male

bighorn

sheep

on

the

mountain.

The

generation

2

large

horns

of

this

species

are

very

attractive

to

hunters,

who

display

1:2:1

them ▲

as

hunting

trophies.

Figure 1 A change in phenotypic

frequency between generations

does not necessarily indicate that

Most

year

horn

of

growth

life

in

takes

male

place

bighorn

between

sheep.

the

They

second

use

their

and

the

horns

fourth

for

ghting

evolution is occurring

other

males

females

length

during

and

of

then

the

mate

four-year-old

breeding

with

season

them.

males

on

to

Figure

Ram

try

2

to

defend

shows

Mountain,

the

groups

mean

between

1975

2002.

a)

Outline

the

trend

b)

Explain

the

concept

example.

456

in

horn

of

length

over

directional

the

study

selection

period.

referring

to

of

horn

this

and

10 . 3

G e n e

P o o l s

a n D

s P e c i a t i o n

........................................................................................ c)

Discuss

the

adaptation

trade-off

in

this

between

short

and

long

horns

as

an

case.

80

mc/ htgnel nroh naem

•

70

••

60

50

•

40

0

1970

1975

1980

1985

1990

1995

2000

2005

year

▲

Figure 2

Source: Reprinted with permission from Macmillan Publishers Ltd: David W. Coltman, “Undesirable

evolutionary consequences of trophy hunting”, Nature, vol. 426, issue 6967 , pp. 655–658

D-bd q

Researchers

born

in

years.

a

carried

London

Data

was

out

a

study

hospital

collected

over

on

on

a

the

3,760

period

children

of

children’s

a)

Identify

the

mode

value

b)

Identify

the

optimum

for

mass

at

birth.

12 mass

at

birth

for

mass survival.

at

birth

the

acts

the

and

study

on

their

was

mass

to

at

frequency

mortality

birth.

of

rate.

determine

The

babies

how

chart

of

each

The

purpose

natural

in

gure

mass

at

of

selection

3

c)

birth

shows

birth.

superimposed

on

the

bar

chart

indicates

mortality

rate

(the

children

that

relationship

between

mass

at

mortality.

Explain

how

this

example

illustrates

the

the pattern

percentage

the

and

The d)

line

Outline

of

natural

selection

called

stabilizing

did selection.

not

survive

for

more

than

4

weeks).

800

100

400

10

200

)elacs gol( %/ytilatrom

htrib ta ssam fo ycneuqerf

600

0

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

mass at birth/kg

▲

Figure 3

Source: W H Dowderswell, (1984) volution, A Modern Synthesis, page 101

457

10

G e n e t i c s

a n d

e v o l u t i o n

( a H l )

D-bd q

In

coho

males

as

salmon

reach

small

as

(Oncorhynchus

maturity

30%

of

as

the

kisutch),

much

body

as

size

some

50 %

of

earlier

other

population.

Success

in

spawning

ghting

b.

sneaking.

and

males

in c)

the

a.

Identify

within depends

on

the

male

releasing

a

size

of

male

sh

that

never

gets

(breeding)

sperm

in

100

cm

(1

m)

by

following

either

close strategy.

proximity

large

males

access

jacks

to

for

to

are

and

4

at

a

at

they

achieved

from

the

the

Determine

contrast,

males

which

by

In

ghting

lose

The

and

d)

gain

to

both

likely

graph

proximity

to

in

females

males

to

40

b)

sneaking

b.

ghting.

Determine

example

illustrates

selection

known

the

as

selection.

5

10

2 ghting

8

12

3 40

sneaking 120

''

28

'

3

3 3

8 6

200

females

by: 25−29

a.

this

natural

10

targeted

more

The

proximity

cm

of

disruptive

large-sized

strategies.

mean

how

pattern

coercing

more

are

sneaking.

35–39

Explain

intermediate-sized

are

and

and

called

disadvantage

they

average

two

the

by

as

to

males

“sneaking”.

at

Small

strategies

small-sized

competitive

large

shows

achieved

a)

spawn.

prevented

gure

different

The

specialized

to

ghts

be

employ

female.

)mc(elamef ot ytimixorp

males

egg-laying

specialized

are

females

the

females.

are

males

jacks

to

35−39

45−49

55−59

65−69

male body size(cm)

Nature, Vol. 313, No. 5997 , pp. 47–48, 3 January 1985

the

size

range

that

gets

nearest

▲

to

Figure 4 Eect of body size and courting strategy on proximity

to females

the

females

by:

thr r irn gris f rprui

isin

Reproductive isolation of populations can be temporal,

behavioural or geographic.

Speciation

existing

is

population

this

happens.

cichlids

species

Lake

of

then

(sh)

to

but

If

are

one

occur

and

isolation

speciation

speciation.

Lake

For

of

the

three

then

is

termed

largest

East

Malawi.

the

be

by

rainy

the

isolate

because

of

gene

allopatric

Annual

season

may

comes,

Lake

when

separation

the

Most

in

water

to

different

populations

This

can

are

result

in

species.

of

gene

occurs,

example,

pools

then

occurs

the

isolation

within

process

can

be

is

the

termed

of

Victoria,

subject

isolated.

one

occur

speciation.

uctuations

then

an

of

vertebrates.

lakes,

are

reproductively

of

of

pool

geographic

families

that

splitting

the

Speciation

African

populations

When

new

of

in

species

can

population.

occurs

speciation

can

of

new

another

isolation

isolation

formation

Sometimes

of

a

barriers

the

pressures.

recombined

area.

the

cichlids

lead

selection

458

If

of

Various

that

Tanganyika

levels

the

formation

from

populations,

The

the

population.

same

geographic

sympatric

behavioural.

When

closely

10 . 3

G e n e

P o o l s

a n D

s P e c i a t i o n

D-bd q: Lacewing songs

Songs

in

are

part

members

of

of

the

process

different

of

mate

species

(a)

selection

within

the

4

genus 2

Chrysoperla

(lacewings).

Males

and

females

of

the 0

same

species

have

precisely

the

same

“song”

and -2

during

the

pre-mating

period

take

turns

making

-4

the

songs.

The

oscillograph

for

two

species

of

0

lacewings

are

shown

in

gure

5

10

15

20

25

30

5.

(b) 1

Compare

the

songs

of

the

two

species

of

4

lacewings.

[3] 2

2

Explain

might

why

lead

differences

to

in

mating

songs

0

speciation.

[3] -2

3

The

ranges

overlap.

of

the

Suggest

two

how

species

currently

differences

in

-4

song 1

could

have

2

3

4

5

6

7

8

9

10

11

12

developed: Figure 5 Pre-mating songs of lacewings: (a) C. lucasina

▲

a)

by

allopatric

b)

by

sympatric

and (b) C. mediterranea. C. lucasina ranges across most

speciation

of Europe and eastward into western Asia, as well as

speciation.

[4] across the northern quarter of Africa. C. mediterranea

ranges across southern to central Europe and across the

north African Mediterranean

related

only

individuals

successfulin

There

can

be

Populations

day.

For

each

the

10

in

time

11

the

already

mate

for

a

in

the

third.

owers

of

all

is

8

orchid

not

the

are

yet

pools

in

own

in

occurs

in

gene

those

or

often

the

9

the

area.

genus

times

to

sudden

between

another,

because,

other

of

Dendrobium

lapse

in

occurs

of

are

different

response

species,

pools

same

the

However,

one

open,

the

of

they

population.

seasons

species

species.

days

of

their

different

Flowering

species

have

of

gene

at

three

Isolation

one

or

of

tropical

day.

in

courtshipbehaviour,

members

ower

owering

withered

their

isolation

single

and

in

or

three

temperature

stimulus

to

temporal

may

example,

ower

drops

differ

attracting

and

at

the

species

have

matured.

dirn ppuins h irn  frqunis

Comparison of allele frequencies of geographically isolated populations.

Online

databases

Database

such

(AlFreD)

as

the

hosted

by

Allele

Yale

Pan I

Frequency

is

a

integral

University

gene

in

cod

membrane

s h

tha t

p r o tei n

co de s

ca l le d

for

A

contains

the

frequencies

humanpopulations.

are

no

ofthe

longer

ease

culture

of

in

Most

a

that

and

to

for

because

signicant

due

Two

of

populations

isolation

the

exists

variety

human

geographic

travel

contact

of

culture

globalization.

of

versions

four

to

alleles

amino

Samples

of

the

of

23locations

in

Pan I

pa nto p hys in

acids

cod

g e ne ,

in

s h

th e

o ne

B

and

tha t

re g io n

we r e

no r th

an

pan t o ph ysi n .

Pan I

di ffer

of

the

co ll e cted

Atl anti c

,

code

by

pr ot e i n .

fr om

a nd

wer e

A

Nonetheless,

patterns

of

variationdo

exist,

tested

to

nd

the

p r o p o r ti ons

of

Pan I

and

B

especially

when

populations

comparing

with

mainland

remote

island

populations.

Pan I

alleles

shown

in

in

pie

each

char ts ,

po p ul a ti on.

numbe re d

T he

r e su l t s

1– 23,

on

a re

the

459

10

G e n e t i c s

map

a

in

a n d

gure

population

6.

to

1.0.

