Class 10 Biology - BeTOPPERS NEET Foundation Series - 2022 Edition

Citation preview

MEDICINE FOUNDATION Class X

BIOLOGY

© USN Edutech Private Limited The moral rights of the author’s have been asserted. This Workbook is for personal and non-commercial use only and must not be sold, lent, hired or given to anyone else.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior written permission of USN Edutech Private Limited. Any breach will entail legal action and prosecution without further notice.

Utmost care and attention to the details is taken while editing and printing this book. However, USN Edutech Private Limited and the Publisher do not take any legal responsibility for any errors or misrepresentations that might have crept in.

Published by

:

USN Eductech Private Limited Hyderabad, India.

PREFACE

Our sincere endeavor in preparing this study material is to enable students to effectively grasp and understand the concepts of IIT foundation. This study material has been compiled by our team of experts who have a decade of experience in various academic fields. These books also proved to be successful in developing of academic skills like concentration power, understanding ability, memory power, retention ability, problem-solving skills, application skills, analytical ability, logical thinking and emotional strengths like interest in learning, self-reliance, confidence, will power, psychological strength, right stir and zeal and physical stamina. The important features of the books are: 1.

Lucidly presented concepts For easy understanding of the concepts, they are presented in simple and easy, comprehensible language. 2. Learning Outcomes Each chapter starts with Learning outcomes which precisely conveys what the students is going to learn in this chapter. 3. Bold-faced key terms The key words, concepts, definitions, formulae, statements, etc., are expressed in bold face, indicating their importance in the content. 4. Tables and charts Numerous strategically placed tables and charts, list out and summarize the important information, making it readily accessible for effective study. 5. Box items Throughout the text, the box items highlight special topics that take the text material to be a more extended level. Students will find them to be a lively and interesting feature as they investigate the subject. 6. Photographs A wide array of visually appealing and informative photographs are used to help the students to understand various phenomena and inculcate interest in the subject. 7. Illustrations Because a picture is worth a thousand words, each chapter has ample number of illustrations that clarify different concepts and enhance learning. 8. Flow diagrams To help students understand the steps in problem-solving, flow diagrams have been included at key locations i.e., at important concepts. These diagrams allow the students to visualize the process of solving a problem. 9. Summary charts At the end of the chapter or important concepts, there is a summary of major concepts covered. Each section is reviewed in a paragraph form. The summary, along with the blueprint, provides a complete overview of the chapter. 10. Concept-wise Formative Worksheet Unlike other books, this book contains concept-wise Formative Worksheet problems. The solutions for these problems shall be discussed by the teacher in the classroom. These questions allow the child to strengthen understanding and application skills.

11. Concept-wise Conceptive worksheet Each Formative Worksheet is followed by a Conceptive worksheet. This contains additional problems of the respective concepts. The problems are expected to be solved by the students for additional practice. This allows the students to get exposed to new style of problems related to the concept. 12. Summative worksheet At the end of each chapter, there is a Summative Worksheet. This worksheet contains problems based on all the concepts of the chapter. Unlike Formative Worksheet and Conceptive Worksheet problems, the problems in this section involve the application of multiple concepts of the given chapter. The worksheet allows the child to strengthen the problem-solving, application and analytical skills. 13. Advanced worksheet Each Summative Worksheet is followed by an HOTS (Higher Order Thinking Skills) worksheet. This worksheet contains problems of advanced type involving Higher Order Thinking Skills. The concepts can be of same chapter or different. The solving of these problems prepares the child to face new patterns of problems that appear in actual IIT and other entrance examinations. Strengthening of all the academic skills of a child is the main objective of this worksheet. 14. IIT JEE worksheet Finally, every chapter ends with a IIT JEE worksheet. This worksheet contains the problems which have appeared in various competitive examinations like IIT, AIEEE, KCET, TCET, JIMPER, BHU, AIIMS, PbCET, CBSE, CET, etc related to the chapter. This part of the worksheets creates awareness and builds confidence as the students get exposed to real problems that appeared in various competitive examinations. 15. Wide variety of problems The problems included in the worksheets cover various models that appear in different competitive examinations. The different models include:

 Non-objective type  Objective type with more than one option correct  Matching type – II (Three columns)  Statement type – II (More than two statements)  Statement and Explanation type  Figurative type  Road Map type

 Objective type with single option correct  Matching type – I (Two columns)  Statement type – I (Two statements)  Assertion and Reason type  True or False type  Comprehensive type  And many more……

We would like to thank all members of the different departments of BeIITIIANS who played a key role in bringing out this student-friendly study material. We sincerely hope that this study material will prove useful to the students undergoing IIT foundation, ensuring their success in various competitive examinations. However, We believe that as there is always scope for improvement, we value constructive criticism of the subject matter, as well as suggestions for improving the book. All suggestions will be duly incorporated in the next edition. Wish you all the best. Academic Team USN Edutech

CONTENTS 1.

Life Processes

..........

1 - 24

2.

Control and Coordination

..........

25 - 44

3.

How do Organsims Reproduce

..........

45 - 86

4.

Heredity & Evolution

..........

87- 110

5.

Our Environment

..........

111 - 122

6.

Management of Natural Resources

..........

123 - 134

7.

Key and Answers

..........

135 - 148

LIFE PROCESSES

CHAPTER

1



Life Processes



Transportation in human beings



Nutrition in Plants



Transportation in plants



Nutrition in Animals



Excretion in human beings



Respiration



Excretion in plants

SYNOPSIS 1 1.

Life Processes • • •

• •

2.

The life process includes the activities performed by the different organs to maintain the body. Nutrition: The processes of obtaining energy through consumption of food. Respiration : The process of acquiring oxygen through breathing and make it available to cells for the process of breaking down of organic substances into simpler compounds is called as respiration. Transportation: Transportation is the process by which the food and oxygen is carried from one organ to other organs in the body. Excretion: It is the process by which the metabolic waste by-products are removed from the different organs and released out from the body.

Nutrition in plants How do living things get their food? The general requirement for energy and materials is common in all organisms, but it is fulfilled in different ways. Some organisms use simple food material obtained from inorganic sources in the form of carbon dioxide and water. These organisms, the autotrophs, include green plants and some bacteria. Other organisms utilise complex substances. These complex substances have to be broken down into simpler ones before they can be used for the upkeep and growth of the body. To achieve this, organisms use biocatalysts called enzymes. Thus, the heterotrophs survival depends directly or indirectly on autotrophs. Heterotrophic organisms include animals and fungi. I. Autotrophic Nutrition Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis. It is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy. This material is taken in the form of carbon dioxide and water which is converted into carbohydrates in the presence of sunlight and chlorophyll. Carbohydrates are utilised for providing energy to the plant. We will study how this takes place in the next section. The carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant. A somewhat similar situation is seen in us where some of the energy derived from the food we eat is stored in our body in the form of glycogen. Sunlight 6CO 2  6H 2 O   C6 H12O 6  6O 2 Chlorophyll

 Glu cose 

Let us now see what actually happens during the process of photosynthesis. The following events occur during this process – (i) Absorption of light energy by chlorophyll. (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates.

10th Class Biology

2 These steps need not take place one after the other immediately. For example, desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day. Let us see how each of the components of the above reaction are necessary for photosynthesis. If you carefully observe a cross-section of a leaf under the microscope (shown in Fig.), you will notice that some cells contain green dots. These green dots are cell organelles called chloroplasts which contain chlorophyll. Let us do an activity which demonstrates that chlorophyll is essential for photosynthesis. Now, let us study how the plant obtains carbon dioxide.

Stomata • • • •

• • •

Stomata which are tiny pores present on the surface of the leaves. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis. Exchange of gases occurs across the surface of stems, roots and leaves as well. As large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink. Based on the two activities performed above, can we design an experiment to demonstrate that sunlight is essential for photosynthesis?

Raw materials required for photosynthesis The raw materials required for photosynthesis are CO2 and H2O and the products formed are carbohydrates and O2. Plants obtain water through their roots. Water is then transported to all plant parts with the help of the xylem. Exchange of gases (entry of CO2 and release of O2) occurs through the stomata. The essential conditions for photosynthesis are:

1.

Sunlight Place a healthy green potted plant in a dark room for 1-2 days. This is done to ensure that the plant consumes all its reserve food and the leaves do not contain any starch. Then, cover a portion of a leaf of this plant on both sides with two uniform pieces of black paper, fixed in position with two paper clips. Now, expose this plant to bright light. After a few hours, remove the leaf, decolourize it with alcohol, and test the presence of food (starch) with iodine solution. You will observe that the portion of the leaf covered with black paper does not show any presence of starch (food).

Life Processes

2.

3

Chlorophyll is essential for photosynthesis Place a variegated plant (i.e., a plant which has both green and non-green areas, for e.g., croton or money plant) in a dark room for 2 – 3 days. This is done to ensure that all the reserve food (starch) is utilized. Place this plant in sunlight for six hours to allow photosynthesis to take place. Then, pluck a leaf from this plant and trace the green areas on a sheet of paper. Now, decolourize the leaf using alcohol and dip it in a dilute solution of iodine for a few minutes. Wash this leaf with water and compare it with the tracings of the leaf done earlier. It will be observed that only the green areas of the leaf could photosynthesize.

Explanation The leaf is treated with alcohol so that it loses its green colour (chlorophyll pigment) and blueblack colour (in presence of starch) obtained after treatment with iodine. The green parts of a variegated leaf contain chlorophyll. Therefore, only these parts could photosynthesize and manufacture food. Thus, the change in colour was observed only in these parts.

3.

Carbondioxide Select two healthy potted plants of nearly the same size and label them as A and B. Place them in a dark room for 2-3 days. Then, place two glass plates under both the plants. Place a watch-glass containing potassium hydroxide besides pot A. Cover both the plants by inverting separate bell jars over them. Potassium hydroxide, as we know, is used to absorb CO 2. Therefore, CO2 is not available for plant A. Now, seal the bottom of the jars to the glass plates with the help of Vaseline. This prevents the entry of CO2 into the set up. Then, place the plants under sunlight for 2 – 3 hours. Test one leaf each from both plants for the presence of starch, using alcohol and iodine (as explained in the previous activity). It will be observed thatplant B has a higher amount of starch as compared to plant A.

Explanation of the activity: This happens because potassium hydroxide present besides plant A absorbs all the CO2. Therefore, plant A is not able to photosynthesize and manufacture food. Hence, the amount of starch present in plant B is higher than plant A.

Two phases of photosynthesis The process of photosynthesis occurs in two phases – the light reactions and the dark reactions. A)

Light reactions As the name suggests, this reaction takes place in the presence of light. Light energy is absorbed by chlorophyll molecules and is utilized for splitting water molecules into hydrogen and oxygen. Additionally in this phase, assimilatory power in the form of ATP and NADPH 2 are produced. Light reactions occur in the membranes of thylakoids.

Events occurring during light reactions:

B)

• Absorption of light energy by chlorophyll molecules • Splitting of water molecules into hydrogen and oxygen atoms • Formation of ATP and NADPH2 Dark reactions This reaction does not require direct light and occurs in the stroma of chloroplasts. During this phase, ATP and NADPH2 (formed during light reactions) are utilized for the reduction of CO2 to carbohydrates (food).

10th Class Biology

4

Event occurring during dark reaction: II.

Reduction of CO2 to form carbohydrates

Heterotrophic Nutrition

Each organism is adapted to its environment. The form of nutrition differs depending on the type and availability of food material as well as how it is obtained by the organism. For example, whether the food source is stationary (such as grass) or mobile (such as a deer), would allow for differences in how the food is accessed and what is the nutritive apparatus used by a cow and a lion. There is a range of strategies by which the food is taken in and used by the organism. Some organisms break-down the food material outside the body and then absorb it. Examples are fungi like bread moulds, yeast and mushrooms. Others take in whole material and break it down inside their bodies. What can be taken in and broken down depends on the body design and functioning. Some other organisms derive nutrition from plants or animals without killing them. This parasitic nutritive strategy is used by a wide variety of organisms like cuscuta (amar-bel), orchids, ticks, lice, leeches and tape-worms.

How do Organisms obtain their Nutrition? As the food and the way it is obtained differ, the digestive system is different in various organisms. In single-celled organisms, the food may be taken in by the entire surface. But as the complexity of the organism increases, different parts become specialised to perform different functions.

Nutrition in Amoeba • • •

In Amoeba takes in food using temporary finger-like extensions of the cell surface which fuse over the food particle forming a foodvacuole ( as shown in fig) . Inside the foodvacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out.

Nutrition in paramoecium • •

In Paramoecium, which is also a unicellular organism, the cell has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia which cover the entire surface of the cell.

WORKSHEET 1 1.

2. 3.

Photosynthesis is an important process in not only that it is the primary process of food production but also that its bye-products are used by animals for respiration. Which gas is produced by plants during the synthesis of food? (A) Carbon monoxide (B) Oxygen (C) Hydrogen (D) Carbon dioxide Plants use carbon dioxide and energy from sunlight to form complex molecules. Plants prepare food in the form of (A) amino acids (B) carbohydrates (C) sulfates (D) fats A leaf wrapped with a dark tape, as shown in the figure, was kept for a week. Following this, the part of leaf that was wrapped was tested for the presence of starch. The test result was negative.

What is the possible reason for the absence of starch? (A) Non-availability of oxygen (B) Non-availability of carbon dioxide (C) Non-availability of sunlight (D) Non-availability of water

Life Processes 4. 5.

6.

7. 8. 9. 10. 11.

12. 13. 14. 15. 16. 17.

5

The sugar manufactured by plants is transported to other tissues through (A) xylem (B) pollens (C) phloem (D) arteries In a certain experiment, a potted plant was kept in an inverted bell jar such that no external air passed into the bell jar. After a span of two weeks, the air in the bell jar was tested on various parameters. It can be concluded from the above experiment that the air in the bell jar had (A) low concentration of oxygen (B) high concentration of oxygen (C) low concentration of water vapor (D) high concentration of carbon dioxide In a certain experiment, plant cells are allowed to grow in a nutrient medium. The cell culture is kept in a dark room. After a week, they are removed and studied. It can be concluded from the above experiment that (A) all cells will die (B) cells will perform photosynthesis, multiply, and grow (C) photosynthetic cells will die (D) cells will be alive but will not perform photosynthesis Which process uses carbon dioxide and produces oxygen as a waste product? (A) Transpiration (B) Respiration (C) Photosynthesis ` (D) Osmosis The raw materials for photosynthesis are (A) CO2 & O2 (B) sunlight and CO2 (C) water and chlorophyll (D) CO2 and water. Most of the photosynthesis (80%) which takes place on this earth is carried out by (A) green plants on land (B) algae present in fresh water (C) algae found in ocean (D) algae present in ocean and fresh water sources. Which of the following ahs no digestive enzyme ? (A) Saliva (B) Bile (C) Gastric juice (D) Intestinal juice Plants are green in colour because (A) they absorb green light only (B) they reflect green light (C) they absorb green light but reflect all other lights (D) none of the above are correct. Full name of N ADP is (A) Nicotinamide dinucleotide phosphate (B) Nicotine adenine dinuceotide phosphate (C) Nicotinamide adenine dinucleotide phosphate (D) None of the above Wavelength of visible light is (A) 200 - 400 nm (B) 400 - 700 nm (C) 700 - 900 nm (D) 100 - 200 nm The presence of sugar in onion leaves can be tested with (A) iodine (B) copper sulphate solution (C) lime water (D) benedict’s solution Chemical reaction takes place during dark reaction of photosynthesis is (A) photolysis (B) hydrolysis (C) carbon dioxide is bonded with RUBP (D) nitrogen fixation Dark reaction and light reaction of photosynthesis takes place in (A) stroma and grana of chloroplast respectively (B) grana and stroma of chloroplast respectively (C) grana only (D) stroma only CO2 acceptor during dark reaction of photosynthesis is (A) RUBP (B) PEP (C) NADPH (D) ATP

SYNOPSIS 2 3.

Nutrition in Human Beings Unlike plants, human beings cannot produce their own food. Thus, their mode of nutrition is heterotrophic. The term ‘heterotroph’ is derived from the Greek word ‘Hetero’ meaning different or other, and ‘troph’ meaning nutrition. In this mode of nutrition, organisms obtain energy from the intake of complex organic substances, generally from plant and animal sources. These organisms are known as heterotrophs. All fungi and animals, including humans and some bacteria are heterotrophs. Eating nutritious food is healthy because it supplies essential nutrients required to sustain life.

10th Class Biology

6

What happens to the food we eat? How are nutrients present in the food utilized by the body? It is by the process of digestion that the nutrients present in food are utilised by the human body. Digestion may thus be defined as the mechanical and chemical reduction of ingested nutrients first into particles, then into molecules, so that they become small enough to move through columnar epithelial cells of the intestine into the blood.

I.

Digestive organs and their functions

(i)

Mouth Digestion of food begins in the mouth. The mouth comprises of the following: Teeth: They tear and break down the food. Saliva: It contains a digestive enzyme called salivary amylase, which breaks down starch into sugar. Tongue: It is a sense organ with taste buds, which help us to differentiate between various food items. The muscular movements in the tongue move the food from the mouth into the throat, or pharynx. (ii) Pharynx: It is a common passageway for food and air. It opens into the oesophagus (which leads to the stomach) and trachea (which leads to the lungs). (iii) Oesophagus The circular smooth muscles in the oesophagus contract when food is swallowed. This prevents the chewed food material from moving back into the mouth. This is followed by the contractions and relaxations of the longitudinal smooth muscles, which push the digested food forward. These movements are called peristaltic movements, which push the food into the stomach. (iv) Stomach The stomach stores and mixes the food received from the oesophagus with the gastric juice. The gastric glands present in the walls of the stomach secrete several substances, which together constitute the gastric juice. The main components of gastric juice are hydrochloric acid, mucus, and pepsinogen. Hydrochloric acid dissolves bits of food and creates an acidic medium. In this medium, pepsinogen is converted to pepsin, which is a protein-digesting enzyme. Acidity Excess production of hydrochloric acid in the stomach can damage the protective lining of the stomach. Sometimes, the valve between the oesophagus and stomach becomes weak and the acid from the stomach reaches the lower part of the oesophagus. This can result in heartburn.

(v)

Small intestine It is the longest part of the alimentary canal. It is made up of three parts- duodenum, jejunum, and ileum. The length of the small intestine depends on the type of food consumed by the organism. Hence, its length differs in various animals. Length of the small intestine in animals Herbivores have long intestines. It is 10-12 times the length of their bodies. This is because grass contains cellulose, which takes a long time to be digested. Carnivores, on the other hand, have a smaller intestine of about 3-7 times the length of their bodies. This is because the meat that enters their body begins to rot soon. Hence, their intestines are shorter in length to excrete meat out of

Life Processes

7

their bodies quickly. The small intestine produces intestinal juice from the glands present in the wall, which helps in further digestion of food. Digestive juices from two glands, namely the liver and pancreas mixes with the food in the small intestine. The liver produces bile juice (which causes emulsification of fats) and the pancreas produces pancreatic juice (for digesting proteins and emulsified fats). The small intestine is the site for complete digestion of carbohydrates, proteins, and fats. This digested food is then absorbed through the intestinal walls. The inner lining of the small intestine has millions of tiny finger-like projections called the villi.

(vi)

These projections increase the surface area of the small intestine for more efficient food absorption. Within these villi, the capillaries absorb nutrients from the digested products of proteins and carbohydrates and lead them into the blood stream. Large intestine The indigestible material and water enters the large intestine. It also has villi to absorb water and some vitamins from the undigested food. This absorption of water helps to compact the faeces. It also performs the function of storage of wastes before they are excreted from the body via the anus.Therefore, the digestion of food starts in the mouth. The process of digestion continues in the stomach and small intestine. The absorption of nutrients occurs in the small intestine through diffusion.

WORKSHEET 2 1. 2. 3.

The raw materials for photosynthesis are (A) CO2 & O2 (B) sunlight and CO2 (C) water and chlorophyll (D) CO2 and water. Most of the photosynthesis (80%) which takes place on this earth is carried out by (A) green plants on land (B) algae present in fresh water (C) algae found in ocean (D) algae present in ocean and fresh water sources. Which of the following ahs no digestive enzyme ? (A) Saliva (B) Bile (C) Gastric juice (D) Intestinal juice

8 4.

5. 6. 7.

8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.

10th Class Biology Plants are green in colour because (A) they absorb green light only (B) they reflect green light (C) they absorb green light but reflect all other lights (D) none of the above are correct. Digestion of food in human starts from (A) duodenum (B) small intestine (C) mouth (D) large intestine The digestion of food is completed in the (A) ileum (B) duodenum (C) stomach (D) large intestine The most important function of villi in the small intestine is (A) to provide strength to the intestine (B) to provide space for capillaries and lacteals (C) to provide increased surface area for absorption of digested food (D) to provide habitat for bacteria Which of the following sections does not contain enzymes ? (A) Bile (B) Pancreatic juice (C) Intestinal juice (D) Saliva The breakdown of food is completed in the (A) large intestine (B) small intestine (C) stomach (D) rectum The saliva present in mouth helps in the (A) mixing of food with gastric juices (B) breakdown of proteins (C) mixing of food with bile juice (D) breakdown of carbohydrates Which organ is a part of respiratory as well as digestive system? (A) Larynx (B) Trachea (C) Bronchus (D) Pharynx Different parts of the digestive system are involved in different functions. Maximum absorption of nutrients from the digested food takes place in the (A) stomach (B) esophagus (C) small intestine (D) large intestine Bile juice is secreted by liver and is stored in the gall bladder. Bile juice is chiefly involved in the digestion of (A) proteins (B) carbohydrates (C) fats (D) glucose Liver secretes (A) bile juice (B) pancreatic juice (C) insulin (D) glycogen Where does the digestion of proteins start in the human body? (A) Mouth (B) Stomach (C) Liver (D) Small intestine Which part of the alimentary tract is not involved in digestion? (A) Stomach (B) Mouth (C) Esophagus (D) Small intestine The absorption of water from undigested food takes place in the (A) small intestine (B) large intestine (C) stomach (D) liver Esophagus connects the (A) mouth to the small intestine (B) small intestine to the colon (C) mouth to the stomach (D) stomach to the large intestine Which feature of small intestine facilitates the absorption of nutrients? (A) Presence of microbes (B) Elongated structure (C) Position in the digestive tract (D) Surface area of villus Which is the longest part of the digestive tract? (A) Esophagus (B) Stomach (C) Small intestine (D) Large intestine Which type of molecule does pepsin digest? (A) Fat (B) starch (C) Protein (D) Lipid Which of the following organs is a part of the alimentary tract and secretes digestive enzymes? (A) Liver (B) Stomach (C) Pancreas (D) Gall bladder What is involved in digesting food in the mouth? (A) Teeth (B) Tongue (C) Saliva (D) Jaws Which organ precedes anus? (A) Large intestine (B) Small intestine (C) Rectum (D) Stomach Which of the following functions is not performed by stomach? (A) Digestion of protein (B) Collection of food (C) Digestion of carbohydrates (D) Production of bile juices Which of the following organs is a part of the small intestine? (A) Colon (B) Villi (C) Appendix (D) Rectum

Life Processes 27. 28. 29. 30.

9

Which of the following fluids is not secreted by stomach? (A) Bile juice (B) Hydrochloric acid (C) Pepsinogen Which is the longest part of the digestive tract with respect to length? (A) Esophagus (B) Small intestine (C) Large intestine Salivary glands are present in the (A) mouth (B) throat (C) tongue If stomach were not a part of the digestive system, then (A) it would not have been possible to consume large quantities of food (B) the organs of the excretory system would become highly inefficient (C) one would continuously feel hungry (D) it would not be necessary to chew food at all

(D) Mucus (D) Colon (D) esophagus

z`

SYNOPSIS 3 4.

Respiration I.

Definition We know that there is a constant exchange of atmospheric gases. Oxygen is inhaled and carbon dioxide is exhaled. If oxygen is inhaled, then it must be used for some activity in the body. Similarly, if carbon dioxide is exhaled out of the body, then it must be because it is not required. This important life process is called respiration.

II.

Inhalation and Exhalation Respiration is the bodily process of inhalation and exhalation. It is the process of taking in oxygen and releasing carbon dioxide. The process involves the consumption of oxygen and liberation of carbon dioxide and water. The oxygen inhaled is used to burn/oxidize/break down the food (glucose). This reaction produces energy required for all activities. Water and carbon dioxide are by-products of this reaction. This process occurs inside the mitochondria and is called cellular respiration. It is exactly opposite to the process of photosynthesis. It can be represented as:

C6 H12O6  O2   6CO2  6 H 2 O  Energy Thus, cellular respiration is the process by which energy is released from the breakdown of organic substances (glucose).

III.

Aerobic and Anaerobic Respirations Is oxygen the only molecule used to burn food and produce energy? What happens to the organisms living in regions with no oxygen? Respiration can occur both in the presence and absence of O2. On this basis, it can be classified into two types: aerobic and anaerobic. Aerobic respiration

Anaerobic respiration

It occurs in the presence of O2.

It occurs in the absence of O2.

It involves the exchange of gases between an organism and outside environment.

Exchange of gases is absent.

It occurs in the cytoplasm and mitochondria.

It occurs only in the cytoplasm.

It always releases CO2 and H2O.

End products may vary.

It yields 38 ATP.

It yields 2 ATP.

Glucose is the simplest molecule that enters a series of reactions called Glycolysis and the Krebs cycle to produce energy. Proteins and fatty acids are broken down and enter the cycle at different regions. Amino acids, depending upon the length of the carbon chain, enter the Krebs cycle at different places. Lipids are fist converted into fatty acids and then into acetyl-CoA, which enters the Krebs cycle.

10th Class Biology

10

Steps involved in Aerobic respiration Step 1 The first step is called glycolysis. It occurs in the cytoplasm of a cell. It does not require oxygen. Here, the 6-carbon molecule glucose is partially broken down into a 3-carbon molecule, pyruvate or pyruvic acid. In this step, one glucose molecule produces 2 molecules of pyruvate. Glucose 2 Pyruvate Step 2: The two pyruvic acid molecules are converted into acetyl CoA, which can easily enter the mitochondria, which is the site for further reactions. Step 3 These acetyl CoA molecules enter the mitochondrial matrix and take part in the Krebs cycle. This occurs in the presence of O2. Step 4: In this step, the energy released in all the above steps is converted to ATP by ATP synthase enzyme. In aerobic respiration, a total of 36 ATP molecules are produced from one molecule of glucose.

Steps inovolved in Anaerobic respiration Step 1 The first step, glycolysis, is the same as that of aerobic respiration. glycolysis Glucose   pyruvic acid Step 2 Pyruvic acid is not transported to the mitochondria. It remains in the cytoplasm. It is then broken down into waste products that can be removed from the cell. This entire process occurs in the absence of oxygen. glycolysis Glucose   Pyruvic acid Anaerobic respiration occurs in the roots of some species of water logged plants, parasitic worms, yeast, animal muscles, and microorganisms. In some microorganisms such as yeasts, anaerobic respiration is called fermentation. In the process of fermentation, ethanol is formed as a by-product. This is represented in the above reaction.

Illustration of anaerobic respiration Aerobic respiration produces large amounts of energy. What about regions where energy is required, but oxygen is not available? In muscle cells, when there is a lack of oxygen, anaerobic respiration occurs where pyruvic acid is converted into lactic acid. This accumulation of lactic acid causes muscle cramps.

Brewing is an industrial application of fermentation. Do you know that brewing industries utilize yeast? Alcoholic fermentation is the conversion of sugar into ethyl alcohol and CO2. One of the by-products, CO2, dissipates into air whereas the other by-product, ethyl alcohol, remains in the medium. This alcohol is processed in the brewing industry and is utilized commercially.

IV

Exchange of gases in plants Plants exchange gases through stomata. This exchange of gases occurs through the process of diffusion. When CO2 is present in high concentration inside the plant body, it moves out into the atmosphere (where its concentration is low) and allows O2 to enter the plants. Now let us learn about the process of respiration in organisms.

V.

Respiration in humans The human respiratory system supplies our body with O2 and also helps in removing CO2, which is a waste product formed during cellular respiration. The intake of O2 and exit of CO2 involves two processes:

Life Processes

1)

2)

11

Inhalation It involves bringing in air from outside the body into the lungs. When we breathe in, the size of our chest increases. This happens because when air enters, the lungs expand and the ribs move outwards. Simultaneously, the diaphragm contracts and becomes flat. Thus, the size of our chest increases. Exhalation It involves removal of CO2 from the body. When we breathe out, the size of our chest decreases. This happens because when air moves out of our lungs, the lungs contract, the ribs move back, and the diaphragm curves upwards into the chest decreasing the size of the chest.

Organs involved in respiration: The organs of the respiratory system extend from the nose to lungs. They include the nose, pharynx, trachea, bronchi, and bronchioles.

1.

