Class 8 Biology - BeTOPPERS NEET Foundation Series - 2022 Edition

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NEET FOUNDATION Class VIII

BIOLOGY

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Published by

:

USN Eductech Private Limited Hyderabad, India.

CONTENTS 1.

Crop Production and Management

..........

01- 16

2.

Microorganisms Friends & Foe

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17- 26

3.

Conservation of Plants and Animals

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27 - 38

4.

Cell - Structure and Functions

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39 - 50

5.

Reproduction in Animals

..........

51 - 60

6.

Reaching the Age of Adolescence

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61 - 72

7.

Pollution of Air and Water

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73 - 84

8.

Key and Answers

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85 - 88

CONTENTS

CROP PRODUCTION AND MANAGEMENT CHAPTER

1

      

Early Man’s Food Agriculture & Farming Food from Plants Food Production & Farm Management Soil Preparation Seed Selection & Sowing Improvising Soil Fertility

      

Weeding Irrigation Harvesting Crop Protection Storage of Grains Food from Fruits and Vegetables Food from Animals

SYNOPSIS 1 1.

Early Man’s Food Early man was primarily a hunter and a flesh-eater. He also ate fruits and seeds. He did not cultivate food He was a food gatherer. He and his family had to go without food when the weather was rough This made him change his habit to domesticating cattle and growing of plants along his dwelling unitsThis enabled him to make use of food available around his home in case he could not go for hunting Since man, animals and plants require water all round the year, people started settling near rivers, lakes and ponds. This was the beginning of food production by man

2.

Agriculture & Farming When man adopted to plant eating along with flesh eating, he started collecting seeds. The seeds were scattered, germinated and grew. The produce of the plants was used as food and the plant body was left as fodder for cattle. With the increase in demand for food, man became aware of taking care of plants. This was the beginning of agriculture. The word agriculture has come from two latin words, ager meaning field and culture meaning cultivation. Agriculture or farming is the cultivation of soil.It includes growing of plant crops and rearing of animals.

3.

Food from Plants Food from plants includes : Cereals, Pulses, Fruits, Vegetables. We also use oils and beverages as part of our food. The plants cultivated on a large scale specially for food are called food Crops. Cereals: The important cereals include Corn, Wheat and Paddy. Cereals provide us, Starch, Fibres, Minerals, Some vitamins, Proteins.

CORN

WHEAT

PADDY

8th Class Biology

2

Pulses: The important pulses include Pea, Beans and Peanuts. Pulses are rich in : Starch, Fibres, Minerals, Some vitamins, Proteins.

CO RN

WHEAT

PADDY

Fruits and Vegetables They provide us: Nutrients, Minerals, Vitamins, Proteins, Carbohydrates, Gel. Crops All the plants that gives us food are grown in groups called Crops. Depending on the time and place of their growth, crops are classified into two types. Herbaceous Crops These are crops grown in a particular season. i) Kharif Crops The seeds of these crops sown June/July.The crops are harvested in September/October. Examples : Sorghum, Sugarcane, Pearl millet, Pulses, oil seeds, etc. ii) Rabi Crops These are also known as Winter Crops. The seeds of these crops sown October/November. The crops are harvested in March/April.Winter flowers and winter vegetables are grown. Examples : Wheat, Barley, Pea, Oats, etc. iii) Zayed Crops These are also known as Summer Crops. The seeds of these crops sown March/April. Summer flowers and Summer vegetables are grown.The crops are harvested in May /June. Examples: Cucurbita, Lagenaria, Bitter Gourd, Melons, etc. Shrubs and Trees These crops are also known as Plantations.They are cultivated in forests, on orchards or farms. Examples: Tea, coffee, cocoa, mango, apple, guava, plums, roses, etc.

4.

Food Production & Farm Management India is primarily an agricultural country.Water is one of the important requirements for growing crops. For water, farmers mainly depend on rain. Need for better Agricultural Practices Monsoons may fail at times. With the help of scientific and technology, arrangements must be made which should help the farmer with water all round the year.Also, more and better yields from fields much be achieved.This is possible by adopting better agricultural practices and farm management.Farming. The tasks performed by a Farmer for tilling a farm and for cultivation is called Farming. Farming Practices The different farming practices are: (i) Soil Preparation (ii) Seed Selection (iii) Seed Sowing & Planting

Crop production and Management

(iv) (vii)

5.

Soil Fertility Harvesting

3

(v) (viii)

Weeding Crop protection

(vi) (ix)

Irrigation Storage

Soil Preparation i)

ii)

iii)

Tilling : The preparation of soil before planting a crop is called tilling of the soil.Compost (manure prepared from decayed animal and plant wastes) is placed in small heaps which is then ploughed. Ploughing: Ploughing helps in loosening and turning the top soil upside down and also in mixing the compost with the top soil.This makes the soil fertile, airy and increases its water retaining capacity.It also helps in uprooting weeds and exposing seeds, worms, insects and pests in the fields. Levelling: Large lumps of soil are broken with a harrow. The soil is then levelled or made into ridges and furrows. Levelling ensures uniform distribution of water in the field.

Tilling

Ploughing

Levelling

Tools in Soil Formation Some of the farming tools are:

Plough

Fork

Sickle

Scythe

Harrow

Trowel

A plough is a sharp pointed wedge that cuts into the soil. It also turns the soil bringing the lower mineral rich soil to the top. Today, farmers use tractors to draw and drag a multipronged plough.

6.

Seed Selection & Sowing Seed Selection Good quality seeds are important for better yield. Some of the good qualities of seeds are: i) Clean, not mixed with the seeds of weeds. ii) Dry, solid and healthy iii) Free from fungal spores, pests or insects iv) Of good breed (hybrid seeds or Gm seeds) Seed Sowing Sowing is the process of putting seeds in the soil

4

8th Class Biology

Method of sowing depends on the type of crop. i) Before sowing the good and healthy seeds are selected and treated with pesticides like ‘agrosan’ ii) Treatment of seeds with pesticide protects the seeds from being eaten away by birds and from fungal or bacterial growth upon them while sprouting. Methods of Seed Sowing i) Broadcasting Sowing of Seeds by spreading or sprinkling in the field is called Broadcasting of seeds.Seeds of crops like barseem and coriander are spread or sprinkled in the field. ii) Dribbling The seed is placed in a small hole in the soil and then the hole is covered with soil. iii) Drill Sowing Seeds are sown with the help of ‘seed drill’. Seeds of wheat, maize, barley and millets are sown in rows and in furrows at a particular depth along the field. Seed drill is a funnel with a long and hollow stem. The farmer puts the seeds into the funnel and the seeds go down the stem, one by one, to get into the soil. Mechanized drills attached to tractors are used on big farms. Seed Sowing – Problems i) Seeds left on the surface of the soil may be carried away by wind are destroyed by the insects and birds. ii) Seeds sown close to one another may result in overcrowding thereby resulting in hampered growth. iii) Seeds placed deep inside the soil may fail to germinate and fail to come out into the air. Seed Sowing – Precautions to be taken i) Except for the seeds which are sown by broadcasting, the seeds are sown at: ii) An appropriate distance from one another iii) A particular depth under the soil Preparing Nursery Plants In the case of paddy specially and most of the seasonal vegetables and flowering plants, initially the seeds are sown in a nursery to obtain saplings. Saplings are then transplanted into the fields placing them at a proper distance from one another. Transplanting helps in planting only healthy plants and at a proper distance from one another . Rearing seedlings to saplings in a nursery helps in eliminating weak saplings.

Crop production and Management

5

WORKSHEET 1 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

What do you understand by agriculture and farming? Is agriculture limited to growing of plant crops? What is ‘mixed farming’? Name some cattle kept by farmers and dairymen. What do you understand by livestock? Name crop plants which yield: a)Starch b)Sugar c)A pulse d)Edible oil List some plantations cultivated as crops. How are healthy seeds obtained from a mixture of healthy, weak and diseased seeds? What is the advantage of treating seeds with a pesticide before sowing? List the various methods of sowing seeds. Explain the method of a) Drill sowing b) Transplanting What is the advantage of transplanting saplings from a nursery instead of sowing seeds directly into the soil in the case of paddy and vegetable crops?

SYNOPSIS 2 7.

Improvising Soil Fertility Top soil supports plant life. Herbs (crops) grow in top soil and derive their mineral nutrition from it. Once a crop is harvested, the top soil in which the top soil has been growing gets poor in minerals.This soil needs enrichment with minerals before another crop is planted on it. First thing a farmer does is to plough the fields. Ploughing turns the soil and brings the leached minerals up from the soil below. Ploughing may not help much in improving the soil fertility. The lost plant nutrients in the soil are replenished with the addition of fertilizers. Fertilizers Fertilizers are the substances which contain nutrients essential for plant growth. The types of fertilizers are: (i)Natural fertilizers or organic fertilizers (ii) Chemical fertilizers or inorganic fertilizers Natural Fertilizers Natural fertilizers include naturally occurring organic materials or naturally occurring mineral deposits. Manure or compost is the decomposed plant and animal waste (farm waste including animal droppings), waste food, dead and dry leave and offal (includes garbage and dried left over flesh from slaughtering animals) goes into the making of the compost Manure – Its Preparation • Compost is prepared by the farmers on their farms • A deep pit is made in a corner of the field which is filled with farm waste, straw and dead leave from time to time • This is covered with a layer of soil and is moistened by sprinkling water over it from time to time • Worms, insects and microbes grow on it and help in decay the organic matter, turning it into humus • Humus is rich in minerals, microbes and decayed organic matter

6

8th Class Biology

Green Manure Green manure is a type of cover crop grown primarily to add nutrients and organic matter to the soil.There is a time gap between harvesting a crop and sowing of the next crop. Instead of leaving the field without any plants on it during the gap period, a fast growing leafy leguminous fodder crop such as Trifolium (Barseem), or Alfalfa or Sasbania is sown This crop come up soon and it yields green leafy fodder for the cattle. The roots of these plants bear root nodules with nitrogen fixing bacteria. This enriches soil with mineral nutrients. While preparing the field for sowing the next crop, the field is ploughed along with green leguminous crop and it’s nodule bearing roots. The green plants along with the roots go into the soil and decompose to form organic manure (compost). Nitrogen Fixation It is the natural way of fixing nitrogen in the soil. Body of living organisms is made of proteins. Proteins are compounds of nitrogen, carbon, oxygen and hydrogen. 78% of air is nitrogen. Air nitrogen is fixed into compounds of nitrogen (nitrogen oxides soluble in water) by certain microorganisms. Microorganisms such as Rhizobium (Bacillus) are present in the root nodules of leguminous plants. Bacterium Rhizobium Rhizobium Root nodules radicicola is capable of fixing air nitrogen. Fixation of nitrogen enriches leguminous crop.These crops grow and mature at the same time. the soil in a natural way.Fert ilizer s For example, corn (maize) and soyabean (legume) or any other need not be added to the soil in which pulse are cultivated together as Kharif or summer crop. crops bearing root nodules with Nitrogen Cycle nitrogen fixing bacteria in them have been grown. Root nodules occur on the roots of plants that associate with symbiotic nitrogen-fixing bacteria. Nitrogen fixed by the bacterium is supplied as additional nitrogenous nutrition to the host plant. In turn, the host provides shelter and carbohydrate food to the bacterium. This process, in which the bacterium and the plant live together for mutual benefit, is called symbiosis. Rotation of Crops Growing of a leguminous crop in between two cereal or vegetable crops is called rotation of crops.In multiple or mixed cropping, two or more crops are sown simultaneously in the same field.One of these is a

Crop production and Management

7

WORKSHEET 2 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

What is the necessity of enriching the soil from time to time? Name the methods of enriching soil. How does ploughing help enrich the soil? How is manure or compost prepared on farm? What is green manure? How do we obtain it? What do you understand by symbiosis? How are root nodules on the roots of leguminous plants useful for the crop? List some common leguminous plants. What is ‘nitrogen fixation’? Why do we consider root nodules a gift from nature? How is the nitrogen in the air fixed apart from nitrogen fixation by Rhizobium? Name the different agencies which help in nitrogen fixation What is rotation of crops? What is the advantage of practicing rotation of crops? What is multiple cropping? Explain giving examples. How is multiple cropping different from mixed farming? List some common cattle and farm animals which are reared by farmers. List some of the natural means by way of which the soil is enriched with nitrogenous nutrition. What is the role played by root nodules found on the roots of leguminous plants? What name has been given to the relationship between two organisms, helping one another with food and shelter?

SYNOPSIS 3 Chemical Fertilizers Any nutrient added to the soil for improving its fertility is called a Fertilizer. Fertilizer may be natural (compost made from farm waste or the green manure) or synthetic (prepared from chemicals in Fertilizer factories).In common use, manure or compost is a natural fertilizer and chemical compounds are synthetic fertilizers or simply fertilizers. Composition Fertilizers are chemical compounds of mineral nutrients for plants. They are prepared in Fertilizer factories. The essential parts of nutrients are, Nitrogen (N), Phosphorous (P) and Potassium (K) Fertilizer may be a mix of three major plant nutrients such as Sulpha mix (NPK) or single nutrient such as Superphosphate (P), Potash (K), or Urea (N). Some common fertilizers used by farmers, in addition to the above are Di-ammonium phosphate (DAP) and Calcium ammonium nitrate (CAN) Examples: Some common fertilizers are: Urea, Super phosphate, Potassium sulphate, Ammonium phosphate, Potassium phosphate, etc. Note: i) Fertilizers are highly hygroscopic (absorb water) and leach soon into the soil. ii) In addition, some micronutrients like sulphur and magnesium compounds are also added to the soil. iii) Lime is often added to the soil to nutralize its acidity

8th Class Biology

8

Application of Chemical Fertilizers Time of application of different fertilizers is different for different crops and at different stages of growth. Some fertilizers are added to the soil at the time of sowing, some at the time of stem elongation and leaf growth, and some towards flowering and reproductive growth. Points to be noted during their application i) Fertilizers should be used with utmost care . ii) Too much use of fertilizers can upset the chemical nature of the soil and also result in the ‘burning’ (browning) of the leaves of the crop plants iii) Fertilizers may also leach into the soil with rainwater to poison the groundwater. Otherwise fertilizer is the sure, fastest and easiest way of providing mineral nutrition to the crop plants. Organic Farming Worms, specially the earthworms, are a great friend of farmers. They flourish well in moist soil rich in decaying organic matter. Worms eat into the soil to burrow themselves, leaving behind the casts and canals, making the soil airy, soft and fertile The Government of India has established National Institure of Organic Farming with its Head Quarters at Ghaziabad and six regional offices, each at Bengalooru, Hissar, Jabalpur, Nagpur, Bhubaneshwar and Imphal, and a centre at Ludhiana.

WORKSHEET 3 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

What are fertilizers? From where do we obtain fertilizers? Name the three essential elements forming a part of the plant nutrition. Name some common fertilizers? Why should we use chemical or inorganic fertilizers in the fields with utmost care? What are the harmful effects of using chemical fertilizers in excess for the enrichment of the soil? What are the advantages of using compost or green manure as against the use of fertilizers for the enrichment of soil? What is organic farming? What are the different stages in the life of a crop when fertilizers are to be used? Why should the earthworms be cultivated in garden soil?

SYNOPSIS 4 8.

Weeding Weeds are plants other than crop plants, growing along with crop. Weeds grow vigorously and draw more nutrition from the soil than the crop plants.This makes the soil poor in minerals and deprives the crop of its mineral needs. They also block full sunlight and air from the crops. So, they should be removed as early as possible, but certainly well before they flower and bear seeds so that they are not able to multiply . Some Common Weeds (i) Chenopodium (bethua) (ii) Amaranthus (chulai) (iii) Convolvulus (iv) Argemone (piladatura) (v) Dhatura (vi) Alfalfa (vii) Wild pea (viii) Wild oat (ix) Other grasses

Crop production and Management

9

The process of removal of Weeds from the crop fields is known as Weeding. Weeding - Methods i) Weeding by Hands: Pulling out weeds with hands is the most common method. ii) Weeding by Herbicides Herbicides are chemicals which are poisonous for weeds but do not affect crop plants. iii) Weeding by Biological Control Some worms and insects have a special affinity for certain weeds on which they flourish, eating and killing them without harming the crop plants. These organisms are cultured and reared on weeds

WORKSHEET 4 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Name some common weeds. What are weeds? Are weeds really unwanted plants? How are weeds useful in nature? Which is the most convenient and common method of weeding? What do you understand by weeding? How is biological control useful in weeding? What are weedicides? Explain their use giving examples. Why should the weeds be weeded out before they flower and bear seeds? Why should the roots from leguminous weeds be left behind in the soil while weeding them out?

SYNOPSIS 5 9.

Irrigation Water is essential for the growth of plants. Different crops need varying amount of water at different phases of their growth.. Proper watering of a crop at the right time is called irrigation. At times, the rains are scarce and the crops fail due to draught or there are heavy rains and crops get damaged due to floods. To overcome the dependence on rain, various irrigation schemes for efficient use of water resources are drawn depending upon the source of water. Irrigation Schemes Canal irrigation, raising of dams, from rivers and streams, Groundwater irrigation from wells, tube wells, lakes and ponds. In almost all the states of India there are dams to store runaway water behind them and canalize them for irrigation. Also, the water falling from dams is used for the generation of hydroelectricity. In certain cases, the fields are flooded with water from tubewells or canals. Too much of water goes waste in this type of flood irrigation. Flood irrigation is required only for paddy crop. Fields are irrigated from time to time to save the crops from draught.Paddy (rice) is the only crop, the saplings of which are planted in flooded fields.Even paddy is watered sparingly towards the maturation of the crop. Vegetable crops are irrigated almost daily with surface irrigation, through drip irrigation or sprinnklers. Sprinkler irrigation is considered most effective for herbs. It saves on water.

8th Class Biology

10

10

Harvesting Gathering the produce(grains, seeds or fruits) on maturity of a crop is called Harvesting Matured crop plants are cut close to the ground by different means. Manual Harvesting It is done with hands with the help of a hand-sickle. This has been a practice for long and small marginal farmers still make use of this method. Dry matured crop plants are cut at the ground level and are stacked in bundles for threshing, Threshing: Threshing is the separation of grains from the chaff. It is done in different ways: a) At a time, small bundle of crop plants is threshed upon a stone slab b) Bullocks are made to tread upon the ‘ears’ full of grain as in corn (maize), etc. c) Mechanical threshers and shellers are used to bring out grains and also remove husk from the grains. Shellers are used specially for removal of husk (shell) from paddy. Winnowing Grains obtained from threshing may be having husk (chaff) mixed with them.Grains are separated from husk by winnowing. The mixture of husk and grains is dropped from a height through a ‘winnow’ Husk is blown off to a distance by wind and grains being heavy fall near the platform. Mechanised Harvesting It is practiced with the help of machines called ‘harvester combine’. It harvests the crop, threshes and separates the husk from grains simultaneously. Clean grains come out from the machine which are stacked in gunny bags. Mechanised harvesting is convenient and fast and it helps in harvesting the crop well before the produce is affected by rain. This helps the farmer in storing or transporting the produce to the market immediately.

WORKSHEET 5 1. 2. 3. 7. 8. 9. 7. 8. 9. 10.

What do you understand by irrigation? What has been the main source of water for irrigating the fields? Name some of the irrigational schemes. Besides irrigation, what is the additional advantage of raising dams? Which crop needs flooded fields while planting saplings? What do you understand by ‘harvesting’? How are crops harvested manually? What is ‘winnowing’? Describe the working of a ‘harvester combine’. What is the advantage of mechanised harvesting?

Crop production and Management

11

SYNOPSIS 6 11. Crop Protection Protection from Intruders 1. Grazing Animals Fence made from barbed wire or spiny (thorny) hedge plants is raised around the field to restrict the entry of intruders. 2. Birds and Wild Animals Farmers put a scarecrow or bet drums to keep them away. Birds are useful for the crop before flowering and fruiting because they eat away insects, larvae and worms which feed on the leaves.Birds are harmful only when the crop starts bearing fruits and seeds, which are eaten away by the birds. 3. Rats and Moles They are killed with the use of poison (rodenticides) in their feed 4. Locusts and grasshoppers They are voracious eaters of leaves, buds and even stems. Locusts are small, brown or deep yellow in colour and grasshoppers are big and green. Protection from Insects 1. Insects and germs are parasites on crops and may also cause diseases in plants. Germs may be bacteria, virus and fungi. To save crops from insects and germs, poisonous chemicals called pesticides are sprayed The pesticides may be: 2. Insecticides like Baygon, Mortein, Malathion, DDT, BHC, Methyl parathion, etc. are used for killing insects 3. Fungicides like Bordeaux mixture, Disyston, dilute solution of copper sulphate(blue vitriol), etc. are used against bacterial and fungal infections.

WORKSHEET 6 1. 2. 3. 4. 5. 6. 7. 8.

Why do crops need protection? Birds damage the fruits and seeds on crops but they are considered as useful. Why? What do you understand by pests? What do you understand by pests? What are insecticides? Give some examples. What are fungicides? Give some examples. Why do we have a fence around a farm? What is a scarecrow?

SYNOPSIS 7 12.

Storage of Grains Grains are dried well before storage, Stored at a dry place away from moisture, Stored in metallic bins or in silos made from mortar (cement-concrete), Stored in gunny bags in big godowns called granaries as a big reserve stock meant for Public Distribution System (PDS) for poor people or as a ‘buffer stock’ to meet emergency requirements. Nitrogen is blown into granaries to push the oxygen out.