The

T he

are

Thefrequency

an

( a H l )

p r o por ti ons

called

of

light

e v o l u t i o n

the

a l l el e

grey

al le l e

can

s e cto rs

of

a ll el e s

va r y

of

in

fr e qu e n c ie s .

the

f r om

pi e

0 .0

ch a rt s

A

show

the

allele

blacksectors

fre q ue ncy

show

the

of

Pan I

a l le le

and

the

fre que nc y

B

of

1

Pan I

State

the

two

populations

with

the

highest

B

PanI

2

allele

Deduce

in

frequencies.

the

which

allele

half

A

of

[2]

frequencies

the

cod

sh

of

a

had

population

the

genotype

A

PanI

PanI

A

,

and

half

had

the

genotype

PanI

B

PanI

3

.

Suggest

[2]

two

populations

geographically

which

are

likely

isolated.

[2]

B

4

Suggest

allele

is

two

possible

more

reasons

common

in

why

the

population

PanI

14

than ▲

population

21.

Figure 6

[2] Source: R A J Case, et al., (2005), Marine Ecology Progress

Series, 201, pages 267–278

TOK

Gruism in spiin

Speciation due to divergence of isolated populations W  d xp

  dmg 

p f  

xpd d?

The coherence test of truth

lters knowledge claims

can be gradual.

There

as

are

two

depicted

series

of

things

in

theories

gure

7,

intermediate

as

beak

length

that are well established.

If the new knowledge

is

in

the

the

forms.

ycneuqerf

through existing theories

about

pace

idea

The

birds

or

of

that

axis

evolutionary

species

label

cranial

slowly

change.

change

“structure”

capacity

in

Gradualism,

through

might

refer

to

a

such

hominids.

structure

claim does not t, it is

more likely to be greeted

with skepticism. While

i t

m

e

polyploidy does occur in

sh and amphibians, it has

always been unexpected

in mammals. The sex

determination system in

mammals is very sensitive

▲

Figure 7 In the gradualist framework, new species emerge from a long sequence of

to extra sex chromosomes. intermediate forms

Since the existence of a

tetraploid mammal was rst Gradualism

was,

for

a

long

time,

the

dominant

framework

in

claimed, the response has palaeontology.

However,

i.e.

of

it

was

confronted

by

gaps

in

the

fossil

record,

been skepticism. Though an

absence

intermediate

forms.

Gradualism

predicted

that

there is still no reasonable evolution

occurred

by

a

long

sequence

of

continuous

intermediate

answer to the question of the forms.

The

absence

of

these

intermediate

T. barrerae origin. imperfections

460

in

the

fossil

record.

forms

was

explained

as

10 . 3

G e n e

P o o l s

a n D

s P e c i a t i o n

Punu quiibrium

gradualism

Speciation can occur abruptly.

Punctuated

species

theory

gaps

of

at

such

new

are

punctuated

all,

as

equilibrium

as

times

there

is

a

8

model

with

no

long

shared

much

compares

long

and

the

of

periods

rapid

gaps

in

sequence

(allopatric

common

of

relative

evolution.

the

of

fossil

range

in

can

record

and

lead

organisms

stability

According

intermediate

speciation)

geographic

more

prokaryotes

Figure

that

periods

isolation

within

change

like

by

equilibrium,

was

geographic

niches

Rapid

holds

“punctuated”

the

to

with

might

forms.

in

to

not

short

be

-

Events

opening

rapid

a

the

of

speciation.

morphology

-

generation

insects.

two

models.

The

top

model

shows

the

gradualist time

slow

equilibrium

over

a

change

model

short

on

period

of

over

the

geological

bottom

time

time.

consists

followed

by

of

The

punctuated

relatively

periods

of

rapid

changes

punctuated equilibrium

stability. ▲

Figure 8

Pypiy n   spiin

Looking for patterns, trends and discrepancies: patterns of chromosome number

in some genera can be explained by speciation due to polyploidy.

A

polyploid

two

sets

can

of

result

different

organism

from

This

duplicate

meiosis

that

a

in

when

original

Polyploidy

it

is

has

102

and

its

living

to

the

cells

are

relative

of

Researchers

propose

produced

the

tetraploid

reproductively

species,

eventually

chromosomes

scholarship

has

an

isolated

shedding

tested

at

this

this

exist

copies

observed

in

four

of

each

that

copies.

gamete

from

can

the

self-

polyploid

plants.

in

plants,

animals.

a

rodent

number

the

whose

red

2n

▲

Figure 9 Tympanoctomys barrerae

from

that

of

this

number

normal

mimax,

though

The

size.

Its

Andean

=

56.

Octomys-like ancestor

offspring

gained

plant

twice

family,

that

that

two

been

produces

chromosome

Octomys

same

genes

only

also

then

hypothesized

roughly

is

has

polyploid

chromosome

Its

several

detected

it

speciation.

barrerae),

been

but

whose

diploid

the

other

complex

polyploidy.

but

a

isolated

commonly

has

are

probes

pair

ancestral

gamete

polyploid

highest

it

is

words,

with

autosome

there

between

same

meiosis

result

sympatric

less

viscacha-rat

were

the

ambiguous:

than

Polyploidy

chromosomes

haploid

The

most

in

and

of

for

other

mate

lead

occur

result

closest

In

more

polyploids

reproductively

occurs

mammal

the

from

The

a

has

events

also

when

(Tympanoctomys

Argentina,

is

with

can

can

also

viscacha

any

occur.

population.

or

are

preparation

fused

Polyploidy

does

occur

become

pollinate

it

There

offspring.

now

that

chromosomes.

originate

can

doesn’t

fertile

has

one

hybridization

species.

chromosomes

species.

is

homologous

(i.e.

4n

from

some

=

their

of

that

parent

the

doubling.

hypothesis

112)

additional

Recent

but

results

are ▲

Figure 10 Octomys mimax

461

10

G e n e t i c s

a n d

e v o l u t i o n

( a H l )

Pypiy hs urr frquny in Allium

Speciation in the genus Allium by polyploidy.

Estimates

of

that

experienced

have

between

50

The

Allium

and

chives,

role

in

the

the

to

number

and

food

of

to

a

of

species

of

polyploidy

angiosperms

event

range

includes

as

of

Many

such

onions,

has

multiple

species

in

taxonomists

an

cultures.

the

as

leeks,

played

genus

Wild

garlic

important

Determining

presents

polyploidy

onion

=

28)

common

within

the

genus.

These

result

in

of

reproductively

isolated

but

A.

angulosum

c.

and

diploidy

number

variants

is

a

for

native

the

such

lavendulae

(2n

as

=

of

plant

A.

c.

North

is

14.

ecristatum

28).

and

Allium

oleraceum

are

species

that

occur

in

Lithuania.

One

is

a

otherwise diploid

similar

and

are

over

pressures.

canadense)

diploid

asexually

advantage

a two

number

selection

there

reproduce

an

events Allium

are

Allium

confer

(Allium

The

However,

of

may

certain

America.

(2n

a

species

polyploidy

under

70%

genus

number

challenge

the

plant

with

16

chromosomes

and

one

is

populations. tetraploid

plant

with

32

chromosomes.

~

▲

Figure 11 Metaphase chromosomes of Allium angulosum,

2n=16

462

▲

Figure 12 Metaphase chromosomes of Allium oleraceum,

2n=32

a

Q u e s t i o n s

Qusins

1

Identify

gures

the

13

stages

and

of

meiosis

shown

(i)

in

Deduce

of

14.

(ii)

for

Suggest

a

S.

other

It

is

unusual

their

nuclei.

Figure 13

▲

The

One

[3]

to

S.

more

arcticum

DNA

than

plants

Explain

of

[1]

and

of

animals

to

chromosomes

how

mosses

chromosomes

in

can

in

have

their

cells.

[2]

Sphagnum

M f

nmb f

p

Dna/pg

mm

0.47

19

S. arcticum

0.95

S. balticum

0.45

19

S. mbriatum

0.48

19

S. olai

0.92

S. teres

0.42

19

S. tundrae

0.44

19

S. warnstori

0.48

19

T able 1

studied

group

in

of

Polypodium

forests The

DNA

content

of

cells

can

be

of

speciation

temperate

in

and

ferns

have

tropical

using

a

stain

that

binds

in

beam

of

light

specically

is

then

to

DNA.

stained

nucleus

have

passed

the

and

stain

the

is

amount

of

the

measured,

of

the

quantity

of

DNA.

similar

1

are

for

(Sphagnum)

leaf

from

cells

the

in

a

give

The

species

Svalbard

habitats.

Compare

the

DNA

results

of

bog

of

bog

in

their

the

S.

a

reason

on

the

the

same

for

six

of

Svalbard

number

the

species

in

from

tropical

the

was

islands

of

Genetic

of

the

all

chromosomes

nuclei.

arcticum

four

at

mountains

species

different

of

in

this

Mexico

group

and

are

distinct.

different

of

in

species

order

within

to

study

each

the

speciation.