Nostrils The air from outside first enters the nostrils, which is divided into the left and the right nostril. These nostrils lead to open spaces in the nose called the nasal passage. This passage contains hair and mucus, which perform the functions of filtering, moistening, and warming the air entering the nasal passage.

2.

Pharynx Air travels from the nasal passage to the pharynx, which is commonly known as throat. The pharynx is lined with a protective mucus membrane and cilia, which removes the impurities entering with air.

10th Class Biology

12

3.

Larynx The air from the pharynx enters the larynx or voice box. It contains two true vocal cords, which are made up of cartilage and fibres. When air passes through this area, the vocal cords vibrate and this produces different sounds. Human beings can control this vibration. Thus, they can make various sounds and are capable of speech.

4.

Trachea From the larynx, the inhaled air moves into the wind pipe or trachea. The trachea is a long narrow tube, which is lined with ciliated mucus membrane. The trachea branches into two tubes, the left and right bronchi. The cilia move the mucus containing dust particles back to the pharynx, where it is swallowed. Do you know that tobacco contains harmful components? These components do not allow proper supply of oxygenated blood and results in many diseases.

5.

Bronchi and bronchioles The air from the trachea moves into the bronchi, which are formed because of the division of the trachea. Each bronchus enters one of the lungs. Inside the lungs, the bronchi further divide into bronchioles. The air moves through these bronchioles.

6.

Alveoli

The bronchiole divides many times in the lungs to create smaller branches. These branches ultimately terminate into tiny air-sacs known as alveoli. These cells are surrounded by many blood capillaries. Do you know that each lung contains 300 – 350 million units called alveoli, making a total of 700 million in both lungs? Alveoli transfers O2 into the blood cells. Let us discuss how alveoli help in the exchange of gases. Gases are exchanged in the lungs during respiration. Are lungs the only respiratory organs? Is the process of respiration similar in all animals? In aquatic animals, gas exchange takes place by the process by diffusion, directly through the body wall. However, complex aquatic animals have gills for the diffusion of gases. For example, in fishes, the water enters through their mouths and quickly moves to the gills. In the gills, O2 gets mixed with blood. The blood then transports this oxygen to all the body cells for respiration. Which organism exhibits faster rate of breathing – terrestrial or aquatic animals? The oxygen source i.e., water is about 800 times denser than air. It contains less O2 as compared to air. Since the content of O2 in water is low, aquatic animals breathe faster to get as much oxygen as possible, resulting in a faster rate of breathing. Therefore, aquatic animals breathe faster than terrestrial animals and also show different adaptations for better gaseous exchange.

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

The process of respiration is concerned with (A) liberation of oxygen (B) liberation of carbon dioxide (C) liberation of energy (D) intake of oxygen The common immediate source of energy for cellular activity is (A) NAD (B) ATP (C) DNA (D) RNA The tissue respiration refers to (A) inspiration (B) external respiration (C) internal respiration (D) expiration If the CO2 concentration in the blood increases, the rate of breathing will (A) decrease (B) stop (C) increase (D) have no effect Vocal cards occur in (A) pharynx (B) glottis (C) bronchial tube (D) larynx In man, which of the following structures is analogous to the spiracles of cockroach ? (A) Alveoli (B) Lungs (C) Bronchioles (D) Nostrils Which of the following prevents collapsing of trachea ? (A) Diaphragm (B) Ribs (C) Cartilaginous ring (D) Muscles Which of the following gases makes the most stable combination with the hemoglobin of red blood cells. (A) CO2 (B) CO (C) O2 (D) N2 Volume of air inspired or expired with each normal breath is called (A) tidal volume (B) inspiratory capacity (C) total lung capacity (D) residual volume

Life Processes 10. 11. 12. 13. 14. 15.

16. 17. 18. 19. 20. 21. 22. 23. 24. 25.

26. 27. 28. 29. 30.

Most of the carbon dioxide in the blood is carried in the form of (A) carbonic acid (B) bicarbonates (C) carbaminohaemoglobin (D) dissolved CO2 What is not produced during cellular respiration? (A) Carbon dioxide (B) Water molecules (C) Glucose molecules (D) ATP molecules The respiratory gases are exchanged in (A) villi (B) pharynx (C) alveoli (D) bronchi The movement of carbon-dioxide-rich air out of the body is known as (A) exhalation (B) perspiration (C) inhalation (D) transpiration Where does the gaseous exchange take place in land animals? (A) Nostrils (B) Trachea (C) Skin (D) Alveoli Which of the following statements about thoracic diaphragm is true? (A) The thoracic diaphragm relaxes during inhalation and exhalation (B) The thoracic diaphragm contracts during inhalation (C) The thoracic diaphragm contracts during inhalation and exhalation (D) The thoracic diaphragm relaxes during inhalation The exchange of gases is possible in lungs because of its (A) large surface area (B) large internal volume (C) suitable temperature (D) suitable humidity Human lungs help in the (A) digestion of blood (B) oxygenation of blood (C) transportation of blood (D) circulation of blood Which of the following components is required only for respiration? (A) Energy (B) Chlorophyll (C) Carbon dioxide (D) Oxygen What are the products of respiration? (A) Carbon dioxide, water, ATP (B) Carbon dioxide, glucose, ATP (C) Oxygen, water, ATP (D) Oxygen, glucose, ATP The oxygen evolved as a by-product during photosynthesis comes from (A) water (B) carbon dioxide (C) glucose (D) chlorophyll Breathing rate in mammals in controlled by a part of the brain called the (A) thalamus (B) hypothalamus (C) medulla oblongata (D) cerebellum In anaerobic respiration (A) O2 is taken in (B) CO2 is taken in (C) O2 is given out (D) CO2 is given out Disease called pleurisy is due to (A) inflammation of pleura (B) inflammation of trachea (C) inflammation of alveoli (D) none of these above Leaves respire with the help of (A) lenticles (B) stomata (C) plasmodesmata (D) cuticle Correct statement is (A) roots of plant respire through lenticles and stomata. (B) stem of plant respire through lenticles (C) both A and B are correct (D) both A and B are incorrect Which of the following is not a characteristic of good respiratory surface ? (A) Thin and moist (B) Large surface area (C) Close to oxygen and gas transport (D) Thick and dry surface Respiration in yeast (A) takes place in the presence of oxygen (B) yields lactic acid and carbon dioxide (C) in anaerobic and produces carbon dioxide (D) takes place only in darkness Muscle cells engaged in vigorous activity build up a high concentration of (A) lactic acid (B) pyruvic acid (C) alcohol (D) cholesterol Exchange of respiratory gases takes place in an earthworm through (A) moist skin (B) gills (C) trachea (D) lungs Oxygen is transported in blood mainly by (A) leucocytes (B) erythrocytes (C) thrombocytes (D) blood plasma

13

10th Class Biology

14

SYNOPSIS 4 5.

Transportation in Plants I.

Understanding Transportation is a life process where substances synthesized or absorbed in one part of the body are carried to other parts of the body. Water absorbed by roots is to be transported to the rest of the plant body. Food produced in the leaves is to be transported to its place of storage. Therefore, there is a requirement for a transport system in plants. How does the transport system in plants function? The transportation system in plants moves the energy stored in leaves to different parts. It also helps in moving raw materials absorbed from the roots to various organs of the plant. However, these are entirely different pathways. These two pathways are explained in the following discussion. The transportation system in plants consists of two different types of conducting tissues. Xylem conducts water and minerals obtained from soil (via roots) to the rest of the plant. Phloem transports food materials from the leaves to different parts of the plant body.

II.

Transport of water Components of the xylem tissue (tracheids and vessels) of roots, stems, and leaves are interconnected to form a continuous system of water-conducting channels, which reaches all parts of the plant. Root hair with adhering soil particles Roots absorb water and mineral salts from the soil. Each soil particle is surrounded by a continuous film of water, loosely held to it by a force known as capillary force. This is known as capillary water. Therefore, water molecules adhere to soil particles with the capillary force. The capillary water is also present in spaces between the soil particles. This capillary water, along with the minerals dissolved in it, is absorbed by the cells in the root hair.

Absorption of water from the soil The cells in the root hair are deficient in water because they continuously supply the absorbed water to the stems and leaves. Thus, the concentration of water in the root hair is less than the water present in soil particles. This creates a concentration gradient, which allows the root hair cells to uptake water actively. As a result, there is a steady movement of water into the root xylem creating a column of water, which is steadily pushed upwards. However, this pressure by itself cannot move the water over greater heights. In order to fulfil this requirement, plants utilize some other stronger force such as transpiration pull or suction pressure. Let us explore what transpiration pull is.

Life Processes

III.

15

Transportation of food The transportation of food from the leaves to other parts of the plant occurs in the vascular tissue, namely the phloem. This process of transporting food is known as translocation. The phloem also transports amino acids and other substances to storage organs of the plant (along with the growing organs) such as roots, fruits, and seeds. The phloem consists of companion cells, sieve tubes, phloem parenchyma, and fibres. The translocation of food occurs in the sieve tubes with the help of companion cells. Translocation in the phloem, unlike the xylem, is achieved by utilizing energy from ATP. For example, a food material such as sucrose is transported into the phloem tissue using ATP energy. As a result, the osmotic pressure in the tissue increases, causing the water to move into it. This pressure moves the material in the phloem to the tissues, which have less pressure. This is helpful in moving materials according to the requirements of the plant.

WORKSHEET 4 1. 2.

3.

4. 5.

6. 7.

8. 9. 10.

In plants, water is transported through (A) petals (B) xylem (C) phloem (D) pollens A plant stem was cut and kept in a red colored solution for approximately one hour. Following this, a thin transverse section was sliced from the plant stem and was observed under a microscope. Few tissues of the sliced section showed red color while others did not.

Which tissue showed red color under the microscope? (A) Meristem (B) Cork (C) Xylem (D) Phloem Xylem is made up of tracheids and vessel elements. Tracheids and vessel elements help plants in being upright against gravity. Which factor explains the above function of tracheids? (A) Water pressure (B) Chemical composition (C) Tracheids are dead tissues (D) Tracheids consist of phloem The organic nutrients manufactured by plants are present in the (A) flowers (B) xylem (C) barks (D) phloem A certain plant is kept in a flask containing blue colored water. After an hour, a cross section of its tissue is observed under microscope. It can be concluded from the above observation that the (A) meristematic tissues will not be stained blue (B) phloem will not be stained blue (C) phloem will be stained blue (D) companion cells will be stained blue Which tissue supplies organic nutrients to the growing tip? (A) Parenchyma (B) Xylem (C) Meristem (D) Phloem In a potato plant, food is manufactured in the leaves that are exposed to the Sun. This food is transported to the underground stem of the potato for storage. Which plant tissue is responsible for the movement of food molecules? (A) Xylem (B) Phloem (C) Parenchyma (D) Fibers Which plant tissue is responsible for the upward displacement of water and minerals? (A) Fibers (B) Collenchyma (C) Phloem (D) Xylem Which plant tissue carries water in roots? (A) Phloem (B) Collenchyma (C) Xylem (D) Parenchyma Osmosis is the movement of : (A) solute particles from higher concentration to lower concentration (B) solvent particles from higher water potential to lower water potential through a semi permeable membrane

10th Class Biology

16

11. 12. 13. 14. 15. 16. 17. 18.

(C) solute particles from higher concentration to lower concentration through a semipermeable membrane (D) solvent particles from lower water potential to higher water potential. The ultimate cause for the movement of water against the gravity in a tree is (A) osmosis (B) transpiration (C) imbibitions (D) photosynthesis Which one of the following is connected with transport of water in plants ? (A) Phloem (B) Xylem (C) Epidermis (D) Cambium Which of the following contributes most to transport of water from the ground to the leaves of a tall tree? (A) Breakdown of ATP (B) Capillary rise of water is xylem (C) Cohesion of water and transpiration pull (D) Root pressure. The process of transpiration in plants helps in (A) opening of stomata (B) absorption of CO2 from atmosphere (C) upward conduction of water and minerals (D) absorption of O2 from atmosphere Opening and closing of stomata is due to (A) pressure of gases inside the leaves (B) changes of turgor pressure in guard cells (C) effect of hormones (D) their genetic constitution The carbohydrates synthesized in the leaves are transported through sieve tubes most commonly in the form of (A) glucose (B) starch (C) sucrose (D) cellulose In a closed circulatory system, blood is completely enclosed with in (A) sinuses (B) vessels (C) heart (D) skeleton An artery is a vessel that carries blood (A) with high concentration of oxygen (B) with high concentration of CO2 (C) away from the heart (D) both A & C

SYNOPSIS 5 Blood consists of a fluid medium called plasma in which the cells are suspended. Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form. Oxygen is carried by the red blood cells. Many other substances like salts, are also transported by the blood. We thus need a pumping organ to push blood around the body, a network of tubes to reach all the tissues and a system in place to ensure that this network can be repaired if damaged.

Our pump — the heart The heart is a muscular organ which is as big as our fist . Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide. The carbon dioxide-rich blood has to reach the lungs for the carbon dioxide to be removed, and the oxygenated blood from the lungs has to be brought back to the heart. This oxygen-rich blood is then pumped to the rest of the body. We can follow this process step by step (as shwon in the figure). Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation. Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do. Valves ensure that blood does not flow backwards when the atria or ventricles contract.

Life Processes

17

Oxygen enters the blood in the lungs The separation of the right side and the left side of the heart is useful to keep oxygenated and deoxygenated blood from mixing. Such separation allows a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature. In animals that do not use energy for this purpose, the body temperature depends on the temperature in the environment. Such animals, like amphibians or many reptiles have three-chambered hearts, and tolerate some mixing of the oxygenated and de-oxygenated blood streams. Fishes, on the other hand, have only two chambers to their hearts, and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body. Thus, blood goes only once through the heart in the fish during one cycle of passage through the body. On the other hand, it goes through the heart twice during each cycle in other vertebrates. This is known as double circulation.

Blood pressure The force that blood exerts against the wall of a vessel is called blood pressure. This pressure is much greater in arteries than in veins. The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.

Blood pressure is measured with an instrument called sphygmomanometer. High blood pressure is also called hypertension and is caused by the constriction of arterioles, which results in increased resistance to blood flow. It can lead to the rupture of an artery and internal bleeding.

The tubes – blood vessels Arteries are the vessels which carry blood away from the heart to various organs of the body. Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls. Veins collect the blood from different organs and bring it back to the heart. They do not need thick walls because the blood is no longer under pressure, instead they have valves that ensure that the blood flows only in one direction. On reaching an organ or tissue, the artery divides into smaller and smaller vessels to bring the blood in contact with all the individual cells. The smallest vessels have walls which are one-cell thick and are called capillaries. Exchange of material between the blood and surrounding cells takes place across this thin wall. The capillaries then join together to form veins that convey the blood away from the organ or tissue.

Maintenance by platelets What happens if this system of tubes develops a leak? Think about situations when we are injured and start bleeding. Naturally the loss of blood from the system has to be minimised. In addition, leakage would lead to a loss of pressure which would reduce the efficiency of the pumping system. To avoid this, the blood has platelet cells which circulate around the body and plug these leaks by helping to clot the blood at these points of injury.

Lymph There is another type of fluid also involved in transportation. This is called lymph or tissue fluid. Through the pores present in the walls of capillaries some amount of plasma, proteins and blood cells escape into intercellular spaces in the tissues to form the tissue fluid or lymph. It is similar to the plasma of blood but colourless and contains less protein. Lymph drains into lymphatic capillaries from the intercellular spaces, which join to form large lymph vessels that finally open into larger veins. Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood.

10th Class Biology

18

WORKSHEET 5 1.

2.

3. 4. 5. 6. 7. 8. 9. 10.

The given figure shows the human heart.

The portion of the heart labeled I is known as (A) atrium (B) aorta (C) ventricle (D) vena cava Circulatory system is composed of __ i ___ and blood vessels, which includes __ ii___, ____ iii___, and ____iv____. The above statement is completed by the information provided in which alternative? (A) i - kidney, ii - alveoli, iii - arteries, iv - valves (B) i - valves, ii - arteries, iii - alveoli, iv - heart (C) i - heart, ii - kidney, iii - valves, iv - veins (D) i - heart, ii - arteries, iii - veins, iv - Capillaries Which is the only vein that carries oxygenated blood? (A) Hepatic vein (B) Pulmonary vein (C) Cardiac vein (D) Renal vein Which is the only artery that carries deoxygenated blood? (A) Pulmonary artery (B) Hepatic artery (C) Cardiac artery (D) Renal artery Deoxygenated blood is transported from the tissues to the heart through (A) arteries (B) veins (C) lymph (D) ventricles Oxygenated blood is transported from the heart to the tissues through (A) veins (B) arteries (C) lymph (D) auricles In the human body, carbon dioxide is transported through (A) blood (B) wind (C) lymph (D) oxygen Heart is divided into (A) two auricles and two ventricles (B) three auricles and one ventricle (C) one auricle and three ventricles (D) two auricles and one ventricle The deoxygenated blood collected from the body is poured into the (A) ventricles (B) auricles (C) lungs (D) arteries Oxygenated blood flows from lungs into the left atrium through the (A) pulmonary artery (B) pulmonary vein (C) inferior vena cava (D) superior vena cava

11.

Deoxygenated blood flows from the body into the (A) I (B) II (C) III

(D) IV

Life Processes 12. 13. 14.

19

Blood is carried away from the heart by and carried back to the heart by . Which alternative completes the above sentence? (A) i - kidney, ii - Lungs (B) i - arteries, ii - veins (C) i - lungs, ii - kidney (D) i - veins, ii - arteries Which blood vessel carries deoxygenated blood from the upper parts of the body to the heart? (A) Pulmonary vein (B) Inferior vena cava (C) Superior vena cava (D) Pulmonary artery The oxygenated blood to be supplied to all parts of the body arises from the heart through the (A) arteriole (B) pulmonary artery (C) pulmonary vein (D) aorta

SYNOPSIS 6

The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion. Different organisms use varied strategies to do this. Many unicellular organisms remove these wastes by simple diffusion from the body surface into the surrounding water. As we have seen in other processes, complex multi-cellular organisms use specialised organs to perform the same function.

I.

Excretion in Human Beings The excretory system of human beings (Fig. 6.13) includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Kidneys are located in the abdomen, one on either side of the backbone. Urine produced in the kidneys passes through the uretersinto the urinary bladder where it is stored until it is released through the urethra. How is urine produced? The purpose of making urine is to filter out waste products from the blood. Just as CO2 is removed from the blood in the lungs, nitrogenous waste such as urea or uric acid are removed from blood in the kidneys. It is then no surprise that the basic filtration unit in the kidneys, like in the lungs, is a cluster of very thin-walled blood capillaries. Each capillary cluster in the kidney is associated with the cup-shaped end of a tube that collects the filtered urine (as shown in the figure). Each kidney has large numbers of these filtration units called nephrons packed close together. Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively reabsorbed as the urine flows along the tube. The amount of water reabsorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra. The bladder is muscular, so it is under nervous control, as we have discussed elsewhere. As a result, we can usually control the urge to urinate.

10th Class Biology

20

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

1.

Which of the following parts of a kidney contains the lowest concentration of urea ? (A) Lop of Henle (B) Branches of renal vein (C) Bowman’s capsule (D) Glomerulus Uriniferous tubules of a kidney are concerned with formation of (A) glucose (B) amino acids (C) hormones (D) urine Excretion is removal of (A) CO2 (B) harmful and useless ingredients (C) extra water (D) metabolic wastes Main function of kidney is (A) passive absorption (B) ultrafiltration (C) selective reabsorption (D) Both B and C Ammonia is converted into urea in (A) kidney (B) spleen (C) liver (D) nephron Function of loop of Henle is (A) conservation of water (B) formation of urine (C) filtration of blood (D) passage of urine Urea is transported through (A) RBCs (B) WBCs (C) Plasma (D) All of the above Major function of contractive vacuole is (A) excretion (B) circulation (C) osmoregulation (D) all the above Which one is a accessory excretory organ (A) Liver (B) Stomach (C) Intestine (D) Heart Healthy human kidneys excrete (A) essential proteins (B) nitrogenous wastes (C) insoluble fats (D) soluble sugars What connects kidneys to the bladder? (A) Nephron (B) Urethra (C) Ureter (D) Uterus Kidneys perform which function? (A) Digestion (B) Reproduction (C) Excretion (D) Respiration Which of the following organs is not an excretory organ? (A) Urethra (B) Kidneys (C) Lungs (D) Heart What are the structural units of kidney? (A) Neurons (B) Alveoli (C) Nephron (D) Axons

Match the column I with Column II. Column-I A. B. C. D.

2.

Step – Step – Step – Step –

Column-II I II III IV

P. Q. R. S.

Electron transport chain Glycolysis Kreb’s cycle Oxidative decarboxylation

Match the column I with Column II. Column-I

Column-II

A. B. C. D.

P. Q. R. S.

Unicellular protozoan’s Coelenterates and sponges Flatworms and round worms Annelids

Cell membrane Excretory tubes Nephridia Contractile vacuoles

Life Processes

3.

Match the column I with Column II. Column-I

4.

5. 6.

7. 8.

16. 17. 18. 19.

20.

21.

21 Column-II

A. Phototropism P. Direction of gravitational force B. Chemotropism Q. Direction of chemicals C. Hydrotropism R. Direction of light D. Geotropism S. Direction of water Spot the mistakes in the given statements and correct them. a) The process of acquiring oxygen through breathing and making it available for cells is called Transportation b) Respiration is the process by which food and water are carried from one organ to the other. Spot the mistakes in the given statements and correct them. a) Certain gymnosperms lack chlorophyll and home mycorrhizal roots. b) The plant absorbs nourishment from humus through their mycorrhizal roots. Spot the mistakes in the given statements and correct them. a) The complex food swallowed is broken down to simpler molecules by action of enzymes of the digestive juices. b) Air we breath contain starch, which is the source of energy. Spot the mistakes in the given statements and correct them. a) With the complete oxidation of pyruvic acid, glycolysis comes to an end. b) The second step of aerobic respiration occurs in cytoplasm. Spot the mistakes in the given statements and correct them. a) In amoeba and hydra, dissolved oxygen in water diffuses through cell membrane; carbon dioxide produced passively diffuses into water. b) Respiration in frog occurs through gills. Spot the mistakes in the given statements and correct them. a) The alveoli surrounded by blood capillaries provide a surface where exchange of gases takes place. b) Rings of cartilage are present in the throat which keep the air passage closed. Spot the mistakes in the given statements and correct them. a) Translocation occurs with the help of companion cells only in downward direction. b) Materials like sucrose are transferred into phloem using energy from ATP. Spot the mistakes in the given statements and correct them. a) Blood picks up waste products like salts from the cells. b) Plasma is otherwise called lymph. Assertion (A): In xylem, vessels and tracheids are inter connected to form a continuos system of water conducting channels. Reasoning (R): Root hair cells release ions. Choose the correct option (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): Loss of water from aerial parts of the plant is known as transpiration. Reasoning(R): During the day when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in the xylem. Choose the correct answer (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): CO2 diffuses out of amoeba when it starts accumulating to harmful levels in the cell. Reasoning(R): In large organisms, diffusion alone is far too slow for adequate distribution of oxygen and food. Choose the correct answer (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.

22 22.

23.

24.

25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42.

10th Class Biology Assertion(A): Fihses are called ammoniatelic animals Reasoning(R): They contains nephrons which filter the blood and form the urine and large amount of ammonia is found in fish excreta. Choose the correct answer (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): Mammals are called ureotelic animals. Reasoning (R): In mammals urea is the main excretory products so they are called ureotelic animals. Choose the correct option (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): All coordinations in the body occur as conscious processes. Reasoning (R): In insects, well developed sensory organ for vision and antennae for olfactory function are present. Choose the correct option (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. a) The organisms that live on other organisms for nourishment are called ________. b) The plants or animals in which the parasites live for nourishment are called _______. a) Saprophytes obtain nutrients from _________. b) WBCs in vertebrates are in _________ function. a) WBC’s engulf the invading germs by producing ____ around the germs and digest the germs. b) In __________ digestion, food is directly taken into the cells and is digested with in the cell. a) During respiration, food materials are ________ (oxidized / reduced) b) The energy released during respiration is stored in __________. a) The two types of respirations are ________ and _______. b) The energy associated with _______ is used to synthesis of ATP. a) Anaerobic respiration is also known as _________. b) In Amoeba and Hydra, respiration takes place through _________. a) ________ is the energy currency for most cellular processes. b) The respiratory passage is lined with _____. a) _________ are present in the throat which prevent the air passage from collapsing. b) The air passage branches repeatedly into smaller tubules which end in ________. a) The plant transport systems will mobilize energy stores, food from _________ and raw materials from ________. b) In Xylem ________ and _________ are the conducting elements. a) Evaporation of water molecules creats a __________ which pulls water from xylen cells of roots. b) Transport of soluble products of photosynthesis is called _______ and it occurs in ________. a) Translocation takes place in ________ of phloem. b) Materials like sucrose are transferred into phloem, which increases ______ pressure in the tissue. a) In amoeba and paramoecium, useful substances are distributed by a process called _________. b) Oxygen enters amoeba through _________. a) Fish: Ammoniatelic ; Birds : __________ b) Glomerulus filters ________ part of the blood to from urine. a) Muscles work together during movement. This is an example for _____. b) In earthworm, the ganglia act as ________ and eye spots act as ______. a) Nervous system consists of tissues which conduct messages called ________. b) In touch - me - not, the response to stimulus is _______ ( Delayed / Immediate) a) The secretions of endocrine system are called _________. b) The common character of enzymes and hormones is that they acts as ______. a) The process of obtaining energy throiugh consumption of food is called ________. b) Autotrophic nutrition is the process by which autotrophic plants consume substances from external sources and convert them into ________ Pick the odd one out from the following. Nutrition, Playing, Respiration, Excretion

Life Processes 43. 44. 45. 46. 47. 48. 49. 50. 51. 52.

23

Pick the odd one out in relation to autotrophic nutrition. Photosynthesis, Plants, Chlorophyll, Deer Pick the odd one out with respect to raw materials of photosynthesis. CO2, O2, Water, Chlorophyll Pick the odd one out with respect to Heterotrophic nutrition. Animals, Green plants, Saprophytes, Parasites Pick the odd one out respect to Cuscutta and Viscum. Parasite, host, Mycorrhizal roots, haustoria Pick the odd one out with respect to intra cellular digestion. Human beings, Amoeba, Paramoecium, Sponges. Pickthe odd one out with regard to digestive juices. Mouth, stomach, oesophagus, duodenum. Pick the odd one out with respect to respiratory system of human beings. Nostrils, Gills, Lungs, Alveoli Pick the odd one out with respect to excretion in invertebrates. Contractile vacuole, kidneys, Cell membrance, excretory tubes. Why is digestion in human called extracellular? Observe the following diagram. Identify A and B.

A

53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68.

69. 70.

B

Differentiate between xylem and phloem. Lymph  X  Y  Veins. What are X and Y? What is the difference between lymph and plasma? What are the functions of plasma? Muscular activities like running, involve many other forms of coordination. List them. How does the leaves in touch - me - not plant shrink? Give examples of (a) Hydrotropism (b) Chemotropism a) What do life processes include? b) Name some life processes in living beings. a) Give the chemical equation for photosynthesis. b) If the fluid is blood, pump is ___________, tubes are __________. What are the raw materials and other necessary items required for photosynthesis. What are haustoria? Give examples. a) Explain the external structure and b) name the parts of the alimentary canal. Write any three needs of nutrient molecules that are contained in food. What is respiratory substrates? What are the kinds of respiratory substrates? What are the uses of transpiration? Osmotic pressure in the phloem tissue allows phloem to move material according to the plant’s needs. Give an example. Say true or false i) The rate of breathing in aquatic organisms is much faster than that in terrestial organisms ii) Phloem transports amino acids iii) The rate of diffusion of oxygen in microscopic organisms in all directions is approximately equal to the rate at which oxygen is consumed in respiration. iv) The cells and tissues and organs in the body of an animals work independently of each other v) The endocrine system consists of ductless glands What is the function of uriniferous tubules? What are the two different types of movements that plants show? Give examples for each.

24

10th Class Biology

CONTROL AND COORDINATION

CHAPTER

2

   

Introduction Animals Nervous System What happens in Reflex Actions? Human Brain

    

How are these Tissues protected? How do animal muscles move? Coordination in Plants Immediate Response to Stimulus Harmones in Animals

SYNOPSIS 1 1.

Introduction In the previous chapter, we looked at life processes involved in the maintenance junctions in living organisms. There, we had started with a notion we all have, that if we see something moving, it is alive.Some of these movements are in fact the result of growth, as in plants. A seed germinates and grows, and we can see that the seedling moves over the course of a few days, it pushes soil aside and comes out. But if its growth were to be stopped, these movements would not happen. Some movements, as in many animals and some plants, are not connected with growth. A cat running, children playing on swings, buffaloes chewing cud - these are not movements caused by growth.