8th Class Biology

12

13.

Food from Fruits and Vegetables Production of food is not limited top cereals and pulses. Vegetables and fruits form a good part of our food. Salad is a mixture of fruit and vegetables. Food from fruits and vegetables can be studied under three headings: Growing vegetables, Growing fruits, Storage of fruits and vegetables. Growing Vegetables The process of growing vegetables is different from cultivating cereal or pulse crops. Vegetables are mostly soft, seasonal and herbaceous plants. Their storage life (shelf life) is too short and they need immediate transportation to market for sale. Only tubers (potato), corms (ol or zamikand), rhizomes (ginger, turmeric) and bulbs (onion, garlic) can be stored that too not for long. Growth of vegetables is better in compost rich soil, which is moist, airy and porous.Use of fertilizers for vegetables must be limited. Vegetable crops are better irrigated through spray or drip method.Excessive watering may harm and destroy the vegetable crop. Growing Fruits The place where fruit trees are grown in called an orchard. Most fruit plants are trees or shrubs and are called plantations. Fruits borne on herbs or creepers are Cucumber, Watermelon, Melon, Strawberry and Raspberry. Each variety of fruit plant is planted and looked after in a different way. Each variety of fruit plant is planted and looked after in a different way.Seedless varieties of guava and grapes or superior varieties of apple and mango are grafted plants Graft is prepared on a rooted cut shoot (stock) from a wild but sturdy variety on which a cut shoot (scion) from a superior quality fruit bearing plant is attached. Care of the fruit Plants • Special care is taken of the fruit plants for better growth, flowering and fruit bearing capacity. • Fruits planted are pruned during non-fruiting season. • They are sprayed with pesticides for protection against pests. • They are also sprayed with hormones for better blossoming and fruit setting. • Honeybees are reared in orchards to help pollination for early and fast setting of fruits. Management & Marketing of Fruits • Fruit management is systematic and important • It is time bound since fruits mature and perish soon after plucking. • Fruits are packed individually and in cartons and marketed immediately thereafter. Storage of Fruits and Vegetables i) Fruits are plucked when fully grown but are yet to mature. ii) Unripe fruits are wrapped individually in old newspaper pieces and then put into crates or packed in cartons. iii) Crates and cartons are then transported to cold storages, located near fruit wholesale markets or they are put for sale. iv) Tubers, corms, rhizomes are put for sale directly or they are stacked in gunny bags in cold storages.

Crop production and Management

14.

13

Food from Animals Primarily, man has been a hunter and a flesh eater. A good amount of his food comes from animal sources. Besides hunting, man has been taming and rearing animals for rood. Some of the food products obtained from animals are: Milk, Meat, Eggs, Honey. Rearing of animals on a large scale at home or on a farm, taking care of their shelter, proper food, health and breeding is called animal husbandry Milk as Food • Cows and buffallos are the main source of milk in India. • In hills and plains, milk from goats and sheep is also consumed as food. • In some places, milk from camel is also used as food, though it is not very good to taste. • Milk yielding animals are called milch animals or milch cattle or dairy animals, as they are linked with dairy. Flesh as Food • The edible flesh is called meat. • It excludes fish and poultry(birds). • Flesh mainly comes from cattle such as cows, ox, buffallo, goat and sheep. • Generally, males of cattle are used for their flesh. • Some cattle are specially bred for their meat. • Crabs and prawns are also eaten for their flesh. Fish as Food • Fish is highly nutritious since it is rich in easily digestible proteins and vitamin A and D. • Fish is common in all the water bodies. • Inland fish, found in ponds, lakes and rivers is the fresh water fish and the fish found in seas is the marine fish or saltwater fish. • Rearing of fish on a large scale is called pisciculture. Sea Food • There is more life in water than on land. • Marine fish is the largest inhabitant of sea. • Sea food also comes from animals like prawn, crab, oyster, squids, etc. • Some of there animals like fish, prawn and oyster are reared. • We get tonnes of fish from sea everyday. • Government has fishery department to take care of the water bodies and to develop fish culture by introducing breeds with better yield and less bones Poultry, Rearing of Birds for Food Poultry is the rearing of birds like fowl(cock and hen), duck, goose and turkey for their meat and eggs. It is also called white meat and is taken as a delicacy. Eggs from birds are rich in proteins. Honey as Food Honey comes from honeycomb made by honey bees. Honeycomb is also called hive.Hone hivet is a special kind of shelter made by bees and the wasps where a colony of bees or wasps live together.A hive made by bees is called a beehive. Since beehive stores honey, it is called honeycomb.Rearing bees for their honey is called apiculture. Apis is the scientific name for honeybee. How are bees reared? For rearing bees, special woodden boxes are placed in and around orchards. Bees move in and out through the pores in the door and develop hive inside the box. These boxes are called apiaries.

8th Class Biology

14

What is Honey? Nectar collected by honeybees from flowers is sugar solution which gets concentrated on dehydration into glucose and fructose solution and gets mixed with enzymes, vitamins and minerals coming from bees Quality of honey depends upon the kind of bees and the type of flowers from where nectar is collected. Good quality honey is medicinal and may also possess antibiotic properties Test for Purity of Honey Pure honey when poured in a glass of water goes down forming a thread of honey in the water.Impure honey made from sugar disperses in water without forming a thread.

WORKSHEET 7 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

1.

2. 3.

List precautions to be taken before storing grains. Why should the grains be stored in metallic bins or silos? Why is nitrogen pushed into the granaries? What is the disadvantage of storing grains in cellars? What are weevil? Which is the most common insect pest on grains? Name some animals which are kept as pets. Name the items of food which come from animal sources. Define ‘animal husbandry’. Which animals are milch animals? Name some common animals the flesh from whom is eaten as food. Name some poultry(birds) and the food we get from them. What is hive? Why do we call beehive as honeycomb too? From where do honeybees collect honey? Give the test for pure honey.

Match items in column A with those in column B. A B (i) Kharif crops (a) Food for cattle (ii) Rabi crops (b) Urea and super phosphate (iii) Chemical fertilisers (c) Animal excreta, cow dung, urine and plant waste (iv) Organic manure (d) Wheat, gram, pea (e) Paddy and maize Give two examples of each. (a) Kharif crop (b) Rabi crop Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.

Crop production and Management

15

4.

Complete the following word puzzle with the help of clues given below. Down 1. Providing water to the crops. 2. Keeping crop grains for a long time under proper conditions. 5. Certain plants of the same kind grown on a large scale. Across 3. A machine used for cutting the matured crop. 4. A rabi crop that is also one of the pulses. 6. A process of separating the grain from chaff.

5.

Continuous cultivation of crops on the same piece of land reduces the nutrient content of soil. Therefore i and ii are added to soil to replenish its lost nutrients. (A) i-manures; ii-fertilizers (B) i-fertilizers, ii-pesticides (C) pesticides, ii-weedicides (D) i-weedicides, ii-manures Seed drill is a modern tool used for sowing seeds in the crop field. Which of the following statements about seed drill is incorrect? (A) It sows seeds at proper distance from each other, thereby avoiding overcrowding. (B) It reduces the chances of pest attack on crops, thereby increasing crop yield. (C) Unlike manual sowing of seeds, it sows seeds at proper depth. (D) Unlike manual sowing of seeds, it is less time consuming. Pooja put a handful of seeds in a container filled with water. After sometime, she observed that some seeds were floating on the surface of water, while others had sunk to the bottom of the container. The seeds floating on the surface of water are (A) damaged as they are hollow (B) damaged as they are solid (C) healthy as they are hollow (D) healthy as they are solid Which of the following tools is used for ploughing the field? (A) Hoe (B) Rahat (C) Dhekli (D) Funnel The ploughing of field is the first step in the process of crop plantation. Which of the following statements about the usefulness of ploughing is incorrect? (A) It promotes the growth of useful microbes in soil (B) It brings nutrients to the top layer of soil (C) It reduces the population of pests in soil (D) It helps in aerating the soil Which of the following crops is a Kharif crop? (A) Wheat (B) Gram (C) Maize (D) Mustard A farmer planted rice plants in his well-irrigated field season after season. The given figure illustrates the yield of rice in his field from 2003 “ 2007. Which of the following statements does not support the given observation? (A) His land fertility is reduced because of the continuous usage. (B) The weeds may have interfered with the yield of the crop. (C) He may have used excessive amount of fertilisers. (D) He may have used excessive manure in his field.

6.

7.

8. 9.

10. 11.

16

8th Class Biology

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Hari sowed some seeds of rice in his fields. Initially, the plants were growing well but after some time he found that their growth had started to decline. After analysing the situation, he applied 2, 4-D in his field. Afterwards, the plants regained their growth The possible cause for the decline in the growth of the crop in Hari’s field is (A) disease in plant (B) lack of nutrients (C) presence of pest (D) presence of weeds A farmer divided his field into 2 parts after ploughing. In part I, he sowed seeds by spraying them manually while in part II, he used a seed drill. The given figure illustrates the position of seeds in both the parts of the fields. He gave the same treatment to both the parts of the field Which of the following statements is correctregarding the given situation? (A) The yield in part I and part II would be the same. (B) The yield in part I would be more than the yield in part II. (C) The yield in part II would be more than the yield in part I. (D) The yield in part I and part II cannot be compared through given set of information. Column A Column B i Cow a. Pig ii. Hen b. Buffalo iii. Fish c. Duck The alternatives in the given table can be correctly matched as (A) i  b, ii  c, iii  a (B) i  a, ii  b, iii  c (C) i  b, ii  a, iii  c (D) i  c, ii  b, iii  a Sudha bought four gram seed samples from four different grocery shops. To test the quality of seed, she performed an experiment. In her experiment, she put 50 gm of seed from each sample in four bowls of water as shown in the figure.

13.

14.

15.

Which of the following samples of gram seeds contains the least amount of damaged seeds? (A) Sample I (B) Sample II (C) Sample III (D) Sample IV 

MICROORGANISMS : FRIENDS AND FOE CHAPTER

2

 Micro-organisms And Their Habitat  Classification Of Microorganisms

 Use Of Micro-organisms In Increasing Soil Fertility

 Use Of Micro-Organisms In The Preparation Of Food

 Micro-organisms As Foe

 Use Of Micro-organisms In Medicines

 Food Preservation

 Methods of Prevention of Diseases

SYNOPSIS 1 1.

Micro-organisms And Their Habitat You must have observed a number of plants and animals in your surroundings. But do you know that there are certain organisms present in our surroundings, which are not visible to us? Living organisms which are not visible to the naked eye are known as micro-organisms. Let us explore micro-organisms in detail by performing a simple activity. Place a moist piece of bread near your window for a day. Observe the bread using a magnifying glass the next day. You will observe many small, black round structures growing on it. These structures are micro-organisms.

• • •

What does this observation suggest? The observation suggests that micro-organisms are present everywhere-in water, air, and soil. In fact, micro-organisms can survive under all types of environment. They are found in different environments, ranging from icy cold mountains to hot springs, and from deserts to marshy lands. Some micro-organisms are also found living on, or inside the body of other organisms including humans. Some Interesting Facts: Do you know that scientists have discovered a bacterium living at a depth greater than 10000 metres in the sea? Microbes outnumber all other species and make up most living matter. Microbes generate at least half the oxygen we breathe.

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2. •

Classification Of Microorganisms Do you know which organisms are classified as microorganisms? Let us find out. Microorganisms can be classified into four major groups depending on their characteristics. Let us study the major groups of microorganisms. Virus Viruses are also types of microorganisms, but they cannot reproduce on their own and require a host cell to complete their life cycle. They are responsible for causing a number of diseases in humans such as polio and chicken pox.

WORKSHEET 1 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

What are microorganisms? Can we find a place without microbes in nature? Name the device which has made the study of microorganism successful. Which microorganisms helps in softening of bread, cakes etc.? What is the size of small microbes? How many cells are generally present per microorganism? Where do microbes grow? How do you compare the number of microbes present in ponds and lakes with those present in water obtained from deep wells or hand pumps? How do yeast make bread light and spongy? Describe the main characteristic of viruses in brief.

SYNOPSIS 2 3.

(i)

Use Of Micro-Organisms In The Preparation Of Food Do you know that micro-organisms are used to prepare a number of food items we consume? Let us explore the use of micro-organisms in the preparation of food. Use in preparing curd and bread You must have seen your mother preparing curd by adding a small amount of curd to warm milk and keeping it to set the whole night. What do you think the small amount of curd contains, which helps in the preparation of curd from milk? Curd contains several micro-organisms like the bacteriumLactobacillus, which promotes the formation of curd. It multiplies in milk and converts it to curd. Bacteria are also used in the preparation of cheese, pickles, and many other food items But how are micro-organisms useful in the preparation of bread? Let us find out by performing this simple activity. Take ½ kg of maida and add some sugar to it. Mix it with warm water and add a small amount of yeast powder to the mixture. Knead the maida to make soft dough. Keep the maida aside and record your

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observation after two hours. You will notice that maida has risen and has become fluffy. Do you know the reason behind the fluffiness of Maida? This happens because yeast added to maida reproduces rapidly, and produces carbon dioxide gas while respiring. This gas fills the dough and increases its volume making it to rise.

ii.

4.

Based on this principle, yeast (which is a micro-organism) is used in the preparation of breads and cakes. It helps in making them spongy. Use in preparing alcohol and wine Micro-organisms are used commercially to prepare alcohol, wine, and vinegar. Yeast is the most common micro-organism, which is used to prepare alcohol and wine. Let us find out how yeast takes part in the production of alcohol.During the preparation of alcohol, yeast is grown on natural sugars present in grains like rice, wheat, barley, or crushed fruit juices. Yeast breakdowns the sugar present in these grains into alcohol, leading to the large-scale production of alcohol. This process of conversion of sugar into alcohol is known as fermentation.

Use Of Micro-organisms In Medicines You know that micro-organisms cause diseases, but do you know that some micro-organisms are also used to prevent diseases? Let us explore. You must have consumed antibiotics when you were ill. What do you think are antibiotics? Antibiotics are medicines which are obtained from certain micro-organisms. They kill, or stop the growth of other disease causing micro-organisms. Thus, they are useful for humans. Antibiotics are currently being obtained from certain bacteria and fungi. Streptomycin, tetracycline, penicillin, and erythromycin are a few examples of the commonly used antibiotics. Apart from treating human diseases, antibiotics are also mixed with livestock and poultry food to check the spread of microbial infection among farm animals.

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Vaccines You must have been given injections to protect yourself against several diseases when you were young. These injections are called vaccines. But what do you think these vaccines contain? Vaccines are the dead or weakened micro-organisms, which help the body fight against diseases. Let us find out how. Our body reacts to infection by micro-organisms by producing certain substances called antibodies. These antibodies kill the invading micro-organisms freeing the body from diseases. So, in order to protect the body from diseases caused by micro-organisms, some dead or weakened microbes are introduced in the body, which cause the production of antibodies. These antibodies then remain in the body for a long period of time protecting the body from diseases. This whole process of introducing vaccines into the body is known as vaccination. Vaccines are available for a large number of diseases like cholera, tuberculosis, small pox, hepatitis, chicken pox, polio etc. Therefore, vaccines are another medium through which micro-organisms are used to treat diseases in humans and other animals.

5.

Use Of Micro-organisms In Increasing Soil Fertility Do you know that some bacteria help in increasing soil fertility? There are some bacteria and blue-green algae, which fix the atmospheric nitrogen into soil and thereby, increase the fertility of soil. They are known as biological nitrogen fixers. One such bacterium is Rhizobium, which is found in the root nodules of leguminous plants like pulses. It lives in symbiotic association with plants and fixes the atmospheric nitrogen in leguminous plants. Micro-organisms not only increase soil fertility, but also help in recycling matter within the ecosystem, and thus help in cleaning the environment. Let us understand how micro-organisms take part in recycling matter by taking a look at the nitrogen cycle. Nitrogen cycle You know that our atmosphere contains 78% of nitrogen. But all this nitrogen cannot be taken up directly by plants and animals. As studied earlier, certain bacteria and blue-green algae fix the atmospheric nitrogen into soil and convert it into compounds of nitrogen. Rhizobium is one such bacterium which does this. It converts the atmospheric nitrogen into usable form, which is then taken up by plants through their roots. This nitrogen is then utilized by plants to synthesise proteins and other such compounds. Nitrogen is then transferred to animals in the form of proteins when they feed on plants. But how does this nitrogen reach back into the atmosphere? When plants and animals die, microorganisms like bacteria and fungi present in soil convert nitrogen present in dead organisms into nitrogenous compounds by the process of decomposition, which can be used by plants again. Some micro-organisms convert these compounds into nitrogen gas, which goes back into the atmosphere. Therefore, micro-organisms help the nitrogen cycle to continue and maintain the percentage of nitrogen present in the atmosphere.

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WORKSHEET 2 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Name any two food items that are prepared using yeast. Is it true that microbes are essential part of our life? Give an account of two important discoveries in the past those had made the study of microorganisms interesting. What is fermentation? How is milk converted into curd by bacterial activity? State some beneficial effects of bacteria. How are fungi useful to us? How are protozoa useful to us? How is algae useful to us? a) Alcohol is produced with the help of ____________. b) ____________helps in the rise of bread or dosa dough. c) Bacteria present in root nodules of pea is ____________. d) The microorganism which contains chlorophyll is ______________. e) ____________bacteria helps in settling of curd.

SYNOPSIS 3 6.

Micro-organisms As Foe You know that micro-organisms are useful to us in a number of ways, but do you know that not all micro-organisms are useful? There are some micro-organisms which are harmful to human beings and other organisms. Micro-organisms which cause diseases in plants, humans, and other animals are known as pathogens. Let us explore about them in detail. The diseases which can spread from one person to another through air, water, or contact are known as communicable diseases. These diseases include cholera, common cold, tuberculosis, chicken pox etc. We discussed earlier that carriers are insects and animals, which carry disease causing micro-organisms. But how do they do this? You must have noticed your mother covering food items to prevent flies from sitting on it. This is so because flies are carriers of a number of diseases. When they sit on garbage, many pathogens get stuck to their body. When they sit on uncovered food, these pathogens get transferred to the food item. Consuming this contaminated food can result in the occurrence of several diseases. Similarly, a mosquito carrying the parasite of malaria transfers the parasite into the human body when it bites a human. What measures can be undertaken to prevent the occurrence of communicable diseases and diseases caused by pathogens in humans? Preventive measures like drinking boiled water, keeping food covered, isolating a diseased person from a healthy person, providing vaccination etc. can be undertaken to prevent the occurrence of communicable diseases in humans.

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Spread of malaria can be prevented by not allowing mosquitoes to breed in our surroundings. Since mosquitoes require a moist place to breed, one should not allow water to collect in places like empty pots, coolers, tyres etc. Therefore, it is essential to keep our surroundings clean Pathogens causing diseases in other animals Certain bacteria cause an acute disease in both humans and cattle known as anthrax. Foot-and-mouth disease is another disease occurring in cattle, which occurs due to an infection from a type of virus. Pathogens causing diseases in plants Do you know that plants also suffer from diseases like humans and other organisms? A variety of plant pathogens cause a number of diseases in plants and can reduce the yield of a crop plant. Therefore, like human diseases, plant diseases also need to be prevented by using certain chemicals, which can kill the pathogens. Let us explore some of the plant diseases, their causative micro-organisms, and their modes of transmission. Illustration Mode of Plant disease Pathogen representing the transmission diseased plant Citrus canker

Bacteria

Air

Rust of wheat

Fungi

Air, seeds

Yellow vein mosaic of bhindi (okra)

Virus

insects

The given table lists some common human diseases, their modes of transmission, the pathogens involved, and the preventive measures to be taken to avoid the occurrence of such diseases. Human Pathogen Mode of Preventive measures (general) disease transmission Patient should be kept in isolation. Tuberculosis Bacteria Air The personal belongings of the patient Measles Virus Air should be kept away from others. Chicken pox Virus Air/contact Vaccination should be given at the proper Polio Virus Air/water time. Water should be boiled and food should Cholera Bacteria Water/food be properly cooked before consumption. Typhoid Bacteria Water One should maintain personal hygiene and good sanitary habits.

Microorganisms Friends & FOE

Human disease

7.

Pathogen

23

Mode of transmission

Hepatitis B

Virus

Water

Malaria

Protozoa

Mosquito

Preventive measures (general) Vaccination should be given at the proper time. Water should be boiled before consumption. The breeding of mosquitoes should not be allowed. One should keep one’s surroundings clean and dry. Mosquito nets and repellents should be used to avoid contact with mosquitoes

Methods of Prevention of Diseases You have learnt that some microorganisms are helpful to animals, while some are not. These microorganisms cause diseases in humans, animals and plants. Disease-causing microorganisms are called pathogens. If you are sitting next to a person who is suffering from cold, then it is likely that you may also catch cold. The virus (pathogen) that causes cold might enter your body through the air and cause the disease. Water, food or a vector are some other means by which diseases can spread. Let us learn about the various preventive measures that can be taken to prevent the spread of diseases. Preventive measures for air-borne diseases 1. Stay away from the infected person 2. Cover your mouth or nose while sneezing or coughing 3. Get vaccinated at the right time Preventive measures for water-borne diseases 1. Ensure proper disposal of sewage 2. Ensure supply of safe drinking water 3. Maintain good sanitary habits 4. Always drink boiled water 5. Get vaccinated at the right time Preventive measures for vector-borne diseases 1. Use mosquito repellent 2. Do not allow water to stagnate in your surroundings 3. Keep your surroundings neat and clean

WORKSHEET 3 1. 2. 3. 4. 5. 6.