[2]

in

and

S.

olai

probably

arose

species

when

meiosis

failed

to

identity

each

assigned

their

to

in

determined

certain

Values

pairs

similarity

was

of

species.

of

between

species

genetic

by

proteins

to

0

comparing

and

and

indicate

identity.

A

genes

1

were

the

value

of

degree

1

would

as

occur

that

all

the

genetic

factors

studied

were

in

identical one

of

live

Members

compared

similarities

mean new

and

bog

of c)

this

[2]

moss

having

of

(form

in

Data

mosses.

Suggest

group

Pleopeltis

America.

mechanisms

b)

temperate

moss

islands.

content

genus

an

group a)

in

Members

morphology

Another

genus

morphologically table

areas

America.

the

light

to

Central estimate

rocky

from

through

altitudes by

in

species

A

from

absorbed

lives

North

structure). narrow

three

estimated

group

a

two

Figure 14

▲

2

having

number

numbers

Give

answer.

mosses.

for

odd

mechanisms

been

of

number

cells.

S. aongstroemii

▲

3

your

leaf

disadvantage

bog

an

leaf

their

olai

have

odd

chromosome

in

reasons

and

d)

the

nuclei

between

the

species

being

compared.

ancestors.

463

10

G e n e t i c s

a)

Compare

the

b)

a n D

two

(i)

the

geographic

distributions

giving

a

reason,

or

genetically

diverse.

similar

the

Suggest

could

[1]

Polypodium

Identify

c)

of

groups.

Identify,

(ii)

e v o l u t i o n

Pleopeltis,

two

which

is

species

d)

group,

Explain

the

[1]

are

the

process

occurred

which

probably

most

that

how

have

of

been

longest

in

the

of

two

groups

genetically

period

of

speciation

Polypodium.

[1]

has

isolated

most

for

time.

[2]

most

genetically.

[1] 4

In

Zea

mays,

dominant

The

allele

over

the

the

over

for

for

plants

for

allele

starchy

allele

breeding

allele

the

were

plants

colourless

a)

with

State

the

the

F

crossed

with

seeds

genotype

individuals

(W)

endosperm

coloured

endosperm

seed

colourless

endosperm

waxy

with

coloured

for

pure

and

is

and

(c).

Pure

starchy

breeding

waxy

the

is

dominant

(w).

seeds

and

(C)

seed

endosperm.

phenotype

produced

as

a

result

of

of

1

this

Po. sibiricum

cross.

genotype

.................................................

0.435

Po. amorphum

phenotype

0.608

0.338

b)

The

F

............................................. [2]

plants

were

crossed

with

plants

1

Po. appalachianum

that

the

F

had

the

genotype

expected

ratio

generation,

of

c

c

w

w.

Calculate

phenotypes

assuming

that

in

there

the

is

2

independent

Pl. polyepis

Expected

The

the

assortment.

ratio

observed

F

...................................... [3]

percentages

generation

are

of

shown

phenotypes

in

below.

2

coloured

starchy

37%

Pl. crassinervata

colourless

coloured

14%

waxy

colourless

The

starchy

16 %

waxy

observed

33 %

results

differ

signicantly

Pl. conzattii

from

the

results

expected

on

the

basis

of

Pl. mexicana

independent

c)

State

the

assortment.

name

of

a

statistical

test

that

could

Pl. polyepis

be

used

to

expected

show

results

that

are

the

observed

signicantly

and

the

different.

[1] Pl. conzattii

Pl. mexicana

d)

Explain

of

the

the

cross

expected Pl. crassinervata

▲

Figure 15 The approximate distribution in Nor th America of

the three species of Polypodium (Po.) and a summary of

genetic identity

Source: C Hauer, E Hooper and J Therrien, (2000), Plant Species

Biology, 15, pages 223–236

464

reasons

for

differing

results.

the

observed

signicantly

results

from

the

[2]

W I T H I N TO P I C Q U E S T I O N S

Topic 10 – data-based questions Page 452 1. coloured, starchy both dominant traits Cc; white, waxy recessive traits Ss; F1 are all CcSs; so F1 × F1; CcSs × CcSs produces typical dihybrid ratio of 9 coloured starchy: 3 coloured waxy: 3 white starchy: 1 white waxy in F2; 2. the actual frequencies do not follow the 9:3:3:1 ratio and so the genes must be linked as they differ from the theoretical ratio for dihybrid crosses; 3. coloured, shrunken CCnn; white, non-shrinken ccNN; F1 coloured, non-shrunken is CcNn are test-crossed with homozygous recessive: ccnn; CcNn × ccnn; typical ratio of 1 coloured non-shrunken: 1 coloured shrunken: 1 white non-shrunken: 1 white shrunken 4. actual frequencies frequencies differ from typical ratio of 1:1:1:1, so genes must be linked; 5. if starchy/waxy and non-shrunken/shrunken are both linked to colour, then they must also be linked to each other; Page 454 1 and 2.

White Crested observed expected

337 188.5

Non-white, Non crested 337 188.5

Non-white Crested 34 188.5

White Non-crested 46 188.5

Total 754 754

3. 3 degrees of freedom expected; 4. critical value for 3 df = 7.815; 5. X2 >>7.815;

6. Ho the traits are not linked and differences between observed and expected are due to sampling error; H1 the traits are linked and differences between observed and expected are not due to sampling error; X2 >>7.815, therefore p.-, . ' :. '"J :

1 .

' Figure 2

as

shows

pet.

shows

a

was

SRY

that

to

female

a

rst

the

the

to

have

introduced

source

of

the

mouse

protein

develop

into

factor

(on

SRY

the

had

gene

development

female

express

genetically

sh

transcription

to

mouse

the

protein

the

is

lead

,

transgenic

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566

and

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specic The sheep are ospring of ewes which have

promoter

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ribosomes

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to treat hereditary A1AT deciency in humans,

which leads to the lung disease emphysema

567

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Marker genes

Marker genes are used to indicate successful uptake.

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Figure 4

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taken up by its chromosome or chloroplast DNA .

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570

the

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Use of tumour-inducing (Ti) plasmid of Agrobacterium tumefaciens to introduce

glyphosate resistance into soybean crops.

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use

way

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gene and an antibiotic

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roots

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resistance gene. Allow

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genes into leaf cells

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Figure 5 clump (callus)

569

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Hepatitis B gene coding

Edible viruses

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virus to allow bulk production of

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Production of Amora potato (Solanum tuberosum) for paper and adhesive industries.

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571

B

B I OT E C H N O L O G Y

environmental

glyphosate

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T able 1 Percentage reduction in the amount of herbicide

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various regions of the US

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Figure 9

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T able 2

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B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

a

Alcanivorax borkumensis is a rod-shaped bacterium

organism’s GI number. It is listed in the title. (GI number

that utilizes oil as an energy source. It is relatively

#110832861). View the genome.

uncommon but quickly dominates the marine microbial Go to the open reading frame nder (http://www.ncbi.nlm.

ecosystem after an oil spill. Scientists sequenced the nih.gov/projects/gorf/). Enter the GI number and specify

genome of this bacterium in an eor t to identify the the range of bases that you are going to search.

genetic aspects of its oil digesting ability. The entire

Perhaps as a class, the genome can be divided up into genome can be accessed from the database GenBank .

2000 bp pieces. Share information with one another

Visit GenBank and search by genome to locate the about the open-reading frames identied.

genome of this organism. Click on FASTA to identify the

toK

Identifying target genes

Bioinformatics plays a role in identifying target genes. W kw  

 b   w

  m f b

  fm?

Bioinformatics

phenomenon.

information

without

is

the

Open

held

stop

in

use

of

computers

reading

a

frames

database

to

to

are

investigate

identied

searches

to

nd

by

biological

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extended

genomic

sequences

codons.

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DNA sequencing and

Once

bioinformatics has evolved

conducted.

an

open

at a rapid pace. In 2009,

BLASTn

the biggest problem for

reading

frame

researchers was developing

species.

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solutions to improve the

translated

reading

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search

frame

acronym

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open

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to

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databases

nucleotide

would

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protein

can

determine

existed

be

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in

database

if

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an

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open

another

based

on

the

frame.

sequencing of DNA. Time and Alternatively,

if

a

researcher

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found

a

protein

and

wants

to

determine

cost limited the production of the

location

of

a

gene,

they

can

conduct

a

tBLASTn

search

using

a

DNA sequence information. computer

search

of

multiple

genomes

using

the

translated

sequence

to

By 2013, researchers can search

for

potential

genes

that

could

have

been

transcribed

to

produce

sequence a whole human the

genome within a single

day. The challenge has now

shifted from sequencing DNA

to managing and analysing

the extraordinary volume

of sequence data that is

being produced. It has been

estimated that ve months

of analysis are needed for

every month's wor th of data

generated.

574

protein.

All

three

methods

play

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role

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identifying

target

genes.

B . 3

e n v i r o n M e n t a l

p r o t e c t i o n

B.3 em 

Understanding Applications Responses to pollution incidents can involve

➔

Degradation of benzene by halophilic bacteria

➔

bioremediation combined with physical and such as Marinobacter chemical procedures.