Why do we associate such visible movements with life? A possible answer is that we think of movement as a response to a change in the environment of the organism. The cat may be running because it has seen a mouse. Not only that, we also think of movement as an attempt by living organisms to use changes in their environment to their advantage. Plants grow out into the sunshine.Children try to get pleasure and fun out of swinging. Buffaloes chew cud to help break up tough food so as to be able to digest it better. When bright light is focused on our eyes or when we touch a hot object, we detect the change and respond to it with movement in order to protect ourselves. If we think a bit more about this, it becomes apparent that all this movement, in response to the environment, is carefully controlled. Each kind of a change in the environment evokes an appropriate movement in response. When we want to talk to our friends in class, we whisper, rather than shouting loudly. Clearly, the movement to be made depends on the event that is triggering it. Therefore, such controlled movement must be connected to the recognition of various events in the environment, followed by only the correct movement in response.In other words, living organisms must use systems providing control and coordination. In keeping with the general principles of body organisation in multicellular organisms, specialised tissues are used to provide these control and coordination activities.

2

Animals Nervous System In animals, such control and coordination are provided by nervous and muscular tissues, which we have studied in our lower clases. Touching a hot object is an urgent and dangerous situation for us. We need to detect it, and respond to it. How do we detect that we are touching a hot object?

10th Class Biology

26

All information from our environment is detected by the specialised tips of some nerve cells. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell.

This information, acquired at the end of the dendritic tip of a nerve cell, sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.

This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland. It is thus no surprise that nervous tissue is made up of an organised network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

An Activity • • •

Put some sugar in your mouth. How does it taste? Block your nose by pressing it between your thumb and index finger. Now eat sugar again. Is there any difference in its taste? While eating lunch, block your nose in the same way and notice if you can fully appreciate the taste of the food you are eating. Is there a difference in how sugar and food taste if your nose is blocked? If so, why might this be happening?Read and talk about possible explanations for these kinds of differences. Do you come across a similar situation when you have a cold?

3

What happens in Reflex Actions? ‘Reflex’ is a word we use very commonly when we talk about some sudden action in response to something in the environment. We say ‘I jumped out of the way of the bus reflexly’, or ‘I pulled my hand back from the flame reflexly’, or ‘I was so hungry my mouth started watering reflexly’. What exactly do we mean by all these?. A common idea in all such examples is that we do something without thinking about it, or without feeling in control of our reactions.Yet these are situations where we are responding with some action to changes in our environment.

Control and Coordination

27

How is control and coordination achieved in such situations? Let us consider this further. Take one of our examples. Touching a flame is an urgent and dangerous situation for us, or in fact, for any animal! How would we respond to this? One seemingly simple way is to think consciously about the pain and the possibility of getting burnt, and therefore move our hand. An important question then is, how long will it take us to think all this? The answer depends on how we think. If nerve impulses are sent around the way we have talked about earlier, then thinking is also likely to involve the creation of such impulses. Thinking is a complex activity, so it is bound to involve a complicated interaction of many nerve impulses from many neurons. If this is the case, it is no surprise that the thinking tissue in our body consists of dense networks of intricately arranged neurons. It sits in the forward end of the skull, and receives signals from all over the body which it thinks about before responding to them. Obviously, in order to receive these signals, this thinking part of the brain in the skull must be connected to nerves coming from various parts of the body. Similarly, if this part of the brain is to instruct muscles to move, nerves must carry this signal back to different parts of the body. If all of this is to be done when we touch a hot object, it may take enough time for us to get burnt! How does the design of the body solve this problem? Rather than having to think about the sensation of heat, if the nerves that detect heat were to be connected to the nerves that move muscles in a simpler way, the process of detecting the signal or the input and responding to it by an output action might be completed quickly.

Reflex Arc Such a connection is commonly called a reflex arc. Where should such reflex arc connections be made between the input nerve and the output nerve? Nerves from all over the body meet in a bundle in the spinal cord on their way to the brain. Reflex arcs are formed in this spinal cord itself, although the information input also goes on to reach the brain. The best place, of course, would be at the point where they first meet each other. Reflex arcs have evolved in animals because the thinking process of the brain is not fast enough.In fact many animals have very little or none of the complex neuron network needed for thinking.So it is quite likely that reflex arcs have evolved as efficient ways of functioning in the absence of true thought processes. However, even after complex neuron networks have come into existence, reflex arcs continue to be more efficient for quick responses.

4

Human Brain Is reflex action the only function of the spinal cord? Obviously not, since we know that we are thinking beings. Thinking involves more complex mechanisms and neural connections. Spinal cord is made up of nerves which supply information to think about. These are concentrated in the brain, which is the main coordinating centre of the body. The brain and spinal cord constitute the central nervous system. They receive information from all parts of the body and integrate it. We also think about our actions. Writing, talking, moving a chair, clapping at the end of a programme are examples of voluntary actions which are based on deciding what to do next. So, the brain also has to send messages to muscles. This is the second way in which the nervous system communicates with the muscles.

10th Class Biology

28

The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord.The brain thus allows us to think and take actions based on that thinking. As you will expect, this is accomplished through a complex design, with different parts of the brain responsible for integrating different inputs and outputs.

Parts of Brain The brain has three such major parts or regions, namely the forebrain, mid-brain and hind-brain. The fore-brain is the main thinking part of the brain. It has regions which receive sensory impulses from various receptors. Separate areas of the fore-brain are specialised for hearing, smell, sight and so on. There are separate areas of association where this sensory information is interpreted by putting it together with information from other receptors as well as with information that is already stored in the brain.Based on all this, a decision is made about how to respond and the information is passed on to the motor areas which control the movement of voluntary muscles, for example, our leg muscles. However, certain sensations are distinct from seeing or hearing, for example, how do we know that we have eaten enough? The sensation of feeling full is because of a centre associated with hunger, which is in a separate part of the fore-brain. Study the labelled diagram of the human brain. Let us look at the other use of the word ‘reflex’ that we have talked about in the introduction. Our mouth waters when we see food we like without our meaning to. Our hearts beat without our thinking about it. In fact, we cannot control these actions easily by thinking about them even if we wanted to. Do we have to think about or remember to breathe or digest food? So, in between the simple reflex actions like change in the size of the pupil, and the thought out actions such as moving a chair, there is another set of muscle movements over which we do not have any thinking control. Many of these involuntary actions are controlled by the mid-brain and hind-brain. All these involuntary actions including blood pressure, salivation and vomiting are controlled by the medulla in the hind-brain. Think about activities like walking in a straight line, riding a bicycle, picking up a pencil. These are possible due to a part of the hind-brain called the cerebellum. It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

5

How are these Tissues protected? A delicate organ like the brain, which is so important for a variety of activities, needs to be carefully protected. For this, the body is designed so that the brain sits inside a bony box. Inside the box, the brain is contained in a fluid-filled balloon which provides further shock absorption. If you run your hand down the middle of your back, you will feel a hard, bumpy structure.

Control and Coordination

29

This is the vertebral column or backbone which protects the spinal cord. How does the Nervous Tissue cause Action? So far, we have been talking about nervous tissue, and how it collects information, sends it around the body, processes information, makes decisions based on information, and conveys decisions to muscles for action. In other words, when the action or movement is to be performed, muscle tissue will do the final job.

6

How do animal muscles move? When a nerve impulse reaches the muscle, the muscle fibre must move. How does a muscle cell move? The simplest notion of movement at the cellular level is that muscle cells will move by changing their shape so that they shorten. How do muscle cells change their shape? The answer must lie in the chemistry of cellular components. Muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses.

WORKSHEET 1 1.

2.

3.

4.

5. 6.

Neurons form the basic unit of the nervous system and transmit information through neurotransmitters. In which part of the neuron are neurotransmitters produced? (A) Axon (B) Dendrites (C) Node of ranvier (D) Presynaptic terminal The unique structure of nerve cells allows the conduction of nerve impulses. The structure in nerve cells that receives signals from other nerve cells is called (A) axon (B) dendrite (C) cell body (D) golgi body Nerve cells or neurons carry messages through electrochemical signals. They transmit signals from the brain to the target organs in the body.

Which of the following body structures do not contain nerve cells? (A) Brain (B) Skin (C) Nails (D) Eyes In humans, body temperature is maintained at 37°C, irrespective of the weather conditions. When climatic temperature increases, body begins sweating and cools down as a result. Sweating is regulated by the (A) nervous system (B) muscular system (C) excretory system (D) circulatory system Contraction of muscles leads to the movement of body. Muscle contraction is controlled by the (A) circulatory system (B) excretory system (C) digestive system (D) nervous system The organ system that controls the senses of the body is the (A) nervous system (B) digestive system (C) muscular system (D) reproductive system

10th Class Biology

30 7.

8.

9.

10.

11.

12.

13.

14.

15.

The brain is an organ of the nervous system and is present in most animals. The function of the brain is to (A) breathe in oxygen (B) remove body waste (C) control body activities (D) pump blood to body parts The spinal cord is a continuation of the brain stem. It is encased in the vertebral column. Which of the following functions is performed by the spinal cord? (A) It controls one’s memory and learning ability (B) It controls body temperature (C) It controls voluntary muscles (D) It controls reflex actions Thermoregulation is the function of an organism to maintain its body temperature. Internal body temperature must be maintained for the efficient functioning of different organ systems. Body temperature is maintained by the (A) hypothalamus (B) cerebellum (C) kidneys (D) lungs The involuntary muscles present in the stomach and heart cannot be controlled at will. Which part of the brain controls involuntary muscles? (A) Medulla (B) Cerebrum (C) Cerebellum (D) Hypothalamus The nervous system is one of the most important organ systems of the body. The nervous system performs the function of (A) transferring information from and to the brain (B) protecting the spinal cord by vertebral column (C) transporting blood to the brain (D) removing waste from the body The vertebrate brain is divided into the forebrain, midbrain, and hindbrain. The hindbrain controls (A) the breathing rate (B) the body balance (C) olfaction (D) memory Heart is a muscle that pumps blood to various parts of the body. Its movement is controlled by the nervous system. Which part of the brain controls heart beat? (A) Cerebrum (B) Brain stem (C) Cerebellum (D) Hypothalamus The muscular system helps in various movements of the body. The signal to contract is provided to muscles by the (A) nervous system (B) skeletal system (C) circulatory system(D) respiratory system The rate of heart beat is under the control of the nervous system. The part of the brain that controls heart beat is the (A) medulla (B) cerebrum (C) cerebellum (D) hypothalamus

16.

In the given figure, Irepresents the

(A) cerebellum

(B) cerebrum

(C) medulla

(D) pons

Control and Coordination 17.

18.

19.

20.

21.

22.

23.

24.

25.

and 

31 are the sites for information processing and controlling.

The information in which alternative completes the given statement? (A) i - Brain, ii - spinal cord (B) i - spinal cord, ii - nephron (C) i - nephron, ii - cell body (D) i - cell body, ii - brain After running some distance, Amy starts breathing heavily. The part of the nervous system that controls breathing is the (A) spinal cord (B) brain stem (C) front lobe (D) back lobe Brain is part of the nervous system. It is made up of nervous tissues. The cells that make up the nervous tissue are known as (A) neurons (B) platelets (C) nephrons (D) leukocytes The brain is the main part of the nervous system. Which of the following functions is not performed directly by the brain? (A) Digestion of food (B) Pumping the heart (C) Controlling movement (D) Secretion of hormones The brain is the most vital organ of the human body. It controls many activities of the body such as sleeping, eating and breathing. The two halves of the brain are known as (A) frontal lobes (B) hemispheres (C) cortex (D) furrows The nervous system consists of two parts, the central and the peripheral nervous systems. The central nervous system comprises the brain and the (A) vertebral column (B) endocrine glands (C) exocrine glands (D) spinal cord Cerebrum is the part of brain which controls thinking, memory, and reasoning.A man sustained head injuries. As a result, his cerebrum lost its functioning. He is made to stand in front of a chair. Which of the following actions is not performed by the man because of his condition? (A) Visualizing the chair (B) Pushing the chair (C) Feeling the chair (D) Using the chair Activities such as walking in a straight line, riding bicycle, and maintaining posture are under the control of region X in the brain. Region X can be identified asthe (A) cerebellum (B) forebrain (C) midbrain (D) medulla ____i_____ is a part of the brain which controls all the involuntary actions of the body, while ____ii_____ is a part of the brain which controls all the voluntary actions of the body. The information in which alternative completes the given statement? (A) i - Medulla, ii - cerebellum (B) i - cerebellum, ii - cerebrum (C) i - cerebrum, ii - hypothalamus (D) i - hypothalamus, ii - medulla

SYNOPSIS 2 7

Coordination in Plants Animals have a nervous system for controlling and coordinating the activities of the body. Plants have neither a nervous system nor muscles. So, how do they respond to stimuli? When we touch the leaves of a chhui-mui (the ‘sensitive’ or ‘touch-me-not’ plant of the Mimosa family), they begin to fold up and droop.When a seed germinates, the root goes down, the stem comes up into the air. What happens? Firstly, the leaves of the sensitive plant move very quickly in response to touch. There is no growth involved in this movement. On the other hand, the directional movement of a seedling is caused by

10th Class Biology

32

growth. If it is prevented from growing, it will not show any movement. So plants show two different types of movement - one dependent on growth and the other independent of growth.

8

Immediate Response to Stimulus Let us think about the first kind of movement, such as that of the sensitive plant. Since no growth is involved, the plant must actually move its leaves in response to touch. But there is no nervous tissue, nor any muscle tissue.

How does the plant detect the touch, and how do the leaves move in response? If we think about where exactly the plant is touched, and what part of the plant actually moves, it is apparent that movement happens at a point different from the point of touch. So, information that a touch has occurred must be communicated. The plants also use electrical-chemical means to convey this information from cell to cell, but unlike in animals, there is no specialised tissue in plants for the conduction of information.Finally, again as in animals, some cells must change shape in order for movement to happen. Instead of the specialised proteins found in animal muscle cells, plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking, and therefore in changing shapes.

Movement due to growth Some plants like the pea plant climb up other plants or fences by means of tendrils. These tendrils are sensitive to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it. More commonly, plants respond to stimuli slowly by growing in a particular direction. Because this growth is directional, it appears as if the plant is moving. Let us understand this type of movement with an activity .

An Activity Fill a conical flask with water. Cover the neck of the flask with a wire mesh. Keep two or three freshly germinated bean seeds on the wire mesh. Take a cardboard box which is open from one side. Keep the flask in the box in such a manner that the open side of the box faces light coming from a window. After two or three days, you will notice that the shoots bend towards light and roots away from light. Now turn the flask so that the shoots are away from light and the roots towards light. Leave it undisturbed in this condition for a few days.

•

Phototropism and Geotropism Have the old parts of the shoot and root changed direction? Are there differences in the direction of the new growth? What can we conclude from this activity?

Control and Coordination

33

Environmental triggers such as light, or gravity will change the directions that plant parts grow in. These directional, or tropic, movements can be either towards the stimulus, or away from it. So, in two differ ent kinds of phototropic movement, shoots respond by bending towards light Geotropism while roots respond by bending Phototropism away from it. How does this help the plant? Plants show tropism in response to other stimuli as well. The roots of a plant always grow downwar ds while the shoots usually grow upwards and away from the earth. This upward and downward growth of shoots and roots, respectively, in response to the pull of earth or gravity is, obviously, geotropism.

•

Chemotropism The movement of a plant part in response to a chemical stimulus is called Chemotropism. One example of chemotropism is the growth of pollen tubes towards ovules, about which we will learn more when we examine the reproductive processes of living organisms.

•

Hydrotropism The movement of a plant part in response to water is called Hydrotropism. The roots of a plant always go towards water and hence show hydrotropism. Let us now once again think about how information is communicated in the bodies of multicellular organisms. The movement of the sensitive plant in response to touch is very quick. The movement of sunflowers in response to day or night, on the other hand, is quite slow. Growth-related movement of plants will be even slower. Even in animal bodies, there are carefully controlled directions to growth. Our arms and fingers grow in certain directions, not haphazardly. So controlled movements can be either slow or fast. If fast responses to stimuli are to be made, information transfer must happen very quickly. For this, the medium of transmission must be able to move rapidly. Electrical impulses are an excellent means for this. But there are limitations to the use of electrical impulses. Firstly, they will reach only those cells that are connected by nervous tissue, not each and every cell in the animal body. Secondly, once an electrical impulse is generated in a cell and transmitted, the cell will take some time to reset its mechanisms before it can generate and transmit a new impulse. In other words, cells cannot continually create and transmit electrical impulses. It is thus no wonder that most multicellular organisms use another means of communication between cells, namely, chemical communication. If, instead of generating an electrical impulse, stimulated cells release a chemical compound, this compound would diffuse all around the original cell. If other cells around have the means to detect this compound using special molecules on their surfaces, then they would be able to recognise information, and even transmit it. This will be slower, of course, but it can potentially reach all cells of the body, regardless of nervous connections, and it can be done steadily and persistently.

Phytohormones These compounds, or hormones used by multicellular organisms for control and coordination show a great deal of diversity, as we would expect. Different plant hormones help to coordinate growth,

10th Class Biology

34

development and responses to the environment. They are synthesised at places away from where they act and simply diffuse to the area of action. When growing plants detect light, a hormone called auxin, synthesised at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot.This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light.Thus, the plant appears to bend towards light. Another example of plant hormones are gibberellins which, like auxins, help in the growth of the stem. Cytokinins promote cell division, and it is natural then that they are present in greater concentration in areas of rapid cell division, such as infruits and seeds.These are examples of plant hormones that help in promoting growth. But plants also need signals to stop growing. Abscisic acid is one example of a hormone which inhibits growth. Its effects include wilting of leaves.

WORKSHEET 2 1.

2.

3.

4.

5.

6. 7. 8.

9.

10.

11.

It is a common observation that roots of plants always grow toward the source of water. The given phenomenon is explained by the concept of (A) gravitropism (B) hydrotropism (C) phototropism (D) thermotropism During the process of seed germination, it is observed that seedlings grow towards the source of light. The phenomenon exhibited by seedlings is known as (A) gravitropism (B) phototropism (C) chemotropism (D) thermotropism Plant roots tend to grow deeper into the soil to absorb more water. This type of behavioral response in plants is called (A) thigmotropism (B) hydrotropism (C) phototropism (D) gravitropism Andrew notices that irrespective of the way he positions a seed for germination, the root always grows toward the ground, while the shoot always grows away from the ground. The described behavior of roots is termed as (A) gravitropism (B) phototropism (C) hydrotropism (D) thigmotropism It is observed that in a field of sunflowers, all the sunflowers face toward Sun. The given phenomenon is an example of (A) gravitropism (B) phototropism (C) hydrotropism (D) thigmotropism The growth of the roots of plants towards a source of water is known as (A) phototropism (B) geotropism (C) hydrotropism (D) chemotropism Which plant hormone promotes cell division? (A) Auxin (B) Cytokinin (C) Gibberellin (D) Abscisic acid Auxins initiate the bending of the shoots of plants towards light by promoting cell (A) elongation in the unshaded side of the stem (B) elongation in the shaded side of the stem (C) division in the unshaded side of the stem (D) division in the shaded side of the stem Just as in humans, plants too have a number of hormones that perform different functions. Which hormone inhibits growth in plants? (A) Auxin (B) Cytokinin (C) Gibberellin (D) Abscisic acid It is a common observation that the roots of plants always grow downwards, while the shoots of plants always grow upwards. Which type of growth movement is responsible for the given observation? (A) Geotropism (B) Phototropism (C) Hydrotropism (D) Chemotropism Sonia places a potted plant in a covered box. Light enters the box through a small hole in the box. After some time, she observes that the shoots of the plant start growing towards the source of light. Which type of growth movement is exhibited by the described plant? (A) Geotropism (B) Phototropism (C) Hydrotropism (D) Chemotropism

Control and Coordination 12.

13.

14. 15.

35

The movement shown by the leaves of touch-me-not on  being  touched  is  known as _____i______. _____ii_____ involves  the  bending  of  shoots  towards  a  source  of  light. The information in which alternative completes the given statements? (A) i - growth-independent movement, ii - Growth-dependent movement. (B) i - growth-dependent movement, ii - Growth-independent movement. (C) i - growth-independent movement, ii - Growth-independent movement also. (D) i - growth-dependent movement, ii - Growth-dependent movement also.

Column A i Mimosa pudica ii Radical iii Plumule iv Growth of pollen tube

a b c d

Column B Phototropism Thigmotropism Chemotropism Geotropism

The alternatives in the given table can be correctly matched as (A) i  b, ii  a, iii  c, iv  d (B) i  c, ii  d, iii  a, iv  b (C) i  b, ii  d, iii  a, iv  c (D) i  c, ii  a, iii  d, iv  b A very tall plant with fewer lateral branches will have auxin: cytokinin ratio of (A) 2:1 (B) 1:1 (C) 1:2 (D) 3:4 Which of the following statements is correct about growth independent movements? (A) This type of movement is apparent. (B) This type of movement is dependent on phytohormones. (C) This type of movement is shown by tendrils of the pea plant. (D) This type of movement is independent of the direction of stimulus.

SYNOPSIS 3 9

Harmones in Animals How are such chemical, or hormonal, means of information transmission used in animals? What do some animals, for instance squirrels, experience when they are in a scary situation? Their bodies have to prepare for either fighting or running away. Both are very complicated activities that will use a great deal of energy in controlled ways.Many different tissue types will be used and their activities integrated together in these actions. However, the two alternate activities, fighting or running, are also quite different! So here is a situation in which some common preparations can be usefully made in the body. These preparations should ideally make it easier to do either activity in the near future. How would this be achieved? If the body design in the squirrel relied only on electrical impulses via nerve cells, the range of tissues instructed to prepare for the coming activity would be limited. On the other hand, if a chemical signal were to be sent as well, it would reach all cells of the body and provide the wide-ranging changes needed. This is done in many animals, including human beings, using a hormone called adrenaline that is secreted from the adrenal glands.

Adrenaline is secreted directly into the blood and carried to different parts of the body. The target organs or the specific tissues on which it acts include the heart.. As a result, the heart beats faster, resulting in supply of more oxygen to our muscles. The blood to the digestive system and skin is reduced due to contraction of muscles around small arteries in these organs.

10th Class Biology

36

This diverts the blood to our skeletal muscles. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the situation. Such animal hormones are part of the endocrine system which constitutes a second way of control and coordination in our body.

Harmones Chemically hormones are proteins or amino acids or steroids. Though the hormones are secreted in small quantities, their performance is profound in action. Pituitary gland It is a tiny gland of the size of a pea attached to the hypothalamus of the brain. Since some of the endocrine glands are regulated by the pituitary gland, it is called as the conductor of endocrine orchestra. Divisions of pituitary : Pituitary gland is differentiated into an anterior lobe called adenohypophysis and a posterior lobe called neurohypophysis.

Harmones of adenohypophysis Somatotropic or Growth harmone (STH or GH) • It brings forth growth in general • Less production in children –Dwarfism with retarded growth • Excess production in children -gigantism with excess growth • Excess production in adolescents acromegaly with large limbs and lower jaw. Thyrotropic or thyroid stimulating hormone (TSH) • It stimulates the growth of thyroid gland and its production Thyroxine Adrenocorticotropic or Adrenal cortex stimulating hormone (ACTH) • It stimulates the adrenalcortex to produce the hormones aldosterone and cortisone. Follicle stimulating hormone (FSH) • It stimulates the maturation of graafian follicles (inthe ovary) in the female, to produc e the eggs and sperm formation in the males. Lutenizing hormone (LH) in female or interstitial cell stimulating hormone (ICSH) in male • LH in female causes discharge of egg from graafian follicle – a process, called ovulation and production of female sex hormone oestrogen and progesterone. • ICSH in male, induces the interstitial cells to produce male sex hormone – testosterone Lactogenic hormone (LTH) • It stimulates the growth of mammary glands in female and milk production after child birth.

Harmones of Hypophysis Oxytocin • It speeds up the child birth process, by stimulating the contraction and relaxation of the uterus in the female. Vasopressin or Antidiuretic hormone (ADH) • It helps in the reabsorption of water, producing concentrated urine in small quantity. • It constricts the blood vessels and raises up the blood pressure • Less production of ADH results in diabetes insipidus,leading to production of excess of dilute urine.

Thyroid Gland Functions of Thyroid Gland • It increases the rate of metabolism. • It stimulates a rise in the body temperature. • It promotes growth and differentiation of tissues. • Since it affects indirectly growth of the body, thyroxine is also called as personality hormone.

Control and Coordination • •

37

It regulates iodine and sugar level in the blood. It controls working of kidneys and urine output.

Thyroid disorders Hypothyroidism – less secretion of thyroxine causes many abnormalities, like simple goitre, myxoedema and cretinism. Hyperthyroidism- The excess production of thyroxine causes exophthalmic goiter or Grave’s disease.

The islets of Langerhans The islets of Langerhans Pancreas is a dual role playing endocrine gland. The exocrine parts produce pancreatic juice. The endocrine portion is called islets of Langerhans.It consists of two type of cells namely, alpha cells and beta cells. Alpha cells produce a hormone called glucagon and Beta cells produce insulin and amylin.

Insulin i) It promotes the uptake of glucose by the cells for tissue oxidation. ii) It favours conversion of glucose, into glycogen and its storage in the liver and the muscles. iii) It prevents the formation of glucose from protein and fat. iv) It maintains normal blood glucose level at 80 – 120 mg / 100 ml of blood. Note: Less production of insulin causes Diabetes mellitus, in which the excess unused glucose is excreted in the urine.

Glucagon a) b)

It is secreted when glucose level in the blood is low. It influences conversion of glycogen into glucose, thus raising the blood glucose level.

•

They are both cytogenic (producing sex cells) and endocrine (producing male sex hormones) in functioning. The endocrine part secretes male sex hormone called testosterones (androgen). Testosterone stimulates the growth of reproductive organs and the production of male sex cell, the sperms. Testosterone determines the secondary sexual characters in male, such as growth of facial hairs, hoarse voice, broadening of shoulder, etc,.

Testes • • •

Ovaries • • • •

Ovaries are both cytogenic (producing egg cells) and endocrine (producing reproductive hormones, such as oestrogen, progesterone and relaxin) in functioning. Oestrogen is responsible for growth of female reproductive organs and the appearance of secondary sexualcharacters in female, such as growth of pubic hairs, soft voice, feminine body, etc., Progesterone maintains pregnancy and regulates menstrual cycle. Relaxin relaxes the muscles of the pelvic region at the time of child birth.

WORKSHEET 3 1.

2.

Hormones are chemicals that affect various functions of the body such as growth, reproduction, metabolism etc. Which of the following hormones regulates glucose level in the blood? (A) Insulin (B) Thyroxin (C) Growth hormone (D) Gonadotrophic hormone Pituitary is one of the most important glands of the endocrine system. It secretes gonadotropic hormones. Gonadotropic hormones regulate the functioning of the (A) reproductive system (B) respiratory system (C) circulatory system (D) excretory system

10th Class Biology

38 3.

4.

5.

6.

7.

The given illustration represents the human endocrine system.

In the given illustration, pituitary gland is labelled as (A) I (B) II (C) III (D) IV Reproductive organs mature and produce sex cells only at a certain age. The growth and maintenance of the reproductive system is essential for reproduction.The growth and maintenance of the reproductive system is under the control of (A) pancreas (B) thyroid gland (C) hypothalamus (D) pituitary gland The increased level of glucose in blood can affect the functioning of various organ systems. Which hormone lowers the blood sugar level to normal? (A) Insulin (B) Thyroxine (C) Progesterone (D) Testosterone Tony takes part in a 4 x 400 m relay. His body temperature rises rapidly while he runs, in response to which, the sweat glands produce sweat to cool his body. Where does the signal to release sweat come from? (A) Pituitary (B) Cerebrum (C) Cerebellum (D) Hypothalamus The given graph illustrates the effect of two hormones “ X and Y on blood sugar level of a person. Xrepresents  the  effect  of

and Y represents  the  effect  of

.

The information in which alternative correctly completes the given statement? (A) i - adrenaline, ii - insulin (B) i - oestrogen, ii - insulin (C) i - insulin, ii - adrenaline (B) i - oestrogen, ii - adrenaline 8.

A type of self-regulating system in which increased output from the system inhibits future production by the system is called negative feedback loop. Which of the following statements is correct for insulin in light of the given information? (A) Insulin regulation rate remains same in all individuals. (B) Insulin is regulated through negative feedback loop. (C) Insulin regulation is independent of the levels of stimulant. (D) Insulin is regulated through reverse of negative feedback loop.

Control and Coordination 9.

39

Insulin is the hormone secreted by ____i_____. Its low secretion in the body leads to ____ii_____. The information in which alternative completes the given statements? (A) i - pancreas, ii - diabetes (B) i - pancreas, ii - goitre

(C) i - pituitary, ii - diabetes 10.

11.

12.

13.

1.

2.

Match the column I with Column II. Column-I Column-II A. White neurons P. B. Grey neurons Q. C. Unipolar neurons R. D. Bipolar neurons S. Match the column I with Column II. Column-I A. B. C.