What are pathogenic microorganisms? Are microorganisms always helpful to us? What are their harmful effects? What are communicable diseases? Name a few. How does a housefly transmit diseases? How are protozoa harmful to us? Name some harmful bacteria and the harms due to them.

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7. 8. 9.

10.

What are the ways through which microorganisms enter our body? How are fungi harmful to us? Match the following items given in Column ‘A’ with that in Column ‘B’:

a) b) c) d) e)

Column 'A’ Column 'B' (i) Tuberculosis (a) Edverd Jenner (ii) Chicken pox (b) Fleming (iii) Malaria (c) L. Pasteur (iv) Rust of wheat (d) HIV (v) Pasteurization (e) Fungi (vi) Antibiotic (f) Virus (vii) Vaccination (g) Bacteria (viii) AIDS (h) Protozoa Cholera, chicken pox are some well-known examples of _________ diseases. Carriers of specific microorganisms are called _________ The disease caused by protozoa is ______ ( tuberculosis/ polio / typhoid malaria) ____________cannot fix atmospheric nitrogen in the soil. ( Rhizobium/ Clostridium/ Azotobacter/ Penicillin) ________causes AIDS. ( protozoa/ A bacteria/ A virus / An algae)

SYNOPSIS 4 8.

(i)

• •

Food Preservation Do you know that apart from causing diseases in plants and animals, micro-organisms are also responsible for spoilage of food? You must have heard about people falling sick after eating some food item. This can happen when a person consumes a food item, which has been spoilt by the action of certain micro-organisms. This condition is known as food poisoning. It can become serious and can even lead to the death of a person. How can we prevent the chances of food poisoning? Food poisoning can be prevented by carefully preserving food items. This process is known as food preservation. It works by preventing the growth of micro-organisms in food items. How is food preservation done? Let us study some common methods of food preservation used in daily use. Chemical methods of food preservation You know that while cooking food, we add salt and oil to the vegetables. They add taste to the food, but do you know that they also help in preventing the food from getting spoilt? Chemicals like salt and oil prevent the attack of microbes on food and are termed as preservatives. Let us find out what preservatives are used to preserve different food items: Preservation by common salt: Common salt is usually used to preserve meat and fish as it checks the growth of bacteria in these foods. It is also used to preserve amla, raw mangoes, and tamarind. Preservation by sugar: Sugar is usually used to preserve jam, jellies, and squashes. Sugar prevents spoiling of food by reducing the moisture content of food, which inhibits the growth of bacteria in it.

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•

Preservation by oil and vinegar: Oil and vinegar are used to preserve vegetables, fruits, fish, and meat. They prevent food from getting spoilt as micro-organisms cannot grow in such an environment. (ii) Food preservation by heat and cold treatment Do you know why we keep food in the refrigerator? This is because low temperature inhibits the growth of micro-organisms. Similarly, boiling also kills many micro-organisms. You must have noticed that packed milk contains the label pasteurized. What do you think it means? Pasteurization is a method of preserving milk, which involves both hot and cold treatment. Pasteurization involves the process of boiling milk at a temperature of 70°C for 15-30 seconds, rapidly cooling it and then storing it. This process prevents the growth of harmful micro-organisms in milk and prevents it from getting spoiled. (iii) Storage and packing For a commercial purpose, vegetables and fruits are preserved by sealing them in air-tight packets, which prevents the attack of micro-organisms.

WORKSHEET 4 1. 2. 3. 4. 5. 6. 7. 8.

What is a vaccine? Describe the importance of vaccination. What are antibiotics? Who discovered Penicillin? Why do we use cold temperature like refrigerator or freeze to protect food products from decay? How does food poisoning occur? Why should we preserve our food? Explain why pasteurized milk can be consumed without boiling. How can the spoilage in food be detected? How can we prevent the chances of food poisoning? Explain the food preservation by chemical treatment.

1.

Food preservation has enabled humans to consume seasonal fruits throughout the year. Which of the following technique is not used to preserve fruits? (A) Drying and jellying (B) Canning and bottling (C) Addition of sugar (D) Addition of salt Salt and sugar have been used for centuries as food preservatives. Salt is used to preserve meat because (A) it betters the taste of the meat and is nutritious (B) it increases the moisture content and thus increases nutrients (C) it promotes multiplication of beneficial bacteria that prevent food spoilage (D) it kills the harmful microbes by drawing moisture to prevent their growth Edible mushrooms are used extensively in cooking and are a rich source of protein, fibres and vitamins. Which o the following groups is used to classify mushrooms? (A) Bacteria (B) Fungus (C) Algae (D) Plant

2.

3.

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4.

5.

6.

7.

8.

9.

10.

11.

12. 13.

14.

15.

When bread is left open in air, certain white and filamentous outgrowth is observed, which makes the bread unsuitable for human consumption. The white filamentous growth is a (A) bacteria (B) fungus (C) protist (D) virus Micro-organisms are the most common cause of food poisonings. Which of the following substances is responsible for causing food poisoning? (A) Vaccines (B) Toxins (C) Antibiotics (D) Probiotics Decomposers decompose matter present in dead plants and animals to ammonia. This ammonia is converted into nitrates which are absorbed by plant roots. This process is called nitrification. Ammonia is converted into nitrates with the help of (A) bacteria (B) fungus (C) protists (D) viruses The nitrogen fixation of atmospheric nitrogen in the soil is a result of the activity performed by certain beneficial micro-organisms, which live in association with plants. The symbiotic nitrogen fixing bacteria found in the root nodules of legumes is known as (A) Azotobacter (B) Rhizobium (C) Anabaena (D) Oscillatoria Viruses are neither living nor dead organisms. However, they are responsible for a large number of diseases occurring in human beings. Which of the following diseases is not caused by a virus? (A) Common cold (B) Chicken pox (C) Tetanus (D) AIDS Yeast is used to manufacture alcoholic beverages like wine and beer. It is used in the production of breads. It is also used as a nutrient supplement for human beings. Which of the following processes uses yeast to make wines and breads? (A) Photosynthesis (B) Fermentation (C) Decomposition (D) Chemosynthesis Chicken pox is a highly contagious disease. It is characterized by the appearance of busters and lesions on the skin. Chicken pox is more common in children and young adults. Which of the following organisms causes chicken pox? (A) Bacteria (B) Viruses (C) Fungi (D) Algae Yogurt is a dairy product. It is produced by the fermentation of milk sugar. Which of the following micro organisms is involved in yoghurt production? (A) Bacteria (B) Protists (C) Fungi (D) Virus Yeast is a type of fungus used for various purposes. It is very beneficial for human beings. Yeast is used in (A) nitrogen fixation (B) alcoholic beverages (C) decomposing waste (D) producing antibiotics Microorganisms are used in the manufacture of many food products and beverages. Which of the following processes occur during the manufacture of wine by microorganism? (A) Respiration (B) Photosynthesis (C) Fermentation (D) Digestion Which of the following statements regarding microorganisms is not true? (A) Microorganisms are found nearly everywhere. (B) Microorganisms act as decomposers in the ecosystem. (C) Microorganisms commonly have a single cell. (D) Microorganisms are visible to the naked eye. Many microorganisms are decomposers. They decompose all dead plants and animals and return matter back into the environment. Microorganisms are a important part of the (A) carbon cycle (B) nitrogen cycle (C) sulfur cycle (D) iron cycle 

CONSERVATION OF PLANTS AND ANIMALS CHAPTER

3

    

Biodiversity The Unknown world of Living Organisms Importance of Biological Diversity Role of Forests Loss of Biodiversity

   

Effects of Deforestation Endangered Species Conservation of Biodiversity National Parks and Sanctuaries in India

SYNOPSIS 1 1.

Biodiversity The earth is full of life. No one knows exactly the varieties of living organisms existing on the earth, etc are innumerable microbes, plants and animals. It is estimated that nearly 10 to 15 million Series (types) of organisms are there on the earth of which nearly 2 million have been discovered, identified and listed. Many of the organisms are still not known to man. In addition, new varieties organisms are evolving and many of the old forms are disappearing from time to time. The total number of life forms (varieties of living organisms) on the earth are referred to as biodiversity (bio meaning life; diversity meaning variety).

Species Species is a group of individuals (organisms) having structural and functional similarity. Species breed freely among themselves to give rise to progeny (children) similar to parents. We make use of terms like conservation, preservation and protection for some purpose but each term has a different connotation (meaning or implication). Human beings are scientifically named as Homo sapiens belonging to one species ‘sapiens’. All Homo sapiens interbreed freely. Study the Following Examples Animals Plants Common name 1. Domestic cat

Scientific name Felis domesticus

Common name 1. Banyan tree

Scientific name Ficus benghalensis

2. Tiger

Felis tigris

2. Peepal tree

Ficus religiosa

3. Leopard Felis leopardus 3. Fig tree Ficus glumeratus 4. Lion Felis leo 4. Rubber tree Ficus elastic All cats are Felis (genus) with thick fur, pointed teeth and sharp claws but they cannot interbreed. Domestic cat cannot interbreed with tiger, leopard or lion; tiger cannot interbreed with domestic cat, leopard or lion. Felis includes different species: F.domesticus, F.tigris, F.leopardus, F.leo. All domestic cats can breed among cats only, all tigers can breed among tigers and so on. The group of individuals which are able to breed freely among themselves form a species. Similarly, in plants though all Ficus plants bear similar fruit but pollens from bengalensis species can pollinate the flowers from same species only and not any other Ficus plants.

Flora and Fauna The term flora is used to include all types of plants at a place. Though this term has come from flora meaning flower but it includes even the non-flowering plants such as ferns, mosses, algae, fungi and bacteria. Similarly, the term fauna is used to include all types of animals.

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Plant population of a place or the variety of species of plants living in their natural half (surroundings) are termed as the flora of the place. Similarly, animal population of a place variety of the animal living in their natural habitat (surroundings) are termed as the fauna place. For example, listing and describing plants found on Simla hills is named as Flora Simlensis. All kinds of life at a place together form the biodiversity of the place.

2.

The unknown world of living organisms Man has been able to identify and enlist nearly 2 million species of organisms out of nearly 10 million estimated to be existing upon the earth. You can well imagine how ignorant we are about variety of life. Many of the organisms have not even been viewed because of their remote location. The unknown organisms are mostly existing on inaccessible high hills, deep sea and land forms. Exact variety of life on earth is many times more that what we may imagine.

3.

Importance of biological diversity Each organism on this earth has its own importance. These organisms while living on the earth are interacting with one another. The interaction between them is mainly for their survival. We have also learnt that one organism is the food for another. Thus each organism is essential for the growth and survival of another. We have also learnt about the FOOD CHAIN. Food chain is a linked system of organisms, and each organism is important for the next to maintain the continuity of life. Ultimately, the entire bio-system is a life support system for human race.

4.

Role of forests Forests are the good abode for WILDLIFE. Wildlife includes all forms of life, both plants and animals. Wild plants may be microbes, algae, fungi, liverworts (bryophytes), ferns, conifers and flowering plants, from minute forms (1 mm in size) to lofty trees (going up to the height of more than 50 m). The animals may be microbes, worms, insects, frogs, fish, birds and mammals (herbivores and carnivores). Plants and animals are interdependent. Forest is the place where both, plants and animals add to the biodiversity. Inaccessible places are the places which are difficult to reach. Such places may be high hills, deep seas or ravines covered with dense forests and wildlife. The life at such places is not disturbed by man. Natural evolution or extinction of life forms goes on at such places. This helps in the natural conservation of biodiversity.

WORKSHEET 1 1.

Assertion (A): Species breed freely among themselves to give rise to progeny (children) similar to parents. Reason (R): Species is a group of individuals (organisms) having structural and functional similarity. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of (C) A is correct and R is wrong. (D) A is wrong and R is correct.

Conservation of Plants and Animals

2.

3.

4.

5. 6.

7.

8.

29

Statement - I: Human beings are scientifically named as Homo domesticus. Statement –II: All cats are Felis (genus) with thick fur, pointed teeth and sharp claws but they cannot interbreed. (A) Statement - I is true, Statement - II is false. (B)Statement - I is false, Statement - II is true. (C) Both statements are true. (D) Both statements are false. Match the following: A Domestic cat P Felis leo B Tiger Q Felis leopardus C Leopard R Felis tigris D Lion S Felis domesticus Match the following: A Banyan tree P Ficus religiosa B Peepal tree Q Ficus benghalensis C Fig tree R Ficus elastic D Rubber tree S Ficus glumeratus i) What is the estimated number of species present on the earth? ii) What is the approximate number of species which have been identified and listed till now? iii) What constitutes flora of a place? Spot the errors in the given statements and correct them. a) Animal population of a place or the variety of species of plants living in their natural half (surroundings) are termed as the flora of the place b) Similarly, plant population of a place variety of the animal living in their natural habitat (surroundings) are termed as the fauna place. Fill in the following blanks. a) ___________is a linked system of organisms, and each organism is important for the next to maintain the continuity of life. b) ___________are the good abode for WILDLIFE. Say True or False a) Forest is the place where both, plants and animals add to the biodiversity. b Man has been able to identify and enlist nearly 2 million species of organisms out of nearly 10 million estimated to be existing upon the earth.

SYNOPSIS 2 5.

Loss of biodiversity In nature, new forms of organisms are evolving and at the same time many of the old forms are disappearing. This biological evolution (coming of new forms) and biological extinction (degeneration of some of the old forms) is a natural phenomenon. It is a very slow process even then it makes a vast difference in life forms over a long period of time. Adding of new forms of living organisms add to the biodiversity. At the same time loss of certain old forms is the degeneration of biodiversity. Real danger to the biodiversity comes from :(A) Natural disasters (B) Human activities

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(A) Natural Disasters 1. 2.

3. 4.

Storms and cyclones are the atmospheric disasters caused by strong winds. Depending up on the speed of the wind and its shape these are termed as hurricanes, typhoons and tornadoes. Strong winds destroy many plants and animals. Earthquakes is the displacement of the rocks below the earth’s crust which causes the grout to shake or vibrate. Powerful earthquakes may result in cracks appearing on the earn which the plant and animal life in the region may get buried. This results in destroying many of the species of organisms. Earthquakes along seacoast may also cause huge sea waves called Tsunamis. Tsunamis destroy life forms along the sea coasts. Climatic changes, draught and floods may also cause destruction of many life forms forever thus disturbing biodiversity. Landslides along the hilly terrain carry many of the life forms with the sliding earth and bill them forever under the debris. Under these debris many of the life forms disappear from the earth forever.

(B) Man-made Disasters Man made disasters have been a major factor in the degeneration of biodiversity. Some of the human activities listed below have changed the face of the ‘LIFE FORMS’ upon the earth:1. Population and Urbanisation Growth in human population and urbanisation has tremendously affected the wild life on the earth. 2. Deforestation Deforestation has been the first act of man to have destroyed many life forms. We have learnt that many organisms are supported by forests. Forests being cut and destroyed are causing the disappearance of many plant and animal species from the face of the earth. 3. Changes in land use patterns Changes in land use patterns for cultivation of crop plants, raising of orchards, building of the houses, laying of roads and canals, raising of dams and creating artificial lakes and all such human activities have caused loss of biodiversity. 4. Energy consumption and Emissions Energy consumption and Emissions have been resulting in the loss of fuel plants, which might have been fodder for the life forms. The life forms disappeared for want of food. Then, the poisonous gases being emitted by burning fuel cause pollution, adversely affecting biodiversity, both directly and indirectly. 5. Pollution Pollution due to excessive use of chemicals, fertilizers, pesticides and weedicides have not only harmed the life on earth but it has also caused the pollution of groundwater resources which are harmful even for man himself. This results in poisoning of biodiversity. Many animals forms die from eating poisoned seeds and fruits and taking polluted water. 6. Exotic species Replacing age old varieties of crop and wild plants with new breeds and genetically modified (Gm) varieties are resulting in the loss of certain indigenous varieties. This is true for crop plants and food yielding animals. 7. Natural resources exploitation Excessive exploitation of natural resources also result in degeneration of certain species. For example, many medicinal plants and fleshy animals have disappeared in the past. Dodo, a flightless bird from Mauritius was easily captured and killed ruthlessly for food resulting in its total disappearance from the island. It is extinct today. 8. Other factors Competition for food and survival comes in the way of preserving wild life. Mechanisation on farms is also affecting the population of cattle like horses, mules, donkeys, ox and bulls, which were kept by farmers as draught animals. These cattle are getting rare.

Conservation of Plants and Animals

6.

31

Effects of deforestation Continuous cutting of trees has a disastrous effect on surroundings. Destroying of forests result in serious consequences. Some of the effects of deforestation are: 1. Desertification: On cutting of a tree soil is left exposed to weather conditions which results in the change of physical property of the soil. Top soil loses water, becomes dry and lose. Over a long period of time it gets sandy as the soil in desert. 2. Soil erosion: Loose soil is easily eroded by wind and water. 3. Harm to groundwater: Due to lack of percolation of rainwater, the water table of the ground water gets low. This is a big loss to the water conservation and augmentation of groundwater. 4. Change in climate: Deforestation results in strong winds, rise in temperature of surroundings and reduced rain. All these changes lead to change in climate of the place. 5. Global warming: Reduced greenery means reduced consumption of carbon dioxide. Deforestation results in increasing the level of carbon dioxide in atmosphere causing global warming. 6. Destruction of habitats: Many plants and animals which survive on resources and homes forest lose their habitats. This results in the loss of wildlife. 7. Decrease in rainfall and affecting water cycle: It is a natural phenomenon that clouds are attracted to areas which are humid. Forest trees transpire great amount of water making atmosphere humid. Thus forests help rain and maintain water cycle. This also augments groundwater. If the forests are cut the soil gets dry.

Forest Reserves Forest reserve is a specified land area which is demarcated into different zones with specific! activities in each zone. The purpose is to preserve both, forests and wildlife. 1. Protected Zone: Human activity in this zone is totally prohibited. The land is covered with well grown trees and undisturbed habitats for wildlife. No cutting of trees. Even collection of deal firewood is prohibited. 2. Buffer Zone: This zone is on the way to develop into a dense forest. Replenishment of lost forest cover by planting saplings for trees has been done in this zone. Simultaneously, habitats are developed for wildlife. 3. Nursery Zone: In this zone nursery for forest trees is maintained. Provision is being made for the protection of shelter and managing source of food for wildlife. This is actually a zone where activities for the development and betterment of forests and wildlife are being undertaken. Many such forest reserves are being maintained in India. Our National Parks and Wildlife Sanctuaries serve this purpose. Large scale afforestation (replanting trees) in forests and also on bare land has been taken up to restore the forest wealth of the country.

WORKSHEET 2 1.

2.

3.

Statement - I: This biological evolution and biological extinction is a natural phenomenon. Statement – II: Storms and cyclones are the atmospheric disasters caused by strong winds. (A) Statement - I is true, Statement - II is false. (B) Statement - I is false, Statement - II is true. (C) Both statements are true. (D) Both statements are false. Spot the errors in the given statements and correct them. a) Earthquakes is the displacement of the water below the earth’s crust which causes the grout to shake or vibrate. b) Climatic changes, draught and floods may also cause destruction of many life forms forever thus disturbing biodiversity. Which of the following human activities results in degeneration of biodiversity? I) Population II) Deforestation III) Farming IV) Pollution (A) I, II, III (B) II, III, IV (C) I, III, IV (D) I, II, IV

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32

4. 5.

6.

8.

9.

10.

What do you mean by a) deforestation b) Extinction c) Soil erosion Fill up the blanks a) Deforestation results in increasing the level of carbon dioxide in atmosphere causing ___________. b) The zone of forest in which the human activity totally prohibited is _________. c) ____________ and ____________ play a major role in maintenance of forest reserves. Match the following: Column A Column B 1. Storms and cyclones a. Natural disasters 2. Urbanization b. Man made disasters 3. Deforestation 4. Earthquakes 7. Which of the following are the consequences of deforestation? (A) Desertification. (B) Harm to groundwater. (C) Global warming. (D) All. Assertion ((A): Deforestation results in desertification. Reason (R): On cutting of a tree soil is left exposed to weather conditions which results in the change of physical property of the soil. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of A. (C) A is correct and R is wrong. (D) A is wrong and R is correct. Assertion ((A): Deforestation results in increase in the level of groundwater. Reason (R): Deforestation results in global warming. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of A. (C) A is correct and R is wrong. (D) A is wrong and R is correct. Assertion ((A): Many plants and animals which survive on resources and homes forest lose their habitats due to deforestation. Reason (R): In nursery zone, nursery for forest trees is maintained. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of A. (C) A is correct and R is wrong. (D) A is wrong and R is correct.

SYNOPSIS 3 7.