➔

Microorganisms are used in bioremediation.

➔

Some pollutants are metabolized by

➔

Degradation of oil by Pseudomonas.

➔

Conversion by Pseudomonas of methyl

mercury into elemental mercury. microorganisms. Use of biolms in trickle lter beds for sewage

➔

Cooperative aggregates of microorganisms can

➔

treatment. form biolms.

➔

Biolms possess emergent proper ties.

➔

Microorganisms growing in a biolm are highly

Skills resistant to antimicrobial agents. Evaluation of data or media repor ts on

➔

Microorganisms in biolms cooperate through

➔

environmental problems caused by biolms.

-_-_-_-_-_-_-_-_-_-_-_-_---=-7

quorum sensing.

~ Bacteriophages are used in the disinfection of

➔

water systems.

Nature of science

Developments in scientic research follow

➔

improvements in apparatus: using tools such

as the laser scanning microscope has led

researchers to deeper understanding of the

. . . . . . . . . . . . . . . . . . . . ~=-= L ............................................................~=-=-=-structure of biolms.

~

Methods used to address pollution incidents

Responses to pollution incidents can involve bioremediation

combined with physical and chemical procedures.

When

or

chemicals

throug h

are

rele ased

carelessness ,

of

ecologica l

disruption.

to

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metalsand

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food

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environmental

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from

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the

relies

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bioac cumulate

incinera ted

to

575

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

concentratethe

properly

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combined

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●

BIOPILE

methods

degrade

volatile

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be

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ca n

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for

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respond

spills

include

procedures

to

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the

use

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that

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incidents.

scrubbers,

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dispersants.

can

that

BIODEGRADATION TRIAL IN PROGRESS

the

and

bioremediation

Chemical-contaminated

●

DO NOT E NTER ' DO NOT TIP RUBBISH

number

with

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●

metal

contained.

removed,

includes

water.

can

be

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to

chemicals.

crushed,

chemicals

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soil

organic

that

sifted

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and

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in

chemical-contaminated

then

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the

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Microorganisms have properties that make them

▲

Figure 1 Soil undergoing bioremediation

useful for bioremediation

at Fawley Renery, an oil renery

and chemical plant located in Fawley,

Microorganisms are used in bioremediation.

Hampshire, UK

Bacteria

can

and

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in

often

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metabolism.

especially

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than

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biopile.

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agent

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Figure

dug

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the

pollution

nutrient

watered.

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in

source

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microbial

contaminants.

Bioremediation relies on microorganism

metabolism

Some pollutants are metabolized by microorganisms. ▲

Figure 2

Microorganisms

and

electron

The

bacterium

been

used

to

compounds

The

the

Figure

with

out ▲

as

3

electron

of

the

to

it

settle

the

(orange).

soil

cellular

and

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ethenogenes

chlorinated

out

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in

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uses

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carbon

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uranium

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Figure 3

of

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bacterium

it.

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cellular

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from

bind

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acceptors

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shows

iron

pollutants

in

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uranium

use

Dehalococcoides

break

bacterium

acceptor

can

acceptors

as

arsenic

a

means

B . 3

e n v i r o n M e n t a l

p r o t e c t i o n

Microorganisms can form biolms

Cooperative aggregates of microorganisms can form biolms.

A

biolm

between

is

molecules

They

a

colony

individual

that

also

recruit

secrete

the

surface

cell

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exchange

normally

uids.

biolm

often

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cells

on

that

that

can

Figure

4

surface

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of

a

the

a

treatment

to

in

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can

the

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to

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is

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a

used

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cooperating

is

colony.

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microorganisms

of

signalling

the

facilitate

the

aficted

cooperation

adhering

community

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a

into

colony.

on

and

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cells

together.

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form

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sticking

patients

of

in

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members

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view

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cells

500

catheter.

urine

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and

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that

cells.

tube

connection

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used

the

in

The

Figure

5

medical

bloodstream.

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▲

Figure 4 Biolm on the bristle of a

used toothbrush

centre

part

is

meant

to

be

hollow

but

is

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in

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white-coloured

biolm.

Emergent properties

Biolms possess emergent proper ties.

Properties

collective

emergent

In

is

an

as

of

property.

and

the

the

interaction

in

the

to

increased

the

to

the

to

(EPS)

it.

single

of

cell

the

members

form

antibiotics;

and

the

colony

self-organize

of

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that

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virulence;

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protects

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move

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the

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the

of

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a

to

use

that

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of

are

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secrete

into

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ability

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into

for

of

water

matrix

▲

considered

Figure 5 Biolm formed on the

inside of a catheter

emergentproperties.

Biolms resist antimicrobial agents

Microorganisms growing in a biolm are highly resistant

to antimicrobial agents.

Hospital

caused

in

a

are

part,

a

the

physical

infections,

biolms.

biolms

There

In

acquired

by

and

is

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concern

of

resistance

barrier

to

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to

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is

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due

to

entry

nosocomial

resistance

infection

infections,

antibiotics

control

mechanisms

the

of

to

for

ofcers

biolm

exopolysaccharide

the

antibiotic

into

are

within

antibiotic

(EPS)

the

commonly

sometimes

occurs

hospitals.

resistance.

matrix

providing

colony.

577

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Antibiotics

biolms,

collective

This

can

often

act

limited

on

mechanisms

supplies

division

rate

especially

be

of

which

true

that

nutrients

of

inhibit

leads

minimizes

to

the

individuals

a

cell

division.

suppression

effect

deeper

antibiotics

into

the

In

of

some

the

can

have.

colony.

Quorum sensing

Microorganisms in biolms cooperate through

quorum sensing.

Quorum

of

In

sensing

population

bacteria

is

a

system

density.

that

form

density.

to

molecules

receptor

When

that

is

the

achieved,

low

pathogen

movement,

another

is

low,

passes

and

the

EPS

cell

a

the

cell

triggered

range

can

released

lead

to

trigger

of

level;

uses

affected

one

the

i.e.,

as

a

cell

by

bind

expression

the

of

of

biolm.

the

signalling

behaviour.

when

molecule

function

organisms.

coordinated

signalling

becomes

of

be

by

concentration

to

aeruginosa

production,

diverse

and

threshold

of

are

development

the

behaviour

Pseudomonas

a

that

expression

the

insufcient

concentration

concentration

The

is

gene

in

molecules

facilitate

density

and

population

the

on

to

behaviours

observed

Signalling

likely

population

molecule

When

are

is

biolms,

population

genes

It

of

the

quorum

reaches

a

is

critical

coordinated.

quorum

aggregation

and

sensing

the

to

coordinate

formation

of

biolms.

locally high signal

molecule concentration

EPS matrix

signal

molecule

secreted

modied

metabolism

•

r-

signal molecule

•

secreted

signal molecule

relatively low concentration of

signal molecule from other cells

•

•

receptors

Free form

▲

Biolm

Figure 6

Using viruses to kill bacteria in water systems

Bacteriophages are used in the disinfection of water systems.

When

bacteria

control

Some

●

of

Figure 7 Bacteriophages (pink) shown infecting

a population of bacteria shown as green

578

●

produce

biolms

the

Biolms

waste

can

heat

that

sulphate

corrode

a

within

damage

Anaerobic

can

▲

of

biolm,

water

can

be

reducing

they

can

systems

done

is

be

difcult

to

eradicate.

The

essential.

includes:

bacteria

produce

sulphuric

acid

which

pipes.

affect

to

the

heat

exchange

environment

is

in

systems

important.

where

the

release

of

B . 3

A

●

proliferating

in

frictional

for

increased

Bacteria

of

can

bacteria

bacteria

be

in

are

biolm

drag,

pumping

difcult

these

biolm

this

community.

bacteriophages

and

of

followed

days

exposure

addition,

when

can

be

diameter

pressure

they

killed

bacterial

are

specic

the

which

are

chlorine

while

may

form

by

of

a

pipe.

which

a

biolm.

disinfectant,

the

pathogen

pathogen.

The

as

can

T4

97

in

This

leads

results

to

a

need

The

but

outer

the

layer

inner

An

of

removed

pathogenic

added

are

to

biolms

as

only

40

bacteria

by

using

treatment

biolms

ensure

is

entire

known

initial

bacteria.

bacteriophage

the

bacteria.

killing

percent

coliform

be

through

bacteria

certain

chlorine.

alone

specic

such

to

success

killed

spread

attack

and

chlorine

be

they

specic

greatest

community,

to

because

Viruses

they

by

there

the

particular

kill

bacteriophages

viruses

In

problem

achieved

combination

of

the

water

sheltered.

solve

study

to

reduce

lowers

p r o t e c t i o n

power.

biolms

Viruses

One

can

which

e n v i r o n M e n t a l

within

ve

percent.

that

are

living

Bacteriophages

reduction

specic

to

a

with

E.

of

in

that

the

coli

Bioremediation in saline conditions

Degradation of benzene by halophilic bacteria such as Marinobacter

The

production

generates

that

as

is

is

and

particular

environment

soluble

lead

to

in

this

in

the

oil

in

as

waste

with

concern

for

cancer.

marine

saline

toluene.

water

case

in

of

contaminated

benzene

of

of

volumes

a

and

is

it

can

time,

is

salt

water

content

that

it

kills

such

(gure

persist

in

i.e.,

the

becomes

may

most

be

it

Some

archaea

environments

(gure9).

adaptation

8)

of

saline

archaea,

moderately

carcinogenic;

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the

wastewater

hydrocarbons

Benzene

as

long

environments

(salty)

can

been

are

adapted

such

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has

as

are

been

be

in

water

useful

Marinobacter

to

living

saline

referred

wastewater.

shown

to

highly

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to

in

as

the

species

extreme

halophiles.

of

halophilic

hydrocarbonoclasticus

able

to

fully

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bioremediation

degrade

has

benzene.

difcult

so

high

populations

ofbacteria.