3.

(B) i - pituitary, ii - goitre

Dwarfism is a deficiency disorder in which a person does not attain normal height and remains short. Dwarfism occurs due to the deficiency of (A) insulin (B) adrenaline (C) growth hormone (D) thyroxin hormone The proper intake of iodine in diet helps prevent goitre. Iodine is essential for the functioning of which endocrine gland? (A) Adrenal (B) Thyroid (C) Testis (D) Ovary Adrenaline is a hormone secreted by the adrenal gland in humans under extreme conditions of stress. Which of the following statements about adrenaline is incorrect? (A) It increases heart beat. (B) It causes the contraction of diaphragm. (C) It causes the contraction of muscles around arteries. (D) It increases the flow of blood to the digestive system. Hormones play an important role in regulating various body functions. Which of the following hormones lower the blood sugar level in the body? (A) Insulin (B) Glucagon (C) Oxytocin (D) Thyroxine

Innermost covering of CNS Middle covering of CNS Outermost covering of CNS

Sensory hair cells Embryonic Nerve tissue White matter of cerebrum Cerebral Cortex Column-II P. Q. R.

Durmeter Piamater Arachnoid membrane

Match the column I with Column II. Column-I Column-II A. B. C.

Cerebrum Thalamus Hypothalamus

P. Q. R.

Sensory and motor signaling Excitement, anger, fear, pleasure Hearing, seeing , tasting

10th Class Biology

40 4.

Match the column I with Column II. Column-I

Column-II

A.

5.

Coordinates the group movements of voluntary muscles as in walking or running B. It relays the information from the cerebrum to cerebellum C. centre for several reflexes involved in the regulation of heartbeat Match the column I with Column II. Column-I

A. B. C.

6.

8.

9.

Spinal cord’s enlargement in neck region Spinal cord’s enlargement in Lumbar region Spinal cord’s filamentous lower end Narrow depression on the mid dorsal side of the spinal cord.

Central Nervous System (CNS)

P.

B. C.

Peripheral Nervous System(PNS) Autonomous Nervous System (ANS)

Q. R.

R.

Pons

Column-II Fore Brain Mid Brain Hind Brain

P. Q. R. S.

Dorsal fissure Lumbar plexus Cervical plexus Filum terminale

Sympathetic nerves and parasympathetic nerves. Cranial Nerves, Spinal Nerves Brain, Spinal Cord

Match the column I with Column II. Column-I Column-II A. STH P. Brings forth growth B. TSH Q. Production of thyroxine C. ACTH R. Aldosterone Match the column I with Column II. Column-I Column-II

P. Q. R.

Cerebellum

Column-II

A.

STH TSH ACTH

Q.

Column-II

Match the column I with Column II. Column-I

A. B. C.

Medulla Oblongata

P. Q. R.

Match the column I with Column II. Column-I A. B. C. D.

7.

Cerebellum and medulla oblongata. Cerebrum, thalamus and hypothalamus. Cerebral aqueduct, Corpora quadrigemina

P.

Brings forth growth Production of thyroxine Aldosterone

Control and Coordination 10.

Match the column I with Column II. Column-I Column-II A. B. C.

11.

15.

16.

17.

18.

19.

Adrenal Gland Aldosterone Cortisone

P. Q. R.

Testes Ovaries

P. Q. R. Q.

Match the column I with Column II. Column-I A. B. C.

14.

P. Q. R.

Bulging of thyroid gland Defective tooth and protrusion of tongue Loss of physical and mental vigour

Glucocorticoid Supra renal gland Mineralocorticoid

Match the column I with Column II. Column-I Column-II A. B.

13.

Simple goiter Myxoedema Cretinism

Match the column I with Column II. Column-I Column-II A. B. C.

12.

41

Parathyroid gland Thymus gland Pineal gland

Oestrogen Testosterone Determines secondary sexual characters in male Determines secondary sexual characters in female Column-II P. Q. R.

Thymos in Melatonin Parathormone

Spot the mistakes in the given statements and correct them. a) Medullated nerve cells are enclosed by Myelin sheath. b) Non - Medullated nerve cells are enclosed by Myelin sheath. Spot the mistakes in the given statements and correct them. a) Association areas are responsible for the initiation of voluntary activities takes place. b) Motor areas are responsible for complex functions like intersensory associations, memory and communication. Spot the mistakes in the given statements and correct them. a) White matter of cerebrum contains Grey neurons. b) Cerebrum is the major conducting centre for sensory and motor signalling. Spot the mistakes in the given statements and correct them. a) The outer region of the cerebrum is called White matter. b) The inner region of the cerebrum is called Grey matter. Spot the mistakes in the given statements and correct them. a) The middle covering of CNS is thin and vascularised and is called Piameter b) The innermost cover of CNS is a very thin delicate membrane and is closely applied on the outer surface of brain and spinal cord and it is called Arachnoid membrane. Spot the mistakes in the given statements and correct them. a) goitreThalamus controls body temperature, urge eat and drink. b) Hypothalamus is the major conducting centre for sensory and motor signaling.

42 20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

10th Class Biology Spot the mistakes in the given statements and correct them. a) Less production of STH causes gigantism in children. b) Excess production of STH causes dwarfism in children. Spot the mistakes in the given statements and correct them. a) LH produces testosterone b) ICSH produces oestrogen and progosterone Spot the mistakes in the given statements and correct them. a) LTH stimulates the growth of mammary glands in female. b) More production of ADH results in Diabetes insipidus. Spot the mistakes in the given statements and correct them. a) Hypothyroidism is due to excess secretion of thyroxine. b) Hyperthyroidism is due to less secretion of thyroxine. Spot the mistakes in the given statements and correct them. a) Alpha cells of Islets of Langerhans produces Glucagon. b) Beta cells of Islets of Langerhans produces Glucagon. Spot the mistakes in the given statements and correct them. a) Diabetes mellitus is caused due to the less production of insulin. b) Glucagon is secreted when glucose level in blood is high. Spot the mistakes in the given statements and correct them. a) Alpha cells produce a hormone called testosterone. b) Beta cells produce insulin and progesterone. Spot the mistakes in the given statements and correct them. a) Progesterone stimulates the growth of reproductive organs and the production of male sex cell, the sperms. b) Testosterone maintains pregnancy and regulates menstrual cycle. Spot the mistakes in the given statements and correct them. a) Mitosis bring the change in chromosome number. b) Meosis bring change in structure and number of chromosmes. Spot the mistakes in the given statements and correct them. a) Meosis – I is called Mitosis. b) Meosis – II is called Reduction. Spot the mistakes in the given statements and correct them. a) The point of contact between the homologous pair of chromosomes are called,crossing over. b) The exchange of segments of chromatids between homologous chromosomes, is called Chiasmata. Assertion (A): Medullated nerve cells appears greyish in colour. Reasoning (R): This neuron is not enclosed by myelin sheath; so it appears greyish in colour. Choose the correct option (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): The inner part of the cerebrum lying below the cerebral cortex is called white matter. Reasoning(R): It consists of bundles of nerve fibres with myelin sheath giving the white colour. Choose the correct answer (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): Less production of ADH causes Diabetes insipidus. Reasoning(R):It helps in the reabsorption of water, producing concentrated urine in small quantity.

Control and Coordination

34.

35.

36.

37.

38.

39.

40.

41.

42.

43

Choose the correct answer (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): Aldosterone is called mineralocortoid. Reasoning(R): Cortisone is called glucocortoid. Choose the correct answer (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): Aldosterone maintains mineral metabolism. Reasoning (R): Cortisone stimulates the breakdown of glycogen into glucose raising the blood glucose level. Choose the correct option (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.. Nerve cells or neurons are the structural and functional units of the nervous system. There are different types of nerve cells. The description of each of the nerve cells is mentioned below. Identify the type of neuron corresponding to the neuron. A. A neuron that has a nerve cell body with a single process or fibre, which will act both as axon and Dendron. B. A neuron whose axon is enclosed by the white fatty myelin cover. C. A neuron whose axon is covered by only neurilemma and Schwann cells. There are different types of neurons in our body present in different parts. Given below are some of the neurons. Identify the site of each of its location. P) White neurons Q) Grey neurons R) Unipolar neurons S) Bipolar neurons T) Multipolar neuron Man is a vertebrate and a mammal belonging to the animal kingdom. But, he stands unique and supreme and this supremacy in the living world is reflected in the organization of the brain. The brain is the central information processing organ and acts as the command and control system. The human brain is mainly divided into three parts – A, B, C. The part A consist of D, E and F. The part C comprises of G, H and I. If B is located between A and C. Then identify A, B, C, D, E, F, G, H and I respectively. Identify the following parts of the brain from their descriptions. X – It is the part of fore brain and nearly two third of the human brain contains X. Y – It is the canal that passes through mid brain. Z – It is the posterior most part of the brain where it merges with the spinal cord. It acts as a coordination pathway for both ascending and descending nerve tracts. Sudha is a X Class student. She used to be very intelligent and score good marks in the examinations. Suddenly due to an accident consciousness, intelligence, memory, imagination and reasoning abilities have come down. Which part of the brain might have affected in the accident ? Krish is a fantasy movie character. Children are crazy of his adventurous activities. During a fight with his enemy, Krish head got a bad hurt. After few days, the following activities of Krish was found to be impaired: hearing, seeing, tasting, smelling and speaking. Which part of the brain of him would have damaged due to which the above impaired activities are found? Three patients named, Ram, Rahim and Anthony are found with the following symptoms. Ram: Non coordination of group movements of voluntary muscles as in walking or running. Rahim: Information related to sleep and respiratory system is not coordinated with the brain.

10th Class Biology

44

43. 44.

45.

46.

47.

48.

Anthony: Improper functioning of the centre for several reflexes involved in the regulation of heartbeat, blood vessel contraction, breathing. Identify the parts of the brain that are affected due to which the above symptoms are seen in them. The endocrine glands present in head region are A, B in neck region are C, D and E is the endocrine gland present in thorax region. Identify A, B, C, D and E. Choose the right statement related to endocrine system. A. Maintaining the homeostasis is the work of endocrine system. B. Endocrines control and coordinate the physical processes of growth, reproduction and sustenance of life. C. Endocrine glands are glands with ducts. D. The hormones produced by endocrine glands are carried by the blood from the site of production to the site of action. Which of the following are the functions thyroxine? A) It increases the rate of metabolism. B) It promotes growth and differentiation of tissues. C) It regulates iodine and sugar level in the blood. D) It controls working of kidneys and urine output. The rate of metabolism and growth is decreased in a person. His kidney are improperly functioning and urine output is uncontrolled. Further the level iodine and sugar in blood are not regulated. Identify the hormone that is not generated properly in this person. A, B and C are the disorders caused due to less secretion of thyroxine. A: This is produced in children and the symptoms are stunted growth, retarded mental development, defective teeth, protrusion of tongue and loose skin. B: It is caused in the adults, the symptoms are, low metabolic rate, loss of mental and physical vigour, increase in weight, thickening of skin, lowered heartbeat, mental dullness, etc,. C: It is due to the deficiency of iodine in our diet. Thyroid gland bulges as a swelling in the neck Identify A, B and C. Raju is suffering from the symptoms of high metabolic rate, high blood pressure, high irritability, profuse sweating, loss of eight, fatigueness and protrusion of eyeballs. Further he is suffering from the Grave’s disease. Identify the cause for this



HOW DO ORGANISMS REPRODUCE CHAPTER

3



A sexual Reproduction



Sexual Cycle in Females



Sexual Reproduction in flowering plants



Birth Control



Sexual Reproduction in animals



Female Foeticide



Fertilization in Humans and



Sexually transmitted diseases

Development of Embryo

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.

Types of reproduction i.

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

It is called asexual reproduction because it does not use special cells called ‘sex cells’ (or gametes) for producing a new organism. In asexual reproduction, a part of the parent organism separates off and grows into a new organism. Thus, in asexual reproduction, only one parent is needed to produce a new organism. But no sex cells are involved in asexual reproduction. Examples: 1. Binary fission in amoeba 2. Budding in Hydra 3. Spore formation in Rhizopus 4. Regeneration in Planaria 5. Fragmentation in spirogyra 6. Vegetative propagation in plants ii. Sexual Reproduction In Sexual Reproduction, the offspring arises from two parents of different sexes : male sex and a female sex. The male parent contains male sex cells (or male gametes) and the female parent contains female sex cells (or female gametes).

10th Class Biology

46

In sexual reproduction, Male Gamete + Female Gamete  Zygote  New organism Our father is a male and our mother is a female. The male and female parents have special organs in them which produce male sex cells and female sex cells respectively. The humans, fish, frogs, hens, cats, dogs, cows, horses, deer, rabbits, lions and tigers all reproduce by the method of sexual reproduction. Most of the flowering plants also reproduce by sexual reproduction. Basic differences between sexual and asexual reproductions The basic difference between asexual and sexual reproduction is that only one parent is needed in asexual reproduction whereas two parents are needed in sexual reproduction. Another difference is that no sex cells (or gametes) are involved in asexual reproduction but sex cells (or gametes) take part in sexual reproduction. We will now study the asexual reproduction and sexual reproduction in detail, one by one. Let us start with asexual reproduction.

ASEXUAL REPRODUCTION In the asexual reproduction method, certain body cells of the parent organism undergo repeated mitotic cell divisions to form two (or more) new organisms of the same kind. Asexual reproduction takes place by six different methods. These are : 1. Fission 2. Budding 3. Spore formation 4. Regeneration 5. Fragmentation 6. Vegetative propagation We will now describe all these methods of asexual reproduction in detail, one by one. Let us start with fission.

3.

Fission In the asexual reproduction method, certain body cells of the parent organism undergo repeated mitotic cell divisions to form two (or more) new organisms of the same kind.

In the process of fission, a unicellular organism splits (or divides) to form two (or more) new organisms. Fission is of two types : Binary fission and Multiple fission I. Binary Fission

Examples: Amoeba, Paramecium, Leishmania a) Binary Fission in Amoeba Amoeba reproduces by binary fission by dividing its body into two parts. This happens as follows: When the Amoeba cell has reached its maximum size of growth, then first the nucleus of Amoeba lengthens and divides into two parts. After that the cytoplasm of Amoeba divides into two parts, one part around each nucleus. In this way, one parent Amoeba divides to form two smaller Amoebae (called daughter Amoebae). And we say that one Amoeba produces two Amoebae.

The two daughter Amoebae produced here grow to their full size by eating food and then divide again to produce four Amoebae, and so on. In the unicellular organisms such as Amoeba, the splitting of the parent cell during fission (or cell division) can take place in any plane.

How do organisms reproduce b)

47

Binary Fission in Paramecium Paramecium is a unicellular animal having short thread-like structures called cilia over its surface. Paramecium also reproduces by the method of Binary Fission. A fully grown Paramecium divides its body into two parts to form two smaller Paramecia.

c)

II.

Binary Fission in Leishmania Leishmania is a unicellular protozoan. It is a parasite which causes the disease known as kalaazar (or black fever). Kala-azar is also known as leishmaniasis. Leishmania has a greater degree of organisation in its body, having a whip-like structure called flagellum at its one end. In Leishmania, the splitting of parent cell during fission (or cell division) takes place in a definite plane (longitudinally) with respect to flagellum at its end. Multiple Fission

Sometimes, a cyst or protective wall is formed around the cell of a singlecelled organism (like that of Plasmodium) .Inside the cyst, the nucleus of cell splits several times to form many smaller nuclei called daughter nuclei. Cytoplasm collect around each daughter nuclei and thin membranes are formed around them. Many new daughter cells are formed from a single parent cell within the cyst. When the favourable conditions arrive, the cyst breaks open and the many daughter cells present in it are released, each forming a new organism Plasmodium is a protozoan which reproduces by the asexual method of multiple fission. About 1000 daughter cells are produced by the multiple fission of one Plasmodium cell. Plasmodium is the malarial parasite which produces malaria disease in human beings. Plasmodium is carried by female Anopheles mosquitoes from one person to another .

10th Class Biology

48

4.

Budding

The asexual reproduction by budding is observed in Hydra and yeast. a) Budding in Hydra 1. Hydra is a multicellular organism with a soft cylindrical body. 2. It bears tentacles surrounding its mouth towards the top. 3. For reproduction by budding, one or more buds bulge from its lateral sides. 4. Each bud grows into a baby hydra. 5. Baby hydra separates out from the parent forming an independent hydra. b) Budding in yeast Yeast is tiny, unicellular, non-green plant (which is a fungus). Yeast reproduces by budding. The Figure below shows a parent yeast cell (which is a complete plant). In yeast, first a bud appears on the outside of the cell wall

The nucleus of parent yeast cell then divides into two parts and one part of the nucleus moves into the bud. Ultimately, the bud separates off from the parent yeast cell and forms a new yeast cell (or new yeast plant). The budding in yeast, however, often takes place so fast that the first buds start forming their own buds and all of them remain attached to the parent yeast 11 forming a chain of yeast cells. After some time, all the yeast cells of the chain separate torn one another and form individual yeast plants. Noteworthy Points Note the formation of buds on the yeast cells and how they separate from the parent cell. In some organisms like sponges and corals, the buds remain attached to the parent organism permanently. These buds then grow and produce buds of their own. In this way, a colony of sponges or corals is formed.

5.

Spore Formation Spore formation is the asexual method of reproduction. The reproduction by spore formation takes place in plants. In spore formation, the parent plant produces hundreds of microscopic reproductive units called ‘spores’. When the spore case of the plant bursts, then the spores spread into air. When these air-borne spores land on food under favourable conditions, they germinate and produce new plants.

Examples

How do organisms reproduce

49

The tiny spores of bread mould (a fungus plant) are almost always present in the air. If we keep a moist slice of bread aside for a few days, then the spores of bread mould plant present in air settle on the moist bread and germinate to form new fungus plants. The bread mould plants first look like a white cottony mass covering the bread slice which later on turns black. If we observe the surface of this slice of bread through a magnifying glass, then the bread mould plant growing on it will appear to be like that shown. Spore formation in Rhizopus • The common bread mould plant consists of fine, thread­like projections called hyphae and thin stems having knob- like structures called sporangia. • Each knob- like structure (or sporangium) contains hundreds of minute spores enclosed in a spore case. When the spore case bursts, the tiny spores are dispersed in air. • These spores are the asexual reproductive units which can produce more bread mould plants under suitable conditions. • These spores are the asexual reproductive units which can produce more bread mould plants under suitable conditions. • If we remove one sporangium from the bread mould, keep it on a slide, put a cover slip over it and observe this slide through a microscope, we can see the spores.

6.

Regeneration •

In some organisms (plants as well as animals) small cut parts of their body can grow (or regenerate) to form whole new organisms complete in all respects. • The simple animals like Hydra and Planaria show regeneration. This means that in these organisms, whole new organisms can be reproduced from their cut body parts. • In other words, if Hydra or Planaria somehow get cut into a number of pieces, then each body piece can grow into a complete organism. Regeneration in Planaria • Planaria is a flatworm which is found in freshwater 2 ponds and slow-moving streams. • Planaria possesses great power of regeneration. 1 • If the body of Planaria somehow gets cut into a number of pieces, then each body piece can regenerate into a complete Planaria by growing all the missing parts. 3 • Planaria is a flatworm which is found in freshwater ponds and slow-moving streams. Planaria possesses great power of regeneration. Regeneration in Hydra • If the body of a Hydra gets cut into a number of pieces, then each body piece of Hydra can grow into a complete Hydra.

10th Class Biology

50

How does regeneration occur? • The cells of cut body part of the organism divide rapidly to make a ‘ball of cells’. • The cells present in the ball of cells move to their proper places within the ball where they have to form various organs and body parts of the organism. • The cells then change their shapes to form different types of tissues. • These different tissues form various organs and body parts of the organism. In this way a complete organism is regenerated. Why regeneration is not possible in multicellular organisms? In complex multicellular organisms,

As complex multicellular organisms have a very high degree of organisation in their body, they cannot be reproduced from their cut body parts by the process of regeneration. A dog is a complex multicellular organism which cannot be regenerated from its cut body part say, a cut tail. This is because the cells present in the cut tail of a dog cannot produce dog’s organs like heart, brain, lungs, stomach, intestines and limbs, etc, needed for the making of a complete dog. The complex multicellular organisms need more complex ways of reproduction like sexual reproduction.

7.

Fragmentation

Examples: Spirogyra and sea anemones reproduces by fragmentation. Fragmentation in Spirogyra Spirogyra is a green, filamentous alga plant which is found in ponds, lakes and slow moving streams. Spirogyra filament simply breaks into two or more fragments on maturation, and each fragment then grows into a new Spirogyra.

•

This breakup of the filament of a mature Spirogyra on its own brings about asexual reproduction. Thus, Spirogyra reproduces by the asexual method of fragmentation.

Note: A mature spirogyra produces three new spirogyra. Both fission and fragmentation are asexual and in both splitting take place. Then why not they are same or what is the difference between them? In fission, a unicellular organism breaks up to form two (or more) daughter organisms, whereas in fragmentation, a multicellular organism breaks up to form two (or more) daughter organisms.

How do organisms reproduce

8.

51

Vegetative propagation

• • •

Vegetative propagation is an asexual method of reproduction. The reproduction by vegetative propagation occurs only in plants. Vegetative propagation usually involves the growth and development of one (or more) buds present on the old part of the plant to form a new plant. • These buds are in the dormant state (inactive state) in the old part of the plant. • When provided suitable conditions (like moisture, warmth, etc.), these buds grow to form new plants. • Please note that vegetative propagation is also called vegetative reproduction. Vegetative propagation in grass It is a common observation that green grass plants spring up in dry fields after the rains. This happens due to vegetative propagation as follows : • The fields have dry stems of the old grass plants all over them. • These dry stems have buds which are in the inactive state. • By getting rain water, the buds present on dry grass stems get activated and grow to produce new grass plants. • Thus, the green grass grows in the fields after rains from the dry, old stems of grass plants present in the fields, by the method of vegetative propagation. Vegetative propagation in Bryophyllum • Buds are present on the stems as well as the leaves of the Bryophyllum plant which can develop into new plants. • Bryophyllum plants can be reproduced by vegetative propagation by using either a piece of its stem or its leaves. • If a broken piece of the stem of a Bryophyllum plant in the ground, we will get a new Bryophyllum plant growing from it in a week’s time. • Even the leaves of a Bryophyllum plant can produce new plants. • The leaves of a Bryophyllum plant have special type of buds in their margins (or edges). • These buds may get detached from the leaves, fall to the ground and then grow to produce new Bryophyllum plants. • The buds can also drop to the ground together with the leaf and then grow to produce new plants. • Sometimes even before a leaf drops off from a Bryophyllum plant, we can see new plantlets already growing on it. • When such a mature leaf of the Bryophyllum plant falls on the ground, then each plantlet can grow into a new plant. • Thus, the leaves of Bryophyllum plant can produce new plants. • Another plant called Begonia also reproduces by vegetative propagation through its leaves. Vegetative propagation in Money Plant • Cut a piece of stem of money plant in such a way that it contains at least one leaf on it Note: The point on stem where a leaf is attached is called a node. • Dip one end of this stem in water. • After a few days we will find that new roots appear at the point where leaf was attached.

10th Class Biology

52 • •

The piece of stem will gradually grow into a new money plant. Note: If we cut the stem of money plant in between two leaves, then it will not grow into a new plant. This is because it does not have a growing point (here a node) in it. Vegetative propagation in Tubers • A tuber is the thickened, underground stem (or root) of a plant which is swollen with stored food. • The tuber has a number of ‘buds’ (called ‘eyes’). • Each bud of the tuber grows into a new plant when the old tuber is planted in the soil in the next growing season.

• • • • • •

There are two types of tubers : stem tubers and root tubers. Potato is a stem tuber whereas sweet potato is a root tuber. Potato tuber is an underground stem of the potato plant. Each potato tuber can produce more than one plant. A potato tuber has many buds (called eyes) on its body. When a potato tuber is planted in the soil, then the various buds of the potato tuber start growing to form new potato plants. Vegetative propagation in Guava plant • The roots of a guava plant have buds which can develop into new guava plants. • In fact, a large number of plants can be reproduced by the method of vegetative propagation. Other examples Potato, Onion, Banana, Garlic, Water hyacinth, Tulip, Mint, Strawberry and Lily.

Artificial propagation of plants

The three common methods for the artificial propagation of slants are: 1. Cuttings 2. Layering 3. Grafting.

9.

Cuttings

Method • A cutting of the parent plant part (say, of stem or shoot) having some buds on it is taken. • Its lower part is buried in the moist soil. • After a few days, the cutting develops roots and shoot, and grows into a new plant. • Cuttings are a means of asexual reproduction in plants. • The new plant formed from a cutting is exactly similar to the parent plant.

How do organisms reproduce

A stem cutting (with bud) planted in soil

53

Stem cutting develops roots and stems

New plant formation

Examples Bougainvillea, Chrysanthemum, grapes, sugarcane, bananas, and cactus, etc., can be grown by means of cuttings. Propagation of rose plants by Cutting • Rose plants are propagated (or reproduced) by means of cuttings from stems (or shoots). • A piece of stem (or side shoot) having bud is cut from an existing rose plant with the help of a knife. • The lower part of this cutting is buried in moist soil. • After a few days, the end of cutting buried in soil develops roots and later on grows to become a new rose plant. Note: An advantage of cuttings method is that by using this method we can produce many new plants from just one plant quickly, without waiting for flowers and seeds.

10. Layering

• After some time, new roots develop from the part of the branch buried in the soil. • The branch is then cut off from the parent plant. • The part of the branch which has developed roots grows to become a new plant. Layering in Jasmine Plant • Jasmine plant (chameli) is propagated or produced by the layering method. • One left side branch and one right side branch of the parent jasmine plant have been buried in moist soil. • The parts of branches which are buried in soil grow their own roots.

10th Class Biology

54 •

When this happens, the branches of the parent plant connecting the newly formed plants are cut off so that the newly formed plants may grow on their own and develop into mature plants (like the parent plant). • Many plants like strawberry and raspberry are propagated by the natural layering method. • The natural layering occurs because these plants form runners (which are soft horizontal stems running above the -round). • Wherever the ends of such runners touch the ground, new plants are formed at those places. In this way, many more strawberry or raspberry plants are formed from the parent plant in a natural way. Examples Jasmine, Strawberry, Raspberry, Lemon, Guava, Hibiscus (China rose), Bougainvillea and many slender ornamental plants.

11. Grafting

This new plant will have the characteristics of both the original plants. • The cut stem of a plant (or tree) having roots (and fixed in soil) is called stock. Stock is the lower part of a plant (or tree) having the roots. • The cut stem of another plant (without roots) is called scion. Scion is the upper part of a plant which may have leaves on it (but no roots). Method • In carrying out grafting, two plants (or trees) are chosen which are to be used as scion and stock. • First, the stem (or branch) is removed from the plant chosen to be made scion (for its desirable characteristics) by making a slanting cut.

• • • •

•

This gives us the scion with a slanting cut . The stem of second Plant (or tree) to be used in grafting is also cut in a slanting way. The lower part of this plant (or tree) is stock. It has also a slanting cut. The scion is placed over the stock The cut surfaces of the scion and stock are fitted together and bound tightly with a piece of cloth and covered properly with polythene sheet (so as to prevent harmful infection by bacteria or fungus, and loss of water and plant sap from the cut and joined ends of stock and scion). While joining the scion to the stock, care should be taken to make sure that the cambium layer of scion is in contact with the cambium layer of stock (because the cambium layer in the stem is responsible for growth).

How do organisms reproduce

55

• •

The cut soon heals and the stock and scion of two plants grow together and become one plant. The scion continues to produce its original leaves, flowers and fruits but it gets water and minerals for making food from the chosen stock. So, the fruits will have the characteristics o: both the plants (from which scion and stock have come). • Grafting is used to breed fruit trees and flowering bushes. Apple, peach, apricot and pear trees are often grafted. Advantages of Grafting (i) Grafting enables us to combine the most desirable characteristics of the two plants (scion and stock in its flowers and fruits. (ii) By grafting method, a very young scion (shoot part of a plant) can be made to flower and produce fruits quite fast when it is grafted to the stock (stem having roots) of a mature plant. (iii) It enables us to obtain flowers and fruits having different desired characteristics by grafting scions from different varieties of plants on the same stock. Many varieties of mango have been produced by grafting method. (iv) Grafting can be used to produce varieties of seedless fruits. Note Artificial vegetative propagation is usually used for the propagation (or reproduction) of those plants which produce either very few seeds or do not produce viable seeds. Examples Banana, Pineapple, Orange, Grape, Rose, etc. Advantages of Artificial Vegetative Propagation Some of the important advantages of the artificial vegetative propagation of plants are given below : 1. The new plants produced by artificial vegetative propagation will be exactly like the parent plants. Any desirable features of the parent plant will be replicated in the new plants. 2. The fruit trees grown from seeds may take many years before they start to bear fruit. But the fruit trees grown from cuttings or by grafting start to bear fruits much earlier (only after a few growing seasons). 3. The plants grown by vegetative propagation usually need less attention in their early years than the plants grown from seeds. 4. Many plants can be grown from just one parent plant by artificial propagation. 5. We can also get seedless plants by artificial propagation. The cuttings, layering and grafting are the traditional methods for the artificial propagation of plants.