Endangered species Endangered species of plants and animals are those which are exposed to danger of extinction (loss forever). Many algae, fungi, bryophytes, ferns and gymnosperms, are disappearing with the destruction of forests. And, each disappearing species may take away with it many species of animals and microbes which depend on them for food and shelter. Similarly list of animals on the verge of being lost is endless. Some of them are: Small creatures: prawns, oyesters, lobsters, crabs, squids, octopus, cuttlefish, beatles, dragonfly, grasshoppers, fish and even frogs are dying of absorbing poisonous gases through their skin. Locust is one insect which has almost disappeared from India. Gloworms and fireflies are almost totally absent from Northern region of India. Similarly, following animals are getting rare :Reptiles: Some lizards, turtles crocodiles and gharials.

Conservation of Plants and Animals

33

Frog breathes through its moist skin and so it finds it difficult to breathe on land with poisonous gases in the air and in polluted water. Cemented water bodies have made it difficult for the frog to lay eggs and breed for survival. Birds: Falcon, Eagle, hawk, vulture, peacock-peahen, pigeon, duck. Mammals Wild cats such as tigers, lions, deers such as chinkara and blackbuck, chiru (Tibetan goat), musk deer, rhino, elephants, blue whale, flying squirrel. In addition the endemic species are in geat danger of extinction. Endemic species of plants and animals are those which are limited to particular zones (areas) or islands. Kiwis and kangaroos are endemic to Newzealand and Australia and the neighbouring islands. As and when an island is lost, the endemic species on it are also lost. Frog:

NOTEWORTHY POINT At one time Dinosaur, ferns and some gymnosperms were wide-spread organisms on the earth. They disappeared from the earth, maybe due to shortage of space and food or due to climatic changes, but they are extinct today.

Project Tiger, Saving disappearing Tigers Tiger has been the most endangered species, especially in India since forests are being cut and destroyed. Then, most tigers are being wiped out by poachers (hunters) killing them for their skin, bones, nails and teeth which are being sold within India and also exported to outside world. At one time there were more than 40,000 tigers in India and hardly 1827 were counted ii The sharp decline in the population of Tigers was because of deforestation, increase in population, poaching and broken ‘FOOD CHAIN’. Ministry of Environment and Forests (MEF) initiated a ‘Project Tiger’, funded by World WlB (WWF) for nature for not only saving tiger population from exploitation by man but for its multiplication in its “Natural Habitat”. For this nearly 18 tiger reserves have been created in India, where efforts are made to provide a natural habitat to tigers and encourage their breeding. Protected Areas for Protecting Wild Life Some better known National Parks and Sanctuaries 1. Gir Sanctuary, Gujarat for Sambhar (deer), Chital and specially for Asiatic lion. 2. Jim Corbet National Park, Uttarakhand (for Tiger). 3. Sariska Sanctuary, Alwar, Haryana, (for Tiger, Neelgai, Deer) 4. Bharatpur Bird Sanctuary (For birds specially migratory birds) 5. Sultanpur Bird Sanctuary, Haryana 6. National Botanical Garden, West Bengal (for rare animal and rare plants.) 7. Kanha National Park, Madhya Pradesh (for Tiger) 8. Nandankanan Biological Park, Bhubaneswar-Orissa (for breeding of White Tigers 9. Simplipal Biosphere reserve, Orissa (Tigers) 10. Kaziranga Sanctuary, Assam (Rhinoceros). 11. Bandipur Sanctuary, Karnataka (Indian Elephants). 12. Madumalai Sanctuary, Tamil Nadu (Indian Elephant). Do You Know Jim Corbett National Park was established in India in 1936.

8

Conservation of Biodiversity Biodiversity is important for all living creatures, including man for the preservation of environment and for economic reasons. Biodiversity is useful in scientific and medical research. The World Summit held a Convention on Biodiversity (CB(D) for the conservation of biodiversity. As a result of this an International Union of Conservation of Nature and Natural Resources (IUCN) has been established to look after the conservation projects. IUCN has now been renamed as World Conservation Union (WCU).

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WWF (World Wide Fund for nature) is an international organisation spreading awareness among people to help conserve wild life. Biodiversity conservation in India : India took many initiatives for the conservation of biodiversity and enacted laws in this connection: 1. The Wildlife Protection Act, 1972 2. The Forest Conservation Act, 1980 3. The Environment Protection Act, 1986 4. The National Biodiversity Strategy & Action Plan (NBSAP), 1999 5. The National BiodiversityAuthority (NB(A) under which each state is to set up State Biodiver­sity Boards, which would advise the state Governments on issues related to the conservation of Biodiversity. Steps suggested to be taken to conserve Biodiversity : First and the foremost is the preservation of FORESTS. Hence, 1. Stop cutting of trees 2. Practice planting of more and more trees (afforestation). “One man one Tree” slogan is to encouraged. Each person to plant at least one tree in his/her lifetime. 3. follow Wildlife Preservation Programmes (A) Provide protection to wildlife in their natural habitat. (B) The Project Tiger under WWF prohibiting hunting of wild cats and also other endangered species and establishment of Tiger Reserves. (C) Ban on hunting of animals, especially those which are threatened species. These threat­ened species have been classified by IUCN into four categories :

(i)

Endangered species Endangered species are heading towards extinction since they are getting rare or their natural growth has slowed down. Examples Tiger, lion, crocodile and alligator, musk deer, blue whale, chiru, bear, duck and among plants Ginkgo trees, Cycads, tree ferns and many weeds including medicinal plants.

(ii)

Vulnerable species Which are at the verge of being endangered if not protected on time. Examples Deer, monkey, langur, pheasant, vulture, porcupine, rhinoceros, tortoise and even frog and grasshopper. Among plants Cycas may perish if not protected. Gingko is already heading towards extinction.

(iii) Rare species These are the species found in small numbers resulting in limited population. Examples Orchids, insectivorous plants and rhinoceros.

(iv) Threatened species These are the species which are likely to disappear soon due to human activities or natural disasters. Examples Snakes, lions, tigers, rabbits, deers, tibetan goat (chiru) musk deer.

Red List or Red Data Book of IUCN A list of threatened species of plants and animals in different parts of the world has been prepared and issued by World Conservation Union (WCU) assigning responsibility of protecting these species to the respective Governments. Ministry of Environment and Forests (MEF) have prepared a red list of endangered species in India, which is topped by White Tigers and Lions.

Conservation of Plants and Animals

35

Other Steps to Conserve Biodiversity are : 1. Regulate and reduce the use of wood as fuel. 2. Grazing to be restricted to Wild Life only. 3. Effective system to prevent forest fires. 4. Enacting laws for conserving biodiversity. 5. Cooperation from Non-Governmental Organisations (NGOs) to be sought for educating people involving them in conservation work. 6. Providing National Parks, Wildlife Sanctuaries and Botanical Gardens, Zoos and development protected areas for endangered species. 7. Long Term Captive Breeding Programmes for the endangered species to help propagate their species.

For Information Only : In India we have more than 27 Tiger Reserves, 87 National Parks, 33 Botanical Gardens, 275Zoos, Deer Parks and Aquaria, 485 Wildlife sanctuaries and 6 International Important Wetlands for™ (conservation of mangrooves and coral reefs). These are all protected areas.

9.

National parks and sanctuaries in india 1. Assam : Kaziranga Sanctuary (one horned rhino), Manas, Dibru 2. Arunachal: Pakhui-Nameri, Namdapha, Dehang Debang 3. Andhra Pradesh: Nagarjunsagar-Sripailam 4. Bihar: Balmiki (Valmiki) Sanctuary. 5. Gujarat: Gir Sanctuary for lion, chital, sambhar 6. Jharkhand : Palamau 7. Karnataka, Kerala, Tamil Nadu: Nilgiri, Bandipur (elephants), Indravati, Panchmarhi 8. Madhya Pradesh: Pench, Bandhav-garh, Panna, Bori-satpura, Kanha. 9. Maharastra: Tadoba-Andheri, Melghat, Pench with M.P. 10. Meghalaya : Norkek 11. Mizoram: Dampha 12 Great Nicobar: Entire island for wetland preserve 13 Orrisa: Similipal (tigers), Nandan-kanan (breeding tigers) 14. Rajasthan: Ranthambore, Sariska (tiger), Bharatpur (birds) 15. Sikkim: Kanchanjunga hills 16 Tamil Nadu: Gulf of Mannar (wetland, corals), Kalakad-Mundanthurai 17. Uttarakhand : Jim Corbet National Park (tiger) 18 West Bengal: Sunderbans, Buxa. In addition, some of the Eastern Coastal areas are being developed as protected areas after the occurrence of earlier Tsunami.

WORKSHEET 3 1.

2.

Statement - I:

Endangered species of plants and animals are those which are exposed to danger of extinction (loss forever). Statement – II: Cat, dog and cow are some endangered species. (A) Statement - I is true, Statement - II is false. (B) Statement - I is false, Statement - II is true. (C) Both statements are true. (D) Both statements are false. Spot the errors in the given statements and correct them. (A) Falcon, Eagle, hawk, vulture, peacock-peahen, pigeon, duck are some birds that are becoming rare. (B) Endemic species of plants and animals are those that are found all over the world.

36

3.

4. 5. 6.

7. 8. 9. 10.

1.

2.

3.

4.

5.

8th Class Biology

Which of the following is true about National parks and sanctuaries in India? I) Gir Sanctuary, Gujarat is for Sambhar (deer) II) Jim Corbet National Park, Uttarakhand is for Tiger. III) National Botanical Garden, West Bengal for rare animal and rare plants. IV) Kazinranga Sanctuary, Assam is Rhinoceros. (A) I, II, III (B) II, III, IV (C) I, III, IV (D) I, II, III, IV What do you mean by (A) Endangered species(B) Endemic species (C) Vulnerable species Write the expanded forms of the following related to conservation of Biodiversity: (A) CBD (B) IUCN (C) WCU (D) WWF Match the following: Column A Column B 1. The Wildlife Protection Act a. 1980 2. The Forest Conservation Act b. 1986 3. The Environment Protection Act c. 1972 Which of the following are the vulnerable species? (A) Langurs (B) Tigers (C) Orchids (D) Lions Which of the following is / are the rare species? (A) Langurs (B) Tigers (C) Orchids (D) Lions Snakes, lions, tigers, rabbits, deers, Tibetan goat (chiru) musk deer are : (A) Endangered species (B) Vulnerable species (C) Rare species (D) Threatened species Which of the following contain a list of threatened species of plants and animals in different parts of the world (A) Black list (B) Red list (C) Green List (D) Yellow list

Certain plants are extensively used for their economical value. However, the industrial use of plants may have repercussions on the environment of a region. Which of the following events is not an aftermath of deforestation? (A) Wild life extinction (B) Water pollution (C) Flash floods (D) Soil erosion Recycling is the process of converting waste material into useable products. Which of the following reasons does not explain the need for recycling? (A) Recycling reduces environmental pollution (B) Recycling is cheaper that disposing wastes (C) Recycling increases the amount of garbage (D) Recycling reduced deforestation Which of the following processes does not cause the extinction of animals? (A) Pollution (B) Poaching (C) Afforestation (D) Constructing dams Trees provide oxygen and food to animals. Trees also provide a number of useful products to human beings such as rubber, timber, and fuel. This leads to deforestation i.e., removal of trees from the environment to exploit their uses. Which of the following is not a result of deforestation? (A) Soil erosion (B) Low rainfall (C) Increase in the water table (D) Decrease in animal population _i_ species are those species of plants and animals that are exclusively found in a particular are _ii_is an endemic fauna of the Pachmarhi biosphere reserve. The information in which alternative completes the given statements? (A) i-Endemic, ii-Sal (B) i-Endemic, ii-Bison (C) i-Extinct, ii-Sal(D) i-Extinct, ii-Bison

Conservation of Plants and Animals

6. 7. 8.

37

Which protected area maintains the traditional life of tribals? (A) National park (B) Zoological park (C) Biosphere reserve (D) Wildlife sanctuary Which term refers to the species that are on the verge of extinction? (A) Extinct (B) Endemic (C) Endangered (D) Threatened Which of the following statements is correct regarding deforestation? (A) It increases the fertility of soil. (B) In involves planting of new trees. (C) It increases the water holding capacity of soil. (D) It involves the cutting of trees for industrial purposes.

9.

10.

11.

12.

13.

14.

15.

16.

Which of the following statements about flora and fauna is true? (A) The various plants species found in an area constitute the flora while the various animal species found in an area constitute the fauna (B) The various plant species found in an area constitute the fauna while the various animal species found in an area constitute the flora (C) The plants and animals found in a region constitute the region’s flora (D) The plants and animals found in a region constitute the region’s fauna i plants and animals are restricted in their distribution to a particular are ii species are those whose numbers are decreasing and might face extinction in the near future. The information in which alternative completes the given statements? (A) i-extinct, ii-endemic (B) i-endemic, ii-endangered (C) i-endangered, extinct (D) i-extinct, ii-endanged Which of the following statements about reforestation is incorrect? (A) It involves the cutting of trees for industrial purposes. (B) It involves the planting of new trees in deforested areas. (C) It can take place with human intervention. (D) It can take place naturally. Which of the following statements about recycling of paper is incorrect? (A) It reduces deforestation. (B) It promotes the conservation of environment. (C) It consumes less energy as compared to the energy consumed for paper making. (D) It requires more harmful chemicals as compared to those used in paper making. Migratory birds fly to faraway places because of the ____i____ in their natural habitat. They go to faraway places to ____ii_____.The information in which alternative completes the given statements? (A) i- cold climate, ii-raise their young ones (B) i- cold climate, ii-escape predators (C) i- pollution, ii-raise their young ones (D) i- pollutions, ii-escape predators Which of the following statements about the Red Data Book is correct? (A) It contains the record of all endangered plant and animal species (B) It contains the record of all extinct plant and animal species (C) It contains the list of all endemic animal species (D) It contains the list of all endemic plant species The population of animal X has drastically gone down. Any further decline in its population could wipe the traces of its species from the surface of the Earth. Animal X belongs to the category of (A) extinct species (B) endemic species (C) threatened species (D) endangered species The primary objective of Project Tiger is to (A) increase the population of tigers as they are an endangered species (B) increase the population of tigers as they are a threatened species (C) protect tigers by keeping them in the enclosures of zoos (D) protect tigers by changing their habitat

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8th Class Biology

17.

Which of the following statements about wildlife sanctuaries is correct? (A) It is a place where the traditional life of tribal’s is conserved (B) It is a place where human activities are permissible (C) It is a place where animals are kept in enclosures (D) It is a place where poaching is prohibited The species that are exclusive to a particular area are known as (A) extinct species (B) endemic species (C) threatened species (D) endangered species The plants found in a particular area are termed as the__i of that are ii refers to the animals found in a particular are. The information in which alternative completes the given statements? (A) i- flora, ii-Fauna (B) i- Fauna, ii-flora (C) i- flora, ii-Flora also (D) i- fauna, ii-Faunna also __i___ is an area in which animals are protected in their natural habitat, while _ii___ is a large protected land where plants, animals, and tribals are conserved in their natural habitat. The information in which alternative completes the given statement? (A) i-Sanctuary, ii-biosphere reseve (B) i-biosphere reseve, ii-national park (C) i-National park, ii-zoo (D) i-Zoo, ii-sancturary Deforestation has adverse effects on the ecosystem. Which of the following statements about deforestation is incorrect? (A) It leads to soil erosion (B) It leads to global warming (C) It increases the occurrence of floods (D) It increases the water-holding capacity of soil Deforestation is a major threat to the ecosystem. Which of the following activities does not lead to deforestation? (A) Using wood for making furniture (B) Constructing biosphere reserves (C) Clearing land for agriculture (D) Using wood as fuel ‘Slash and burn’ is a method of felling trees, which is used for procuring land for agricultural proposes. In this method, in order to clear a piece of land, trees are cut down and then the stumps are burnt down. Which of the following statements is incorrect regarding this method? (A) It speeds up the process of soil erosion. (B) It increases the chances of reforestation. (C) It leads to decrease in the soil nutrients. (D) It increases the chances of natural calamities. The given list represents some facts about reforestation. I. Reforestation can occur both naturally and also by human intervention. II. Plants of the same species are planted in the forests. III. Trees whose stumps are burnt down cannot be re-grown. IV. The number of trees planted is equal to the number of trees cut from the forests. (A) only I is incorrect (B) only II is incorrect (C) both I and III are incorrect (D) both II and IV are incorrect i leads to the increase in the levels of ii gas in the atmosphere, which disturbs the iii on earth. The information in which alternative completes the given statement? (A) i-deforestation, ii-carbon dioxide, iii- Water cycle (B) i-deserification, ii-carbon dioxide, iii- nitrogen cycle (C) i-deforestation, ii-carbon dioxide, iii- nitrogen cycle (D) i-deserification, ii-carbon dioxide, iii- Water cycle Deforestation can be caused by many means. Forest fires and i are the ii causes of deforestation. (A) i-drought, ii-man-made (B) i- felling of trees, ii-natural (C) i-drought, ii- natural (D) i-felling of trees, ii-man-made

18. 19.

20.

21.

22.

23.

24.

25.

26.



CELL-STRUCTURE AND FUNCTIONS CHAPTER

4

   

Discovery of the Cell The cell Organisms show Variety in Cell Number, Shape and Size Cell Structure and Function

 

Parts of the Cell Comparison of Plant and Animal Cells

SYNOPSIS 1 Introduction You have already learnt that things around us are either living or non-living. Further, you may recall that all living organisms carry out certain basic functions. Can you list these functions? Different sets of organs perform the various functions you have listed. In this chapter, you shall learn about the basic structural unit of an organ, which is the cell. Cells may be compared to bricks. Bricks are assembled to make a building. Similarly, cells are assembled to make the body of every organism.

1.

Discovery of the Cell Robert Hooke in 1665 observed slices of cork under a simple magnifying device. Cork is a part of the bark of a tree. He took thin slices of cork and observed them under a microscope. He noticed partitioned boxes or compartments in the cork slice.

These boxes appeared like a honeycomb. He also noticed that one box was separated from the other by a wall or partition. Hooke coined the term ‘cell’ for each box. What Hooke observed as boxes or cells in the cork were actually dead cells. Cells of living organisms could be observed only after the discovery of improved microscopes. Very little was known about the cell for the next 150 years after Robert Hooke’s observations. Today, we know a lot about cell structure and its functions because of improved microscopes having high magnification.

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2.

The Cell Both, bricks in a building and cells in the living organisms, are basic structural units [Fig. 8.2(a), (b)]. The buildings, though built of similar bricks, have different designs, shapes and sizes. Similarly, in the living world, organisms differ from one another but all are made up of cells. Cells in the living organisms are complex living structures unlike non-living bricks.

The egg of a hen represents a single cell and is big enough to be seen by the unaided eye.

3.

Organisms show Variety in Cell Number, Shape and Size How do scientists observe and study the living cells? They use microscopes which magnify objects. Stains (dyes) are used to colour parts of the cell to study the detailed structure. There are millions of living organisms. They are of different shapes and sizes. Their organs also vary in shape, size and number of cells. Let us study about some of them. Number of Cells Can you guess the number of cells in a tall tree or in a huge animal like the elephant? The number runs into billions and trillions. Human body has trillions of cells which vary in shapes and sizes. Different groups of cells perform a variety of functions. A billion is a thousand million. A trillion is a thousand billion. Organisms made of more than one cell are called multicellular (multi : many; cellular : cell) organisms. The number of cells being less in smaller organisms does not, in any way, affect the functioning of the organisms. You will be surprised to know that an organism with billions of cells begins life as a single cell which is the fertilised egg. The fertilised egg cell multiplies and the number of cells increase as development proceeds. The single-celled organisms are called unicellular (uni : one; cellular : cell) organisms. A singlecelled organism performs all the necessary functions that multicellular organisms perform. A single-celled organism, like amoeba, captures and digests food, respires, excretes, grows and reproduces. Similar functions in multicellular organisms are carried out by groups of specialised cells forming different tissues. Tissues, in turn, form organs.

Shape of Cells How do you define the shape of Amoeba in the figure? You may say that the shape appears irregular. Infact, Amoeba has no definite shape, unlike other organisms. It keeps on changing its shape. Observe the projections of varying lengths protruding out of its body.

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41

These are called pseudopodia (pseudo : false; podia : feet), as you learnt in Class VII. These projections appear and disappear as Amoeba moves or feeds. The change in shape is due to formation of pseudopodia which facilitates movement and help in capturing food. A white blood cell (WBC) in human blood is another example of a single cell which can change its shape. But while WBC is a cell, amoeba is a full fledged organism capable of independent existence. What shape would you expect in organisms with millions of cells? The figure below shows different cells such as blood, muscle and nerve cells of human beings. The different shapes are related to their specific functions. Generally, cells are round, spherical or elongated. Some cells are long and pointed at both ends.

They exhibit spindle shape. Cells sometimes are quite long. Some are branched like the nerve cell or a neuron. The nerve cell receives and transfers messages, thereby helping to control and coordinate the working of different parts of the body. Can you guess, which part of the cell gives it shape? Components of the cell are enclosed in a membrane. This membrane provides shape to the cells of plants and animals. Cell wall is an additional covering over the cell membrane in plant cells. It gives shape and rigidity to these cells. Bacterial cell also has a cell wall. Size of Cells The size of cells in living organisms may be as small as a millionth of a metre (micrometre or micron) or may be as large as a few centimetres. However, most of the cells are microscopic in size and are not visible to the unaided eye. They need to be enlarged or magnified by a microscope. The smallest cell is 0.1 to 0.5 micrometre in bacteria. The largest cell measuring 170 mm ×130 mm, isthe egg of an ostrich. The size of the cells has no relation with the size of the body of the animal or plant. It is not necessary that the cells in the elephant be much bigger than those in a rat. The size of the cell is related to its function. For example, nerve cells, both in the elephant and rat, are long and branched. They perform the same function, that of transferring messages.