H

H

C

H

C

C

C

C

C

H = hydrogen

H

H

H

C = carbon

benzene

▲

▲

Figure 8 Benzene molecule

Figure 9 The colour in this salt pan pool is a indicator of the

presence of a population of halophilic bacteria

579

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Bioremediation of oil spills

Degradation of oil by Pseudomonas.

In

natural

through

environments,

cracks

members

of

the

communities

and

carbon

involve

as

also

and

as

to

urea

an

rate.

oil

droplet

spill

of

oil

use

a

at

oil

to

the

oil

such

an

bacteria

population

the

often

in

of

these

energy

will

as

often

,,

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potassium

oil

at

sprayed

their

..

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in

Pseudomonas.

are

in

as

spills

metabolize

suspended

seeps

oor.

thrive

crude

with

nutrients

aid

ocean

substances

nutrients

to

petroleum

the

Pseudomonas

can

require

shows

in

Clean-up

the

These

spill

Figure10

a

they

seeding

some

vents

genus

source.

microbes

faster

and

a

on

work.

bacteria

degrading

water.

▲

Figure 10

Bioremediation of methyl mercury

Conversion by Pseudomonas of methyl mercury into elemental mercury.

Mercury

ends

component

light

this

bulbs.

up

of

in

mercury

desulfuricans.

enters

paints

Elemental

environment

methyl

garbage

some

food

to

by

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mercury

the

the

form

chains

dumps

and

highly

is

toxic

it

the

of

soluble

organic

more

and

can

adheres

dissolve

in

the

to

cell

can

bioaccumulate

within

the

and

it

can

up

putida

methane

bacteria

ion

as

insoluble

an

can

and

then

use

electron

eleme ntal

convert

the

the

acceptor

me rcury

being

cell a

bioreactor,

such

elemental

mercury

can

be

membrane.

biomass

biomagnify

in

to

reformed.

easily

the

from

waste

water

as

it

is

insoluble

and

of will

organisms

Other

mercury

separated It

Pseudomonas

mercury

ion.

resulting

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bacterium

methyl

mercury

in

Desulfovibrio

mercury

because

The

a

types

converted

bacterium

of

as

some

food

sink

due

to

its

density.

chain.

Biolms used in trickle lter beds

Use of biolms in trickle lter beds for sewage treatment.

The

consequence

allowing

it

to

enrichment,

or

This

algal

favours

algae

die,

bacterial

is

called

Many

leads

biolm

has

loss

a

the

sewage

of

When

of

bed

make

that

are

bacteria.

rocks.

of

the

water.

of

because

matter.

of

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can

use

be

up

by

water

process

of

trickling

colonized

Sewage

The

A

of

to

a

is

spraying

▲

580

oxygen

aerobic

demand.

plants

rocks

adds

and

nutrient

mats

organic

eutrophication.

rock

is

bodies

the

oxygen,

dead

oxygen

The

aerobic

onto

a

the

treatment

deep.

of

sprayed

to

on

address

system

2metres

treating

watercourses

blooms.

biological

to

not

into

eutrophication

activity

sewage

biolms

lter

it

of

ow

Figure 11

to

the

bacteria

sewage,

to

which

digest

the

is

necessary

sewage

for

content.

B . 3

e n v i r o n M e n t a l

p r o t e c t i o n

Media reports on biolms

Evaluation of data or media repor ts on environmental problems caused by biolms.

Biolms

as

they

are

properties.

solutions

they

commonly

have

a

number

They

to

are

novel

employed

problems.

havebeen

featured

of

At

the

implicated

in

the

and

as

a

on

survive

said

of

expect

meats

products,

time

number

people

raw

can

innovative

same

in

“Most

media

interesting

but

on

to

fruits,

which

nd

don’t

are

Salmonella

consider

vegetables

not

always

that

or

it

dry

cooked,”

Ponder.

environmentalissues: In

Virginia

Tech

evidence

scientists

that

to

surfaces

at

work

and

in

pathogen

biolms

the

build

have

–

provided

bacteria

protective

survival

of

the

that

moist

conditions,

reproduce

new

environment,

adhere

on

coatings–are

genes

them

human

out

from

over

from

the

of

every

Control

makes

six

illnesses

according

and

to

could

food

caused

the

Prevention.

Salmonella

measures

Americans

contaminated

million

bacteria,

each

by

curb

to

Salmonella

ill

year,

it

with

for

out

in

dry

various

Salmonella

Centers

Finding

resistant

help

becomes

Researchers

afliated

Life

Institute

Science

this

the

antibacterial

with

and

bleach,biolms

preserve

extremely

the

dry

the

sanitizers

the

conditions,

bacteria

are

that

Outbreaks

of

such

as

such

nuts,

milk

and

pet

over

900

illnesses

were

because

the

a

and

a

dry

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but

turn

protecting

environment.

have

in

the

to

dry

spices,

been

last

to

normal

of

the

with

was

for

up

tested

system.

storage

Salmonella

free-oating

disease.

survive

years.

to

be

it

of

and

to

in

30

a

large

were

cells

the

storing

days.

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simulated

Salmonella

in

survived

numbers

more

but

resilient

treated

the

stomach,

the

intestines,

the

with

need

Biolms

harsh,

where

associated

may

better

reduce

likelihood

thus

of

allowed

acidic

its

to

with

the

dry

likely

the

to

Salmonella

environment

shape

biolm

hopefully

of

results

food

of

reaching

in

the

poisoning.

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by

sanitation

another

the

chances

infection

help

to

to

more

regulations

for

equipment,

stops

them

increasing

research

strategies

These

response

made

Administration’s

safe

product

stress

also

the

This

dried

powdered

associated

ve

thought

nature

it

resilience

drying

powder

bacteria’s

cause

as

again

associated

cereals,

the

by

conditions.

symptoms

previously

the

microbial

foods

milk

conditions

bacteria

and

subjected

Salmonella

tested

points

biolm

The

in

from

digestiveprocesses.

foods

to

into

Fralin

Salmonella

heat-processing

foods

produce

biolm

long-term

than

outbreaks.

discovered

additiontoprotecting

when

cease

thrive

thrust

detrimental

gastrointestinal

Disease

what

same

in

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eating

a

they

which

Researchers

One

Salmonella

abundantly.

and

Drug

highlighting

and

new

formation

decreasing

on

the

outbreak.

growth. Source: http://www.sciencedaily.com/releases/2013/04/

130410154918.htm

a

●

The development of biolms on equipment and

piping systems in industry such as paper making Choose one or more of the following environmental facilities. issues related to biolms. Create a brief research repor t

outlining the scope of the problem. Ensure that you

●

The development of biolms in clean water pipes at

water treatment facilities.

include the role of biolms. Evaluate possible solutions

to the problems caused by the biolm. ●

●

The binding of positively charged heavy metals to

negatively charged biolms.

The role of biolms in increasing biological oxygen

demand in eutrophic bodies of water. ●

The sequestering of toxins within the biolm.

581

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Laser microscopes have enhanced our knowledge of biolms

Developments in scientic research

follow improvements in apparatus:

using tools such as the laser scanning

microscope has led researchers to

deeper understanding of the structure

of biolms.

Biolms

of

have

individual

and

the

EPS

functions.

living

in

complex

in

matrix

structure.

relation

to

inuences

Three-dimensional

cells

carried

a

cells

serving

out

using

combination

different

a

roles

dyes.

position

another

and

visualization

functions

laser-scanning

with

The

one

This

can

of

be

microscope

technique ▲

allows

direct

disrupting

its

observation

of

the

biolm

Figure 12

without

structure. generated

Figure

12

extracted

shows

from

an

image

amniotic

of

a

uid.

fragment

The

of

image

biolm

was

dots

grey

using

indicate

dots

a

EPS,

laser

scanning

green

represent

host

dots

microscope.

indicate

Red

bacteria

and

cells.

B.4 M (ahl)

Understanding Applications ➔

Infection by a pathogen can be detected by ➔

Use of PCR to detect dierent strains of

the presence of its genetic material or by its inuenza virus. antigens. ➔

➔

Tracking tumour cells using transferrin linked to

Predisposition to a genetic disease can be luminescent probes. detected through the presence of markers.

➔

➔

Biopharming of antithrombin.

➔

Use of viral vectors in the treatment of Severe

DNA microarrays can be used to test for genetic

predisposition or to diagnose the disease. Combined Immunodeciency (SCID).