12. Tissue Culture

The growth medium (or culture solution) used for growing plant tissues is very important in this process because it contains various plant nutrients in the form of jelly (called agar) and plant hormones which are necessary for plant growth. Process 1. A small piece of plant tissue is taken from the growing point of the plant (tip of the plant) and placed on a sterile jelly which contains nutrients and plant hormones. 2. The hormones make the cells in the plant tissue divide rapidly producing many cells which form a shapeless lump of mass called callus.

10th Class Biology

56

3.

The callus is then transferred to another jelly containing suitable plant hormones which stimulate the callus to develop roots. 4. The callus with developed roots is then put on a yet another jelly containing different hormones which stimulate the development of shoots. 5. The callus having roots and shoots separates into tiny plantlets . 6. In this way, many tiny plantlets are produced from just a few original plant cells (or tissue). 7. The plantlets thus produced are transplanted into pots or soil where they can grow to form mature plants. Examples Orchids, dahlia, carnation, Chrysanthemum, etc. The production of plants by the method of tissue culture is also known as micro propagation (due to the extremely small amount of plant material used). Advantages of Tissue Culture 1. Tissue culture is a very fast technique. Thousands of plantlets can be produced in a few weeks’ time from a small amount of plant tissue. 2. The new plants produced by tissue culture are disease free. 3. Tissue culture can grow plants round the year, irrespective of weather or season. 4. Very little space is needed for developing new plants by tissue culture.

13. Do Organisms Create Exact Copies of Themselves in Asexual Reproduction Asexual reproduction usually results in the production of genetically identical offsprings, the only genetic variation arises as a result of occasional inaccuracies in DNA replication (or DNA copying) at the time of cell division. Why are the offsprings identical? • The material which carries genetic information from the parents to the offsprings is DNA-Deoxyribo Nucleic Acid (which is present in the form of chromosomes in the nuclei of all the cells). • The basis of asexual reproduction is mitosis. This is the division of a nucleus into two identical daughter nuclei .

How do organisms reproduce

57 • Each daughter nucleus has the same genetic make up because of the replication of DNA (or copying of DNA) of the parent cell. • After the division of the nucleus, the rest of parent cell divides to form two genetically identical daughter cells. The daughter cells can then form two offsprings. From this conclude that all the offsprings produced by one parent as a result of asexual reproduction are usually genetically identical. Clones • The new organisms (or offsprings) produced by one parent through asexual reproduction (which are genetically identical to the parent) are called clones. • The clones possess exact copies of the DNA (or genes) of their parent and hence show remarkable similarity to the parent and to one another. • The clones of plants can be produced by the asexual methods of reproduction such as cutting layering, grafting, tissue culture, etc. • These days techniques have been developed to clone even in animals. Dolly, the sheep hit the headlines in 1997 as the first successfully produced animal clone. • The process of producing genetically identical new organisms (or offsprings) by asexual reproduction methods is called cloning. Variations are introduced in asexual reproduction. • The replication (or copying) of DNA in the cell is done by certain biochemical reactions which synthesize more of genetic material. No biochemical reaction can reproduce 100 per cent same results. • When the DNA already present in the nucleus of the parent cell is replicated (or copied) by making more DNA at the time of asexual reproduction, then slight variations come in the two copies formed. • Due to this, the two DNA molecules formed by replication will be similar but may not be exactly identical to the original DNA. These slight variations in the replication of DNA molecule will lead to slight variations in the offsprings produced by asexual reproduction. • Although the offsprings produced by asexual reproduction are said to be genetically the same as the parent organism, but still they have occasional variations. This means that the organisms do not always create exact copies of themselves in asexual reproduction. • It is to be noted that the importance of DNA copying in asexual reproduction is that the characteristics of the parent organisms are transmitted to its offsprings and at the same time some occasional variations are also produced in the offsprings. Importance of variations introduced in reproduction. • The importance of variations in organisms introduced during reproduction is that it helps the species of various organisms to survive and flourish even in adverse environment. The following discussion make it clear • There may be some drastic changes like excessive heat or cold or shortage of water (drought), etc., in the habitat of a species of organisms. • If all the organisms of a population living in that habitat are exactly identical, then there is danger that all of them may die and no one would survive under those conditions. • This will eliminate the species from that habitat completely. However, if some variations are present in some individual organisms to tolerate excessive heat or cold or survive on meagre water supply, then there is a chance for them to survive and fluorish even in adverse environment. • In this way, the introduction of variations during reproduction provides stability to the populations of various species by preventing them from getting wiped out during adverse conditions. • For example, if there is a population of certain bacteria living in temperate water (which is neither very hot nor very cold) and the temperature of water increases too much due to global warming, then most of these bacteria will not be able to tolerate excessive heat and hence die. • But some bacteria which had variations to resist heat would survive and grow further.

10th Class Biology

58

WORKSHEET 1 1.

2. 3. 4. 5.

6. 7. 8.

9. 10. 11.

12.

13. 14.

15. 16.

Asexual reproduction is : (A) a fusion of specialised cells (B) a method by which all types of organisms reproduce (C) a method producing genetically identical offspring (D) a method in which more than one parent are involved One of the following organisms does not reproduce by binary fission. This is : (A) Amoeba (B) Plasmodium (C) Leishmania (D) Paramecium The micro-organism which reproduces by multiple fission is the one which causes the disease known as: (A) Kala-azar (B) marasmus (C) malaria (D) amoebiasis The protozoan having a flagellum at its one end is : (A) Amoeba (B) Paramecium (C) Hydra (D) Leishmania In the list of organisms given below, those which reproduce by the asexual method are : (i) banana (ii) yak (iii) yeast (iv) Amoeba (A) (ii) and (iv) (B) (i), (iii) and (iv) (C) (i) and (iv) (D) (ii), (iii) and (iv) One of the following organisms does not reproduce by budding . This is : (A) Sponge (B) Yeast (C) Hydra (D) Planaria The disease kala-azar is caused by a micro-organism known as : (A) Planaria (B) Leech (C) Leishmania (D) Plasmodium Reproduction is essential for living organisms in order to : (A) keep the individual organ alive (B) fulfil their energy requirements (C) maintain growth (D) continue the species for ever The unicellular organism which reproduces by budding is : (A) Spirogyra (B) Hydra (C) Planaria (D) Yeast A multicellular organism which reproduces by budding is : (A) Amoeba (B) Yeast (C) Leishmania (D) Hydra The offsprings formed by asexual reproduction method have greater similarity among themselves because: (i) asexual reproduction involves only one parent (ii) asexual reproduction involves two parents (iii) asexual reproduction involves gametes (iv) asexual reproduction does not involve gametes (A) (i) and (ii) (B) (i) and (iii) (C) (ii) and (iv) (D) (i) and (iv) A simple multicellular animal having tentacles which lives in freshwater usually reproduces by the asexual process of: (A) binary fission (B) spore formation (C) budding (D) fragmentation One of the following does not reproduce by spore formation method. This is : (A) Rhizopus fungus (B) Penicillium fungus(C) Yeast fungus (D) Mucor fungus The factors responsible for the rapid spreading of bread mould on slices of bread are : (i) presence of large number of spores in air (ii) presence of large number of thread-like branched hyphae (iii) presence of moisture and nutrients (iv) formation of round shaped sporangia (A) (i) and (iii) (B) (ii) and (iv) (C) (i) and (ii) (D) (iii) and (iv) One of the following reproduces by forming spores. This in : (A) Fern (B) Planaria (C) Spirogyra (D) Potato Asexual reproduction through budding takes place in : (i) Amoeba and Yeast (ii) Yeast and Hydra (iii) Hydra and Plasmodium (iv) Corals and sponges

How do organisms reproduce 17.

18. 19. 20. 21.

22. 23.

24.

25.

26.

27.

59

(A) (i) and (ii) (B) only (ii) (C) (i) and (iii) (D) (ii) and (iv) A feature of reproduction that is common to Amoeba, Yeast and Bacterium is that: (A) they are all multicellular (B) they are all unicellular (C) they reproduce only sexually (D) they reproduce asexually One of the following organisms does not reproduce by fission. This is : (A) Amoeba (B) Leishmania (C) Planaria (D) Plasmodium An organism which may be considered to be a kind of plant and reproduces by budding is : (A) Paramecium (B) Bread mould (C) Hydra (D) Yeast An animal which reproduces by the process of budding is : (A) Plasmodium (B) yeast (C) Hydra (D) Planaria In Spirogyra, asexual reproduction takes place by : (A) division of a cell into two cells (B) breaking up of filaments into smaller bits (C) division of a cell into many cells (D) formation of a large number of buds The ability of a cell to divide into several cells during reproduction in Plasmodium is called : (A) budding (B) fragmentation (C) binary fission (D) multiple fission In Rhizopus fungus, the fine thread-like structures spread on the whole surface of slice of bread are called (A) rhizoids (B) stems (C) roots (D) hyphae Vegetative propagation refers to the formation of new plants from the following existing organs of the old plants : (A) stems, roots and flowers (B) stems, roots and leaves (C) stems, flowers and fruits (D) stems, leaves and flowers There are four tiny organisms A, B, C and D. The organism A is a parasitic protozoan which causes a disease known as kala-azar. The organism B is a microscopic single-celled animal which causes malaria disease in human beings. The organism C is a unicellular animal which can change its body shape according to need, it has no fixed shape. The organism D is also a unicellular animal which is slippershaped having a large number of tiny hair all around its body. (a) Name the organisms A, B, C and D (b) Name one characteristic body feature of organism A. (c) Name the insect which carries organism B and transmits it from one person to another. (d) What name is given to the asexual method of reproduction of A and B? (e) Where do organisms C and D live ? Two very small organisms X and Y both reproduce by the method of budding. Organism X is industrially important because it is used in making alcohol from sugar. It is also used in making bread. Organism lives in freshwater. If organism Y gets cut into a number of parts accidently, each cut part can grow to form complete organism. (a) What are organisms X and Y ? (b) What is the name of the process in which X converts sugar into alcohol ? (c) To which class of organisms does X belong ? (d) Name an important body feature of organism Y. (e) Which organism is multicellular and which one is unicellular ? When a moist slice of bread was kept aside for a few days then some organism grew on it to form a cottony mass which later turned black. When this slice of bread was observed through a magnifying then fine thread-like projections and thin stems having bulb-like structures at the top were seen.

(a) What is the common name and scientific name of the organism which grew on the moist slice of bread (b) How did this organism grow on the moist slice of bread automatically ? (c) What are the fine, thread-like projections on the surface of slice of bread known as ?

10th Class Biology

60

(d) What name is given to the knob-like structures and what do they contain ? (e) What is the name of this method of reproduction ? (f) Name one unicellular organism which reproduces by this method. (g) Name two non-flowering plants which reproduce by this method. 28.

29.

30.

31.

A scientist removed some cells from the growing point of a plant and placed it in a suitable medium leading to the formation of a shapeless lump of mass X. X is then transferred to another medium which stimulates it to develop roots. When X with developed roots is placed in a yet another medium, then it develops shoots to form tiny plantlets. These plantlets can then be transplanted in pots or soil where they can grow to form mature plants. (a) What is the shapeless lump of mass X known as ? (b) What name is given to this method of producing new plants ? (c) The growth medium used in this method contains plant nutrients in the form of a ‘jelly’. Name this jelly. (d) What is the general name of chemicals used to stimulate the growth of plant cells and development of roots and shoots ? (e) Name any two plants which are produced by this method. (f) What is the other name of this method [other than that given in (B) above] ? The stem of a fruit tree X fixed in soil is cut in a slanting way. The upper part of stem of another fruit tree of different variety of same species is also cut in a slanting way. The cut stem of tree Y, without roots but having some leaves, is placed over the rooted cut stem of tree X in such a way that their cut surfaces fit together properly. While joining the two cut stems, care is taken to make sure that the layer Z of one cut stem is in contact with layer Z of the other cut stem. The joint of cut stem is bound tightly with a piece of cloth and covered properly with polythene. Soon the cut heals and the two stems grow together and become one fruit tree producing leaves, flowers and fruits. (a) What is the name of this method of producing plants or trees ? (b) What name is given to the cut stem of tree X having roots ? (c) What name is given to the cut stem of tree Y which has no roots but has some leaves ? (d) Name the layer Z. (e) Why should the layer Z of one cut stem be in contact with the layer Z of the other cut stem ? (f) Name any four fruit trees which are usually bred by this technique. (g) State any one advantage of producing fruit trees by this technique. A small part of the shoot of a plant is removed with a sharp knife. When the lower end of this small part of the shoot is buried in moist soil, it gradually develops roots and shoots and grows to become a new plant. (a) What is the name of this method of propagating plants ? (b) What care should be taken while removing a small part of the shoot from the parent plant with a knife? (c) Name any two plants which provide us with food directly or indirectly and are grown by this method. (d) Give one advantage of this method of producing new plants. (e) State whether it is a sexual method of reproduction or an asexual method. Why ? (f) What special name can be given to the genetically identical new plants produced by this technique? When the branches of a plant growing in the field are pulled towards the ground and a part of th covered with moist soil (leaving the tips of the branches exposed above the ground), then after some new roots develop from the parts of branches buried in the soil. On cutting these branches from the p plant, new plants are produced from the cut parts of branches which had developed roots. (a) What is this method of propagation of plants known as ? (b) What type of branches should a plant have to be able to be propagated by this method ? (c) Name any two plants which are grown for their flowers and propagated by this method.

How do organisms reproduce

32.

33.

34.

35.

61

(d) Name any two plants which are grown for their fruits and propagated by this method. (e) Name one plant which gets propagated by this method naturally by forming runners (soft horizontal stems running above the ground). A worm X found in freshwater and slow-moving streams has been accidently cut into three pieces. It was observed that in due course of time, each cut piece of the worm develops to become a complete worm by growing all the missing parts. (a) Name the worm X which can exhibit this phenomenon of making complete worm from its cut body parts. (b) Name another organism Y which possesses the same characteristic of growing fully from its cut body parts. (c) What is the name of this process in which a complete organism is formed from its cut body part. (d) State whether X and Y are unicellular and/or multicellular organisms. (e) Can a dog be produced completely from its cut body part (say, a cut tail) just like organisms X and Y? Why ? A thickened underground stem X of a plant which is swollen with stored food has a number of points Y on its surface. When the old stem X is planted in the soil of a field in the next growing season, then each point Y present on its surface grows into a new plant. (a) What is the general name of the underground stems like X ? (b) Give one example of X. (c) What are points Y present on X known as ? (d) Is it necessary to plant the whole of stem X in the ground to obtain its new plants ? Explain your answer. (e) What is the name of this method of reproduction of plants ? (f) What is the advantage of growing new plants from the underground stems like X ? A filamentous alga X is found in ponds, lakes and slow-moving streams. The filament of this alga simply breaks into two (or more) pieces on maturing and each piece then grows to become a complete new alga. (a) Name an alga which X is likely to be. (b) What is the colour of X ? (c) What is the method of forming new algae by the breaking of parent alga known as ? (d) An Amoeba also breaks up to form two daughter Amoebae. What is the difference in the splitting of Amoeba and splitting of this alga as a method of reproduction ? (e) Name one marine animal which reproduces in the same way as alga X. When a broken piece of the stem of a plant X is planted in the soil, a new plant grows from it in a week’s time. The leaves of plant X also have many small entities Y in their margins which can fall to the ground alone or along with leaves and grow into new plants. (a) Name a plant which X could be. (b) What are the entities Y present on the leaves of X known as ? (c) Name a plant other than X which can be reproduced from its leaves. (d) Name a common plant grown in many homes which can be propagated from its broken stems like plant X. (e) Name a kind of dormant organs present in dry stems of old grass plants lying in the fields which get activated and produce green grass plants after the rains.

10th Class Biology

62

SYNOPSIS 2 SEXUAL REPRODUCTION Sexual reproduction takes place by the combination of special reproductive cells called sex cells. Sex cells are of two types : male sex cells and female sex cells. The sex cells are commonly known as gametes. Gametes are of two types : male gametes and female gametes. In sexual reproduction, a male gamete fuses with a female gamete to form a new cell called zygote. This zygote then grows and develops into a new organism in due course of time. It is to noted that the sex cells or gametes are also sometimes called germ cells.

14. Sexual Reproduction in Flowering Plants The plants in which the sex organs are carried within the flowers and the seeds are enclosed in a fruit are called angiosperms. Angiosperms are commonly known as flowering plants. The flowering plants reproduce by sexual reproduction method.The sex organs (or reproductive organs) of a plant are in its flowers.

In other words, flowers contain the sexual reproductive organs of a plant figure . In most of the plants, the same flower contains the male organ as well as the female organ. In other words, the majority of plants are bisexual having the male and female reproductive organs in the same plant (or same flower). In fact, the reproductive part of higher plants is the flower. The function of a flower is to make male and female gametes and to ensure that fertilisation will take place to make new seeds for the reproduction of plant (see the above Figures). Sexual reproduction is the most common method of reproduction in flowering plants. From all this discussion we conclude that flowers are for sexual reproduction in plants. A flower makes both male and female gametes needed for sexual reproduction in plants. The sexual reproduction in plants takes place in the following steps: 1. The male organ of flower called ‘stamen’ makes the male gametes (male sex cells) of the plant. These male gametes are present in pollen grains. 2. The female organ of a flower called ‘carpel’ makes the female gametes (female sex cells) of the plant. These female gametes are present in ovules. The female gametes present in ovules are also called ‘ova’, ‘egg cells’ or just ‘eggs’. 3. The male gametes present in pollen grains fertilise the female gametes or egg cells present in ovules. 4 The fertilised egg cells grow within ovules and become seeds. 5. The seeds produce new plants on germination (under suitable conditions of water, warmth, air and light, etc.). We will now describe the various parts of a flower including the sexual reproductive organs. And then we will discuss the sexual reproduction in plants in detail. The main parts of a flower are : Receptacle, Sepals, Petals, Stamen and Carpel. These main parts of a flower are shown in Figure. 1. Receptacle: The base of a flower to which all the parts of a flower are attached is called receptacle.

How do organisms reproduce

63

Stamen (Male part of flower)

Petal

Carpel (Female part of flower) S epal Receptacle

Flower stem

Diagram to show the parts of a flower

2.

3.

4.

Sepals: The green, leaf-like parts in the outermost circle of a flower are called sepals . All the sepals taken together are called calyx.The function of sepals (or calyx) is to protect the flower in its initial stages when it is in the form of a bud. Petals: The colourful parts of a flower are called petals . The petals lie inside the sepals.All the petals taken together are called corolla. The petals are usually scented. The function of petals (or corolla) is to attract insects (for pollination) and to protect the reproductive organs which are at the centre of the flower. Stamen: The little stalks with swollen tops just inside the ring of petals in a flower are called stamens. Stamen is the male reproductive organ of the plant.

Male reproductive organ of a plant

A dia gra mma tic view of a typical a na tropous ovule

Stamen produces pollen grains. The stamen is made of two parts : a filament and an anther.The stalk of stamen is called filament and the swollen top of stamen is called anther. It is actually the anther of a stamen which makes the pollen grains and stores them (The pollen grains appear to be yellow, powderlike substance to us). Pollen grains contain the male gametes (or male sex cells) of the plant.It is clear from this discussion that the male gametes of a plant are made in the anther of stamen. Another point to be noted is that a flower usually has a number of stamens in it.

10th Class Biology

64 5.

Carpel: In the centre of a flower, there is a flask-shaped organ called carpel. Carpel is the female reproductive organ of the plant. A carpel is made of three parts : stigma, style and ovary . The top part of carpel is called stigma. Stigma is for receiving the pollen grains from the anther of stamen (during pollination). Stigma is sticky so that pollen can stick to it. The middle part of carpel is called style. Style is a tube which connects stigma to the ovary. The swollen part at the bottom of a carpel is called ovary . The ovary makes ovules and stores them. Ovules contain the female gametes (or female sex cells) of the plant. There are usually many ovules the ovary. Each ovule contains only one female gamete of the plant. The female gamete This picture shows the -T female sex cell) of the plant which is present inside the ovule is called carpel of a tulip flower um’ or ‘egg’. surrounded by many It is clear from this discussion that the female gametes of a plant are made brown stamens. in the ovary of carpel. Please note that the female organ of a plant is known by two names : carpel and pistil. Another point to be noted is that the female organ called carpel is surrounded by a number of male organs called stamens in the flower . The flowers which contain only one sex organ, either stamens or arpels, are called unisexual flowers. The flowers of papaya and watermelon plants are unisexual flowers.On the other hand, the flowers which contain both the sex organs, stamens as well as carpel, are called bisexual flowers. The flowers of Hibiscus and mustard plants are bisexual flowers.A new seed of the plant is formed when the male gamete present in a pollen grain unites with the female gamete present in the ovule. This happens in two steps : pollination and fertilisation.

15. Pollination For the male gamete to be able to combine with the female gamete, it is necessary that first the pollen grains from the anther of stamen should be carried to the stigma of carpel. The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination. Thus, pollination is said to take place when pollen grains are carried from the anther to the stigma of the flower.

Pollination is done by insects (like bees and butterflies), birds, wind, and water. Pollination can occur in two ways : self-pollination and cross-pollination.When the pollen grains from the anther of a flower are transferred to the stigma of the same flower (or another flower on the same plant), it is called selfpollination. When the pollen grains from the anther of a flower on one plant are transferred to the stigma of a flower on another similar plant, it is called cross-pollination. Insects help in cross-pollination as follows :

How do organisms reproduce

65

When an insect sits on the flower of a plant for sucking nectar, then the pollen grains from the anther of this flower stick to its body. And when this insect now sits on another flower of another similar plant, then the pollen grains sticking to its body are transferred to the stigma of this second flower .In this way the insect transfers the pollen grains from the anther of flower in one plant to the stigma of flower in another plant and causes cross-pollination. The blowing wind also carries pollen grains from one flower to another flower and helps in cross pollination .

16. Fertilisation After a pollen grain falls on the stigma, the next step is fertilisation. Fertilisation occurs when the ma gamete present in pollen grain joins with the female gamete (or egg) present in ovule. This happens follows. When a pollen grain falls on the stigma of the carpel, it bursts open and grows a pollen downwards through the style towards the female gamete in the ovary .

A male gamete moves down the pollen tube. The pollen tube enters the ovule in the ovary . The tip of pollen tube bursts open and male gamete comes out of pollen tube. In ovary, the male gamete of pollen combines with the nucleus of female gamete or egg present in ovule to form a fertilised egg (called zygote) . And we say that fertilisation has taken place. Formation of Fruits and Seeds The fertilised egg (or zygote) divides several times to form an embryo within the ovule. The ovule develops a tough coat around it and is gradually converted into a seed (containing the baby plant). In fact, all the eggs in the ovules present in the ovary of a flower get fertilised by male gametes from pollen grains and grow to become seeds. The ovary of flower develops and becomes a fruit (with seeds inside it). The other parts of flower like sepals, petals, stamens, stigma and style dry up and fall off. Only the ovary is left behind.

66

10th Class Biology

So, at the place on plant where we had a flower originally, we now have a fruit (which is the ovary of the flower containing seeds). A fruit protects the seeds . Some fruits are soft, sweet and jucy like mangoes and oranges. But some fruits are hard, dry and woody like the peanuts and almonds, etc. A seed is the reproductive unit of a plant (which can be used to grow a new plant). The seed contains a baby plant (or embryo) and food for the baby plant .

The part of baby plant in seed which develops into shoot with leaves is called plumule and the part which develops into root is called radicle.The part of seed which contains stored food for the baby plant is called cotyledon. The wheat grains, gram iima), corn, peas, and beans, are all seeds . The baby plant present inside a seed is in the active state (called dormant state).

When the seed gets suitable conditions like water, air and warmth, etc., it germinates and a new plant grows out of the seed. In this way, the parent plant reproduces more plants like itself by forming seeds through flowers. Germination of Seeds The seeds obtained from a plant are usually very dry. In this dry state, the seeds can remain alive but inactive for long periods. They are said to be dormant. When a seed gets water, air and warmth, etc., it begins to grow. When a seed begins to grow, it is said to germinate. Thus, the beginning of the growth of seeds is called germination of seeds. Germination begins when the seed absorbs water, swells and bursts through the seed coat. The water helps the enzymes to function in the seed. The enzymes digest the stored rood in cotyledons and make it soluble. This soluble food makes the radicle and plumule present in the seed to grow. The germination of a bean seed is shown in Figure. The radical of the seed grows first to form the root.

How do organisms reproduce

67

The root pushes down into the soil and begins to absorb water and minerals from the soil. After this the plumage grows upwards to form the shoot . The shoot and root grow further . When the shoot comes up above the ground, it develops green leaves . The green leaves of the shoot begin to synthesis own food in the presence of sunlight. This seedling grows gradually and ultimately becomes a new plant.

WORKSHEET 2 1. 2.

3. 4.

5. 6. 7.

8. 9. 10. 11.

In sexual reproduction of flowering plants, the first event involved in this is. (A) fertilization (B) germination (C) regeneration (D) pollination Which of the following statements are false? P) Angiosperms contain sex organs. Q) Angiosperms are commonly known as flowering plants. R) The male reproductive organ of flower is called carpel. S) The female reproductive organ of flower is called stamen. (A) P, Q (B) R, S (C) P, R (D) Q, S The product of triple fusion which acts as nutritive tissue for the development of embryo is (A) zygote (B) placenta (C) scutellum (D) endosperm The disadvantage of self pollination is (A) There is no wastage of pollen grains, (B) The seeds are less in number (C) Self pollination is sure in bisexual flowers (D) Flowers need not depend on agents of pollination The male reproductive part of the flower (A) Calyx (B) Corolla (C) Androecium (D) Gynoecium The female reproductive part of the flower (A) Calyx (B) Corolla (C) Androecium (D) Gynoecium During pollination, pollen grains are transferred from (A) anther to stigma (B) stigma to anther (C) corolla to calyx (D) androceium to gynoceium Which of the following are the pollinating agents? (A) Wind (B)Water (C) Insects (D)All The pollination by ________ is called Ornithophily (A) snakes (B) lizards (C) birds (D)mammals The pollination by animals is called (A) Anemophily (B) Hydrophily (C) Zoophily (D)All The pollination by wind is called (A) Anemophily (B) Hydrophily (C) Zoophily (D)Ornithophily

10th Class Biology

68 12. 13. 14. 15. 16. 17. 18.

19.

20.

21.

22.

23.

Hydrophily is pollination by (A) Animals (B) Wind (C) Insects (D)Water The fusion of a male gamete with egg is known as (A) Fusion (B) Fission (C) Pollination (D) Fertilization The fusion of secondary nucleus with the second male gamete is known as (A) Binary fusion (B) Triple fusion (C) Pollination (D) Fertilization The nucleus developed by triple fusion is called (A) perisperm (B) ectosperm (C) endosperm (D) zoosperm A nutritive tissue meant for the development of the embryo (A) perisperm (B) ectosperm (C) endosperm (D) zoosperm The process of fusion of a male gamete with egg and the other gamete with secondary nucleus is known as (A) Single fertilization (B) Double Fertilization (C) Triple Fertilization (D) All Match the following: Column-1 Column-2 A. Stamen P. Eggs B. Carpel Q. Male gamates C. Polleng grains R. Female reproductive organ of flower D. Eggs S. Male reproductive organ of flower Match the following: Column-1 Column-2 A. Receptacle P. Outer circle of a flower B. Sepals Q. Base of the flower C. Petals R. Male reproductive organ of a flower D. Stamen S. Colourful parts of a flower Match the column I with Column II. Column-I Column-II A. Androecium P. Stigma B. Gynoecium Q. Seed C. Ovary R. Stamens D. Ovule S. Fruit Match the column I with Column II. Column-I Column-II A. Self pollination P. Allogamy B. Cross pollination Q. Ornithophily C. Bird pollination R. Anemophily D. Wind Pollination S. Autogamy Statement - I: Sexual reproduction takes place by the combination of special reproductive cells called ‘sex cells’. Statement – II: The sex cells are commonly known as gametes. (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. Statement - I: In sexual reproduction, a male gamete fuses with a female gamete to form a new cell

called Embryo. Statement – II: The sex cells or gametes are also sometimes called germ cells. (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.

How do organisms reproduce 24.

25.

26.

27. 28.

29.

30.