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WORKSHEET 1 1. 2.

3. 4.

5.

6.

Which cell structure was observed by Robert Hooke when he studied cork cells? (A) Nucleus (B) Cell wall (C) Cytoplasm (D) Cell membrane Robert Hooke was the first scientist who coined the term ‘cell’. Which cell did he observe under the microscope? (A) Fiber (B) Cork (C) Root (D) Leaf Which of the following organisms is multi-cellular? (A) Hydra (B) Amoeba (C) Paramecium (D) Dinoflagellate All living organisms are made up of cells. Cells are often referred to as the ‘building blocks’ of life. Which of the following organisms is not a unicellular organism? (A) Bacteria (B) Coral (C) Yeast (D) Archaea Organisms that are made up of many cells are called multi-cellular organisms; whereas organisms that are made up of only a single cell that performs all functions are called unicellular organisms. Which of the following organisms is unicellular? (A) Pine (B) Algae (C) Sundew (D) Amoebae Bob and his father visit a construction site. Bob observes workers placing bricks in a sequence to construct a house. The architect tells them that the house will consist of four bedrooms, a dining hall, one study, and a garage. Bob’s father explains to Bob that bricks are the building units of the house. Which of the following is known as the building block of life? (A) Oxygen (B) Heart (C) Water (D) Cell

7.

8.

9. 10.

11.

12.

Which common feature is present in the illustrated organisms? (A) Cells (B) Organs (C) Tissues (D) Systems Multicellular organisms are made of a large number of cells, wherein each cell performs a specific function. Which of the following organisms is not multicellular? (A) Plants (B) Protists (C) Monkey (D) Mushrooms Which of the following organisms is not multicellular? (A) Banyan tree (B) Pea plant (C) Diatom (D) Leech An organism made up of a single cell is known as a unicellular organism. Which of the following organisms is not unicellular? (A) Bacterium (B) Mushroom (C) Paramecium (D) Dinoflagellate In a multicellular organism, different cells are specialized to perform different functions. Which of the following organisms is multicellular? (A) Diatom (B) Bacteria (C) Euglena (D) Hydra In a unicellular organism, the single cell performs all the functions necessary for its survival. Which of the following organisms is unicellular? (A) Pine (B) Moss (C) Amoeba (D) Earthworm

Cell Structure and Functions

43

SYNOPSIS 2 4.

Cell Structure and Function You have learnt that each living organism has many organs. You have studied in Class VII about the digestive organs which together constitute the digestive system. Each organ in the system performs different functions such as digestion, assimilation and absorption. Similarly, different organs of a plant perform specific/specialised functions. For example, roots help in the absorption of water and minerals. Leaves, as you have learnt in Class VII, are responsible for synthesis of foo(D) Each organ is further made up of smaller parts called tissues. A tissue is a group of similar cells performing a specific function. Paheli realised that an organ is made up of tissues which in turn, are made up of cells. The cell in a living organism is the basic structural unit.

5.

Parts of the Cell Cell Membrane The basic components of a cell are cell membrane, cytoplasm and nucleus. The cytoplasm and nucleus are enclosed within the cell membrane,also called the plasma membrane. The membrane separates cells from one another and also the cell from the surrounding medium. The plasma membrane is porous and allows the movement of substances or materials both inward and outwar(D) The boundary of the onion cell is the cell membrane covered by another thick covering called the cell wall. The central dense round body in the centre is called the nucleus. The jelly-like substance between the nucleus and the cell membrane is called cytoplasm.

You have learnt earlier that the cell membrane gives shape to the cell. In addition to the cell membrane, there is an outer thick layer in cells of plants called cell wall. This additional layer surrounding the cell membrane is required by the plants for protection. Plant cells need protection against variations in temperature, high wind speed, atmospheric moisture, et(C) They are exposed to these variations because they cannot move. Cells can be observed in the leaf peel of Tradescantia, Elodea or Rhoeo. You can prepare a slide as in the case of onion.

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Cytoplasm It is the jelly-like substance present between the cell membrane and the nucleus. Various other components, or organelles, of cells are present in the cytoplasm. These are mitochondria, golgi bodies, ribosomes, et(C) You will learn about them in later classes. Nucleus It is an important component of the living cell. It is generally spherical and located in the centre of the cell. It can be stained and seen easily with the help of a microscope. Nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. This membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus. With a microscope of higher magnification, we can see a smaller spherical body in the nucleus. It is called the nucleolus. In addition, nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. The chromosomes can be seenonly when the cell divides. Gene Gene is a unit of inheritance in living organisms. It controls the transfer of a hereditary characteristic from parents to offspring. This means that your parents pass some of their characteristics on to you. If your father has brown eyes, you may also have brown eyes. If your mother has curly hair, you might also end up having curly hair. However, the different combination of genes from parents result in different characteristics. Nucleus, in addition to its role in inheritance, acts as control centre of the activities of the cell. The entire content of a livinhg cell is known as protoplasm. It includes the cytoplasm and the nucleus. Protoplasm is called the living substance of the cell. The nucleus of the bacterial cell is not well organised like the cells of multicellular organisms. There is no nuclear membrane. The cells having nuclear material without nuclear membrane are termed prokaryotic cells. The organisms with these kinds of cells are called prokaryotes (pro : primitive; karyon : nucleus). Examples are bacteria and blue green algae. The cells, like onion cells and cheek cells having well organised nucleus with a nuclear membrane are designated as eukaryotic cells. All organisms other than bacteria and blue green algae are called eukaryotes. (eu : true; karyon: nucleus). While observing the onion cells under the microscope, did you notice any blank-looking structures in the cytoplasm? It is called vacuole. It could be single and big as in an onion cell. Cheek cells have smaller vacuoles. Large vacuoles are common in plant cells. Vacuoles in animal cells are much smaller. You might have noticed several small coloured bodies in the cytoplasm of the cells of Tradescantia leaf. They are scattered in the cytoplasm of the leaf cells. These are called plastids. They are of different colours. Some of them contain green pigment called chlorophyll. Green coloured plastids are called chloroplasts. They provide green colour to the leaves. You may recall that chlorophyll in the chloroplasts of leaves, is essential for photosynthesis.

Cell Structure and Functions

6.

45

Comparison of Plant and Animal Cells If you recall Activities 8.3 and 8.4, you should be able to compare plant and animal cells. Observe the plant and animal cell carefully. Let us tabulate the similarities and disinguishing features of plant and animal cells. Only a few features are mentione(D)

Sl. No.

Part

Plant Cell

Animal Cell

1

Cell membrane

Present

Present

2

Cell wall

Present

Absent

3

Nucleus

4

Nuclear membrane

5

Cytoplasm

6

Plastids

7

Vacuole

WORKSHEET 2 1.

2.

3. 4.

Prokaryotes are distinguished from eukaryotes by the (A) presence of cell wall (B) absence of nucleus (C) presence of ribosomes (D) absence of chloroplasts Which of the following statements about prokaryotes is true? (A) All prokaryotes have a cell wall (B) Nucleus is absent in all prokaryotes (C) Prokaryotes are larger than eukaryotes (D) Ribosomes are larger in prokaryotes as compared to eukaryotes Nucleus controls all life processes because of the presence of (A) nuclear membrane (B) nuclear pores (C) chromosomes (D) lysosomes Which arrow diagram correctly illustrates the arrangement of cell organelles starting from the outermost layer of plant cells? (A) Plasma membrane  cell wall  cytoplasm  nucleus (B) Cell wall  plasma membrane  cytoplasm  nucleus (C) Cell wall  cytoplasm  plasma membrane  nucleus (D) Plasma membrane  cytoplasm  cell wall  nucleus

46

5. 6. 7.

8.

9.

10.

11.

12. 13.

14.

15.

8th Class Biology

In plant cells, nucleus is found atthe periphery of cells because of the presence of a central (A) plastid (B) lysosome (C) ribosome (D) vacuole Living organisms are grouped into eukaryotes and prokaryotes on the basis of (A) ribosomes (B) nucleus (C) plasma membrane (D) chloroplast In multi-cellular organisms, cells are usually (A) independent of each other (B) dependent upon each other (C) incapable of transporting substances (D) incapable of multiplication Cytoplasm is composed of all cell organelles except nucleus. The contents of nucleus are separated from cytoplasm by the nuclear membrane. Nucleus and nuclear membrane together form nucleoplasm. Cytoplasm and nucleoplasm are together referred to as (A) protoplast (B) cytonucleus (C) protoplasm (D) nucleolus Which of the following functions holds true for plasma membrane? (A) It protects and gives structural support to cells (B) It contains the genetic material (C) It regulates substances moving in and out of cells (D) It maintains the shape of cells The nucleus of a cell is a membrane-bound organelle that contains the genetic material i.e., DN(A) The cellular material present outside the nucleus is called cytoplasm.

Which membrane separates the components of nucleus and cytoplasm? (A) Protoplasm (B) Nucleolus (C) Plasma membrane (D) Nuclear envelope Cytoplasm is a water-like substance that is present outside the nucleus and contains all cellular organelles. In animal cells, it occupies nearly half of a cell’s volume. It occupies less space in plant cells. Cytoplasm occupies less space in plant cells because of the (A) presence of cell wall (B) presence of vacuoles (C) absence of cell wall (D) absence of vacuoles Which organelle forms the outermost layer in animal cells? (A) Mitochondria (B) Plasma membrane (C) Cell wall (D) Nuclear membrane Chloroplasts are cell organelles found mostly in all plant cells. Chloroplasts facilitate the process of (A) respiration (B) photosynthesis(C) lipid production (D) protein production Plant cells can perform certain functions which animal cells cannot perform. The function unique to a plant cell is the (A) exchange of gases B) absorption of water (C) production of starch (D) transport of nutrients Cells perform the essential life functions in an animal body. Which of the following functions is not performed by animal cells? (A) Digestion (B) Respiration (C) Protein synthesis (D)Carbohydrate synthesis

Cell Structure and Functions

16. 17.

18. 19. 20. 21.

22. 23.

24.

25.

1.

2.

3.

47

The flow of molecules in and out of a cell is regulated by (A) cell membrane(B) mitochondria (C) golgi body (D) nucleus Cell wall is the most distinguishing feature of plant cells. Which of the following functions is not performed by plant cell wall? (A) Manufacturing proteins (B) Giving support to the cell (C) Providing shape to the cell (D) Protecting cellular contents Which cell organelle produces oxygen? (A) Mitochondrion (B) Chloroplast (C) Lysosome (D) Ribosome Which cell organelle produces glucose? (A) Vacuole (B) Lysosome (C) Chloroplast (D) Mitochondrion Chloroplasts perform the function of (A) osmosis (B) respiration (C) transpiration (D) photosynthesis The vacuoles present in animal cells are (A) small, centrally located, and a few in number (B) large, centrally located, and a few in number (C) small, scattered, and more in number (D) large, scattered, and more in number Which of the following processes does not occur in animal cells? (A) Photosynthesis (B) Respiration (C) Excretion (D) Osmosis As compared to plant cells, animal cells are found in a variety of shapes. Animal cells are found in a verity of shapes because of the presence of a flexible (A) vacuole (B) nucleus (C) cell wall (D) cell membrane Vacuole is cell structure present in both plant and animal cells. Which of the following statements about plant and the animal cell vacuoles is true? (A) The plant cell has many small vacuoles, but the animal cell has one large vacuole. (B) The plant cell has one large vacuole, but the animal cell has many small vacuoles. (C) The plant as well as the animal cell has many small vacuoles. (D) The plant as well as the animal cell has one large vacuole. Chlorophyll plays a major role in plant photosynthesis. Chlorophyll performs the function of (A) absorbing water in leaves (B) trapping light energy in leaves (C) releasing carbon dioxide into atmosphere (D)releasing manufactured food into atmosphere

Green plants produce oxygen which is utilized by all animals. The cell organelle that produces oxygen in a plant cell is the (A)mitochondrion (B) chloroplast (C) vacuole (D) nucleus A certain cell organelle controls various activities of the cell such as protein synthesis. It also contains the hereditary information of an organism. The described cell organelle is the (A) nucleus (B) ribosome (C) chloroplast (D) mitochondrion Which of the following cell organelles is found only in the animal cell? (A)Nucleus (B) Vacuole (C) Centriole (D) Ribosome

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4.

5.

Plant and animal cells are surrounded by the plasma membrane. The main function of the plasma membrane is to (A) control the movement of substances across the cell (B) control the cellular activities within the cell (C) carry out protein synthesis (D) carry out lipid synthesis Cell wall is present in only in the plant cell. The main function of the cell wall is to (A) protect the cell (B) control cellular activities (C) carry out photosynthesis (D) perform cellular respiration

6.

7. 8.

9.

10.

Which figure represents a plant cell? (A)IV (B)III (C)II (D) I Which of the following structures is prominent in plant cells? (A) Vacuole (B) Centriole (C) Ribosome (D) Chloroplast Prokaryotes are primitive cells. They lack an organized nucleus and other membrane-bound organelles. Which of the following structures is not found in prokaryotic cells? (A) Cell membrane (B) Mitochondrion(C) Chromosome (D) Cytoplasm The presence of a thick cell wall is one of the important factors that differentiate plant cells from animal cells. The cell wall surrounds the cell or plasma membrane. The presence of cell wall allows plant cells to (A) exhibit mobility (B) synthesize their own food (C) separate internal contents of the cell (D) withstand changes in their surroundings A plant cell with four labeled portions is depicted in the given figure.

The labeled organelle present in both animal cell and plant cell is (A) IV (B) III

(C) II

(D) I

Cell Structure and Functions

11.

A plant cell with four labeled portions is depicted in the given figure.

12.

The labeled portion responsible for photosynthesis is (A) I (B) II (C) III (D) IV The given figure depicts a diagram of a eukaryotic animal cell. It shows organelles labeled I and II.

13. 14.

15.

16.

17.

18.

49

The function of the part of the cell marked as I is to (A) absorb energy from the sun and prepare food (B) perform aerobic respiration and synthesize acids (C) regulate the exit and entry of substances in the cell (D) control cell metabolism, and form ribosomes, DNA and RNA Which of the following cell components is present only in plant cells and absent in all animal cells? (A) Cell membrane (B) Cell wall (C) Vacuole (D) Nucleus Chloroplasts are cell organelles in plants which help to produce food for the plant.Which of t he following is a source of energy used by chloroplasts to produce food? (A) Air (B) Sun (C) Soil (D) Water Animal and plant cells differ from each other in a number of ways. Which cell organelle is absent in animal cells? (A) Mitochondria (B) Chloroplast (C) Vacuole (D) Nucleus All single cell organisms are known as prokaryotes. The single cell performs all the functions required for the organism to survive. Which of the following cell organelles is not present in prokaryotes? (A) Nucleus (B) Cell wall (C) Ribosome (D) Cell membrane A cell consists of a number of organelles that perform various functions. Which cell organelle controls the movement of particles in and out of the cell? (A) Cell membrane (B) Mitochondria (C) Lysosomes (D) Cytoplasm The vacuole is a cell organelle present in both plant and animal cells. It stores food, water, toxic waste etc. The vacuole present in a plant cell differs from that of an animal cell because the former has (A) many small vacuoles (B) double membrane vacuole (C) a single membrane vacuole (D) a large centrally placed vacuole

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19.

20.

The given figure is that of a cell.

In the given figure, the cell wall is present at position (A) I (B) II (C) III Cell membrane has a common function in both plants and animals. Cell membrane performs the function of (A) controlling the movement of materials in and out of the cell (B) manufacturing energy to carry out various functions (C) controlling the activities of the cell (D) storing food, water, and waste 

(D) IV

REPRODUCTION IN ANIMALS

CHAPTER

5

    

Introduction Asexual Reproduction Sexual reproduction Life Cycle of Butterfly Life Cycle of Silkworm moth

   

Life Cycle of Mosquito Reproduction in Toads and Frogs Reproductioni in Birds Cloning

SYNOPSIS 1 1.

Introduction All living organisms have an instinct to live their own lives and then survive through their generations. Living things take birth, grow old and die. Before death individuals give birth to the off springs (children) to continue their race. Have you ever provoked you mind to know the process that leads to off springs? The answer is right here . . . This survival instinct is helped by the process of Reproduction. Giving birth to off springs, which are similar to parents, is known as reproduction. Importance of Reproduction Reproduction is one of the most important characteristics of life. Reproduction is the creation of new life of its own kind. Reproduction is essential for the continuation of species. A species will disappear from the face of the earth if it does not reproduce. Reproduction takes place in both, plants and animals.

2.

Modes of Reproduction Asexual Reproduction In asexual reproduction, a single parent gives rise to new individuals. Binary fission in Amoeba and Budding in Hydra are Asexual reproductions.

Binary Fission The asexual reproduction in which nucleus of the parent splits into two and gives rise to two new individuals, is called Binary Fission. Eg: Amoeba, paramoecium, Euglena

Binary Fission in Amoeba 1. 2. 3. 4.

Amoeba, the unicellular organisms, multiplies by binary fission. First, the nucleus divides into two. Then, the body cell divides into two parts, each part receiving a nucleus. Each with a single nucleus separates out into two independent amoebae.

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Budding in Hydra 1. 2. 3. 4. 5.

3.

Hydra is a multicellular organism with a soft cylindrical body. It bears tentacles surrounding its mouth towards the top. For reproduction by budding, one or more buds bulge from its lateral sides. Each bud grows into a baby hydra. Baby hydra separates out from the parent forming an independent hydra.

Sexual Reproduction Look around and see for the young ones from different animals. Kitten, puppy, chick and calf some of the common young ones from different animals. Have you ever wondered as to how babies are born? The babies are the result of Sexual Reproduction. A mode of reproduction involving the fusion of female gamete and male gamete, which forms a zygote that potentially develops into genetically distinct offspring is called Sexual Reproduction

Oviparous & Viviparous Animals The animals that lay eggs to produce young ones are called Oviparous Animals. Examples: Insects, frogs, snakes, turtles and birds lay eggs.

Viviparous Animals The animals that give birth to young ones are called Viviparous Animals. Examples: Cat, dog, cow, man and elephant give birth to young ones. Note: All mammals (milk yielding animals) give birth to young ones.

WORKSHEET 1 1.

2.

3. 4.

Assertion (A): Reproduction in living organisms essential. Reason (R): Reproduction is essential for the continuation of species (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of B (C) A is correct and R is wrong. (D) A is wrong and R is correct. Statement - I: Asexual reproduction takes place only in unicellular organisms. Statement – II: Hydra, a multicellular organism multiplies by asexual reproduction. (A) Statement - I is true, Statement - II is false. (B) Statement - I is false, Statement - II is true. (C) Both statements are true. (D) Both statements are false. What would happen if there is no reproductive process among plants and animals? Assertion (A): Human beings are viviparous animals. Reason (R): Human beings give birth to young ones. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of B (C) A is correct and R is wrong. (D) A is wrong and R is correct.

Reproduction in Animals 5.

6.

7.

53

Match the following: A

Elephant

P

Oviparous

B

Insects

Q

Viviparous

C

Frog

D

Tiger

Match the following: A

Amoeba

P

Sexual Reproduction

B

Tortoise

Q

Asexual Reproduction

C

Dog

D

Paramoecium

Statement - I:

Birds and Turtles are oviparous animals.

Statement – II: Whale and cow are viviparous animals.

8.

(A)

Statement - I is true, Statement - II is false.

(B)

Statement - I is false, Statement - II is true.

(C)

Both statements are true.

(D)

Both statements are false.

Assertion (A): Crocodile is a oviparous animal. Reason (R): As it gives birth to young ones, it is a oviparous animals. (A)

A is correct and R is the correct explanation of A.

(B)

A is correct and R is not the correct explanation of B.

(C)

A is correct and R is wrong.

(D)

A is wrong and R is correct.

SYNOPSIS 2 Reproduction in Oviparous Animals All egg laying animals are called oviparous animals. Insects, worms, frog, etc. are oviparous animals. We have already learnt about the lifecycle in some of the animals. Let’s study the life cycle of few of the oviparous animals.

4.

Life Cycle of Butterfly In butterfly male and female are separate. The female lays the eggs. The eggs laid are actually zygotes. The eggs are fertilized within the body of the mother (female) with the sperms from father (male). Fertilization in butterfly (insects) is internal. Eggs (zygotes)  Larva  Pupa  Adult

8th Class Biology

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5.

Life Cycle of Silkworm moth

6.

Life Cycle of Mosquito • • • •

7.

Larva or caterpillar in mosquito is popularly called Wriggler since it is seen going down and coming up in pond water in which they develop. They come up to the surface for breathing. Pupa in mosquito is seen as if suspended from the water surface. They breathe through minute tubes coming out of water into the air.

Reproduction in Toads and Frogs Toads and frogs are common near a pond during early rains. Late in the rainy season or in the beginning of winter the male frog which is smaller and dark seeks the company of a big female frog. The female is fat with her belly full of eggs. Both, male and female frogs swim around the pond for some time and then they come near the shore where the female starts laying eggs. The big mass of eggs emerge from the body of the female, the male sheds sperms over them. Sperms swim to the eggs. Fusion of a sperm with an egg is called fertilization

Reproduction in Animals

55

During fertilization, One sperm fuses with one egg (ovum) to form Zygote. Note: 1. Fertilization in frog takes place in water. 2. Fertilization in frog is EXTERNAL (outside the body of the mother). 3. The fertilized eggs are enclosed by a thick jelly. 4. The whole mass of zygotes in a jelly is called spawn.