➔

Metabolites that indicate disease can be

detected in blood and urine.

➔

Tracking experiments are used to gain

Skills

information about the localization and ➔

Analysis of a simple microarray.

➔

Interpretation of the results of an of ELISA

interaction of a desired protein.

➔

Biopharming uses genetically modied diagnostic test.

animals and plants to produce proteins for

therapeutic use.

➔

Nature of science

Viral vectors can be used in gene therapy.

➔

Developments in scientic research follow

improvements in technology: innovation in

technology has allowed scientists to diagnose

and treat diseases. 582

B . 4

M e d i c i n e

( a h l )

Innovations in diagnostic techniques

Developments in scientic research follow improvements in technology: innovation

in technology has allowed scientists to diagnose and treat diseases.

To

be

useful,

disease

use.

and

new

must

They

be

should

increases

such

a

result.

more

way

In

a

to

of

prevents

the

result

diagnose

that

out

can

is

spread

of

to

the

on

to

do

that

not

faster

of

certain

in

in

and

bacterial

the

same

or

by

by

microscopic

the

organism

Diagnosis

been

or

parasites

by

done

swabs

has

analysis

or

by

to

evidence

bacterial

can

often

for

taken

an

the

has

samples

from

carried

diagnosed

presence

levels

which

can

growth

be

of

some

plated

the

characterize

of

this

a

procedure

microorganisms

Further,

is

present

pathogens

are

culture.

of

urine

or

stool,

site.

of

genetic

by

If

and

the

reliability

of

a

searching

unusual

increased

diseases

reviewing

Improvements

traditionally

infected

of

out

observation

of

activity.

infection

collecting

be

its

the

limitation

different

to

sample

for

colonies

way.

slow

the

look

pathogen.

been

look

of

exists,

to

The

sometimes

Diagnosis

Infection

media

disease.

difcult

treatment

infection

culture

kind

timely

treatment

diseases,

lead

bacterial

a

simple

complications

infectious

diagnosis

to

preferably

carry

long-term

case

accurate

which

time

used

and

provide

the

that

the

methods

accurate

has

for

metabolites

in

methods

specicity,

traditionally

combination

of

the

the

in

of

presence

the

urine

diagnosis

speed

and

been

clinical

of

or

high

blood.

have

the

diagnosis.

High levels of metabolites can indicate disease

Metabolites that indicate disease can be detected in blood

and urine.

“Inborn

errors

genetically

of

these

diseases

often

resulting

of

substances

necessary

shows

and

for

three

urine

Newborn

are

in

of

foot.

phenylpyruvate

enough,

r

the

diet

to

are

toxic

function

and

subjected

the

child

the

amino

in

acid

a

term

is

in

single

enzyme.

to

a

genes

This

of

broad

that

that

in

a

of

enzymes

build-up

molecules

Table

detected

in

1

blood

affected.

to

a

heel

a

prick

blood

affected,

there

the

phenylalanine

prevent

test

sample

will

child

to

to

is

be

detect

taken

lacks

tyrosine.

severe

from

elevated

an

If

the

levels

enzyme

diagnosed

consequences

Mb w    f

Lesch–Nyhan

for

symptoms.

are

of

majority

code

results

secondary

group

The

important

metabolites

indicating

can

to

metabolism.

shortage

the

is

applied

affect

leading

which

blood

modication

d

or

individual

are

in

a

non-functional

(PKU),

If

is

that

mutations

diseases

an

infants

converting

a

normal

such

when

the

disorders

due

which

phenylketonuria

heel

metabolism”

inherited

for

of

for

quickly

the

child.

Mb   

Production of purines

Uric acid crystals in the urine

I

syndrome

Alkaptonuria

Breakdown of the amino acid tyrosine

High levels of homogentisic acid detected in both the

urine and the blood by thin layer chromatography

I Zellweger

Assembly of peroxisomes (organelles essential

syndrome

for the degradation of long chain fatty acids)

I

▲

I

and paper chromatography

Elevated very long chain fatty acids in the blood

I

J

T able 1

583

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Indicators of infection by a pathogen

Infection by a pathogen can be detected by the presence

of its genetic material or by its antigens.

Modern

molecular

discriminating

the

process

pathogen

The

an

and

they

is

of

that

it

antibodies.

as

don’t

the

present

advantage

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the

PCR

can

that

have

is

usually

response

Recent

the

be

Immunosorbent

antibodies

immune

such

have

pathogens.

can

of

be

being

much

automated

challenge

of

having

to

to

better

speed

at

up

culture

the

separately.

Enzyme-Linked

presence

test

methods

between

p24

pathogens.

only

to

to

same

of

the

the

the

nucleotide

the

HIV

test

detects

with

patient

resulting

ELISA

genetic

(ELISA)

challenge

once

pathogen

from

detect

Assay

The

effective

the

versions

antigen

used

the

to

in

for

has

the

the

the

this

diagnostic

developed

production

antigen

of

directly

virus.

material

sequence

as

of

the

a

pathogen.

genetic

If

material

primers

of

the

The ELISA test

Interpretation of the results of an ELISA diagnostic test.

An

of

ELISA

test

infection

testing

for

antigens

for

the

can

by

the

of

a

be

used

presence

the

to

pathogen.

of

pathogen.

detect

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test

the

presence

works

antibodies

to

Alternatively,

can

test

they

A

1

shows

capture

gure,

the

basis

molecule

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capture

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positive

to

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test

surface.

are

for

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p24

capsid

sample

surface.

a

a

added.

be

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positive

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to

test,

free

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the

version

version

capture

the

away.

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which

wash

last

molecule

step

changes

is

to

is

rinsed.

away

molecule.

target

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solution

would

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a

and

add

colour

the

In

free

positive

they

the

test,

are

not

substrate

when

acted

of

upon

the

antibodies

by

the

by

a

enzyme.

coloured

A

positive

solution

test

(see

is

therefore

gure

indicated

2).

to 2

shows

a

tray

of

wells

containing

human

protein.

tested

they

the

to

this

HIV .

blood

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of

enzyme.

test,

enzyme

Figure the

an

bind

washed

antigendirectly.

the Figure

to

negative

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it

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is

target

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of

+

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the

to

the

molecules

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are

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capture

capture

capture

present

for

in

molecules.

molecule

molecule

is

serum

from

antibodies

remain

colour

that

to

different

the

uncoloured

to

the

hepatitis

are

has

C

virus.

negative.

yellow/orange

patient

individuals

are

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positive

antibodies

for

being

that

and

tested

which

change

conrm

hepatitis

C

virus.

is

+

colour change

by activity of

conjugated

substrate

enzyme

+

Y captu re antibody

Y detection ant ibody

g

Ii>'

antigen

enzyme attached to detection antibody

converts substrate to coloured product

▲

584

Figure 1 Steps in a positive ELISA test

▲

Figure 2 Results of multiple ELISA tests for the Hepatitis C virus

B . 4

pathogen

only

are

occur

Another

probes

if

added

the

way

in

a

to

to

a

detect

to

the

from

material

the

microarray.

complementary

sample

genetic

of

presence

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can

pathogen

of

be

in

the

the

patient,

then

pathogen

a

is

pathogen

used

to

samples

is

detect

from

a

amplication

M e d i c i n e

( a h l )

will

present.

to

use

mRNA

DNA

sequences

patient.

2

a

Figure 3 shows a standard curve that relates quantity of

.D.O

antigen present in the test serum to optical density, a

measure of the colour of solution. The darker the colour,

1

the higher the optical density.

1

Explain how the standard curve could be used.

[2 ]

2

Determine the concentration of antigen present

0

0

at an optical density of 1.0.

100

200

300

400

500

[1] 1

antigen concentration /pg mL

▲

Figure 3

PCR as a diagnostic tool

Use of PCR to detect dierent strains of inuenza virus.

There

can

are

some

such

This

number

as

clinical

by

infection

swine

includes

u

Further,

an

with

needs

such

patients

to

patients

as

the

some

signs

more

as

serious

pregnant

infection

that

For

strains

quickly.

women,

immune

can

can

tests

virus.

diagnosed

whose

strains

and

inuenza

be

patients

or

compromised,

death.

of

infection

people,

elderly

is

a

indicate

result

produce

system

mRNA

and

sample

DNA.

that

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positive

is

was

cDNA

to

bind

the

increases,

sought

the

modication

a

in

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sample

present

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double-stranded

double-stranded

will

recent

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test.

more

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prevent

a

In

addition,

serious

epidemic.

be

to

rapid

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detection

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test

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:::::::::::::::) t

can

side

I I I I I I I I I I I I I I I I I

serious

reverse transcriptase

most

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likely

the

to

virus

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the

able

infects

inuenza

identify

a

the

specic

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person.

virus

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mRNA

cDNA

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reverse

transcriptase

will

transcription

(RT-PCR)

produce

a

is

used.

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from

an

RNA

template

called

cDNA.