69

Assertion(A): Sexual reproduction in plants take place in flower. Reasoning(R): Both male and female reproductive organs are present in flower itself. (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): Self pollination is known as autogamy. Reasoning (R): This is because pollen grains from the anther of a flower to the stigma of the same flower or another flower of the same plant are tranferred. (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. . Spot the mistakes in the given statements and correct them. a) Androecium is the male reproductive organ of a flower. b) Gynoecium is the male reproductive organ of a flower. Spot the mistakes in the given statements and correct them. a) Andorecium contains ovary or carpels. b) Androecium is a group of stamens. Spot the mistakes in the given statements and correct them. a) Self pollination is also known as allogamy. b) Cross pollination is also known as autogamy. Spot the mistakes in the given statements and correct them. a) The process of fusion of a male gamete with egg and the other gamete with secondary nucleus is called triple fusion. b) The fusion of secondary nucleus with the second male gamete is known as triple fusion. Spot the mistakes in the given statements and correct them. a) The ovary develops into a seed. b) The ovule develops into a fruit.

SYNOPSIS 3 17. Sexual Reproduction in Animals In order to understand sexual reproduction, we should know the meanings of some important terms like male sex, female sex, gametes, sperms, ova (or eggs), fertilisation, zygote and embryo, which are involved in sexual reproduction.These are discussed below : Male and Female A man is said to have male sex and a woman is said to have female sex. Similarly, a boy has a male sex and a girl has a female sex. An animal having male sex cells called ‘sperms’ in its body is called male. On the other hand, an animal having female sex cells called ‘ova’ (or ‘eggs’) in its body is called female. We will now discuss gametes. Gametes The cells involved in sexual reproduction are called gametes. In other words, gametes are the sexual reproductive cells (or sex cells). Gametes are of two types : male gametes, and female gametes. The male gamete in animals is called ‘sperm’ and the female gamete in animals is called ‘ovum’ or ‘egg’.

Structure of a sperm

70

10th Class Biology Sperms and ova (or eggs) are extremely small cells which can be seen only with the help of a high power microscope.Please note that a female gamete (or female sex cell) is usually known by two names : ovum and egg. So, whether we use the term ‘ovum’ or ‘egg’, it will mean the same thing.Another point to be noted is that the plural of ovum is ova. The ovum or egg contains water and stored food. The important part of ovum or egg is its nucleus . The sperm cell is hundreds or even thousands of times smaller than the ovum or egg and it has a long tail . The sperms are motile which can move independently with the help of their tails. The nuclei of the sperm and ovum contain chromosomes which carry the genes. It is clear from the above discussion that sperms are the male gametes of animals. And ova are the female gametes of animals. In other words, sperms are the male sex cells of animals and ova are the female sex cells of the animals.As we will study after a short while, fusion of gametes gives rise to a single cell called zygote. We can also say that the cell which is formed by the fusion of a male gamete and a female gamete is called zygote.In most simple words, zygote is a ‘fertilised ovum’ or ‘fertilised egg’. All the multi-cellular animals start their life from a single cell called zygote through sexual reproduction.The process of fusion of gametes is called fertilisation. This is discussed below. Fertilisation For sexual reproduction to occur, a male gamete must combine with a female gamete.The fusion of a male gamete with a female gamete to form a zygote during the sexual reproduction, is called fertilisation. Since the male gamete of an animal is called sperm and the female gamete of an animal is called ovum, therefore, we can also say that: The fusion of a sperm with an ovum to form a zygote during sexual reproduction, is called fertilisation. It is clear that the process of fertilisation produces a new cell called zygote. The zygote is actually ‘fertilised ovum’ or ‘fertilised egg’. The zygote grows and develops to form a new baby.The unborn baby in the uterus in the early stages of development is called an embryo.On the other hand, the unborn baby in the uterus in the later stages of development is called a foetus.

Internal and External Fertilisation We have just studied that the fusion of a sperm with an ovum is called fertilisation.Now, the ovum is made in the body of the female animal.So, the fertilisation of an egg by a sperm can take place either inside the body of the female animal or outside its body. This leads to two modes of fertilisation in animals : internal fertilisation and external fertilisation. The fertilisation which occurs inside the female body is called internal fertilisation.In internal fertilisation, the female animal’s eggs are fertilised by sperms inside her body. In mammals , birds and reptiles, the fertilisation occurs inside the female body. In other words, internal fertilisation takes place in mammals , birds and reptiles. In internal fertilisation, the male animal puts his sperms into the female animal’s body. This transfer of sperms from the testes c: the male animal into female animal’s body occurs at the time of copulation. Copulation is the act by which the male animal transfers his sperms into the female animal’s body.During copulation, very large number of sperms are discharged into the female body.These sperms fertilise the eggs inside he: body. For example, during copulation a man puts his sperms inside a woman’s body through an orgar. called penis. These sperms then fertilise the egg inside the woman’s body. So, this is a case of internal fertilisation.The fertilisation which occurs outside the female body is called external fertilisation. In external fertilisation, the female animal’s eggs are fertilised by sperms outside its body. In amphibians and fishes, the fertilisation of eggs occurs outside the female animal’s body. In other words, in amphibians and fishes, external fertilisation takes place.

How do organisms reproduce

71

In external fertilisation, the male and female animals release their sperms and eggs in water where fertilisation takes place by collisions between sperms and eggs. For example, the males and females of frogs and fishes release their sperms and eggs in water in which they live. The sperms then collide with the eggs and fertilise them outside the leads to fertilisation. This is an example of external fertilisation, body of female frog or fish . The fertilisation in humans, cats, dogs and birds are the examples of internal fertilisation. The fertilisation in frogs and fishes are the examples of external fertilisation. We know that the new cell which is formed by fertilisation is called ‘zygote’. And this zygote then grows and develops into a full organism (or baby animal). The method in which a zygote grows and develops into a full organism also varies in different animals. For example, in human beings the zygote grows and develops into a baby inside the female body .And then the mother gives birth. to the baby. Just like humans, the animals like cats and dogs also give birth to their young ones. But the process is entirely different in the animals which lay eggs.For example, a hen sits on its fertilised eggs for a considerable time to give them warmth. During this period, the zygote grows and develops to form a complete chick. This chick then comes out of the egg by breaking its shell. It is clear from this discussion that all the organisms do not give birth to individuals like humans do. The Advantages of Sexual Reproduction The sexual reproduction has many advantages over asexual reproduction. In asexual reproduction, the off springs are almost identical to their parent because they have the same genes as their parent. So, much genetic variation is not possible in asexual reproduction. This is a disadvantage of asexual reproduction because it inhibits the further evolution of the organism. In sexual reproduction the off springs, although similar to their parents, are not identical to them or to one another. This is because the off springs receive some genes from the mother and some from the father. Because of the mixing of genes of mother and father in various different combinations, all the offsprings ave genetic variations. In this way, sexual reproduction leads to a greater variety in population. This means that a species can adapt more quickly to changes in its surroundings .This is because there are always likely to be some individuals which are more suited to the changes than others, and these individuals will survive and reproduce themselves. From the above discussion we conclude that sexual reproduction promotes diversity of characters in the offsprings by providing genetic variation. Sexual reproduction plays an important role in the origin of new species having different characteristics.This genetic variation leads to the continuous evolution of various species to form better and still better organisms.All this is not possible in the case of asexual reproduction. Why the Amount of DNA Does Not Get Doubled During Sexual Reproduction In sexual reproduction, though the genetic material DNA from two gametes, male and female gemetes, combines together to form a new cell ‘zygote’ but the amount of DNA m zygote does not get doubled. This can be explained as follows : The gametes are special type of cells called reproductive cells which contain only half the amount of DNA as compared to the normal body cells of an organism. So, when a male gamete combines with a female gamete during sexual reproduction, then the new cell ‘zygote’ will have the normal amount of DNA (or normal number of chromosomes in it). For example, the human sperm has 23 chromosomes and the human egg has also 23 chromosomes. So, when a sperm and an egg fuse together during fertilisation, then the zygote formed will have 23 + 23 = 46 chromosomes, which is the normal number of chromosomes. How Sexual Reproduction in Animals Takes Place Sexual reproduction is the most common method of reproduction in animals. The sexual reproduction in animals takes place in the following steps : 1. The male parent produces male gametes called sperms. The sperm is a small cell with a long tail for movement . 2. The female parent produces female gametes called ova . The ovum is a much bigger cell than the sperm, having a lot of cytoplasm .

10th Class Biology

72

3.

The sperm enters into the ovum and fuses with it to form a new cell called ‘zygote’. This process is called fertilisation. So, the zygote is a fertilised ovum. 4. The zygote then divides again and again to form a large number of cells (all of which remain together And ultimately zygote grows and develops to become a new baby. From the above discussion we conclude that the whole process of sexual reproduction in animals involves the formation of sperms and eggs; joining together of sperm and egg to form a zygote; and then the growth and development of zygote to form a baby animal. In complex multicellular animals there are special reproductive organs to make sperms and eggs; to bring together sperms and eggs for fertilisation; and for the growth and development of zygote into a baby. We will study all this in the human reproductive system. Before we describe the human reproductive system, we should; know the meaning of the term ‘puberty’. This is discussed below. Puberty When a child is small, sometimes it becomes difficult to tell from appearance whether it is a boy or 3 girl. This is because small boys and girls have the same body shape. A time of rapid growth. and body changes starts in the early teens which makes the boy and the girl appear different and also behave differently . These changes start earlier in girls than in boys. We call the time between childhood and adulthood ‘adolescence/ The production of male and female ‘sex hormones’ in the bodies of boys and girls increases dramatically at this stage and causes a wide-ranging changes in their bodies. The testes and ovaries make different hormones, so the boys and girls develop in different ways. Ultimately the boys and girls become sexually mature and their reproductive systems start functioning. The age at which the sex hormones begin to be produced and the boy and girl become sexually mature is called puberty. Puberty tends to start earlier in females than in males. Generally boys attain puberty at the age of 13 to 14 years while girls reach puberty at a comparatively lower age of 10 to 12 years. On attaining puberty, the male gonads called testes start producing male gametes called sperms and the female gonads called ovaries start producing female gametes called ova. In addition to producing sex cells male and female gonads also produce and secrete sex hormones with the onset of puberty. The testes produce the male sex hormone called testosterone, and the ovaries produce two female sex hormones, oestrogen and progesterone. The sex hormones play an important role in the process of reproduction because they make the reproductive organs to mature and start functioning. Puberty is the age at which the reproductive organs reach maturity and secondary sexual characteristics develop. The various changes which occur in boys at puberty are : Hair grow under armpits and in pubic regions between the thighs.Hair also grow on other parts of the body like chest and face . Body becomes more muscular due to the development of muscles. The voice deepens. Chest and shoulders broaden.

How do organisms reproduce

73

The penis and testes become larger. The testes start to make sperms. Feelings and sexual drives associated with adulthood begin to develop. All these changes in boys are brought about by the male sex hormone ‘testosterone’ made in testes. The various changes which occur in girls at puberty are : Hair grow under armpits and pubic region This change is the same as in boys). Mammary glands develop and enlarge. The hips broaden. Extra fat is deposited in various parts of the body like hips and thighs. Fallopian tubes, uterus and vagina enlarge. Ovaries start to release eggs. Menstruation start. Feelings and sexual drives associated with adulthood begin to develop. All these changes in girls are brought about the female sex hormones ‘oestrogen’ and ‘progesterone’ made in ovaries. It is to be noted that the hormone oestrogen’ is also written and spoken as ‘estrogen’.

Human Reproductive System The humans use sexual mode of reproduction. The organs associated with the process of reproduction nin human males and human females are different, so the reproductive systems in males and females are different which are known as male reproductive system and female reproductive system, respectively. The reproductive systems in human beings become functional at a definite age called puberty. We will now describe the human male reproductive system and female reproductive system in detail, one by one.

18. Male Reproductive System The human male reproductive system consists of the following organs : Testes, Scrotum, Epididymis, Vas deferens or Sperm duct), Seminal vesicles, Prostrate gland and Penis. The human male reproductive system is shown in Figure .Scince the human male is called man, so we can also say that is the reproductive system of man. Testes are the oval shaped organs which lie outside the abdominal cavity of a man. A man has two testes . Testes are the primary reproductive organs in males.The function of testes is to make the male sex cells called sperms and also to make the male sex hormone called testosterone. It is noted that the testes of a man make the sex gametes from puberty onwards, throughout his life. The testes of a man lie in small muscular pouch called scrotum. The male reproductive outside the abdominal cavity . The testes are outside the abdominal cavity of the body, because the sperm formation requires a lower temperature than the normal body temperature. Being outside the abdominal cavity, the temperature of The male reproductive system in humans scrotum is about 3°C lower than the temperature inside the body. In this way, the testes provide an optimal temperature for the formation of sperms. The sperms formed in testes come out and go into a coiled tube called epididymis . The sperms get stored temporarily in epididymis. From epididymis, the sperms are carried by a long tube called vas deferens which joins with another tube called urethra coming from the bladder . Along the path of vas deferens, the glands called seminal vesicles and prostrate gland add their secretions to sperms so that the sperms are now in a liquid. This liquid plus the sperms it contains is called semen. The secretions of seminal vesicles and prostrate gland provide nutrition to the sperms and also make their further transport easier.Urethra forms a common passage for sperms and urine. Urethra carries the sperms to an organ called penis which opens outside the body. The penis passes the sperms from the man’s body into vagina in the woman’s body during mating for the purpose of reproduction. It is to noted that in male there is only one opening for the urine and sperms to pass out of the body.

10th Class Biology

74

19. Female Reproductive System The human female reproductive system consists of the following organs : Ovaries, Oviducts , Uterus, and Vagina. The human female reproductive system is shown in Figure. Since the human female is called woman, so we can also say that it is the reproductive system of woman. Ovaries are the oval shaped organs which are inside the abdominal cavity of a woman near the kidneys. A woman has two ovaries. Ovaries are the primary reproductive organs in a woman . The function of ovaries is to make mature female sex cells called ‘ova’ or ‘eggs’, and also to make the The female reproductive system in humans (front view) female sex hormones . Each ovary is composed of several thousand follicles . At puberty these follicles mature to form the ripe eggs or ripe ova. Just above the ovaries are the tubes called oviducts. The oviducts are not directly connected to ovaries but have funnel shaped openings which almost cover the ovaries .The ovum released by an ovary goes into the oviduct through its funnel-shaped opening. The fertilisation of egg by a sperm takes place in the oviduct. The two oviducts connect to a bag like organ called uterus at their other ends .The growth and development of a fertilised ovum into a baby takes place in the uterus. The uterus is connected through a narrow opening called cervix to another tube called vagina which opens to the outside of the body . Vagina receives the penis for putting sperms into the woman’s body. Vagina is a tubular structure.Vagina is also called ‘birth canal’ because it is through this passage that the baby is born after the completion of development inside the uterus of the mother. Please note that in female the opening for passing out urine and the vaginal opening are separate. It is obvious from the above discussion that the female reproductive system in humans is more complex than that of the male reproductive system. The complexity in structure and function of the female reproductive system is necessary for the union of sperms and ovum inside the female body and the development of the baby in the mother’s uterus.

20. Fertilisation & Embryo Development In human beings, internal fertilisation takes place. The sperms made in the testes of man are introduced into the vagina of the woman through penis during copulation. In this a ay, millions of sperms are released into the vagina at one time. The sperms are highly active and mobile .The sperms move up through cervix into the uterus. From uterus, the sperms pass into the oviducts . One of the oviducts contains an ovum (or egg cell) released by the ovary during ovulation.Only one sperm fuses with the ovum in the oviduct to form a zygote. This is called fertilisation.Thus, the fertilisation of the ovum (or egg) takes place in the oviduct.

How do organisms reproduce

75

Development of Embryo When the ovum is fertilised in the oviduct, then a zygote is formed. The zygote divides rapidly by mitosis as it moves down slowly in the oviduct and forms a hollow ball of hundreds of cells.This hollow ball of cells, now called an embryo, sinks into the soft and thick lining of the uterus and gets embedded in it . The embedding of embryo in the thick lining of the uterus is called implantation.

After implantation, a disc-like special tissue develops between the uterus wall (called uterine wall) and the embryo , which is called placenta. It is through the placenta that all the requirements of the developing foetus like nutrition, respiration, and excretion, etc., are met from the mother’s body. In other words, the exchange of nutrients, oxygen and waste products between the embryo and the mother takes place through the placenta.

10th Class Biology

76

The time period from the fertilisation up to the birth of the baby is called gestation.The average gestation period in humans is about nine months.During the gestation period, the foetus grows to become a baby. Birth begins when the strong muscles in the walls of the uterus start to contract rhythmically.The rhythmic contraction of uterus muscles gradually pushes the baby out of the mother’s body through vagina. This is how a baby is born . All of us were born from our mother in this way. Differences Between Zygote, Embryo and Foetus

A zygote is formed after fertilisation. A zygote develops and becomes an embryo. And finally, an embryo develops and becomes a foetus. The main differences between zygote, embryo and foetus are given below:

Zygote 1

2.

3.

Embryo

Foetus

A zygote is formed by the fusion of male and female gametes (sperm and egg) A zygote is the beginning of the formation of a baby.

1.

An embryo is formed by the repeated cell division of a zygote.

1.

A foetus is formed by the growth and development of an embryo.

2.

2.

A foetus is an unborn baby in the uterus in the later stages of development (after 8 weeks till birth).

A zygote is a single cell. It is smaller than a full stop (.)

3.

An embryo is an unborn baby in the uterus in the early stages of development (up to 8 weeks after fertilisation) An embryo is multicellular. The body features of growing baby in the embryo are not much developed.

3.

A foetus is also multicellular. The body features of developing baby (like hands, legs, head, eyes and ears, etc.) can be identified.

How do organisms reproduce

77

21. Sexual Cycle in Females : Menstruation We will now describe the sexual cycle in human females. Please note that when a girl child is born, her ovaries already contain many thousands of immature ova which are contained in immature follicles.When a girl reaches the age of puberty, then one follicle develops at a time to form a mature ovum. On maturing, the follicle bursts and the ovum shoots out of the ovary. This is called ovulation. Thus, the release of an ovum (or egg) from an ovary is called ovulation. In a normal, healthy woman, ovulation takes place on the 14th day of the beginning of menstrual cycle of 28 days. This means that ovulation takes place in the middle of the menstrual cycle. In human females, the ovaries start releasing ovum or egg once every 28 days from the age of puberty. That is, in girls ovulation starts when they attain puberty. Please note that ovulation does not take place every day after puberty.It takes place after a period of every 28 days. Before every ovulation, the inner lining of the uterus becomes thick and soft with lot of blood capillaries in it . These changes in the uterus are necessary because in case the ovum. released by the ovary gets fertilised by the sperm, then the uterus has to keep this fertilised ovum for further development and supply it with food and oxygen, etc., so that it may grow into a baby in due course of time.

If, however, a sperm is not available at the time of ovulation, then fertilisation of ovum does not take place. Since the ovum is not fertilised, so the thick and soft uterus lining having lot of blood capillaries in it is not required. Thus, the unfertilised ovum dies within a day and the uterus lining also breaks down. Since the thick and soft uterus lining contains a lot of blood vessels, so the breaking of the uterus lining produces blood alongwith other tissues. This blood and other tissues come out of the vagina in the form of ‘bleeding’. We can now say that the breakdown and removal of the inner, thick and soft lining of the uterus along with its blood vessels in the form of vaginal bleeding is called menstrual flow or menstruation. Menstruation occurs if an ovum released by the ovary of a woman does not get fertilised due to nonavailability of sperm at the time of ovulation. Since the process of menstruation in a woman occurs again and again after a fixed period of 28 days (to 30 days), so it is also known as menstrual cycle. Menstruation occurs every 28 days because ovulation occurs every 25 days. In everyday language, menstruation is called ‘periods’. We will now describe the menstruation point-wise which can be reproduced in the examination. The sexual cycle in females is called menstruation or menstrual cycle. This is described below :

10th Class Biology

78 1.

When a girl reaches puberty at the age of about 10 to 12 years, the sex hormones released into he: blood cause some of the ova in her ovaries to become mature. 2. Usually one mature ovum is released from the ovary into the oviduct once every 28 days. This is called ovulation. 3. Before ovulation , the inner lining of uterus becomes thick and spongy, and full of tiny blood vessels , and prepares itself to receive the fertilised ovum or egg. 4. If the ovum does not get fertilised then the thick and soft inner lining of uterus is no longer needed and hence it breaks. So, the thick and soft inner lining of uterus alongwith the blood vessels and the dead ovum comes out of the vagina in the form of a bleeding called menstruation. 5. Menstruation usually occurs 14 days after ovulation and usually lasts for about 3 to 5 days. 6. After menstruation is over, the inner lining of the uterus starts building up again so that it may become ready to receive the next ovum in case it gets fertilised. 7. If the ovum does not get fertilised even now, then menstruation takes place again. This cycle of menstruation is repeated again and again in women after every 28 days . The menstrual cycle is controlled by hormones. Menstruation stops temporarily when the ovum gets fertilised and the woman gets pregnant. This is because in this case the thick and soft lining of the uterus containing lot of blood vessels is needed for the growth and development of the fertilised ovum to form a baby. Menstruation restarts after the birth of the baby. Menarche and Menopause The first menstruation begins at puberty (when the girl or woman is around 10 to 12 years of age). The first occurrence of menstruation at puberty is called menarche. Menarche is the beginning of the reproductive life of a girl. In other words, menarche is the time from which a girl becomes capable of having a baby.Menstruation stops permanently when a woman reaches the age of about 45 to 50 years. With the permanent stoppage of menstruation, a woman loses her ability to bear children. She becomes infertile. The permanent stoppage of menstruation in a woman is called menopause. Menopause occurs in women at the age of about 45 to 50 years.A woman stops ovulating at menopause and can no longer become pregnant. Menopause is the end of the reproductive life of a woman. We can now say that the reproductive life of a woman starts at menarche and ends at menopause.

22. Birth Control The population of our country is increasing rapidly day by day . Though our country has sufficient food resources but still many people do not get sufficient food for their large families due to poverty. So, every year it is becoming very difficult for our Government to provide sufficient food, adequate clothing, good housing and proper education to every citizen of the country. It is, therefore, very important for the couples (husbands and wives) who are in the reproductive stage of their lives to control the size of their families by having fewer children by practising family planning through birth control measures. Family planning enables a couple to decide on the number of children it wants to have and when to have them. If a couple has less number of children, it can provide good food, good clothes, and good education to each child.This will make the parents as well as the children happy. So, a small familyis a happy family.It should be noted that having fewer children also keeps the mother in good health. We should remember that to keep the size of our family small by having less number of children is in our own interest as well as in the interest of our Nation. Family planning can be done by practising birth control measures. Birth control can be done by preventing pregnancy in females. And pregnancy can be prevented by adopting a method or procedure by which

How do organisms reproduce

79

sperms produced during copulation between man and his wife can be prevented from meeting the ovum and fertilising it. It is possible to prevent fertilisation because the ovum is available for fertilisation only for a short period. Since frequent pregnancies have a very bad effect on the mother’s health, and also add to our already exploding population, so a number of techniques or methods have been developed to prevent pregnancies in women. We can call them birth control measures, family planning measures or population control measures. These are discussed below.

BIRTH CONTROL METHODS The prevention of pregnancy in women (by preventing fertilisation) is called contraception. And any device or chemical (drug) which prevents pregnancy in woman is called a contraceptive. All the birth control methods can be broadly divided into three categories : 1. Barrier methods, 2. Chemical methods, and 3. Surgical methods. We will now discuss all these methods of contraception in women briefly. 1. Barrier Methods In the barrier methods of preventing pregnancy, the physical devices such as condoms and diaphragm (or cap) are used. Condoms are used by males . Condom is called ‘nirodh’ in Hindi. Diaphragm is used by females. Condom as well as diaphragm prevent the sperms from meeting the ovum (or egg) by acting as a barrier between them. An important benefit in the use of condom is that it protects a person from the sexually transmitted diseases such as gonorrhoea, syphilis and AIDS. No other method of contracepticr provides protection against sexually transmitted diseases. 2. Chemical Methods In the chemical methods of preventing pregnancy, the females use two types of pills : oral pills and vaginal pills, which are made of specific drugs. The oral pills contain hormones which stop the ovaries from releasing ovum into the oviduct. Oral pills are also called Oral Contraceptives.This is a very effective method of preventing pregnancy so long as the pills are taken at the right time. Some women, however, do experience unpleasant side effects on taking oral pills because they change the hormonal balance in the body. So, it is important that the women on pills have regular check-ups with their doctor. The vaginal pills contain the chemicals called spermicides which kill the sperms. 3. Intra-Uterine Contraceptive Device (IUCD) The use of intrauterine contraceptive device called Copper-T is also very effective in preventing pregnancy. A Copper-T is placed inside the uterus by a doctor or a trained nurse. The IUCD or Copper-T prevents the implantation of fertilised egg in the uterus. If a woman uses a Copper-T as a method of contraception for avoiding unwanted pregnancies, then Copper-T cannot protect her from acquiring sexually transmitted diseases. 4. Surgical Methods Surgical methods of birth control are available for males as well as females. In males, a small portion of the sperm duct is removed by surgical operation and both the cut ends are ligated properly. This prevents the sperms from coming out. The surgical procedure carried out in males is called Vasectomy’. In females, a small portion of the oviducts is removed by surgical operation and the cut ends are ligated.This prevents the ovum from entering into the oviducts. The surgical procedure carried out in females is called tubectomy.

Stop Female Foeticide ! Surgical operations can also be used for the termination of pregnancies in women particulary after eight weeks of conception. Such surgical termination of pregnancy is allowed by law only in certain circumstances where the doctors decide that continuance of pregnancy can affect the health of mother or of unborn child gravely. Some people, however, misuse the technique of surgical termination of pregnancy for ulterior motive to get rid of female foetus.

10th Class Biology

80

23.

n order to have a male child , some misguided people in our country get the sex of their unborn child determined by ultrasound technique , and if it is a female foetus, they get it removed by surgery.This killing of the unborn girl child is called female foeticide. Female foeticide is reducing the number of girls drastically in some societies of our country.For a healthy society, the male-female sex ratio must be maintained at almost the same level.Due to reckless female foeticide, the male-female child sex ratio is declining at an alarming rate in some sections of our society. This must be stopped immediately. Female foeticide is a matter of shame for the couples who go for it nd also for the doctors who perform such surgical abortions for earning some quick money. Let us not forget that our mother is a female, our sister is a female, and our wife is also a female.Then why not have a female as our daughter ? Remember, daughters are no less than sons.Our Government has already enacted laws to ban prenatal determination of sex of foetuses. These laws must be enforced strictly to save our society from the grave dangers of female foeticide in the long run. Sexually Transmitted Diseases (STD) The diseases which are spread by sexual contact with an infected person are called sexually transmitted diseases (or STD). Thus, a healthy person can get STD by making sexual contact with an infected person. Some of the common sexually transmitted diseases are : Person suffering from AIDS (i) Gonorrhoea, (ii) Syphilis, and(iii) A I D S Human Immun odeficiency Virus (Acquired Immune Deficiency Syndrome). Gonorrhoea and syphilis are caused by bacteria. The bacteria which cause these diseases spread through sexual contact with an infected person. The most common symptoms of the these sexually transmitted diseases are burning sensation at urination, passing of urethral discharge (containing pus) and sores in the genitals. Gonorrhoea and syphilis are curable diseases. AIDS disease is caused by a virus called HIV (Human Immunodeficiency Virus). AIDS damages the body’s immune system so that the body becomes weak and cannot protect itself against infection. So, AIDS is a very dangerous disease which leads to death. No definite cure has been found for the AIDS disease so far.

WORKSHEET 3 1. 2. 3.

4.

5.

6.

One of the following is not a part of the human male reproductive system. This is : (A) testis (B) oviduct (C) seminal vesicle (D) prostrate gland Which of the following is not a sexually transmitted disease ? (A) gonorrhoea (B) hepatitis (C) syphilis (D) AIDS Which of the following method of contraception protects a person from acquiring a sexually transmitted disease? (A) oral pills (B) condom (C) copper-T (D) surgery In which one of the following birth control methods, a small portion of oviducts of a woman is removed by surgical operation and the cut ends are ligated ? (A) copper-T (B) tubectomy (C) vasectomy (D) diaphragm One of the following is a surgical method which prevents the sperms from reaching the ovum and pregnancy does not occur. This method is : (A) IUCD (B) vasectomy (C) condom (D) tubectomy Fertilisation results immediately in the formation of: (A) a zygote (B) an embryo (C) a placenta (D) a foetus

How do organisms reproduce 7.

8. 9. 10.

11. 12.

13.

14.

15.

16.

17.

18.

19.