Some points to be noted 1. 2. 3. 4.

The tadpole stage in frog is an intermediate stage between aquatic and land habitat. Tadpole has gills for breathing under water and finned tail to swim in water. Adult frog has lungs for breathing in air. In addition to lungs frogs also breathe through their moist skin. The changes taking place through stages during the development of an animal from an egg to an adult is called metamorphosis. In tadpoles secretion of hormone thyroid initiates metamorphosis.

8.

Reproduction in Birds Hen and cock represent the birds. Chick or chickens come from hen. Hen is an oviparous animal. It lays eggs. The eggs are fertilized internally before laying. Note: In case cocks (male hen) are not around, he eggs laid by a hen are not fertilized.

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9.

Cloning i. ii. iii. iv. v. vi. vii. viii. ix.

Cloning is induced (artificial) asexual reproduction. Cloning is the forming of a baby from a body cell. In the process of cloning, egg or ovum from a black faced female sheep ‘A’ was taken out of its womb. Its nucleus was replaced with a nucleus from a ‘baby cell’ taken from the mammary gland of another white faced female sheep ‘B’. This cell with changed nucleus is implanted onto the womb of sheep ‘A’, where it developed into a normal baby sheep. The baby thus born was found to be exactly similar to the sheep ‘B’ and it is termed a ‘clone’. The clone had no similarities with the sheep ‘A’ in whose womb it developed. It resembled the white faced sheep ‘B’ from whom the nucleus from its body cell was obtained. The clone was named ‘Dolly’.

WORKSHEET 2 1.

2.

Spot the errors in the given statements and correct them. a) The life cycle of butter fly is : Larva  Egg  Pupa  Adult. b) Fertilization in insects is internal. Assertion (A): Larva of mosquito is popularly known as Wriggler Reason (R): It moves up and down in the water. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of B. (C) A is correct and R is wrong. (D) A is wrong and R is correct.

Reproduction in Animals

3.

4.

5.

6. 7.

8.

9.

10.

11.

57

Statement - I: Larva of mosquito goes deep into the water to breathe and take dissolved oxygen in water. Statement – II: {Pupa in mosquito is seen as if suspended in water. (A) Statement - I is true, Statement - II is false. (B) Statement - I is false, Statement - II is true. (C) Both statements are true. (D)Both statements are false. Fill in the following blanks. a) Larva of mosquito is popularly called __________. b) The stage between larva and adult in the life cycle of silk work is ________. Say True or False (A) The female frog is fatter than the male. (B) For reproduction, the male and female frog come together late in winter season. (C) Fertilization is Frog is internal. (D) The whole of zygotes of the frog in a jelly is called Spawn. A fuses with egg and B is its product. C is the whole mass of zygotes enclosed in thick jelly of frog and D is the intermediate stage between aquatic and land habitat in frog’s life cycle. Identify A, B, C and D. Identify A, B, C, D in the life cycle of a frog.

Assertion (A): Tadpole stage of frog has both gills and fins. Reason (R): Gills help in breathing and fins help in swimming. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of (C) A is correct and R is wrong. (D) A is wrong and R is correct. Match the following: A) Frog P) External Fertilization B) Fish Q) Internal Fertilization C) Insects D) Human being Match the following: A) Fins P) Tadpole B) Lungs Q) Adult Frog C) Gills D) Four Limbs Assertion (A): Cloning is induced (artificial) asexual reproduction. Reason (R): Cloning is the forming of a baby from a body cell. (A) A is correct and R is the correct explanation of A. (B) A is correct and R is not the correct explanation of (C) A is correct and R is wrong. (D) A is wrong and R is correct.

58

8th Class Biology

12.

Statement - I: The baby thus born was found to be exactly similar to the sheep ‘B’ and it is termed a ‘clone‘. Statement – II: The clone had no similarities with the sheep ‘A’ in whose womb it developed. (A) Statement - I is true, Statement - II is false. (B) Statement - I is false, Statement - II is true. (C) Both statements are true. (D) Both statements are false.

1.

Budding is a type of asexual reproduction found in very few animals such as, coelenterates and ascidians. In budding, the new organism is formed by the (A) breaking of the parent body into many parts (B) formation of a bud on the body of the parent (C) breaking of the parent body and the release of spore (D) formation of a bud on the spores released by the parent The given diagram shows the life cycle of a frog.

2.

3.

4.

5. 6.

Stage A in the life cycle of a frog is known as (A) larva (B) pupa (C) tadpole (D) nymph In humans, the reproductive system produces gametes that unite to form an embryo. The main components of the reproductive system are the (A) testis and the kidney (B) liver and the kidney (C) testis and the ovary (D) ovary and the liver Sexual reproduction occursin most multi-cellular organisms.It is advantageous because it (A) results in theformation of offsprings that are not identical to the parents (B) results in theformation of several offsprings (C) requires lesser investment of energy (D) requires lesser amount of time Fertilization is an event that takes place during sexual reproduction. During fertilization, the (A) male and female gametes fuse (B) male gamete divides into two cells (C) female gamete divides into two cells (D) female and male gametes are produced Frogs undergo complete metamorphosis. Which figure represents the life cycle of frogs?

(A)

(B)

(C)

(D)

Reproduction in Animals

7.

59

Butterflies undergo complete metamorphosis. Which figure represents the life cycle of butterflies?

(A)

(B)

(C)

(D)

8.

Daniel wants to depict the stages of complete metamorphosis in their order of occurrence. Which arrow diagram represents the stages of complete metamorphosis in their order of occurrence? (A) Egg   larva  pupa  adult (B) Egg  pupa  larva   adult (C) Larva  egg  pupa  adult (D) Pupa  egg  larva  adult

9.

The given figure shows the eggs of a frog. In the stage that follows the one shown in the given figure, the egg matures and looks like

(A) 10. 11.

12.

13.

14.

(B)

(C)

(D)

In human females, fertilization takes place in the (A) Ovary (B) fallopian tube (C) Uterus (D) vagina Sex organs play a vital role in human sexual reproduction. The functions of sexual organs include production of gametes, child bearing, and child birth. In human females, egg cells are produced in the (A) vagina (B) clitoris (C) uterus (D) ovary Human beings give birth to live young babies. They need to be nourished externally before they grow into adults. The mode of reproduction in humans is called (A) oviparous (B) viviparous (C) ovoviviparous (D) ovooviparous Fertilization is the process in which the fusion of sperm and ova takes place in fallopian tubes. The fertilized egg or zygote transforms into blastocyst through a series of cell divisions. The implantation of blastocyst occurs in (A) ovaries (B) cervix (C) uterus (D) fallopian tubes In the human reproductive system, two gametes are involved in the process of reproduction. The male gamete is called sperm and the female gamete is called ovum. The fusion of these two gametes in the female reproductive system results in the formation of new offsprings. How many eggs do ovaries produce in one cycle under normal conditions? (A) One (B) Two (C) Three (D) Four

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15.

The reproductive system is correctly labelled in which diagram?

(A)

(C)

(B)

(D)

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REACHING THE AGE OF ADOLESCENCE     

Introduction Asexual Reproduction Sexual reproduction Life Cycle of Butterfly Life Cycle of Silkworm moth

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Life Cycle of Mosquito Reproduction in Toads and Frogs Reproductioni in Birds Cloning

SYNOPSIS 1 1.

How babies are formed? Among human beings we find mother and father, the parents. The mother in human beings give birth to babies that resemble their parents. Babies then grow into young adults. Method of reproduction is sexual reproduction. Basic process of sexual reproduction in human beings is the same as in all other animals. Both males and females bear special reproductive cells, the gametes. The male gamete is the sperm and the female gamete is the ovum (the egg cell). The two gametes unite during fertilization forming zygote. Fertilization in human beings is internal since it takes place inside the body of the female (mother). Zygote develops into an embryo and embryo into a baby. Baby may be a girl or a boy. Mother gives birth to a baby.

2.

Reproductive Organs

A.

The male sex organs : (a) A pair of testes (singular is testis). Each testis lies in a scrotal sac. The scrotal sacs lie hang outside the body. Millions of sperms (male gamates) are produced within the testes everyday stored in epididymis. When a boy reaches puberty, the testes are stimulated by the pituitary gl to produce ‘testosterone’, the male sex hormone. This hormone stimulates the formation of sperms. (b) Epididymis is one on each testis. It stores sperms till they are pushed out of the urethra. M of the sperms may stay in the epididymis, where they eventually die and are reabsorbed into tests. (c) Vas deferens are a pair of sperm ducts running from epididymis to the urethra on penis. They carry the sperms through them. (d) Penis, the muscular organ having a drainage duct (urethra) inside through which urine a sperms are pushed out. The sperm is a male gamete with a head, body and a long tail (flagellum). The head bearl nucleus. It is a single cell. Sperms while passing through vas deferens into the urethra collect fluid their way from seminal vesicle, prostate glands and cowper’s glands. This fluid along with sperms the semen.

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B.

The female sex organs (a) A pair of ovaries (singular is ovary). The ovaries lie inside the abdomen, in the hip region the body, one on each side of the uterus. Each ovary is placed just below the funnel-shaped opening of the fallopian tube. Each ovary produces eggs (ova, singular is ovum), in a limited number. Only one egg is released by one of the ovaries every month by a process called ovulation. This egg passes through the fallopian tube and oviduct to reach the uterus. An egg is a single cell and is the female gamete. When a girl reaches puberty, the ovaries are stimulated by the pituitary gland to produce ‘oestrogen’ and ‘progesterone’, the female sex hormones. Oestrogen stimulates the formation of ova (eggs) and progesterone regulates reproductive (menstrual) cycle. (b) A pair of oviducts or fallopian tubes. The oviducts have a funnel shaped opening over the ovaries and the tube runs up to the uterus. Ova being shed from the ovary enters the funnel of the oviduct and passes through the fallopian tube to reach the uterus. (c) Uterus or the womb is a sac well supplied with blood vessels along its walls. The wall develops a spongy cushion (endometrium) which disintegrates every month except when a baby is developing on it. On the upper side of the uterus fallopian tubes open into it. On the lower side, it itself opens out into vagina. (d) Vagina is a tubular cavity which opens to the outside through an opening called vulva.

3.

Fertilization & Embryo development The ovum from the ovary moves into the oviduct (falopian tube). Millions of sperms are transferred into the female and the sperms swim into the uterus reaching the oviduct. If an egg from the ovary has also reached the oviduct, ONLY one of the sperms may fuse (unite) with it forming a zygote (oospore). The uniting sperm loses its tail outside and only its head enters the egg. Rest of the sperms degenerate. Fusion of male gamete (sperm) and the female gamete (egg) is called fertilization. Fertilization takes place while the egg is passing through the fallopian tube or the oviduct. Zygote then moves into the uterus and gets attached to the endometrium (spongy cushion) on its wall. In human beings and in animals such as cats, dogs, cows and birds fertilization takes place in­side the body of the female. Fertilization taking place inside the body of the female is called internal fertilization.

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POINTS TO NOTE 1. 2.

3.

In size, sperm is many times smaller than the size of the egg or ovum. Each of the gametes contains one-half of the chromosomes from its parent cell. One half set of 23 chromosomes come from egg or the ovum (the female gamete) and the other half set of 23 chromosomes come form sperm (the male gamete). The male and the female gametes join together during Fertilization. The zygote formed as a result ofthe fusion of male and female gametes has one complete set of 23 pairs of chromosomes. Development of embryo Embryo is the baby in the early stages of formation. In the case of man embryo remains within the body of the mother. It is only the baby (fully developed embryo) which takes birth on the completion of gestation period. How babies develop inside the mother? Zygote formed as a result of fertilization divides and redivides into a ball of 2, 4, 8,16, 32 and into numerous cells. The cells inside the ball starts getting differentiated into organs of a baby forming young embryo. By this time, the embryo gets attached to the wall of the uterus from where it starts drawing nutrition in the form of blood from the mother through a cord (called the umbilical cord). The point of attachment of the cord to the wall of the uterus is called placenta. By the time embryo is five weeks old it will have rudimentary eyes and a beating heart. By the time it is twelve weeks old it is a miniature baby. It takes about 270 to 280 days for embryo to grow into a ‘baby’. This period of growth of the embryo to a baby inside the mother’s womb is called “pregnancy”, or the gestation period. The embryo (the baby) within the womb of the mother during pregnancy is called foetus. When the foetus is a complete baby with all the organs, the mother gives birth to it.

WORKSHEET 1 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Do human beings lay eggs as a hen does or they give birth to a baby? In which organ are the sperms produced? What is the function of epididymis? What happens to the sperms which stay within epididymis for long? Draw and label the structure of a sperm or male gamete. What is the function of ovaries? How many eggs (ovum) are released by the ovaries every month? Name the male hormone which stinulatesth formation of sperms in the testes. Name the two female sex hormones and their function. What do you understand by ‘fertilization’? Name the product of the fusion of a sperm wit ovum. In which organ of the female fertilization takes place? What do you understand by (a) internal fertilization, {b) external fertilization? What is an embryo? From where does the developing embryo obtains its nourishment? Name the point of attachment of the cord to the wall of the uterus. What do you understand by pregnancy? What is foetus ?

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SYNOPSIS 2 4.

Characters from parents to Children Fertilization is the process in which the sperm cell from the father fuses with the egg cell from the mother to form a zygote. The nucleus in each sperm and egg has chromosomes. These chromosomes on the sperm carry the characters of father and the chromosomes on the egg carry the characters of the mother. When these chromosomes unite in pairs in a zygote, they transfer the characters to the new baby. The baby therefore inherits some characteristics from the father and some from the mother. The children, therefore, resemble their parents in body features and also in habits.  Look to the features on brothers and sisters in your school or neighbourhood. Most brothers and sisters look alike.  Observe carefully the features on your friend and his/her parents. You may find many similarities. From this we learn that the characteristics from parents are inherited by the children due to the process of fertilization.

5.

The Sex of the Baby The chromosomes in the sperm, except for one. In each egg there are 23 chromosomes of which 22 are similar to that of a sperm and the 23rd may be different. We describe this 23rd chromosome in egg as X chromosome. All eggs carry X-chromosome only. In some of the sperms the 23rd chromosome may be an X chromosome and in some it may be a Y chromosome. X and Y chromosomes are “sex chromosomes”. Xchromosome stands for female and Y chromosome for male character. When an egg is fertilized by sperm having Xchromosome, the zygote is XX, and the baby developing from it is a female baby (a girl child). When an egg is fertilized by sperm having Y chromosome, the zygote is XY, and the baby developing from it is a male baby (a boy child). Sex of the child depends upon the sex chromosome present in the sperm fertilizing the egg. Thus, sperm from the father is responsible for the sex of the child. Medically it is possible to identify the sex of the foetus, but this practice of learning about the sex of a foetus is illegal and punishable under law. Some ignorant people misuse the information for aborting foetus (foeticide) of the unwanted child.

Points to note   

In human body each cell has 46 chromosomes (23 pairs of chromosomes) of which 23 come from an egg (mother) and 23 come from a sperm (father). The sex of a baby is determined by the XX and XY chromosomes in a zygote. It is a “chance” combination of an egg with an X-sperm or Y-sperm that determines the sex of a child.

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Gender Issues 1. Many people blame the mother for giving birth to a girl. Do you think it is true? In many tribes the people have a disliking for having a girl child because of social reasons. They seek the help from doctors for determining the sex of the foetus while inside the mother’s womb. In case, the foetus happens to be female they get it aborted (killing of the foetus inside the mother’s womb). This practice is called female infanticide. Government has made it illegal to find out the sex of the foetus to put a stop to the female infanticide.

6.

How are twins formed? At times mother delivers two or more babies than one. Twins are two babies from a mother taking birth at the same time. Twins may be ‘identical twins’ or ‘paternal twins’. Identical twins come from the same ovum (egg). After fertilization the zygote splits into two, each developing into an independent baby. These twins are ‘identical’ in many respects and are of the same sex.

Paternal twins are the result of double fertilization and they need not be of the same sex. They can be a boy and a girl, or two boys or two girls.

WORKSHEET 2 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

What is the importance of fertilization in sexual reproduction? Why do children resemble their parents? Pairing of chromosomes takes place when and unite to form a zygote. Why do most brothers and sisters look alike? How many chromosomes are there in the nucleus of a single sperm? How many chromosomes are there in the nucleus of a single egg? How many chromosomes come together in a zygote? Do all the sperm carry similar set of chromosomes? What do you understand by X and Y chromosomes? What will be the sex of a baby developing from XX zygote? What will be the sex of a baby developing from XY zygote? What is foeticide?

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SYNOPSIS 3 7.

Endocrine System

Hormones are secretions from endocrine glands. These are the chemical substances which are distributed into the various parts ofthe body through blood to stimulate growth and reproduction.

Endocrine Glands Endocrine glands and their functioning is called the endocrine system. The endocrine glands secrete the hormones produced by them directly into the blood stream. There are six endocrine glands in human body. These are: 1. Pituitary gland 2. Thyroid glands 3. Parathyroid glands 4. Adrenal glands 5. Pancreas 6. Testes in males, and Ovaries in females. In addition to the six endocrine glands listed above an additional gland “thymus Gland” is located in the chest, may be near the heart. This gland is large in babies and gets smaller and reduced as the child grows older. Thymus produces ‘thymosin’ hormone which protects the child from diseases. Endocrine glands, their location in the body, the hormone they secrete and the activity they control: 1. Pituitary Gland is the master gland located underneath the brain. It regulates the functioning of all other glands. It secretes hormones like growth hormone (GH), Trophic hormone (T.H), Prolactin, Vasopressin and Oxytocin to (i) stimulate physical growth of the body (ii) stimulate thyroid gland to secrete thyroxin hormone (iii) stimulate adrenal gland to secrete adrenalin (iv) stimulate mammary glands for the production of milk (v) regulates blood pressure (vi) facilitates childbirth (vii) stimulates testes to produce male sex hormone, the testosterone (viii) stimulates ovaries to produce female sex hormone, the oestrogen and progesterone. 2. Thyroid Gland is bilobed located on windpipe. See picture. It absorbs iodine and other materials to produce: (i). Thyroxine(e) which regulates physical and mental growth, metabolism (cell formation) and blood cholestrol. Tall, short, fat and thin body is regulated by thyroxin. (ii). Calcitonin which maintains calcium level in blood. 3. Parathyroid Glands are four tiny glands located on larynx. Parathyroid hormone (PTH) regulates calcium and phosphate in the body.

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Adrenal Glands are two, located one on each kidney. They produce hormone adrenalin and four other hormones which regulate emotional status such as excitement, fear, anger, sadness, happiness and increase in energy level in the body. It also regulates. (i) heart beat, breathing rate and blood pressure, (ii) food, sodium and potassium metabolism, (iii) water balance in blood, and Under stress (fear) secretion from adrenalin increases and results in heavy sweating and lowering of body temperature. Pancreas produces digestive juices which are let into the intestine through ducts. In addition, it has tiny ‘islets of Langerhans’ which secrete two endocrine hormones: (i) glucagon helps breakdown of glycogen in liver to raise blood glucose level, and (ii) insulin reduces blood glucose level. Deficiency of insulin results in diabetes. Sex Glands are testes in male and ovaries in female. They secrete ‘sex hormones’, which are responsible for male or female characteristics. a)

6.

Testes in male produce the hormone ‘testosterone’ which helps male sex characters production of sperms. Sex Glands are testes in male and ovaries in female. They secrete ‘sex hormones’, which are responsible for male or female characteristics. (b) Ovaries in female produce two hormones:  Oestrogen which helps in regulating whole set of female sex characters, including formation of ova.  Progesterone to regulate reproductive (menstrual) cycle.

8.

From Infancy to Adolescence

From baby to childhood is infancy. This period is generally up to the age of 7 to 8 years. Then begins the reproductive maturity. Girls at the age of 11 to 12 years and boys at the age of 14 to 15 years attain puberty (the reproductive maturity). Simultaneously, some major changes in the body of the girls and boys take place which continue up to the age of 19 or 20 to bring about complete maturity. This period of development from childhood to womanhood or manhood is the period of adolescence. Adolescence is a phase of rapid physical, mental and sexual growth. This growth can be confusing to youngsters as they may feel certain emotional and social interactions. Changes in the body of a youth during adolescence The pituitary gland activates all other endocrine glands from time to time and they start secreting hormones which bring about many changes in the body ofthe youth. These changes are In Boys  Increase in height and better development of muscles. Strong muscles.  Change in body shape with broader shoulders and wider chests.  Voice change due to better growth of larynx, which may protrude on the throat forming ‘Adam’s apple! The voice in boys is deep and hoarse.  More of secretions from oil glands (Sebaceous Glands) making the skin oily and shining.(glowing).Many youths develop acne and pimples on their faces.  Attain mental, intellectual and emotional maturity. Confidence building takes place. Learning capacity increases.  Secondary sex characters develop:  In both, boys and girls, hair start growing in arm pits and the pubic region above the thighs.  Moustaches and beard appear due to growth of facial hair, a distinguishing character of males.