'

called

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of

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variation

polymerase

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primer 3

+ T aq polymerase

of

infected

converted

specic

tested

to

an

to

for

involves

into

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are

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patient.

cDNA.

strain

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in

purifying

the

of

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inuenza

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/

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step

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cells

rst

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that

bind

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▲

Amplication

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cDNA (target)

Figure 4

585

B

B I OT E C H N O L O G Y

chromosome 17

A N D

B I O I N F O R M AT I C S

chromosome 13

Genetic markers

Predisposition to a genetic disease can be detected

through the presence of markers.

Genetic

markers

are

particular

alleles

which

are

associated

with

a

BRCA 2

predisposition

to

having

a

genetic

disease.

They

can

be

single

nucleotide

BRCA 1

polymorphisms

achieved

Markers

may

contribute

that

lie

The

to

is,

tandem

such

part

the

the

marker

that ▲

be

to

inuences

near

or

through

a

be

should

an

be

allele

a

be

be

for

of

marker

sequence;

separated

the

possible

can

i.e.,

linked

non-coding

being

which

of

the

be

DNAproling.

genetically

useful,

avoid

number

and

non-coding

may

To

to

PCR,

or

they

gene

Detection

as

coding

or

condition.

defective

should

there

of

disease

the

repeats.

methods

to

they

the

markers

by

population

genotypes

need

crossing

is

at

may

gene

to

over.

polymorphic;

the

locus.

Figure 5 Chromosomal location of

Researchers

look

for

expected

chance

alleles

which

are

found

more

frequently

than

the BRCA 1 and BRCA 2 genes

For

123456789

by

example,

increased

gene

are

of

amino

detects

presence

For

a

to

diseases

or

were

such

establishing

and

the

by

to

The

by

the

BRCA

cancer

cancer.

disease.

2

genes

in

indicate

women

The

genes

and

are

an

the

found

on

respectively.

mutations.

In

during

arrows

different

proteins

Figure

this

and

synthesis

indicate

a

blot

shows

the

radioactively

and

photographed

mutations

in

6

case,

protein

electrophoresis

the

of

various

the

from

types

BRCA

an

the

using

1

of

gene.

individual

would

cancer.

linked

to

a

diseases

polygenic,

considerable

statistical

of

13

BRCA

marker

are

1

ovarian

supplied

by

Where

are

BRCA

and

onset

radioactivity.

which

though

of

affected

electrophoresis.

produced

power.

environment

the

by

predisposition

predictive

power,

of

the

chromosome

separated

proteins

indicate

in

people

cancer

alleles

acids

lm

that

and

proteins

were

The

▲ Figure 6

17

products

marker

breast

different

separation

labelled

of

contributes

chromosome

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those

mutations

risk

itself

in

single

are

gene,

strongly

particular

progress

probabilities

has

from

the

markers

been

more

marker

inuenced

have

made

has

by

less

predictive

recently

complex

more

the

in

inheritance

patterns.

DNA microarrays

DNA microarrays can be used to test for genetic

predisposition or to diagnose the disease.

A

microarray

sequences

is

forexpression

The

sample

formed

as

is

a

small

adhering

to

from

synthesis,

of

be

the

a

to

surface

its

very

large

tested

is

mRNA

uorescent

exposed

to

the

cDNA

sequences

to

bind

to

the

mRNA

using

dyes

has

xed

large

of

be

to

and

of

DNA

used

sequences

expressed

the

enough

probes

range

can

transcriptase.

linked

long

DNA

being

reverse

are

a

Microarrays

number

sample

the

that

surface.

cDNA.

for

then

any

the

by

At

to

probe

test

simultaneously.

a

cell.

the

The

cDNA

same

time

microarray

complementary

chip

is

rinsed.

The

▲ Figure 7 A DNA microarray car tridge being

chip loaded into a machine that will be used to

analyse the results from this test

586

is

then

exposed

to

laser

light

which

will

cause

the

uorescent

is

B . 4

probes

cDNA

to

give

and

higher

the

off

the

light

DNA

level

of

where

probes

gene

there

within

has

the

expression

in

been

chip.

that

hybridization

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brighter

between

the

light,

M e d i c i n e

( a h l )

the

the

region.

A

1.28 cm

A

1.28 cm

A A

C

T

A

T

T

T

C

T

A

T

A

A

A

A

C

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C

T

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A

A

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C G

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actual size of

A

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T

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T

GeneChip® array

T

T

non-hybridized

DNA

millions of DNA strands

built in each location

6.5 million locations on actual strand =

hybridized DNA

each GeneChip® array 25 base pairs

▲ Figure 8

Interpreting a microarray

Analysis of a simple microarray.

As

an

example

experimenter

level

of

would

gene

would

dye.

red

modify

They

dye.

chip

to

may

this

cells,

They

to

in

then

microarray,

assess

a

control

this

with

a

green

expose

allow

1

cells

and

time

cell.

for

and

They

and

They

uorescent

it

and

with

microarray

hybridization

Spot DNA fragments on glass

then

cDNA.

wash

The

uorescent

green

light

expressed

where

are

from

label

the

an

range

sample.

mRNA

cDNA

then

the

cancerous

extract

produce

samples,

a

from

cDNA

would

of

from

cDNA

would

both

use

want

mRNA

labelled

cancerous

the

expression

extract

produce

of

red

of

2

is

in

chip

would

light.

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is

red

by

is

expressing

be

of

a

only.

is

chip

part

the

regions

the

of

being

the

chip

sequences

cancerous

combination

to

to

where

sequences

The

where

the

unhybridized

exposed

the

indicates

light

which

remove

then

control

corresponds

are

to

part

observed

the

expressed

light,

light,

cells

chip

there

being

Yellow

the

cells

of

where

only.

green

both

and

types

sequence.

Isolate mRNA from cells

slide to make microarray

normal

3

cancerous

Use mRNA to produce cDNA for

stability and label with dyes

4

Mix and wash over microarray.

Yellow: equal activity for

Scan with laser and detect levels both cell types

of binding/expression using

Green: higher gene activity

uorescent detection

for normal cells

Red: higher gene activity

for cancer cells

▲

Figure 9

587

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Protein tracking experiments

Tracking

about

experiments

the

are

localization

used

and

to

gain

interaction

information

of

a

desired

protein.

Proteins

probes

circulating

researchersto

alsoallow

target

in

areattached

to

follow

the

blood

them.

can

Such

distribution

researchers

to

be

traced

tracking

and

determine

if

radioactive

experiments

localization

how

the

can

patterns.

proteins

allow

They

interact

can

with

the

tissue.

Radioactive

atoms

distribution

can

or

be

molecules

tracked

with

can

be

PET

attached

to

the

proteins

and

their

scans.

Tracking experiments involving transferrin

Tracking tumour cells using transferrin linked to luminescent probes.

Transferrin

is

is

by

taken

up

surrounding

Figure

using

10

a

molecule

more

shows

a

sequence

The

dyes

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bound

dots

zero

to

image

shows

complexes

have

minutes,

membrane

the

on

iron.

than

of

complex

It

by

being

in

used

to

study

lymphoma

transferrin

surface

load

taken

transferrin

the

the

is

photos

the

of

dye.

is

shown

cells.

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The

bottom

receptor–transferrin

entered

their

(top

is

uorescent

some

having

delivered

transferrin

binds

cells

to

endocytosis

receptors

represent

of

linked

experiment

receptor-mediated

cells.

which

tumour

cells.

luminescent

molecules.

by

the

of

cell.

iron,

recycled

Once

the

to

they

receptor–

the

cell-surface

right).

▲

Figure 10

Biopharming

Biopharming uses genetically modied animals and

plants to produce proteins for therapeutic use.

There

are

three

antibodies,

main

human

categories

proteins

and

of

proteins

viral

or

used

bacterial

in

therapy:

proteins

(used

invaccines).

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production

such

as

carried

of

588

insulin

out

more

in

of

s i mp le

and

gene ti ca l l y

complex

huma n

g r o wth

r e c ombi n a nt

hor mone ,

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the r a p euti c

has

ba c t e ri a .

pr otei n s

is

pr ot e i ns

be e n

m os t

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m or e

f or

t h er a py,

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d if c u lt

the

to

pr od uc t io n

pr odu c e

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in

these

l iving

required

sugars.

these

systems.

Sometimes,

onl y

these

cows,

sheep

milk.

and

factors

goats

cells

a

do

such

are

protein.

Plant-made

therapeutic

cell

therapeutic

cultures.

protein

symptoms

of

of

not

as

carry

t he

ca pable

May

Gaucher’s

have

milk.

out

the

addition

of

of

performing

as

for

a

made

rst

in

to

of

these

humans

enzyme-replacement

by

yields

two

large

whole

plant-made

of

high

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relatively

using

the

varieties

produce

engineered

yield

been

use

to

combination

can

the

addresses

domestic

bred

been

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have

2012,

approved

(FDA)

animals

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selectively

animals

proteins

In

was

Administration

been

their

herd

farm

problem.

animals

into

small

therapeutic

plant

transgenic

have

female

proteins

means

in

modication

Lactating

recombinant

Drug

mammal

proteins

post-translational

and

systems

modication

( a h l )

modications.