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

 In Girls        





9. 1. 2.

Reproductive functioning begins with the release of Follicle Stimulating Hormone (FSH) from pituitary gland which makes testes to release testosterone hormone to initiate the formation of sperms (gametes) in the testes. Primary and secondary sex characters are activated with the release of male hormone (testosterone) from testes. Increase in height and better development of muscles. Shapely muscles. Change in body shape with broader shoulders, narrow waist and the region below the waist and around the hip girdle gets wider. Voice change without protruding larynx and high pitched voice (shrill but sweet). More of secretions from oil glands (Sebaceous Glands) making skin soft, oily and glowing. May developacne (pimples). Attain mental, intellectual and emotional maturity. Confidence building and learning capacity increases. Secondary sex characters develop : In both, boys and girls, hair start growing in arm pits and the pubic region above the thighs. Hormone from ovaries, the estrogen makes the breasts develop along with milk secreting glands inside. However, production of milk is under the control of a hormone from pituitary gland which gets activated only after a baby is delivered. Milk from the mother is available to the baby for about a year. Reproductive functioning begins with the maturation of sex organs and with the secretion of Follicle Stimlating Hormone (FSH) from the pituitary gland. This makes the ova (eggs) maturein the ovaries and preparing the uterus to receive zygote. In girls puberty begins at the age of10 to 12 years. During puberty, ova begin to mature in the ovaries. One ovum from any one ofthe two ovaries is released into the fallopian tube once in about 28 to 30 days. The sperm from male joins the ovum in the fallopian tube to form zygote. The zygote moves into the uterus and gets attached to the spongy and cushiony wall formed in the uterus. This is the onset (beginning) of pregnancy. Before a zygote is received in the uterus, the uterus wall becomes thick with a lining of soft and spongy tissue full of blood vessels. This is to receive the zygote. In case fertilization does not take place, the ovum (egg) along with the lining and the blood vessels is shed off. This results in bleeding in women which continues for 2 to 3 days. This is called menstruation. Since menstruation occurs once in about 28 to 30 days it is also called “period” or menstrual cycle. First menstrual flow is called menarche and begins with puberty. At the age of 45 to 50 years the reproductive ability stops and then menstrual cycle also stops. Stoppage of menstruation is called menopause, which is the termination of puberty.

Reproductive Health During adolescence and during parenthood both the parents must take care of personal health and hygiene. For this, one needs : Physical Exercise: Exercise and outdoor games keep the body fit and strong. Rope skipping is one of the good exercises for girls and boys. Walks and breathing fresh air is good for health. Personal Hygiene: Right from childhood to the end of the life it is necessary to observe personal hygiene in every walk of life. For this :

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Take bath daily at least once a day. Teenagers and adults should be particular about bath since sweat may make the body smell bad. Sweat is also a good abode for the germs causing various diseases. Clean all the body parts, including reproductive organs. Foreskin on penis and urethra should be cleaned to save them from infection. Proper nutrition : Balanced diet during adolescence helps in proper development of reproductive organs and a beautiful healthy body. No drugs and No smoking: Drugs are bad not only for health but for intelligence also. Drugs make one dull in learning and in physical activities. Syringes used for drugs may also infect you with AIDS (Acquired Immune - deficiency syndrome). Sexual contact of any kind which may result in (AIDS) or any other sexually transmitted diseases TD) should be avoided. Also, adolescent pregnancy is harmful. The right age for motherhood is 20above, when one crosses “teens”. A couple should take up the responsibilities of parenthood onlyen properly settled in life. This keeps one mentally, physically, emotionally and financially healthy and only then able to care for the child in a better way. Marriageable age prescribed under law is years for girls and 21 years for boys. Below this age they are ‘minors’ and the marriage between minors is illegal. Reproductive health care is a must for healthy parents for having healthy children.

10. Gender Issues and Social Taboos It has been since times immemoriable that the man became selfish and he discriminated against the “fair sex”, the girls or the female child. Since women were more apt to work in homes and fie they were kept occupied as labour and man used to be busy whiling away his time in gossiping am in games. To be exact ‘most men lived as parasite on women’. She was the bread earner. One used to keep many wives. Even today when the law is ‘one man one wife’, in certain tribal societies they permit man to keep more than one wife. In contrast, in many of our social groups, girls are considered a burden since marrying them subjugates them to the families in which their sisters or daughters are married. Whereas, in some social groups “dowry” has become a menace. To overcome all this, “female foeticide” has become a practice. Overall result is that in some areas the female population is on the decline. There are less number of girls available to marry the boys. We must leave things for nature to decide. Chance combination of X and Y sperms with ova when left to nature automatically results in balancing the population of the two sexes. Then, we must respect WOMEN, since only they help in bringing up of babies, and not the man. Today, women have been able to do better than men in every field of life.

Some Myths and Social Taboos Due to ignorance there are many misgivings about man and woman and their sex life. Some of the myths 7are :  Girls are not as intelligent as the boys are.  Girls are not capable of performing certain feats as boys.  Loss of semen is the loss of energy.  A girl should not handle food during menstruation.  Physical contact (even touching) makes a girl pregnant.  The mother is responsible for the sex of her child. A mother of many girls is considered ‘unlucky’ and responsible for bearing female child only.

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WORKSHE ET 3 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

What are glands? What are duct glands? Name any two. What are ductless glands? Name any two. List the six endocrine glands found in human body. Who do we call pituitary gland as the master gland? Which hormone causes sweating under fear? What do you understand by ‘puberty’? Which is the age of adolescence? What changes occur in the body of a boy during adolescence? Why do we call the age of a youth between 12 and 20 as teenage? List the similar changes taking place in both boys and girls during adolescence. List the changes taking place in girls only during adolescence. What do you understand by secondary sex characters? What is the duration of reproductive activity in (a) boys, (b) girls? What is the function of FSH (hormone) from pituitary? List some do’s and don’ts for reproductive health. When should one take up the responsibility of parenthood? What is ‘female foeticide’?

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The given chart shows the average growth in Age (in years) % of maximum height the height of both boys and girls. Boys Girls If Anjali is 10 years old and 130 cm tall, then 8 72 77 what will be Anjali’s height at the end of the 9 75 81 growth period? 10 78 84 (A) 154.76 cm (B) 153.86 cm 11 81 88 (C) 160.76 cm (D) 161.86 cm 12 84 91 Secondary sexual characteristics are 13 88 95 characteristics that help distinguish between 14 92 98 males and females. Which of the following 15 95 99 characteristics is observed only in boys at the 16 98 99.5 time of puberty? 17 99 100 (A) Increase in height 18 100 100 (B) Growth of hair in underarms (C) Increase in the size of larynx (D) Growth of hair in the pubic area Which of the following secondary sexual characteristics is observed only in girls at the time of puberty? (A) Development of testes (B) Development of breasts (C) Growth of hair in underarms (D) Growth of hair in the pubic area Which of the following secondary sexual characteristics is not observed in boys? (A) Growth of facial hair (B) Enlargement of larynx (C) Enlargement of ovaries (D) Growth of hairs on chest The given illustration represents the human endocrine system. In the given illustration, pancreas is labelled as

(A) I (B) II (C) III (D) IV The changes that occur in the body of adolescents are under the control of hormones. Which hormone controls the development of secondary sexual characteristics in males during puberty? (A) Testosterone (B) Thyroxin (C) Estrogen (D) Insulin In females, ovaries produce a hormone that helps in the development of breasts at the onset of puberty. Which hormone is secreted by ovaries for the described function? (A) Testosterone (B) Estrogen (C) Thyroxin (D) Insulin

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The adrenal gland secretes adrenalin. Which of the following statements about adrenalin is correct? (A) It regulates the level of sugar in the blood (B) It maintains the balance of salt in the body (C) It controls the development of breasts in females (D) It controls the development of facial hair in males The absence of thyroxin hormone results in goitre. Which endocrine gland secretes thyroxin? (A) Testes (B) Ovaries (C) Thyroid (D) Pancreas Testes and ovaries secrete hormones that are responsible for the development of male and female secondary sexual characteristics. Hormones from which gland stimulate testes and ovaries to secrete their respective hormones? (A) Thyroid (B) Pancreas (C) Adrenal gland (D) Pituitary gland In frogs, the metamorphosis of a tadpole into an adult frog is under the control of a hormone. Which hormone stimulates metamorphosis in frogs? (A) Testosterone (B) Adrenalin (C) Estrogen (D) Thyroxin The first menstrual flow in females is termed as _____i_____. It begins at ____ii______. The information in which alternative completes the given statement? (A) i- menarche ii- puberty (B) i- menarche ii- Birth (C) i- menopause ii- puberty (D) i- menopause ii- birth _____i_____ and _____ii_____ are iron-rich food items that promote blood formation. Hence, they are essential for adolescents. The information in which alternative completes the given statements? (A) i- Spinach ii- Rice (B) i- Wheat ii- Gram (C) i- Gram ii- Spinach (D) i- Spinach ii- Cabbage Balanced diet includes food items from all food groups such as proteins, fats, carbohydrates, and vitamins. Which of the following food items is not a part of a balanced diet? (A) Boiled rice (B) Soft drinks (C) Fruit juice (D) Cooked cereal The increased activity of which gland in adolescents makes the body smelly? (A) Thyroid gland (B) Sweat gland (C) Sebaceous gland (D) Salivary gland AIDS is a disease that weakens the ability of the body to fight against diseases. Which organism causes AIDS? (A) Virus (B) Bacteria (C) Fungi (D) Protozoa Which of the following statements about AIDS is incorrect? (A) It is caused by virus (B) It is a sexually transmitted disease (C) It can be transmitted by eating food with an infected person (D) It can be transmitted from one person to another by sharing syringes

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POLLUTION OF AIR AND WATER

CHAPTER

7

       

Sources of Air Pollution Effects of Air pollution on living organisms Effect of Air pollution on Non living objects Green house effect and Global warming Initiatives to reduce air pollution and global warming Water pollution Effects of Water pollution on living organisms Conservation and Purification of water

SYNOPSIS 1 1.

Sources of Air Pollution Air is everywhere around us and we all need clean air for breathing. But did you know that as a result of the addition of some substances to air, it is increasingly becoming toxic for living organisms? The contamination of air with unwanted substances, which have harmful effects on both plants and animals, is known as air pollution. The substances that cause the contamination of air are called air pollutants.  Sources of air pollution There are two source of air pollution are: (i) Natural sources and (ii) Man-made sources Natural sources You may have seen on television that during the summer season some forests catch fire. These fires are caused when, as a result of high temperatures, dead plant materials such as barks, twigs, and leaves, which are lying on the forest floor, start burning. These fires emit large amounts of smoke into the atmosphere, thereby polluting the air. The other natural source of air pollution is volcanoes. Volcanoes emit large amounts of harmful gases and dust particles into the atmosphere, thus contributing to air pollution. Man-made sources Although natural sources contribute to air pollution, did you know that human activities contribute the most toward air pollution? Human activities that cause air pollution include emissions from power plants, automobile exhausts, and factories; burning of fossil fuels and firewood, etc. Let us now explore various air pollutants and their sources. I. Carbon monoxide Carbon monoxide is a toxic, colourless gas. It is produced by the incomplete burning of fossil fuels. It is mainly produced by vehicles. II. Smog Smog is formed by the combination of smoke and fog. It is a highly noxious mixture of pollutants that affects the health of living organisms. Smog is a common winter phenomenon in a large number of modern day cities such as Delhi. III. Oxides of sulphur and Nitrogen Sulphur dioxide and nitrogen dioxide are major oxides of sulphur and nitrogen that act as pollutants. These are released from petroleum refineries and also from power plants that use coal as a fuel.

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V.

2.

Chlorofluorocarbons Chlorofluorocarbons are also known as CFCs. They are used in refrigerators, air conditioners, and aerosol sprays. They cause damage to the ozone layer in the atmosphere. Suspended Particulate Matter (SPM) These are tiny particles that are produced on the burning of coal and petroleum. They are also released during industrial processes such as mining and making of steel.

Effects of Air Pollution On Living Organisms Air pollution has significant health effects on all living organisms including human beings. Various air pollutants cause diseases that range from skin cancers to respiratory disorders. Let us examine in detail the effect that each pollutant has on living organisms. I. Carbon monoxide Carbon monoxide is a pollutant that is released as a result of the incomplete burning of fuels such as diesel and petrol. What effect does carbon monoxide have on the health of humans? Carbon monoxide combines with haemoglobin, which is present in the red blood cells, and decreases the oxygen-carrying capacity of blood.

II.

III. IV.

VI.

VII.

Sulphur dioxide Sulphur dioxide is a pollutant that is produced during the combustion of fuels such as coal. It causes many respiratory problems such as cough and throat irritation when inhaled in small amounts. Continuous exposure to sulphur dioxide may cause permanent damage to the lungs. Nitrogen dioxide Exposure to nitrogen dioxide causes damage to the lungs apart from other respiratory disorders. Smog Some of you may have seen a thick fog-like layer in the atmosphere during the winter months. This is smog. Smog is formed when smoke mixes with fog. Smog is made up of many air pollutants such as the oxides of nitrogen. It causes breathing difficulties such as asthma, cough, and wheezing among children. Chlorofluorocarbons (CFCs) Chlorofluorocarbons are responsible for damaging the ozone layer and have led to the formation of the ozone hole in the atmosphere. A rapidly depleting ozone layer allows the harmful UV radiations of the sun to reach the Earth, which is responsible for an increase in the cases of skin cancers. Suspended particles Suspended particles are tiny particles that are produced because of the burning of fossil fuels. They trigger many respiratory diseases such as asthma and sneezing when inhaled.

Pollution of Air and Water

75

The hair present in the nostrils prevents the suspended dust particles from entering our lungs. However, some dust particles are so small that they cannot be trapped in the nostrils and they enter the respiratory system.

3.

Effect of Air Pollution on Non-Living Objects All of us have seen the Taj Mahal, either in reality or in pictures. Did you know that the Taj Mahal is in danger because of rising air pollution levels? Taking the Taj Mahal as a case study, let us explore how air pollution affects non-living objects such as buildings and monuments. The industries present around the Taj Mahal, especially the Mathura oil refinery, are primarily responsible for the damage caused to the monument. Acid rains are very harmful. These rains cause widespread damage to several materials and property, especially to monuments, which undergo heavy corrosion as a result of these rains. Acid rains have corroded the marble of the Taj Mahal, a phenomenon also known as Marble-cancer. This particulate matter released from Mathura oil refinery is responsible for the yellowing of the marble of the Taj Mahal. What are we doing to protect the Taj Mahal or other monuments from the harmful effects of air pollution? Let us find out. The Supreme Court of India has taken many steps in the direction of protecting the Taj Mahal from pollution. It has directed the industries around the Taj Mahal to use cleaner fuels such as LPG (Liquefied Petroleum Gas) and CNG (Compressed Natural Gas). In addition, all vehicles have been ordered to switch-over to unleaded petrol. CNG and LPG are clean fuels. Hence, they do not produce soot on burning.

WORKSHEET 1 1. 2. 3.

4.

5.

6. 7.

Which of the following sources of energy causes environmental pollution? (A) Hydal energy (B) Solar energy (C) Wind power (D) Fossil fuels Atmosphere does not get polluted by (A) mining (B) farming (C) transportation (D) manufacturing The oxides of which of the following pairs of elements cause acid rain? (A) Sulphur and nitrogen (B) Sodium and nitrogen (C) Magnesium and sulphur (D) Carbon and phosphorus The ozone layer protects us from the harmful ultraviolet rays from the Sun. Which of the following air pollutants is destroying the ozone layer? (A) Carbon monoxide (B) Oxides of sulphur (C) Oxides of nitrogen (D) Chlorofluorocarbons Chlorofluorocarbons (CFCs) are substances that pollute the air. These are produced from man-made devices. The use of which of the following commodities does not produce CFCs? (A) Petroleum (B) Refrigerators (C) Aerosol sprays (D) Air conditioners Which of the following air pollutants is produced from the incomplete burning of vehicle fuels? (A) Carbon monoxide (B) Carbon dioxide (C) Sulphur trioxide (D) Sulphur dioxide The discharge of excessive chemicals from industries, households, etc., into ponds is responsible for which of the following effects? (A) It makes the pond water toxic for algae (B) It increases the level of oxygen in the pond (C) It reduces the temperature of water in the pond (D) It decreases the population of aquatic organisms

8th Class Biology

76 8.

Gases produced from vehicles, power plants, cooling devices, etc. cause diseases such as respiratory problems, breathing difficulties and skin diseases.Which table correctly matches the pollutant gases with the diseases caused by them? (A)

Pollutant gas Smog

Asthma

Carbon monoxide

Skin disease

Sulphur dioxide

Lung damage Reduce the oxygen carrying capacity of blood

Chlorofluorocarbons

(C)

Pollutant gas

10.

11.

12. 13.

14.

Disease

(B)

Pollutant gas Smog

Sulphur dioxide

Asthma Reduces oxygen carrying capacity of blood Lung damage

Chlorofluoroca rbons

Skin disease

Carbon monoxide

(D)

Disease

Pollutant gas

Disease

Smog

Skin disease

Smog

Asthma

Carbon monoxide

Lung damage

Carbon monoxide

Sulphur dioxide

Asthma Reduce the oxygen carrying capacity of blood

Lung damage Reduces the oxygen carrying capacity of blood Skin disease

Chlorofluoroca rbons

9.

Disease

Sulphur dioxide Chlorofluoroca rbons

Air pollutants cause serious damage to health. Which gas is paired correctly with the disease caused by it? (A) Smog - Asthama (B) CO - Lung damage (C) SO2 - Skin disease (D) Chlrofluro carbons - Reduce the oxygen carrying capacity of blood. In a city, a thermal power plant produces a large amount of smoke while generating electricity. Which of the following problems is not a result of the smoke released by the factory? (A) Smog (B) Acid rain (C) Air borne diseases (D) Breathing disorders The burning of fossil fuels such as coal and petroleum leads to an increase in the concentration of sulfur dioxide in atmosphere. This sulfur dioxide changes into sulfuric acid in the atmosphere, causing acid rains.Which of the following effects is not a consequence of acid rains? (A) Damage to buildings and monuments (B) Increase in the temperature of Earth (C) Reduction in the growth of trees (D) Reduction of marine population The burning of fossil fuels does not lead to (A) smog (B) acid rain (C) snowfall (D) air pollution Consider the following statements regarding the case study of Taj Mahal.I.Corroding of the marble of the monument is caused by carbon dioxide and sulphur dioxide.II.Suspended soot particles emitted by Mathura oil refinery cause the yellowing of the marble.III.One of the steps to save the Taj is to use CNG and LPG in the automobiles in the Taj zone. Among the given statements, (A) only I is correct (B) only III is correct (C) I and II are correct (D) II and III are correct Chlorofluorocarbon (CFC) is another kind of pollutant that causes damage to the environment. Which of the following statements is correct regarding the environmental problem caused by CFCs? (A) It causes acid rain. (B) It reduces the visibility. (C) It causes global warming. (D) It damages the ozone layer.

Pollution of Air and Water 15.

77

Taj Mahal is one of the Seven Wonders of the world. It is situated on the banks of river Yamuna. Environmental pollution has damaged the marble of the monument. The Taj Mahal is threatened by which type of pollution? (A) Air (B) Soil (C) Water (D) Noise

SYNOPSIS 2 4.

5.

Greenhouse Effect And Global Warming Greenhouse effect Have you seen a greenhouse in a nursery where plants are kept? A greenhouse is a structure that traps the sun’s heat and does not allow it to escape. This provides a warm atmosphere for the plants to grow. We know that the sun’s rays keep the Earth’s surface warm. Some of the solar radiation is absorbed by the Earth, while a part of it is reflected back into space. This reflected radiation is trapped by the atmosphere of the Earth. This phenomenon, which imitates the greenhouse of a nursery, is known as the greenhouse effect. How does the greenhouse effect affect our environment? There are a few gases in the atmosphere that aggravate the greenhouse effect. These gases are called greenhouse gases. The levels of these gases in the atmosphere have increased as a result of increasing pollution levels. Carbon dioxide is one of the gases that cause the greenhouse effect. Carbon dioxide (CO2) is a natural component of the atmosphere. How can a natural part of the Earth pose a threat to life? All of us know that plants absorb carbon dioxide from the atmosphere to synthesize their own food through the process of photosynthesis. However, as a result of deforestation, the number of trees has gone down drastically. This has reduced the uptake of carbon dioxide by trees, which in turn has led to an increase in its concentration in the atmosphere. The burning of fossil fuels further adds to the carbon dioxide levels in the atmosphere. As a result, more and more solar radiation is being trapped in the atmosphere, thereby leading to an increase in the Earth’s temperature. This warming-up of the Earth is termed as global warming. Other gases such as methane, nitrous oxide, and water vapour also contribute to the greenhouse effect. What are the likely consequences of global warming? Global warming will result in extreme temperature conditions. There will be changes in the precipitation patterns that may lead to floods and droughts. The water trapped in the ice caps of the Polar Regions will start melting at a rapid rate, which will cause the sea levels to rise. Even a marginal increase in the temperature of the Earth (i.e., +0.5°C) may lead to serious disasters. Initiatives to Reduce Air Pollution and Global Warming Air pollution  and  global  warming  pose  a  serious  threat  to  the  Earth. What initiatives can we take to reduce these problems? The government of Delhi has taken several initiatives to reduce the levels of air pollution in the city. Delhi was ranked among the most polluted cities of the world till a few years ago. The air in the city was heavily laden with fumes and poisonous gases from automobiles. On the intervention of the Supreme Court, a decision was taken to introduce CNG (Compressed Natural Gas) as a fuel to run the public transport system of Delhi. In addition, the use of unleaded petrol was made compulsory. The results of these initiatives reflected in the quality of air. The air in Delhi now is much cleaner as compared to the

8th Class Biology

78

past. Thus, the use of CNG and unleaded petrol are a few of the measures that can be taken to reduce air pollution. Measures to help combat air pollution One measure of preventing air pollution and global warming involves the switching over from traditional fuels to alternative, cleaner fuelssuch as solar energy, wind energy, and hydropower energy. Unlike fossil fuels, these alternative sources of energy do not cause pollution and can be tapped from nature, where these are available in abundance. The burning of dry leaves causes  a lot of pollution. Therefore, instead of burning  them, one can bury these leaves in a compost pit. The leaf compost thus obtained can be used as manure for plants. Planting of trees is another measure that can be taken to reduce air pollution. Plants use carbon dioxide during photosynthesis. Thus, planting more trees will increase the utilization of carbon dioxide from the atmosphere. This will reduce the carbon dioxide concentration in the atmosphere and will help in reducing the growing effects of global warming. In India, Van Mahotsav is celebrated every year during the rainy season in the months of July and August. During this period, large scale plantation of trees is carried out.

WORKSHEET 2 1.

2. 3.

4.

5.

6.

7.

8.

Fossil fuels such as coal and petroleum are found deep inside Earth’s surface. They are extracted from Earth by mining. Mining does not result in (A) soil erosion (B) global warming (C) the lowering of water table(D) the contamination of water Which of the following human activities does not contribute to global warming? (A) Deforestation (B) Transportation (C) Communication (D) Industrialization Human activities contribute to global warming by increasing the concentration of carbon dioxide, (A) CH4, and O3in atmosphere (B) CH4, and SO2 in atmosphere (C) NO2 and methane in atmosphere (D) SO2 and NO2 in atmosphere The global average temperature change is shown in the given graph. Earth’s global average temperature has been increasing gradually since 1860. The change in Earth’s global average temperature has been recorded by investigating (A) soil (B) clouds (C) fossils (D) rainfall Which of the following human activities results in global warming? (A) Fishing (B) Mining (C) Cultivation (D) Afforestation Rapid deforestation results in i in the amount of ii released into the atmosphere, which contributes significantly to global warming. (A) i- an increase; ii-nitrogen (B) i-a decrease; ii-nitrogen (C) i-an increase; carbon dioxide (D) i- a decrease; ii- carbon dioxide The weather change that can be attributed to global warming is (A) an increase in extreme weather activities (B) a decrease in humidity and rainfall (C) a decrease in global temperature (D) an increase in acid precipitation Air pollution leads to global warming, acid rain, ozone depletion and a wide variety of respiratory diseases. Which of the following activities does not contribute to air pollution? (A) Mining of heavy metals (B) Exhaust from motor vehicles (C) Application of fertilizers to soil (D) Emission of CFC’s in the atmosphere

Pollution of Air and Water 9.

10. 11.

12.

79

Four events that result in the greenhouse effect are resulted below:I. Earth reflects a part of sunlightII. Trapped radiation heats up the atmosphereIII. The Earth’s atmosphere traps the reflected sunlight.IV. Sunlight falls on the surface of the Earth. Which arrow diagram correctly represents the sequence of events that result in the greenhouse effect? (A) I   II    III    IV (B) I   IV    III    II (C) IV   III    II    I (D) IV   I    III    II Which of the following gases is not a greenhouse gas? (A) Carbon dioxide (B) Nitrous oxide (C) Ammonia (D) Methane Anand burns crackers on all occasions. Every year Sameer plants a tree on his birthday. Mehar cleans up her house and dumps the wastes in an open area in her colony. Basheer collects dry leaves and twigs from the garden and burns them. Who contributes to reducing environmental pollution? (A) Anand (B) Sameer (C) Mehar (D) Basheer Consider the following statements regarding air pollution.I. Use of mass transit system reduces air pollution.II. Fuels such as CNG should be encouraged to reduce air pollution.III. Burning crackers reduces the CO2 content of  air. Among the given statements, (A) only statement I is true (B) only statement III is true (C) statement I and II are true (D) statement II and III are true

SYNOPSIS 3 6.

What is water pollution? The addition of harmful substances to water which causes its physical, chemical and biological properties to change is called water pollution. The substances that pollute water are called water pollutants. Sewage, toxic chemicals, silt etc. are examples of water pollutants. Sources of water pollution All of you are aware that Ganga is one of the most important holy rivers of India. It supports the lives of millions of people living in the northern plains. According to a study by the WWF, Ganga is one of the ten most endangered rivers. The river Ganga is practically dead at many places. This is because the pollution levels in the river are so high that it cannot support any life form. The portion of the river that flows through the city of Kanpur is a stretch that is completely dead. The factors that have contributed to the increase in the pollution levels of the river are • Dumping of large quantities of garbage into the river • Releasing of untreated sewage water into the river • Throwing of dead bodies into the river • Washing, bathing, and defecating near the shores of the river • Throwing flowers and idols of gods and goddesses into the river • Dumping non-biodegradable substances such as polythene bags into the river These are common factors that are responsible for polluting the rivers of our country. In addition, factories manufacturing fertilizers, detergents, leather goods, and paints that are located near a river, throw their industrial wastes and toxic chemicals into the river. This makes the water of the river unfit for use by living organisms. In order to address all the above mentioned problems, the Ganga Action Plan was launched in the year 1985 with the purpose of reviving the river. However, unplanned urbanisation and industrialization has taken its toll on the river and it has been damaged beyond repair.

8th Class Biology

80

7.

Effects of Water Pollution on Living Organisms I.

Industrial waste:

In the absence of proper treatment facilities for industrial wastes, most of these wastes are directly dumped into the rivers. The industrial wastes from oil refineries, chemical factories, sugar mills, and fertilizer plants carry toxic substance such as arsenic, lead, mercury, and fluoride. These substances cause toxicity in plants and animals. II.

III.

They also pollute the soil by increasing its acidity, decreasing its fertility, and affecting the growth of worms which are beneficial for the soil. Pesticides and fertilizers We know that fertilizers and pesticides are a farmer’s friends as these help in killing the pests and weeds and increasing the fertility of the soil.The chemicals that are contained in these pesticides and fertilizers get dissolved in the water and eventually get washed away to the water bodies. They also seep into the ground and pollute the ground water. On entering the water bodies, these pesticides and fertilizers increase the nutrient content of the soil as they contain various nutrients. This accelerates the growth of algae in the water bodies. You may have observed that some water bodies appear green in colour. This is because of the excessive growth of algae in water. When these algae die, they are decomposed by the action of micro-organisms that are present in water. Consequently, the number of these micro-organisms in water bodies increases. Since they consume a large quantity of oxygen that is present in the water, it leads to a decrease in the levels of oxygen. The absence of oxygen eventually leads to the death of the living organisms. Sewage Sewage is waste water that contains faecal matter, urine, food wastes, detergents, and other solid substances. Sewage contains many disease-causing pathogens such as bacteria, fungi, viruses, and parasites. When drinking water gets contaminated with sewage water, these harmful organisms enter the bodies of the living organisms and cause several diseases. Some of the diseases caused by the drinking of contaminated water and the names of the respective causal organisms are listed in the table. Name of the disease Causal organism Cholera

Bacteria

Typhoid

Bacteria

Diarrhoea

Bacteria

Hepatitis

Virus

Amoebic dysentery

Protozoan

Several bacteria are present in the faeces of mammals. If the water is contaminated with faeces, then these bacteria function as indicator organisms for the quality of water i.e., the number of these faecal bacteria indicates the extent to which the water is contaminated by faecal matter.

8.

Conservation and Purification Of Water Water is a precious resource and we need to conserve it. Water can be conserved by following the simple principle of reduce, reuse, and recycle. This can be practiced easily at homes. Some examples are • Reusing the waste water from the kitchen (water that has been used to wash vegetables etc.) to water the plants in the garden • Reusing the water after washing clothes to wipe the floor or to clean the car • Turning the tap off while brushing or shaving • Checking for leaky taps and fixing them up

Pollution of Air and Water

81

Thus, we can reduce the total amount of water consumed by us by recycling and reusing most of the waste water for other purposes. The waste water from industries first needs to be treated in sewage treatment plants. This water can then be used for growing plants and other industrial purposes. Purification of water Potable water is the water that is safe for drinking. Although  the  water  may  look  clean  on  mere observation, it may contain disease-carrying micro-organisms. In order to prevent the occurrence of diseases, this water has to be cleaned and only then can it be used safely for drinking. Methods to purify water I. Physical methods • Filtration: It is one of the common methods used for removing impurities from water. A simple filter paper can be used to obtain clean water. Candle-type filters that are commonly used in households are also based on the principle of filtration. • Boiling: Boiling the water helps in killing the germs present in water. II. Chemical Methods • Chlorination Adding chlorine to water is one of the most commonly used methods of purifying water. Chlorine, when used in the prescribed amount, kills the germs present in water and makes it safe for consumption. You may have observed that tap water sometimes appears milky. This is because it contains chlorine. • Adding bleaching powder helps in purifying water.

WORKSHEET 3 1.

2. 3.

4.

5.

Human activities play a major role in water pollution. Which of the following human activities does not cause water pollution? (A) Discharge of human waste into water (B) Leaching of pesticides into water (C) Exhaust from automobiles (D) Mining of heavy metals Which of the following chemical elements does not make water toxic? (A) Chlorine (B) Fluorine (C) Arsenic (D) Lead Environment has been negatively affected by an increase in industrialization. Waste material from various industries is dumped into rivers or lakes. As a result, rivers and lakes get polluted.Which of the following occurrences is not a result of water pollution? (A) Water borne diseases (B) Breeding of mosquitoes (C) Reduction in potable water (D) Decrease in fish population Bald Eagle is the national bird of the United States of America. These birds prefer habitats near sea coasts, rivers, large lakes, and other large bodies of open water with an abundance of fish. Bald Eagles were on the brink of extinction in the late 20th century because of the consumption of DDT contaminated fish. The consumption of polluted fish caused the Bald Eagles to lay thin shelled eggs that cracked before hatching.The primary reason for the near extinction of the Bald Eagles was (A) air pollution (B) land pollution (C) waterpollution (D) noise pollution Which of the following diseases is caused by the consumption of polluted water? (A) Jaundice (B) Malaria (C) Dengue (D) Filaria

82 6.

7.

8.

9.

10.

11.

12.

8th Class Biology The given graph shows the number of fishes that died in a certain lake as a result of industrial pollution, between the years 2001-2006. The number of fishes that died as a result of industrial pollution over the years has (A) increased continuously (B) decreased continuously (C) first increased and then decreased (D) first decreased and then increased In a certain town, a factory discharges its chemical waste directly into a small lake. The water in this lake is then used by farmers for irrigation purpose. Which of the following changes will not be noted in this town? (A) The quality of the water in the lake will decrease. (B) The marine life in the lake will get seriously affected. (C) The people living nearby will suffer from water borne diseases. (D) The fertility of the lands irrigated by the lake water will increase. The given table lists the causes of the death of fishes in various Cause of death Number of states of the United States. of fishes U.S. states reporting it The reduction in the number of fishes is mainly a result of Agricultural 24 (A) agricultural practices (B) industrial practices practices (C) land disposal (D) oil spill Municipal 16 The excessive use of fertilizers increases the nutrient content of facilities 17 soil. If these nutrients find their way to a nearby lake, then it would Oil spill result in the Industrial 13 practices (A) immediate death of all aquatic life Land B) immediate increase in fish population 6 disposal (C) increase in the growth of aquatic vegetation (D) increase in the amount of dissolved oxygen in water Which of the following consequences can be caused by an oil spill? (A) Increase in fish population (B) Increase in aquatic vegetation (C) Increase in the amount of toxins (D) Increase in the amount of dissolved oxygen In a city, the waste from the factories is disposed directly into a river. The given graph shows the reduction in the quantity of fish caught (in quintals) from the river in the past 25 years. The reduction in the quantity of fish caught from 1980 to 2005 is (A) 24 quintals (B) 20 quintals (C) 16 quintals (D) 12 quintals Which of the following changes is not a result of an increase in water pollution? (A) Increase in the cases of jaundice and cholera (B) Increase in the amount of rainfall and floods (C) Increase in the chemical content of water bodies (D) Increase in the biological activity in water bodies

Pollution of Air and Water 13.

14.

15.

16.

17.

18.

19.

20.

83

The spilling of oil on the surface of oceans and seas is known as oil spill. Which of the following changes is not a consequence of an oil spill? (A) Reduction in the amount of sunlight obtained (B) Increase in the concentration of toxins in water (C) Increase in the population of marine organisms (D) Reduction in the amount of dissolved oxygen in water Environment has been negatively affected by an increase in industrialization. Waste material from various industries is dumped into rivers or lakes. As a result, rivers and lakes get polluted. Which of the following species is the least affected by polluted rivers? (A) Kingfisher (B) Goldfish (C) Parrot (D) Turtle Water pollution is a phenomenon in which unwanted substances enter into a water body and thus into the water cycle. Which of the following is a consequence of water pollution? (A) Eutrophication (B) Greenhouse effect (C) Increase in aquatic life forms (D) Increase in the oxygen content of water Fertilizers, if used in excess, can run-off into water bodies. This results in an increase in the nutrient content of water.The increase in the nutrient content of water will lead to an increase in the population of (A) small fishes (B) large fishes (C) crustaceans (D) algae Which of the following measures does not help in purifying tap water? (A) Boiling (B) Storing in earthen pots (C) Adding chlorine tablets (D) Filtering through candle filters The most polluted stretch of the river Ganga is the stretch that flows through the city of Kanpur in Uttar Pradesh.Which of the following activities is not the major factor responsible for the pollution of Ganga? (A) Defecation in the river (B) Excess fishing in the river (C) Immersing idols of gods in the river (D) Disposing polythene bags into the river A compound of calcium ‘X’ is used in the purification of water. It reacts with water to form another compound ‘Y’ with the evolution of gas ‘Z’. When carbon dioxide gas is passed through ‘Y’, it turns milky. Gas ‘Z’ helps in the purification of water. Which of the following statements regarding the given piece of information is correct? (A) X is bleaching powder, Y is calcium hydroxide, and Z is water vapour. (B) X is calcium hydroxide, Y is bleaching powder, and Z is chlorine gas. (C) X is bleaching powder, Y is calcium hydroxide, and Z is chlorine gas. (D) X is calcium hydroxide, Y is bleaching powder, and Z is water vapour. The aim of Ganga action plan is to (A) prevent cutting of banks by Ganga (B) reduce the pollution level in river Ganga (C) save the endangered species present in Ganga (D) make proper use of the Ganga water for farming



84

8th Class Biology

KEY/ANSWERS CROP PRODUCTION & MANAGEMENT NOTE: Questions of worksheets 1 to 7 are conceptual. COMPETITIVE WORKSHEET 1. 2.

(i) -e; (ii)-d; (iii)-b; (iv)-c (a) Kharif crop  Paddy, maize



(b) Rabi crop

Wheat, gram

3.

4.

Down 1. IRRIGATION

2. STORAGE

5. CROP

Across 3. HARVESTOR

Q.no Ans

5 A

4. GRAM

6 B

7 A

8 A

6. WINNOWING

9 C

10 C

11 D

12 D

13 C

MICRO-ORGANISMS – FRIENDS & FOE WORKSHEET-1 1. 3. 5. 7. 9.

Tiny organisms that are visible under microscope Microscope / Electron microscope Few microns They grow on specific organisms and hosts. Conceptual

2. 4. 6. 8. 10.

No Yeast Single celled Densely populated Conceptual

WORKSHEET-2 1. 4.

Bread, Beer & wine Conceptual 6 to 10 are conceptual

2. 5.

True 3. Conceptual By bacteria like lacto bacillus and Maphylococcus

14 A

15 C

8th Class Biology

86

WORKSHEET-3 1.

Micro-organsims that cause diseases.

2.

Both useful & harmful

3.

Cholera, flu, leprosy

5.

Cause diseseases

6.

B.tuberculosis, B. pneumonia, B. typhus, B. influenza, vibrio cholera,

7.

air, water, infected person, food or othe edible things,

8.

Conceptual

9.

(i) – (g); (ii) – (f); (iii) – (h); (iv) – (e); (v) – (c); (vi) – (b); (vii) – (a); (viii) – (d)

10.

(a) communable

4.

Conceptual

(b) vectors

(c) malaria

(d) pencillin

(e) virus NOTE: Worksheet-4 is conceptual COMPETITIVE WORKSHEET Q.no Ans Q.no Ans

1 D 11 A

2 D 12 B

3 B 13 C

4 B 14 D

5 B 15 B

6 A

7 B

8 C

9 B

10 B

CONSERVATION OF PLANTS & ANIMALS WORKSHEET-1 1.

A

2.

B

3.

5.

(a) 10 to 15 million

7.

(a) Food chain (b) Forests

(b) 2 million 8.

ABCD/SRQP

4.

ABCD/QPSR

(c) all types of plants

6.

Both statements are correct

(a) True

(b) False

WORKSHEET-2 1.

C

2.

(a) is incorrect

5.

(a) Global warming

(b) Protect zone

6.

1234/abba

D

7.

3.

8.

D

4.

Conceptual

(c) National parks & wild life sanctuaries A

9.

D

10. B

WORKSHEET-3 1.

A

2.

5.

(a) CBD

– Convention on Biodiversity

(b) IUCN

– International Union of Conservation of Nature and Natural Resources

(c) WCU

– World Conservation Union

(d) WWF

– World Wide Fund for nature

123/cab

7.

6.

(b) is incorrect

A

3.

8.

C

D

9.

4.

D

Conceptual

10.

B

Worksheet Key & Answers

87 COMPETITIVE WORKSHEET

Q.no Ans Q.no Ans Q.no Ans

1 C 11 A 21 D

2 C 12 D 22 B

3 C 13 A 23 B

4 C 14 A 24 B

5 B 15 D 25 A

6 C 16 A 26 C

7 C 17 D

8 D 18 B

9 A 19 A

10 B 20 A

CELL – STRUCTURE & FUNCTIONS WORKSHEET-1 Q.no Ans Q.no Ans

1 B 11 D

2 B 12 C

3 A

4 B

5 D

6 D

7 A

8 B

9 C

10 B

7 B 17 A

8 C 18 B

9 C 19 C

10 D 20 D

7 B 17 A

8 D 18 D

9 D 19 A

10 B 20 A

WORKSHEET-2 Q.no Ans Q.no Ans Q.no Ans

1 B 11 B 21 C

2 B 12 B 22 A

3 C 13 B 23 D

4 B 14 C 24 B

5 D 15 D 25 B

6 B 16 A

COMPETITIVE WORKSHEET Q.no Ans Q.no Ans

1 B 11 B

2 A 12 C

3 C 13 B

4 A 14 B

5 A 15 B

6 B 16 A

REPRODUCTION IN ANIMALS WORKSHEET-1 Q.no Ans

1 A

2 B

3

4 A

5 A,D-p; B,C-q

6 A,D -q; B,C-p

7 C

WORKSHEET-2 1.

(a) is incorrect

2. A

3. B

5.

abcd/TFFT

6. A=sperm; B = Zygote; C=Spawn; D=Tadpole

7.

A=Fertilized ova; B=Zygote; C=Tadpole Larva; D = Tadpole without tail

9.

A,B-P; C,D-Q

10. A,C-P: B,D-Q

4. (a) wriggler (b) pupa

11. A

12. C

8. A

8 C

8th Class Biology

88 COMPETITIVE WORKSHEET Q.no Ans Q.no Ans

1 B 11 D

2 C 12 B

3 C 13 C

4 A 14 A

5 A 15 C

6 A

7 A

8 A

9 B

10 B

9 C

10 D

REACHING THE AGE OF ADOLESCENCE NOTE: Questions of worksheets 1 to 3 are conceptual. COMPETITIVE WORKSHEET Q.no Ans Q.no Ans

1 B 11 D

2 C 12 A

3 B 13 D

4 C 14 B

5 B 15 B

6 A 16 A

7 B 17 C

8 B

POLLUTION OF AIR AND WATER WORKSHEET-1 Q.no Ans Q.no Ans

1 D 11 B

2 B 12 C

3 A 13 D

4 D 14 D

5 A 15 A

6 A

7 D

8 B

9 A

10 C

6 C

7 A

8 C

9 D

10 C

6 A 16 D

7 D 17 B

8 A 18 B

9 C 19 C

10 C 20 B

7 D 17 D

8 B 18 C

9 D 19 D

10 B 20 C

WORKSHEET-2 Q.no Ans Q.no Ans

1 B 11 B

2 C 12 C

3 A

4 C

5 B

WORKSHEET-3 Q.no Ans Q.no Ans

1 C 11 B

2 A 12 B

3 B 13 C

4 C 14 C

5 A 15 A

COMPETITIVE WORKSHEET

Q.no Ans Q.no Ans

1 A 11 D

2 D 12 B

3 C 13 B

4 C 14 D

5 B 15 B

6 D 16 B