Producing

of

Pr okaryotic

post- transla tional

M e d i c i n e

mass

of

plants

human

the

US

therapy

Food

to

treat

and

the

disease.

Biopharming to produce ATryn

mammary

Biopharming of antithrombin. gland-specic

gene of

Antithrombin

deciency

is

a

condition

that

regulatory

puts

isolate oocytes interest

sequences

patients

and

at

risk

surgery.

of

blood

ATryn

is

clots

the

during

& enucleate

childbirth

commercial

name

+

of

transfer

antithrombin

that

has

been

produced

in

the reconstructed

mammary

glands

of

genetically

modied

goats. embryo into

recipient female

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achieve

interest

added.

that

and

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the

this

genetic

specic

specic

gene

is

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additional

promoter

expressed

the

sequences

sequence

in

gene

milk

is

of

have

that

will

necessary

to

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be

ensure

in

target protein

creating

the

gene

construct.

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addition,

a

signal

fuse transgenic

expression vector

sequence

has

to

be

added

to

ensure

that

the

cell to enucleated

protein

verify presence oocyte

is

produced

reticulum

free

in

by

rather

the

than

cytoplasm.

antithrombin

cells

ribosomes

rather

protein

than

by

on

endoplasmic

ribosomes

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is

the

is

to

secreted

released

that

ensure

by

the

transfect

cells

are

that

the

l

select

of transgene

cell

mammary

▲

intracellularly.

Figure 11

Gene therapy

Use of viral vectors in gene therapy.

Some

inherited

results

is

one

in

the

such

disea ses

lack

of

disease.

a

It

is

transmembraneprote in

chloride

ions

out

of

are

caused

partic ular

caused

by

(CFTP).

cells

and

by

a

d efe ctive

enzy me

the

This

i nto

or

lack

of

protein

mucus.

gene,

protein.

cysti c

brosis

brosi s

normally

The

that

Cystic

chloride

tra nsports

ions

draw

589

B

B I OT E C H N O L O G Y

A N D

retroviral vector

B I O I N F O R M AT I C S

water

adenoviral vector

out

of

the

cells

a nd

ma ke

muc u s

w at e r y.

C ys t i c

capsid

brosis

envelope

in

the

patients

suf fe r

f r om

thi ck

muc u s,

wh ic h

b u i ld s

up

airways.

reverse

transcriptase

Gene

therapy

may

offer

a

cure

for

inherited

diseases

DNA genome

like

cystic

brosis.

In

gene

therapy,

working

copies

of

RNA genome

the

To

defective

do

this,

Figure12

a

gene

gene

shows

are

inserted

delivery

two

into

system,

different

a

person’s

or

ways

vector,

of

genome.

is

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needed.

viruses

as

cell membrane

vectors.

are

not

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a

the

might

common

homologous

between

areas.

local

or

alignment.

Using BLAST to align two proteins

Use of software to align two proteins.

There

are

a

sequences.

sequence

number

The

of

alignment

tool

nlm.nih.gov/protein/).

alignment

species

of

classied

using

threatened

sequence

same

gene

of

▲

596

of

In

species

this

for

over

sequence

that

this

will

in

be

for

we

Borneo

will

and

tarsier

( Tarsius

of

which

often

the

▲

sequence

is

The

syrichta).

of

There

tarsier

to

a

cox1

sequence

used

two

variously

and

is

it

resolve

controversy.

Figure 4 Horseld’s tarsier

a

for

bancanus ,

Horseld's

is

protein

Sumatra.

to

BLAST

conduct

tarsier,

Tarsius

compared

protein

the

(http://www.ncbi.

(cox1)

Horseld's

and

two

using

website

oxidase

classication

comparison

aligning

are

example,

bancanus

Philippine

the

NCBI

tarsiers.

lives

tarsier

the

the

cytochrome

called

for

instructions

at

Cephalopachus

for

uncertainty

type

the

primates

as

applications

following

Figure 5 Philippine tarsier

the

some

is

this

this

kind

B . 5

B i o i n F o r M a t i c s

( a h l )

Choose the protein

8

ationaJ Ce.nter for 8 01e

CJ

1

x

database from the

NCBI site and enter

www.ncbi.nlm.nih.gov

31

cox1 tarsius

8 HowTo 8

JCBI

[.._P _r_o_te_,n_ _ _ _:...,) ~ ox 1 tarsi us

~rfor ilogy lnformatlcn

r 1.

ochrome c oxida e subunit I 513 aa protein

arslus bancanus

From the nex t screen,

choose FASTA and the

sequence for the

Accession. NP_ 148740.1 GI: 14602228 GenPept FASTA

protein will be shown.

Alternatively, copy the

two accession numbers:

L 2.

cytoehrome c oxidase subunit I [Tarslus syrichtaj

NP_148740.1 and

YP_002929466.1

513 aa protein

Go to the BL AST home page,

Accession: YP_002929466.1 GI: 238866977 GenPept FASTA Graphics Related Sequences

(http://blast.ncbi.nlm.

Identical Proteins nih.gov/Blast.cgi),

choose protein, blast.

Basic BLAST Choose a BLAST program to run.

ISearchAlgorithms: a nucleotide database using a nucleotide query blastn, megablast, discoo ·guous megablast protein blast ISearch protein database using a protein query Algorithms: blaslp, psi-blast, phi-blast, delta-blast

nucleotide blast

Enter Query Sequence Entw accHalon number(•~ gl(a), or FASTA uquence(a)

P_1 48740. l

On the Enter Query

Sequence page, check

the box for ‘‘sequence

alignment’’, paste in the

accession numbers and

click on the BL AST

Or, upload file button.

JabTIUe

Align two or more sequences

Enter Subject Sequence Entar accualon number. gl, or FASTA sequence

VP_002929466. l

Scroll down to review

the dierences between

the sequence for this

Or, upload file

C!!_oose rn,

protein in the two

species.

Program Selection AlgorlU,m

Se.,.h pn,t.ln aequence using B!utp I lltow tN~lU In • new wfndaw

▲

Figure 6 Using BL AST to align two proteins

597

B

B I OT E C H N O L O G Y

A N D

B I O I N F O R M AT I C S

Multiple sequence alignment

Multiple sequence alignment is used in the study

of phylogenetics.

Phylogeny

A

is

the

phylogenetic

When

multiple

identied

position

sequences

then

the

the

in

Most

have

to

amino

is

for

have

acid

can

case

at

be

the

or

a

species

a

an

a

caused

sequences

10

G

by

sequence

a

consensus

that

example,

position

have

or

are

at

if

of

species.

G,

sequence

appears

you

A,

position

actual

are

is

at

aligned

G,

G,

C

often

a

certain

six

and

G,

10.

evolutionary

similarities

which

group

phylogeny.

nucleotide

As

will

of

sequences

several

sequence

a

match

in

is

by

a

coding

less

that

many

However,

the

is

to

use

all

are

said

same

by

for

to

chance

are

in

a

mutations

have

results

in

a

the

change

population.

DNA

computer

sequence

where

mutations

which

persist

higher

Nonetheless,

can

positions

not

region

likely

chance

sequences.

developed

have

times.

mutation

protein

been

acid

sequences.

sequence

of

describes

analogous.

A

evolutionary

that

compared,

nucleotides

which

homologous

effect.

are

amino

Alternatively

as

probability

it

the

history

diagram

sequences

occurred

same

in

the

in

homologous.

referred

on

consensus

relationships

a

aligned

and

Similarities

is

sequences

based

in

evolutionary

tree

sequences

based

alignments

The

than

algorithms

to

suggest

relationships.

Constructing phylograms and cladograms using computer applications

Use of software to construct simple cladograms and phylograms of related

organisms using DNA sequences.

A

phylogenetic

cladistics

is

a

tree

methods

cladogram.

that

is

created

discussed

This

type

of

in

using

the

sub-topic

5.4

tree

only

shows

3

pattern

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the

length

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included

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not

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represent

change

phylogram

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lengths

amount

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that

time

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the

that

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character

tree

(see

a

Under

Highlight

branch.

that

proportional

change

to

title

has

following

types

of

activity

software:

requires

ClustalX

the

and

use

is

based

on

an

activity

want

to

be

tree.

the

Genomic

choose

regions,

transcripts

and

‘FASTA ’.

all

of

the

example

sapiens

DNA

sequence

including

the

‘>gi|196123578:5667-7670

neanderthalensis’.)

8).

of

two

PhyloWin.

developed

Open

on

a

either

Notepad

from

your

PC

or

TextEdit

Mac.

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activity

(for

Homo

the

gure

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you

relative

along

phylogenetic

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that

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spans

species

a 4

branching

Choose

Paste

your

sequence

into

the

text

editing

by document.

the

American

Museum

of

Natural

History.

In

7 this

activity,

we

will

conduct

multiple

Repeat

with

different alignment

a

number

for

of

the

gene

primate

for

cytochrome

oxidase

species.

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the

2

Search

NCBI

website

and

8

choose

Edit

from

organisms.

the

titles

and

but

to

remember

separate

underscore.

For

primate’. neanderthalensis.

598

sequences

to

words

include

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the

the

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gene.

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sequence

example:

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