81

Which one of the following best describes the function of the umbilical cord ? It: (A) feeds the embryo with digested substances. (B) conveys nutrients and wastes to and from the embryo respectively (C) removes waste matter from the embryo to the mother’s blood. (D) supplies oxygenated blood from the mother to the embryo. The sexually transmitted disease which is caused by bacteria is : (A) malaria (B) diarrhoea (C) gonorrhoea (D) AIDS AIDS is a deadly disease which is caused by: (A) a protozoan (B) a fungus (C) a bacterium (D) a virus The advantage that internal fertilisation has over external fertilisation is that in internal fertilisation : (A) new off-springs are exactly like the parent (B) production of large numbers of gametes is unnecessary (C) copulation and fusion of gametes is passive (D) fewer individuals are produced The characteristics transmitted from parents to offspring are present in : (A) cytoplasm (B) ribosome (C) golgi bodies (D) genes Characters that are transmitted from parents to offspring during sexual reproduction show : (A) only similarities with parents (B) only variations witin parents (C) both similarities and variations with parents (D) neither similaritesnor variations with parents The number of chromosomes in parents and offsprings of a particular species remains constant due to : (A) doubling of chromosomes after zygote formation (B) halving of chromosomes during gamete formation (C) doubling of chromosomes after gamete formation (D) halving of chromosomes after gamete formation The correct sequence of organs in the male reproductive system for the transport of sperms is : (A) testis  vas deferens  urethra (B) testis  ureter  urethra (C) testis  urethra  ureter (D) testis  vas deferens  ureter In human males, the testes lie in the scrotam outside the body because it helps in the : (A) process of mating (B) formation of sperms (C) easy transfer of sperms (D) all the above Which among the following are not the functions of testes at puberty ? (i) formation of germ cells (ii) secretion of testosterone (iii) development of placenta (iv) secretion of estrogen (A) (i) and (iii) (B) (i) and (iii) (C) (ii) and (iv) (D) (iii) and (iv) During adolescence, several changes occur in the human body. Mark one change from the following associated with sexual maturation in boys : (A) loss of milk teeth (B) increase in height (C) cracking of voice (D) weight gain In human females, an event that indicates the onset of reproductive phase is : (A) growth of body (B) change in hair pattern (C) change in voice (D) menstruation The offsprings formed as a result of sexual reproduction exhibit more variations because : (A) sexual reproduction is lengthy process (B) genetic material comes from two parents of different species (C) genetic material comes from two parents of same species (D) genetic material comes from many parents

82 20.

21.

22. 23.

24. 25.

26.

27.

28.

10th Class Biology One of the following occurs in the reproductive system of flowering plants as well as that of humans. This is: (A) vas deferens (B) anther (C) ovary (D) style Which among the following statements are true for unisexual flowers ? (i) They possess both stamen and pistil (ii) They possess either stamen or pistil (iii) They exhibit cross pollination (iv) Unisexual flowers possessing only stamens cannot produce fruits (A) (i) and (iv) (B) (ii), (iii) and (iv) (C) (ii) and (iii) (D) (i), (iii) and (iv) One of the following process does not lead to the formation of clones. This is (A) fission (B) fertilisation (C) fragmentation (D) tissue culture The correct sequence of reproductive stages occurring in flowering plants is : (A) gametes, zygote, embryo, seed (B) zygote, gametes, embryo, seed (C) seed, embryo, zygote, gametes (D) gametes, embryo, zygote, seed The ratio of number of chromosomes in a human zygote and a human sperm is : (A) 2:1 (B) 3 : 1 (C) 1:2 (D) 1 : 3 The normal body cell of an organism contains 28 pairs of chromosomes. The number of chromosomes present in its germ cell will be : (A) 28 (B) 14 (C) 56 (D) 42 When a human female reaches a certain age then vaginal bleeding occurs for a few days after regular time intervals. (a) What is this process known as (i) in scientific terms, and (ii) in everyday language ? (b) At what approximate age this process starts in human females ? What is the human female said to have attained at this stage ? (c) After how much time is this process repeated ? For how many days this process usually lasts ? (d) What does the onset of this process in human females signify ? (e) At which particular event in the life of a human female this process stops temporarily but starts again? (f) At which approximate age of human female this process stops permanently ? X and Y are two human beings. The organ A in the reproductive system of X releases a mature gamete B once a month which goes into a tube-like structure C through a funnel-like opening. The organ D in the reproductive system of Y makes and releases gametes E which pass through a duct F and are introduced by an organ of Y, into the body of X. B and E fuse together in C to form a new cell G. The cell G divides repeatedly to form a ball of cells H which gets embedded in the lining of organ I of reproductive system of X where it grows and develops into a baby. (a) Name (i) organ A, and (ii) gamete B. (b) Write two names of tube-like structure C. (c) Name (i) organ D, and (ii) gamete E. (d) Write two names of duct F. (e) Name (i) cell G (ii) ball of cells H, and (iii) organ I. (f) Out of X and Y, which one is (i) male, and (ii) female ? When a fertilised egg E formed in the oviduct of a human female divides repeatedly to form an embryo, the embryo gets implanted in the thick and soft lining of the uterus. After this a disc-like special tissue T develops between the uterus wall and embryo through which all the requirements of the developing embryo (and foetus) are met from the mother’s body. The embryo is connected to the tissue T through a string like structure S. (a) What is the other name of fertilised egg cell E ? (b) What is the name of tissue T ?

How do organisms reproduce

29.

30.

31.

32.

33.

83

(c) Name the string-like structure S . (d) Name two substances which pass from mother’s blood to embryo through tissue T and, one type of substance which passes from embryo to mother’s blood. (e) What happens to S when the baby is born ? Why ? When a female child is born, her ovaries already contain thousands of immature eggs (or ova) contained in immature structures A. On maturing, A bursts open and an egg shoots out of the ovary in a process called B. The process B starts in the females at puberty and occurs again and again after a time period x. Before every occurrence of process B, the inner lining of uterus becomes thick and soft with lots of blood vessels in it. When the egg cell gets fertilised by a sperm, then an event C occurs in the life of mature human female which lasts for time period y leading to the birth of baby. If, however, the egg cell released by the ovary does not get a sperm to fuse with, then the thick and soft inner lining of uterus breaks down and comes out of the female’s body in an event called D. The occurrence of event D is controlled by chemical substances E. (a) What are A ? (b) What is process B ? (c) What is the time period x ? (d) Name the event C. (e) How much is the time period y ? (f) What is the name of process D ? (g) Name the chemical substances E. In the surgical method of birth control available for males, the structures A in the reproductive system are cut and ligated (tied up) at both ends. This prevents the reproductive cells B from coming out from the organs C where they are made in the male body. Since B cannot come out from the male body, they cannot fuse with cell D in the body of a female and hence pregnancy is prevented. (a) What are structures A ? (b) What are cells B ? (c) Name the organs C. (d) What is cell D ? (e) What is the name of this surgical procedure for birth control available to males ? In the surgical method of birth control available for human females, the structures P in the reproductive system are cut and ligated (tied up) properly at both ends. This prevents the reproductive cell Q released by an organ R from entering the structures P so that Q is not available to fuse with another reproductive cell S coming from the male reproductive system. In this way, pregnancy is prevented. (a) What are structures P ? (b) What is cell Q ? (c) Name the organ R. (d) What is the reproductive cell S ? (e) What is the name of this surgical method of birth control available to females ? The human males use a device X made of a very thin rubber sheet as a covering on the male organ to prevent pregnancy. This device traps the gametes Y in it. In order to prevent pregnancy, the human females use a device Z which is a circle of rubber with a metal spring around it. The device Z is put inside the vagina to cover the cervix. It stops Y from going into the uterus. (a) What is device X ? (b) What are Y ? (c) Name the device Z. (d) What is the general name of these methods of birth control (or preventing pregnancy) ? (e) The use of which contraceptive device, X or Z, can protect the persons from sexually transmitted diseases ? A woman uses pills A as a method of birth control (or preventing pregnancy). The pills A stop the ovaries from releasing ovum into oviducts. Another woman uses pills B as a method of birth control. The pills B kill the sperms and prevent pregnancy. (A) What do the pills A contain ? (B) What is the common name of pills A ? (C) What do the pills B contain ? (D) What is the common name of pills B ? (e) What is the general name of these methods of birth control ?

84

1.

2.

3. 4. 5.

6. 7. 8.

9. 10.

11. 12.

13. 14.

15.

16.

17.

10th Class Biology

The two organisms which can regenerate fully from their cut body parts are : (A) Paramecium and Hydra (B) Hydra and Amoeba (C) Planaria and Leishmania (D) Hydra and Planaria The two types of organisms which produce colonies by the process of budding are : (A) Hydra and Corals (B) Yeast and Sponges (C) Corals and Sponges (D) Hydra and Yeast Spore formation is the most common asexual method of reproduction in : (A) protozoa (B) tubers (C) fungi (D) algae An alga which reproduces by the asexual reproduction method called fragmentation is : (A) Rhizopus (B) Salmonella (C) Plasmodium (D) Spirogyra The organisms which can reproduce by fragmentation are : (A) Corals and Sponges (B) Corals and Spirogyra (C) Sea anemone and Spirogyra (D) Sponges and Sea anemones Binary fission describes the type of reproduction where the organism divides to form : (A) Many spores (B) Two daughters (C) Many buds (D) Two hyphae The cut part of a plant stem (without roots) which is used in grafting is called : (A) stock (B) stump (C) scion (D) graft The cut part of plant stem (having roots and fixed to ground) which is used in the process of grafting is known as : (A) stock (B) scion (C) cutting (D) bud Multiple fission occurs in one of the following. This is : (A) bread mould (B) kala-azar parasite (C) flatworm (D) malaria parasite An organism having a whip-like structure at one end which reproduces by the process of binary fission is : (A) Hydra (B) Paramecium (C) Leishmania (D) Plasmodium A tiny animal having tentacles which reproduces by growing buds on the sides of its body is : (A) Planaria (B) Yeast (C) Amoeba (D) Hydra An organism which can reproduce by two asexual reproduction methods one similar to the reproduction in yeast and the other similar to the reproduction in Planaria is : (A) Spirogyra (B) Bryophyllum (C) Hydra (D) Sea anemone Stock and scion are involved in the artificial propagation method known as : (A) tissue culture (B) layering (C) grafting (D) cuttings In asexual reproduction, two offsprings having the same genetic material and the same body features are called : (A) callus (B) twins (C) clones (D) chromosomes The method of asexual reproduction in plants in which callus is produced is : (A) micro propagation (B) vegetative propagation (C) regeneration (D) fragmentation A Planaria worm is cut horizontally in the middle into two halves P and Q such that the part P contains the whole head of the worm. Another Planaria worm is cut vertically into two halves R and S in such a way that both the cut pieces R and S contain half head each. Which of the cut pieces of the two Planaria worms could regenerate to form the complete respective worms ? (A) only P (B) only R and S (C) P, R and S (D) P, Q, R and S The anther contains : (A) sepals (B) ovules (C) carpel (D) pollen grains

How do organisms reproduce 18. 19.

20.

21.

22.

23.

24. 25. 26.

27.

85

Which of the following is not a part of the female reproductive system in human beings ? (A) ovary (B) uterus (C) vas deferens (D) oviducts In a flower, the parts that produce male and female gametes are respectively : (A) sepal and anther (B) filament and stigma (C) anther and ovary (D) stamen and style Which of the following is the correct sequence of events of sexual reproduction in a flower ? (A) pollination, fertilisation, seed, embryo (B) seed, embryo, fertilisation, pollination (C) pollination, fertilisation, embryo, seed (D) embryo, seed, pollination, fertilisation The length of pollen tube depends on the distance between : (A) pollen grain and upper surface of stigma (B) pollen grain on upper surface of stigma and ovule (C) pollen grain in anther and upper surface of stigma (D) upper surface of stigma and lower part of style Which of the following statements are true for flowers ? (i) flowers are always bisexual (ii) they contain sexual reproductive organs (iii) they are produced in all groups of plants (iv) after fertilisation they give rise to fruits (A) (i) and (iv) (B) (ii) and (iii) (C) (i) and (iii) (D) (ii) and (iv) Which of the following statements are true for sexual reproduction in flowering plants ? (i) it requires two types of gametes (ii) fertilisation is a compulsory event (iii) it always results in the formation of zygote (iv) offsprings formed are clones (A) (i) and (iv) (B) (i), (ii) and (iv) (C) (i), (ii) and (iii) (D) (ii), (iii) and (iv) The part of a seed which grows and develops into root on germination is : (A) cotyledon (B) plumule (C) follicle (D) radicle The male gametes in a flower and in a human are produced respectively in : (A) stigma and ovary (B) anther and style (C) ovary and testes (D) anther and testes The flask-shaped organ A at the centre of a flower is surrounded by a number of little stalks B having swollen tops which lie just inside the ring of petals. (a) Name A. What are the various parts of A ? (b) Which part of A contains gametes ? (c) Name B. What is the swollen top of B known as ? (d) What does the swollen top of B contain ? (e) Out of A and B, which one is (i) male part, and (ii) female part of the flower ?

When an insect sits on the flower of a plant then some particles A present in the top of little stalks in flower attach to its body hair. When this insect now sits on the flower of another similar plant, then particles A attached to the hair of insect are put on the top of a flask-shaped organ at the centre of flower. The particle A grows a long tube B from the top of flask-shaped organ through which C moves down and reaches the bottom part of flask-shaped organ. Here C fuses with the nucleus of D contained in structure E. The fusion of C and D forms a new cell F which grows and develops into a seed of the plant. (a) What are particles A ? What is the process of transferring A from one flower to another flower of similar plant by the insect known as ? (b) What is the name of tube B ? (c) What is C which moves down through the tube B ? (d) Name D and E. (e) What is F ?

86 28.

29.

30.

10th Class Biology A woman uses a device X made of a common metal for preventing pregnancy. This device works by preventing the implantation of fertilised egg cell (or embryo) in the female organ Y. (a) What are the two names of device X ? (b) Name the organ Y. (c) Can this method of contraception protect a woman from acquiring a STD ? A, B and C are three common STDs. A and C are caused by bacteria whereas B is caused by a virus D. The virus D reduces the immunity of the infected person to such a low level that the person can die of even very mild diseases. (a) What could A and C be ? (b) What is B ? (c) Name the virus D ? (d) How can A, B and C be caused ? (e) Out of A, B and C, which one does not have a definite cure as yet ? The germ cell A produced by a person X is round in shape and it fuses with another germ cell B ha long tail and produced by a person Y. The fusion of A and B produces a new cell C. The cell C divides repeatedly and grows inside the organ D of person X to form E in which the body features of the unborn baby are not much developed. E grows further to form F in which the various body features of the unborn baby (like hands, legs, head, eyes, and ears, etc.) can be identified. F grows further and ultimately forms a baby. What are A, B, C, D, E and F ? Out of the two persons X and Y, which one is male and which one female ?

HEREDITY & EVOLUTION

CHAPTER

4 1.



Variations



Evolution



Rules for the inheritance of Traits :



Darwin’s Theory of Evolution

Mendel’s Contribution



Speciation



Acquired and Inherited Traits

Introduction A recognisable feature of a human being like height, complexion, shape of hair, colour of eyes, and shape of nose and chin, etc, are called ‘characters’ or ‘traits’. The transmission of characters from the parents to their offsprings is called heredity.

2.

Variations •

The differences in characters from their off springs are known as variations. • Here is an example of variations in human beings which involves our ears. The lowest part of our ear is called earlobe. In most of the people, the earlobe is ‘hanging’ and it is called free earlobe. In some people, however, the earlobe is closely attached to the side of the head and it is called attached earlobe. Thus, most people have free earlobes whereas some people have attached earlobes. So, the free earlobes and attached earlobes are the two variations found in human population. • The number of variations produced during sexual reproduction is, however, very large. Accumulation of Variations • The variations produced in organisms during successive generations get accumulated in the organisms. • The great advantage of variation to a species is that it increases the chances of its survival in a changing environment.

3.

Pre-requesites: Understanding of Basic Terms • •

•

•

Chromosome is a thread-like structure in the nucleus of a cell formed of DNA which carries the genes . Different organisms have different number of chromosomes in their nuclei. A gene is a unit of DNA on a chromosome which governs the synthesis of one protein that controls a specific characteristic of an organism. Genes are actually units of heredity which transfer characteristics from parents to their offsprings during reproduction. Genes work in pairs. Genes are represented by letters. Genes controlling the same characteristics are given the same letters. For example, the gene for tallness is represented by the letter T whereas the gene for dwarfness is represented by the letter t. The gene which decides the appearance of an organism even in the presence of an alternative gene is known as a dominant gene. It dominates the recessive gene for the same characteristic on the other chromosome of the pair. The gene which can decide the appearance of an organism only in the presence of another identical gene is called a recessive gene. A single recessive gene cannot decide the appearance of an organism. The dominant gene is represented by a capital letter and the corresponding recessive gene is represented by the corresponding small letter.

10th Class Biology

88 •

•

• •

4.

1.

Genotype is the description of genes present in an organism. Genotype is always a pair of letters such as TT, Tt or tt (where T and t are the different forms of the same gene). Thus, the genotype of a tall plant could be TT or Tt whereas that of a dwarf plant is tt. The characteristic (or trait) which is visible in an organism is called its phenotype. For example, being ‘tall’ or ‘dwarf (short) are phenotypes of a plant because these traits can be seen by us or they are visible to us. When two parents cross to produce progeny , then their progeny is called First Filial Generation or F1 generation. When the first generation progeny cross (or breed) among themselves to produce second generation progeny, then this progeny is called Second Filial Generation or F2 generation. In other words, the generation produced by crossing two F1 progeny is called F2 generation.

Rules for the inheritance of Traits : Mendel’s Contribution Inheritance is the transmission of genetically controlled characteristics (or traits) from one generation to the next. We will now describe how Mendel studied the inheritance of characters or traits in various generations of pea plants cultivated by him. Monohybrid Inheritance and the Law of Segregation In order to trace the inheritance of a single pair of contrasting characteristics among the pea plants (like tall stem and short stem), Mendel crossed (cross-bred) the pure-bred pea plants differing in these traits and noted their occurrence in the progeny of succeeding generations. (i) Mendel first crossed pure-bred tall pea plants with pure-bred dwarf pea plants and found that only tall pea plants were produced in the first generation or F1 generation . No dwarf pea plants were obtained in the first generation of progeny. Conclusion: The first generation (or F1cross) showed the traits of only one of the parent plants : tallness. The trait of other parent plant, dwarfness, did not show up in the progeny of first generation.

(ii)

He crossed the tall pea plants of the first generation (F1 generation) and found that tall plants and dwarf plants were obtained in the second generation (or F2 generation) in the ratio of 3 : 1. Conclusion: Mendel noted that the dwarf trait of the parent pea plant which had seemingly disappeared in the first generation progeny, reappeared in the second generation.

Heredity & Evolution

89

Mendel said that the trait of dwarfness of one of the parent pea plant had not been lost, it was merely concealed or supressed in the first generation to re-emerge in the second generation. Mendel called the repressed trait of ‘dwarfness’ as ‘recessive trait’ and the expressed trait of ‘tallness’ as the ‘dominant trait’. So, the traits may be dominant or recessive. Other observations (i) All the pea plants produced from the hybrid tall parents of F1 generation, were either tall or dwarf. There were no plants with intermediate height in-between the tall and dwarf plants. So, the traits are inherited independently. This is because if the traits of tallness or dwarfness had blended , then medium sized pea plants would have been produced. (ii) The ratio of tall plants to dwarf plants in the F2 generation is 3 : 1. Since tallness is a dominant trait and dwarfness is a recessive trait, so we can also say that the contrasting progeny in the F2 generation occur in the ratio of 3 dominant to 1 recessive. The ratio 3 : 1 is known as the monohybrid ratio. Mendel’s first law of inheritance : The characteristics of an organism are determined by internal ‘factors’ which occur in pairs. Only one of a pair of such factors can be present in a single gamete. Explanation of Results of Monohybrid Inheritance (i) Each trait is determined by a pair of factors. This means that the pure-bred tall pea plant has two factors TT for the trait of tallness, and the pure-bred dwarf pea plant also has two factors tt for the trait of dwarfness. (ii) The factors of inheritance of tallness TT separate into two gametes T and T, and the factors for inheritance of dwarfness tt separate into two other gametes t and t. (iii) The gametes of tall pea plant then cross with the gametes of the dwarf pea plant by the process of fertilisation to form zygotes which then produce various progeny in the F1 generation (or first generation) which consists of all tall plants. Thus, the F1 generation possesses one factor of inheritance from each parent plant which were carried in gametes. The parental cross is shown clearly in the following chart :

(iv)

In the F1 generation shown above, all the progeny plants have factors Tt in which T is the factor for tallness which is a dominant trait. Since all the plants in the F1 generation have the factors Tt, so all of them are tall. The small letter t represents recessive trait of dwarfness, which does not show up in first generation in the presence of dominant trait T. When two hybrid, tall pea plants (Tt) produced in the first generation (Fj) are now cross-bred with each other, then they will produce second generation (F2) pea plants. This again happens by the separation of factors of inheritance of these tall plants into individual gametes and then crossing of the gametes during fertilisation as shown below :

10th Class Biology

90

2.

We can see from the above chart that in the F2 generation , the pea plants produced have genotype or inheritance factors TT, Tt, Tt and tt. Now, the plants having genotype TT, Tt and Tt all contain the factor T for dominant trait ‘tallness’, so all the three plants (TT, Tt and Tt) are tall. The plant having the genotype tt has both factors t for the recessive trait ‘dwarfness’, so it is a dwarf plant. Please note that though a single copy of factor T is enough to make a plant tall but both copies of factor t (that is tt) are necessary to make a plant dwarf (or short). In the F2 generation, we get 1 plant having genotype TT, 2 plants having genotype Tt and 1 plant having genotype tt. So, the genotypic ratio in monohydrid cross will be : TT : Tt : tt = 1 : 2 : 1 Again, in the F2 generation, we get 3 tall plants and 1 dwarf plant, so the phenotypic ratio in monohybrid cross will be : Tall plants : Dwarf plants = 3:1 This result is the same as that obtained by Mendel through experiments. Dihybrid Inheritance and the Law of Independent Assortment Dihybrid inheritance involves the inheritance of two Dihybrid inheritance involves the inheritance of two pairs of contrasting characteristics at the same time. The two pairs of contrasting characteristics chosen by Mendel were shape and colour of seeds : round-yellow seedsand wrinkled-green seeds . In order to trace the inheritance of two pairs of contrasting traits, Mendel crossed pea plants having round yellow seeds with pea plants having wrinkled-green seeds and noted their occurrence in the succeeding generations of pea plants. Mendel made the following observations: (i)

(ii)

Mendel first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea plants having wrinkled-green seeds and found that only round-yellow seeds were produced in the first generation. No wrinkled-green seeds were obtained in the F1 generation. Conclusion: Round shape and yellow colour of the seeds were dominant traits over the wrinkled shape and green colour of the seeds. When the F1 generation pea plants having round-yellow seeds were cross-bred by self pollination, then four types of seeds having different combinations of shape and colour were obtained in second generation or F2 generation. These were round-yellow, round- green, wrinkled-yellow and wrinkled-green seeds. Mendel collected a total of 556 F2 seeds and counted them shape wise and colour wise. He got the following result : Round-yellow seeds 315 Round-green seeds 108 Wrinkled-yellow seeds 101 Wrinkled-green seeds 32

Heredity & Evolution

91

The phenotypic ratio of different type of seeds can be written as : Round Round Wrinkled Wrinkled yellow : green : yellow : green = 315 : 108 : 101 : 32 seeds seeds seeds seeds = 9 : 3 : 3 : 1 Thus, the ratio of each phenotype (or appearance) of the seeds in the F2 generation is 9 : 3 : 3 :1. This is known as the dihybrid ratio. Explanation of Results of Dihybrid Inheritance In the dihybrid cross, the parent plants having the phenotype round-yellow seeds have the factors of inheritance or gene combination RRYY (in which RR are the dominant genes for round shape whereas YY are the dominant genes for yellow colour). On the other hand, the parent plants having the phenotype wrinkled-green seeds have the factors of inheritance or gene combination rryy (in which rr are the recessive genes for wrinkled shape and yy are the recessive genes for green colour). Keeping these points in mind, we can now show the dihybrid cross by drawing a chart as we did in the case of a monohybrid cross. The chart showing the dihybrid cross between pea plants having round-yellow seeds and wrinkled-green seeds is given below.

10th Class Biology

92

F2 ration:

Round yellow = 9 ; Round green = 3 Wrinkled yellow = 3; Wrinkled green = 1. This result is the same as that obtained by Mendel through experiments. An amazing thing about Mendel’s work is that he worked out the underlying rules of inheritance before any knowledge of DNA, chromosomes or genes became available. Let us answer one question now. How are characteristics (or traits) transmitted to progeny • Genes work in pairs. There is a pair of genes for each characteristic of an organism . Each parent possesses a pair of genes for each characteristic on a pair of chromosomes. However, each parent passes only one of the two genes of the pair for each characteristic to its progeny through gametes. • The male gamete and female gamete carry one gene for each characteristic from the gene pairs of parents. When a male gamete fuses with a female gamete during fertilisation, they make a new cell called zygote with a full set of genes . This zygote grows and develops to form a new organism having characteristics from both the parents which it has inherited through genes. The two genes responsible for a particular characteristic are always present on the corresponding positions of the pair of chromosomes. • For example, in the adjacent figure the two genes for the same characteristic (length of plant stem), are present on the corresponding positions of the pair of chromosomes. One gene of the pair is for ‘tallness’ and the other is for ‘dwarfness’. Please note that though the progeny inherits two genes for each trait from its parents but the trait shown by the progeny depends on which inherited gene is dominant of the two. How do Genes Control the Characteristics (or Traits) A gene is the section of DNA on a chromosome which codes for the formation of a protein controlling a specific characteristic (or trait) of the organism. Suppose a plant progeny has gene for the characteristic called ‘tallness’. Now, the gene for tallness will give instructions to the plant cells to make a lot of plant growth hormones. And due to the formation of excess of plant growth hormones, the plant will grow too much and hence become tall. On the other hand, if the plant has the gene set for dwarfness, then less plant growth hormones will be produced due to which the plant will grow less, remain short and hence become a dwarf plant.

Heredity & Evolution

93

Just like plants, the characteristics in animals (including human beings) are also transmitted from the parents through genes by the process of sexual reproduction. How Blood Groups are Inherited A person has one of the four blood groups : A, B, AB or O. This blood group system is controlled by a gene which has three different forms denoted by the symbols IA, IB and 1°. The genes IA and IB show no dominance over each other, that is, they are codominant. However, genes IA and IB both are dominant over the gene 1°. In other words, the blood gene 1° is recessive in relation to genes IA and IB. Although there are three gene forms (called alleles) for blood, but any one person can have only two of them. So, the blood group of a person depends on which two forms of the genes he possesses. (i) If the genotype (gene combination) is IAIA, then the blood group of the person is A. And if the genotype is IA1° even then the blood group is A (because 1° is a recessive gene). (ii) If the genotype is IBIB, then the blood group of the person is B. And if the genotype is IB 1° even then the blood group is B (because Pis a recessive gene). (iii) If the genotype is IAIB, then the blood group of the person is AB. (iv) If the genotype is I°I°, then the blood group of the person is O. Sex Determination The process by which the sex of a person is determined is called sex determination. Genetics is involved in the determination of the sex of a person. This can be explained as follows. The chromosomes which determine the sex of a person are called sex chromosomes. There are two types of sex chromosomes, one is called X chromosome and the other is called Y chromosome. (i) A male has one X chromosome and one Y chromosome . This means that half the male gametes or half the sperms will have X chromosomes and the other half will have Y chromosomes. (ii) A female has two X chromosomes but no Y chromosomes. This means that all the female gametes called ova (or eggs) will have only X chromosomes. The sex of a child depends on what happens at fertilisation : (a) If a sperm carrying X chromosome fertilises an ovum (or egg) which carries X chromosome, then the child born will be a girl (or female). This is because the child will have XX combination of sex chromosomes.

10th Class Biology

94 (b)

If a sperm carrying Y chromosome fertilises an ovum which carries X chromosome, then the child born will be a boy . This is because the child will have XY combination of sex chromosomes. Please note that it is the sperm which determines the sex of the child. This is because half of the sperms have X chromosomes and the other half have Y chromosomes. Thus, there is a 50 per cent chance of a boy and a 50 per cent chance of a girl being born to the parents. This is why the human population is roughly half males and half females.

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

10. 11. 12. 13.

14.

15.

Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings ? If the trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier ? Mendel said that the characteristics or traits of organisms are carried from one generation to the next by internal factors which occur in pairs. What is the modern name for these factors ? Some plants occur in one of the two sizes : tall or dwarf. This characteristic is controlled by one pair of genes. Tallness is dominant to dwarfness. Choose suitable letters for this gene pair. The sex of an infant is not a case of inheritance of characteristics. True or false. A new born child has an XY pair of chromosmes. Will it be a baby boy or a baby girl ? What type of plants were used by Mendel for conducting his experiments on inheritance ? The gene for red hair is recessive to the gene for black hair. What will be the hair colour of a person if he inherits a gene for red hair from his mother and a gene for black hair from his father ? Fill in the following blanks with suitable words : (a) Genes always work in ............................... (b) In pea plants, the gene for dwarfness is ............... whereas that for tallness is.............. (c) Most people have ....................... earlobes but some have ....................... earlobes. (d) A human gamete contains ....................... chromosomes whereas a normal body cell has ....................... chromosomes in it. (e) All races of man have ....................... blood groups. (f) The ................... chromosomes for a ................ are XX whereas that for a ................. are XY. Which of the following represent tall plants and which represent short plants (or dwarf plants) ? (a) Tt (b) tt (c) TT A man having blood group O marries a woman having blood group B and they have a daughter. What will be the blood group of the daughter ? In the F2 generation of a cross, progeny having different traits are produced in the ratio 3:1. State whether it is a monohybrid cross or a dihybrid cross ? Give one example of such a cross. (a) What is the genotype of dwarf plants which always produced dwarf offspring ? (b) What is the genotype of tall plants which always produced tall offspring ? (c) What is the genotype of (i) dwarf plants, and (ii) tall plants, whose parental cross always produces tall offspring ? (a) If a normal human cell has 46 chromosomes, how many chromosomes will be there in a human (i) sperm cell, and (ii) zygote ? (b) What sizes of plants are produced if both parents have genes Tt ? In a human, how many chromosmes are present in : (a) a brain cell ? (b) a sperm in the testes ? (c) an egg which has just been produced by the ovary ? (d) a skin cell ? (e) a fertilised egg ?

Heredity & Evolution 16.

17. 18.

19. 20.

21. 22. 23. 24.

25.

26.

27.

28.

29.

30.

31.

95

Gregor Mendel’s first law of genetics states “Of a pair of contrasted characters, only one can be represented in a gamete by its internal ‘factor’. (a) Give the modern name for this ‘factor’. (b) State where these factors are found in gametes. Does genetic combination of mother play a significant role in determining the sex of a new born baby ? Give the contrasting traits of the following characters in pea plant and mention which is dominant and which is recessive : (a) Yellow seed (b) Round seed When two parents are crossed, the offspring are referred to as (A) recessives (B) test cross (C) F1 generation (D) F2 generation A cross between two individuals results in a ratio of 9 : 3 : 3 : 1 for four possible phenotypes of progeny. This is an example of a : (A) dihybrid cross (B) monohybrid cross (C) test cross (D) none of these For his experiments on heredity, Mendel used : (A) papaya plants (B) potato plants (C) pea plants (D) pear plants The human animal which has an XY pair of chromosomes is called : (A) male (B) hybrid (C) female (D) doomed The science of heredity is known as : (A) biology (B) embryology (C) genetics (D) biochemistry A gene is a : (A) hybrid (B) heritable trait (C) pure breed (D) part of a chromosome that transmits a trait A normal cell of human body contains 23 pairs of chromosomes. The number of chromosomes in a sex cell (sperm or ovum) of a human being is most likely to be : (A) 46 (B) 23 (C) 21 (D) 42 In order to ensure that he had pure-breeding plants for his experiments, Mendel : (A) cross-fertilised each variety with each other (B) let each variety self fertilise for several generations (C) removed the female parts of the plants (D) removed the male parts of the plants. In the human blood grouping, the four basic blood types are type A, type B, type AB, and type O. The blood proteins A and B are : (A) simple dominant and recessive traits (B) incomplete dominant traits (C) codominant traits (D) sex-linked traits A plant with two ‘small’ genes breeds with a plant with two ‘tall’ genes to produce : (A) small plants and tall plants in the ratio 1:3 (B) all small plants (C) all tall plants (D) tall plants and small plants in the ratio 3 :1 A pregnant woman has an equal chance of her baby being blood group A or blood group AB. Which one of the following shows the possible genotypes of the woman and the father of her child ? (A) IAIA and IB1° (B) IAIB and IB1° (C) IA1° and IB1° (D) IAIB and IA1° The palisade cells of a species of plant contain 28 chromosomes. How many chromosomes will there be in each gamete produced by the plant ? (A) 56 (B) 28 (C) 14 (D) 4 The sex of a child is determined by which of the following ? (A) the length of the mother’s pregnancy (B) the length of time between ovulation and copulation (C) the presence of an X chromosome in an ovum (D) the presence of a Y chromosome in a sperm

96 32. 33.

34. 35.

36.

37.

38.

39. 40.

41.

42. 43.

44.

45.

10th Class Biology A zygote which has inherited an X chromosome from the father will develop into : (A) baby boy (B) baby girl (C) adult (D) either boy or girl Which of the following statement is incorrect ? (A) for every hormone there is a gene (B) for every protein there is a gene (C) for production of every enzyme there is a gene (D) for every type of fat there is a gene If the ratio of each phenotype of the seeds of pea plants in the F2 generation is 9 : 3 : 3 : 1, it is known as: (a) tetrahybrid ratio (B) monohybrid ratio (C) dihybrid ratio (D) trihybrid ratio In humans, if gene B gives brown eyes and gene b gives blue eyes. What will be the colour of eyes of the persons having the following combination of genes ? (a) Bb (b) bb (c) BB Pure-bred pea plants A are crossed with pure-bred pea plants B. It is found that the plants which look like A do not appear in ¥x generation but re-emerge in F2 generation. Which of the plants A and B are : (i) tall, and (it) dwarf ? Give reason for your answer. Pure-bred tall pea plants are first crossed with pure-bred dwarf pea plants. The pea plants obtained in F1 generation are then cross-bred to produce F2 generation of pea plants. (a) What do the plants of F1 generation look like ? (b) What is the ratio of tall plants to dwarf plants in F2 generation ? (c) Which type of plants were missing in F1 generation but reappeared in F2 generation ? A plant has two varieties, one with red petals and the other with white petals. When these two varieties are cross-pollinated, all the offsprings have red petals ? (a) Which gene is dominant ? (b) Choose suitable letters to represent the two genes. A red-haired woman marries a brown-haired man, and all the children are brown haired. Explain this genetically. A black mouse mates with a brown mouse, and all the offsprings are black. (a) Why are no brown offsprings produced ? (b) If two of the black offpsrings mate with each other what kind of offspring would you expect and in what proportions ? Give reason for your answer. (a) E is the gene for brown eye colour and and e is the gene for blue eye colour. Which gene is (i) recessive, and (ii) dominant ? (b) Both father and mother have the genes Ee in their cells. What colour are their eyes ? (c) Which combination of genes in the zygote will produce children with blue eyes ? (d) Which combinations of genes in the zygote will produce children with brown eyes ? What are the possible blood groups likely to be inherited by children born to a group A mother and a group B father ? Explain your reasoning. A couple with a newborn baby is troubled that the child does not resemble either of them. Suspecting that a mixup occurred at the hospital, they check the blood type of the infant. It is type O. Because the father is type A and the mother type B, they conclude that a mixup has definitely occurred. Are they correct ? Give reason for your answer. A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits—blood group A or O — is dominant ? Why or why not ? A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggested that the genetic make up (or genotype ) of the tall parent can be depicted as : (a) TTWW (b) TTww (c) TtWW (d) TtWw Give reason for your choice.

Heredity & Evolution

97

SYNOPSIS 2 5.

Acquired and Inherited Traits • • •

• • •

•

A trait (or characteristic) of an organism which is ‘not inherited’ but develops in response to the environment is called an acquired trait. Suppose the tail of a mouse gets cut. The ‘cut tail’ of this mouse is also an acquired trait which has been been brought about by some agent in its environment. A man may know how to swim or roller skate or speak French or may have a scar on the face from a cut he got in an accident. All these are acquired traits (or characteristics) which the man has picked up (or acquired) himself as he goes through life. The man is not born with these traits and he cannot pass on these traits to his children. The acquired traits of organisms cannot be passed on to their future generations. The changes in the non-reproductive body cells of an organism cannot be inherited by its offsprings. This will become clear from the following examples. When the weight of a beetle is reduced too much due to starvation, then though there is a change in the normal body cells of the beetle but no change takes place in the genes (or DNA) present in its reproductive cells (or gametes). And since there is no change in the genes (or DNA) of gametes, this acquired trait (of low weight) of beetle cannot be inherited by its offsprings. So, if some generations of beetles are low in body weight because of the availability of less food, then this is not an example of evolution because this change cannot be inherited over generations. Whenever these beetles will get sufficient food, they will become healthy again and the trait of ‘low body weight’ will disappear. Let us discuss the other example now. If we breed some mice, all the progeny of mice will have tails, just like their parents. Now, if we cut the tails of these first generation mice surgically and breed them, we will get new mice, all with full tails. It has been observed that even after cutting the tails of mice for a number of generations, a tail-less mouse is never born. Actually, the cut tail of mice is an acquired trait which is never passed on to their progeny.

(a) First generation mice. All these have full tails

•

(b) The tails of all the mice are cut surgically.

(c) Second generation mice produced by breeding cut tail mice have full tails.

This is because cutting the tails of mice does not change the genes of their reproductive cells (or gametes). And since the acquired trait of ‘cut tails’ does not bring about a change in the genes of mice, this trait cannot be passed on to their next generations. From this discussion we conclude that the experiences of an individual during its life time (called acquired traits) cannot be passed on to its progeny, and hence cannot lead to evolution (because they are not caused by the change in genes). A trait (or characteristic) of an organism which is caused by a change in its genes (or DNA) is called an inherited trait. Inherited traits can be passed on to the progeny of the organism because they have produced changes in the genes (or DNA) of the organism. Suppose there is a population of red beetles in the green bushes. Again suppose that a colour variation arises during reproduction so that there is one beetle which is green in colour (instead of red). This change of green colour in the beetle has been broughtabout by a change in the genes (or DNA) of the reproductive cells. The green colour of this beetle is an inherited trait which can be passed on to the next generations.

98

•

•

6.

10th Class Biology The change from red beetle to green beetle can be considered to be an example of evolution because it helps in its survival by mixing with green bushes. Inherited traits actually mean the characteristics which we receive from our parents. This point will become more clear from the following example. Suppose a father has red curly hair, brown eyes, a snub nose and a cleft chin . Again suppose that the mother has straight black hair, blue eyes, a long thin nose and a pointed chin The children in the family inherit some characteristics from each of their parents. For example, two children have red hair like father but one of them has straight red hair while the other one has curly red hair. The two children have black hair like the mother. Again, two children have brown eyes like father but the other two have blue eyes like the mother. And finally, two children have snub nose and cleft chin like father whereas the other two have a long thin nose and a pointed chin.

Evolution Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of years in which new species are produced. Since the evolution is of the living organisms, so it is also called ‘organic evolution’. It is through the constant process of evolution taking place in the organisms since the origin of life that such an enormous variety of plants and animals have come to exist on this earth at present. All the plants and animals (or organisms) which we see today around us have evolved from some or the other ancestors that lived on this earth long, long ago.

The development of ‘pterosaur’ (an ancient flying reptile) from a big lizard is an example of evolution. The process of evolution will become clear from the following example of ‘pterosaur’. Pterosaur is an anicient flying reptile which lived on the earth about 150 million years ago. The development of pterosaur is an example of evolution. It began life as a big lizard which could just crawl on land Over millions of years, small folds of skin developed between its feet which enabled it to glide from tree to tree. Over many, many generations, spread over millions of years, the folds of skin, and the bones and muscles supporting them grew to form wings which could make it fly [see Figure 26(c)]. In this way, an animal which crawled on ground evolved into a flying animal. This evolution led to the formation of a new species (of a flying reptile). EVIDENCES FOR EVOLUTION 1. Homologous Organs Provide Evidence for Evolution There are many organs in different groups of animals or plants which all seem to be built from the same basic design but are used for many different purposes. These are called homologous organs. For example, the forelimbs of a man, a lizard (reptile), a frog (amphibian), a bird and a bat (mammal) seem to be built from the same basic design of bones , but they perform different functions. The forelimbs of a human (man), a lizard, a frog, a bird and a bat have the same basic design of bones.

Heredity & Evolution

2.

99

They are homologous organs, forelimbs of a human (man) are used for grasping; the forelimbs of a lizard are used for running; the forelimbs of a frog are used to prop up the front end of its body when at rest, and also act as shock absorbers when the frog lands back on the ground after a leap; whereas the forelimbs of a bird and a bat are modified for flying. Since the forelimbs of a human, a lizard, a frog, a bird and a bat have similar structures (or design) but perform different functions, they are the homologous organs. The presence of homologous forelimbs in humans (man), a lizard, a frog, a bird and a bat indicate that all these forelimbs have evolved from a common ancestral animal which had a ‘basic design’ limb. In other words, it tells us that a human, a lizard, a frog, a bird and a man, all have evolved from a common ancestor. Thus, the presence of homologous organs in different animals provides evidence for evolution by telling us that they are derived from the same ancestor who had the ‘basic design’ of the organ on which all the homologous organs are based. Please note that the wings of a butterfly (which is an insect) and the wings of a bat cannot be considered to be homologous organs because they have different basic designs (though they are used for the same purpose of flying). Analogous Organs Provide Evidence for Evolution Those organs which have different basic structure (or different basic design) but have similar appearance and perform similar functions are called analogous organs. The analogous organs provide the evidence for evolution. This point will become clear from the following discussion.

(a) wing of insect (b) Wing of bird There are many organs in different groups of animals which seem to be built from different basic structure but appear to be similar in shape and perform similar functions. These are called analogous organs. For example, the wings of an insect and a bird have different structures (the insects have a fold of membranes as wings which are associated with a few muscles whereas a skeleton, flesh and feathers support bird’s wings) but they perform the same function of flying . Since the wings of insects and birds have different structures (or different designs) but perform similar functions, they are analogous organs. Now, since the analogous organs have different basic design, so they do not indicate a common ancestor for the organism. The analogous organs provide evidence for the evolution in another way. The presence of analogous organs indicates that even the organisms having organs with different structures can adapt to perform similar functions for their survival under hostile environmental conditions. Thus, the presence of analogous organs in different animals

10th Class Biology

100

3.

provide evidence for evolution by telling us that though they are not derived from common ancestors, they can still evolve to perform similar functions to survive, flourish and keep on evolving in the prevailing environment. The analogous organs actually provide a mechanism for evolution. Fossils Provide Evidence for Evolution The remains (or impressions) of dead animals or plants that lived in the remote past are known as fossils. The fossils provide evidence for evolution. For example, a fossil bird called Archaeopteryx looks like a bird but it has many other features which are found in reptiles. This is because Archaeopteryx has feathered wings like those of birds but teeth and tail like those of reptiles. Archaeopteryx is, therefore, a connecting link between the reptiles and birds, and hence suggests that the birds have evolved from the reptiles. Thus, fossils provide the evidence that the present animals (and plants) have originated from the previously existing ones through the process of continuous evolution. We will now describe how fossils are formed. Usually, when organisms (plants or animals) die, their bodies will decompose by the action of micro-organisms in the presence of oxygen, moisture, etc. Sometimes, however, the conditions in the environment are such (like absence of oxygen or moisture, etc), which do not let the body of the organism to decompose completely. It is such body (or body part) of an organism which we get as fossil on digging the earth. In many cases the soft parts of the organisms get decomposed and what we get as a fossil is a skeleton of hard parts (like bones, etc). Even the soft parts of the plants and animals (which usually decompose quickly) are sometimes preserved as fossils in the form of their impressions inside the rocks. For example, if a dead leaf gets caught in mud, it will not decompose quickly. The mud around the leaf will set around it as a mould, gradually harden to form a rock and retain the impression of the whole leaf. This forms a leaf fossil which can be dug out from the earth a long time later . The fossil of a dead insect caught in mud is also formed in a similar way to leaf fossil. All such preserved impressions of the body parts of the once living organisms are also called fossils. Fossils are obtained by digging into the earth. The age of fossils can be estimated in two ways : by the relative method, and by the carbon dating method. The relative method works like this : When we dig into the earth, we find fossils at different depths. The fossils which we find in layers closer to the surface of the earth are more recent; the fossils which are found in deeper layers are older; whereas the fossils found in the deepest layers of earth are the oldest ones. Fossils which we find today were once living objects. All the living objects contain some carbon-14 atoms which are radioactive. When a living object dies and forms fossil, its carbon-14 radioactivity goes on decreasing gradually. In the carbon dating method, the age of fossils is found by comparing the carbon-14 radioactivity left in fossils with the carbon-14 radioactivity present in living objects today. There are various kinds of fossils. Some of the important fossils which have been studied are those of ammonite, trilobite and dinosaur. Ammonites were the invertebrate animals (molluscs) with a flat, coiled, spiral shell which lived in the sea [Figure (a)]. The estimation of the age of ammonite fossils have told us that they are about 180 million years old. This means that ammonites lived in the sea about 180 million years ago. Another invertebrate animal fossil which has been studied is that of trilobite [Figure (b)]. Trilobites were marine arthropods which were common between 400 to 600 million years ago. Dinosaurs are extinct carnivorous or herbivorous reptiles The estimation of the age of dinosaur fossils [Figure (c)] have told us that they first appeared on earth about 250 million years ago and became extinct about 65 million years ago. It is clear from the above discussion that we can even study about those species which are extinct (no longer exist), by studying their fossils which are found during the digging of earth.

Heredity & Evolution

(a) Fossil of ammonite

7.

101

(b) Fossil of trilobite

(c) Fossil of dinosaur skull

Darwin’s Theory of Evolution Charles Robert Darwin gave the theory of evolution in his famous book ‘The Origin of Species’. The theory of evolution proposed by Darwin is known as ‘The Theory of Natural Selection’. This theory is called the theory of natural selection because it suggests that the best adapted organisms are selected by nature to pass on their characteristics (or traits) to the next generation. Darwin’s theory of evolution applies to plants as well as animals. Darwin’s theory of evolution can be described as follows : 1. Within any population, there is natural variation. Some individuals have more favourable variations than others. 2. Even though all species produce a large number of offsprings, populations remain fairly constant naturally. 3. This is due to the struggle between members of the same species and different species for food, space and mate. 4. The struggle for survival within populations eliminates the unfit individuals. The fit individuals possessing favourable variations survive and reproduce. This is called natural selection (or survival of the fittest). 5. The individuals having favourable variations pass on these variations to their progeny from generation to generation. 6. These variations when accumulated over a long period of time, who gave the theory of evolution, lead to the origin of a new species. Understanding Darwin’s Theory We will now understand Darwin’s theory of evolution by ‘natural selection’ by taking an example. No two animals are ever exactly alike. So some changes always appear when animals produce their progeny by sexual reproduction. For example, one of the progeny may be tall (having long legs) than the other progeny. Thus, there may be a variation of height in the progeny [Figure (a)]. Now, the advantage of long legs to the progeny is that when no food (grass, etc.) is available on the ground, then this progeny having long legs can reach the leaves on tall trees, eat them as food and survive [Figure (b)]. On the other hand, the progeny which have short height (due to short legs) cannot reach the leaves on tall trees, they will not get any food, they will starve and hence die . Thus, nature has selected the animal with long legs to survive (because it is the fittest animal under these circumstances). Now, since long legs help in survival, the long-legged animals will live long enough to produce their offsprings. The offspring will inherit long legs. So, all the future generations will have long-legged animals [Figure (c)]. In this way, the animals having short legs have evolved into animals having long legs due to variation. This is an example of evolution.

(a)

(b)

(c)

10th Class Biology

102

Natural selection is the process of evolution of a species whereby characteristics which help individual organisms to survive and reproduce are passed on to their offspring, and those characteristics which do not help are not passed on. Though Darwin’s theory was widely accepted, but it was criticised on the ground that it could not explain ‘how the variations arise’. With the progress in genetics, the source of variations was explained to be the ‘genes’. Genes vary in natural population. Genetic variation is the raw material of evolution. So, the Darwin’s theory was modified accordingly. These days, the most accepted theory of evolution is the Synthetic Theory of Evolution in which the origin of species is based on the interaction of ‘genetic variation’ and ‘natural selection’. Sometimes, a species may completely die out. It may become extinct. Dodo was a large flightless bird which has become extinct . Once a species is extinct, its genes are lost for ever. It cannot re-emerge at all. The small numbers of surviving tigers are a cause of worry from the point of view of genetics because if they all die out and become extinct, their genes will be lost for ever . Our coming generations will not be able to see tigers at all. We should, therefore, make all out efforts to protect tigers to prevent them from extinction.

8.

Speciation A species is a population of organisms consisting of similar individuals which can breed together and produce fertile offspring. The process by which new species develop from the existing species is known as speciation. In simple words, the formation of new species is called speciation. Important factors which could lead speciation are as follows: (i) Geographical isolation of a population caused by various types of barriers (such as mountain ranges, rivers and sea). The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population. (ii) Genetic drift caused bv drastic changes in the frequencies of particular genes by chance alone. (iii) Variations caused in individuals due to natural selection. Evolution of Eyes First of all the rudimentary eye (basic eye) like that of a flatworm (Planaria) was formed. The eyes of flatworm are very simple that are actually just ‘eye-spots’ which can detect light. Even these rudimentary eyes provide a survival advantage to flatworm. Starting from this basic design, more and more complex eyes were then evolved in various organisms. Most of the animals have eyes. For example, the insects, octopus and invertebrates, all have eyes. The structure of eyes in each of these organisms is, however, different which suggests their separate evolutionary origins. The evolution of simple eyes called rudimentary eyes, eye is an example of evolution by stages. Evolution of Feathers Sometimes an evolutionary change produced in an organism for one purpose later on becomes more useful for an entirely different function. For example, birds evolved feathers as a means of providing insulation to their bodies in cold weather but later on these feathers became more useful for the purpose of flying. Even some dinosaurs had feathers though they could not fly by using these feathers. Birds, however, adapted feathers for flying. The presence of feathers on birds tells us that the birds are very closely related to reptiles because dinosaurs (which had feathers) were reptiles Evolution by Artificial Selection In the evidence for evolution we have studied that very dissimilar looking structures can evolve from a common ancestral body design. But that was all guesswork about what happened in history long time ago. We will now give an example from the present time which will show that different looking organisms can in fact be created from the same basic design of the ancestor. The wild cabbage plant is a good example to prove that entirely different looking organisms can evolve from the same organism by the process of evolution. The only difference is that here we are using

Heredity & Evolution

103

artificial selection for evolution in place of natural selection. This will become clear from the following discussion. The farmers have been cultivating wild cabbage as a food plant for over two thousand years and have produced (or evolved) entirely different looking vegetables like cabbage, broccoli, cauliflower, kohlrabi and kale from it by artificial selection. (i) Some farmers wanted to have very short distances between the leaves of wild cabbage and produced the common variety of ‘cabbage’. (ii) When farmers opted for the arrested flower development of wild cabbage plant, it led to the production of another variety of cabbage called ‘broccoli’. (iii) Some farmers went in for sterile flowers of wild cabbage and developed another variety of cabbage called ‘cauliflower’. (iv) When farmers opted for the swollen parts of wild cabbage, it led to the evolution of a yet another variety of cabbage called ‘kohlrabi’. (v) And finally, the farmers wanted to grow large leaves of wild cabbage and ended up producing a leafy vegetable called ‘kale’ which is also a variety of wild cabbage. Now, wild cabbage is the ancestor and cabbage, broccoli, cauliflower, kohlrabi and kale are all its varieties which have been obtained by evolution ‘induced artificially’ by the farmers. The ordinary cabbage, broccoli, cauliflower, kohlrabi and kale look so different from their ancestor wild cabbage that if people had not seen it being done with their own eyes, they would never have believed that vegetables having such different structures can be evolved from the same ancestral vegetable plant. Evolution Should Not be Equated With Progress There is no real progress in the concept of evolution. Evolution is just the production of diversity of life forms and shaping of this diversity by the environmental selection. The only progress in evolution appears to be that more and more complex body designs of organisms have emerged over the ages. This will become clear from the following examples. When a new species is formed, it is not necessary that the old species will disappear (or get eliminated) from earth. It will all depend on the environment. Also it is not as if the newly formed species are in any way better than the older ones. It is simply that genetic drift and natural selection processes have combined to form a population having different body design which cannot interbreed with the older population. It is a common belief that chimpanzees are the ancestors of human beings. It is, however, not true that human beings have evolved from chimpanzees. Actually, both chimpanzees and human beings had a common ancestor long time ago. The two offsprings of that ancestor evolved in their own separate ways to form the modern day chimpanzees and human beings. Again, it is not as if the body designs of older organisms were inefficient. This is because many of the older and simpler forms of organisms still survive on earth. For example, one of the simplest and primitive life forms called ‘bacteria’ still inhabit some of the most inhospitable (or unfavourable) habitats such as hot springs, deep-sea thermal vents and the ice in Antarctica. Most other organisms cannot survive in such harsh environments.

9.

Human Evolution Human evolution has been studied by using the various tools of tracing evolutionary relationships like excavating (digging earth), carbon-dating, studying fossils and determining DNA sequences. There is so much diversity of human body and features on the earth that for a long time people used to talk about different ‘races’ of human beings. The human races were even identified on the basis of their skin colour and named as white, black, yellow or brown. It is now known that the so called human races have not evolved differently. In fact, there is no biological basis for dividing human beings into different ‘races’. All human beings (whether, white, black, yellow or brown) are a single species (called Homo sapiens). It has now been established by research that the earliest members of the human species {Homo sapiens) came from Africa. So, irrespective of where we have lived for the past few thousand years, we all come

10th Class Biology

104

from Africa. In other words, our genetic footprints tell us that we have African roots. About hundred thousand years ago, some of our ancestors left Africa while others stayed back. Those who left Africa slowly spread across the whole earth. Mendel’s experiments tell us the mode of inheritance of traits from one generation to the next and Darwin’s theory of evolution tells us how organisms develop from simple to more complex forms. But neither tells us anything about how life originated on earth (or began on earth). We will now discuss the origin of life on earth briefly. Origin of Life on Earth A British scientist J.B.S. Haldane suggested in 1929 that life must have developed from the simple inorganic molecules (such as methane, ammonia, hydrogen sulphide, etc.) which were present on the earth soon after it was formed. He said that the conditions on earth at that time (including frequent lightning) could have converted simple inorganic molecules into complex organic molecules which were necessary for life. These complex organic molecules must have joined together to form first primitive living organisms. Haldane also suggested from theoretical considerations that life (or living organisms) originated in the sea water. The theory of origin of life on earth proposed by Haldane was confirmed by experiments conducted by Stanley L. Miller and Harold C. Urey in 1953. They assembled an apparatus to create an early earth atmosphere which was supposed to of gases like methane, ammonia and hydrogen sulphide, etc., (but no oxygen), over water. This was maintained at a temperature just below 100°C and electric sparks were then passed through the mixture of gases (to simulate lightning) for about one week. At the end of one week, it was found that about 15 per cent of carbon (from methane) had been converted into simple compounds of carbon including ‘amino acids’ which make up protein molecules found in living organisms. This experiment provides the evidence that the life originated from inanimate matter (or lifeless matter) like inorganic molecules.

WORKSHEET 2 1. 2. 3. 4.

5. 6.

What name is given to the sequence of gradual changes over millions of years in which new species are produced ? State whether the following statement is true or false : Human beings have evolved from chimpanzees. The forelimbs of a frog, a bird and a man show the same basic design (or basic structure) of bones. What name is given to such organs ? Out of the wing of a bird, wing of an insect and the wing of a bat : (a) which two are homologous organs ? (b) which two are analogous organs ? Choose the one term from the following which includes the other three : broccoli, wild cabbage, cauliflower, cabbage Fill in the following blanks with suitable words : (a) The human forelimb and bat’s forelimb are an example of organs whereas an insect’s wing and a bat’s wing are an example of organs. (b) The evolution of eye is an example of evolution by (c) The scientific name of all human beings is (d) Broccoli has evolved from by the process of artificial selection. (e) The theory of natural selection for evolution was proposed by..................................

Heredity & Evolution 7.

8. 9. 10. 11. 12. 13. 15. 16. 17. 18.

19.

20.

21.

23.

105

Match the terms given in column I with those given in column II : Column I Column II (i) Fossil (a) A famous evolutionist (ii) A theory of evolution (b) Survival of the fittest (iii) Probable ancestor of birds (c) Petrified remains of prehistoric life (iv) Charles Darwin (d) Father of genetics (v) Gregor Mendel (e) Archaeopteryx In evolutionary terms, we have more in common with : (A) a Chinese school boy (B) a chimpanzee (C) a spider (D) a bacterium The human species has genetic roots in : (A) America (B) Africa (C) Australia (D) Antarctica Which of the following gas was not present in early earth atmosphere ? (A) Ammonia (B) Oxygen (C) Hydrogen sulphide (D) Methane A gradual change, over a long period, in a form of life is known as : (A) erosion (B) evolution (C) revolution (C) evaluation Scientists believe that all life originated in : (A) the sea (B) the soil (C) the ground (D) the air According to scientists, aves have evolved from : (A) mammals (B) amphibians (C) reptiles (D) arthropods The theory of evolution of species by natural selection was given by : (A) Mendel (B) Darwin (C) Dalton (D) Lamarck The term ‘father of genetics’ is used for the scientist : (A) Morgan (B) Mendel (C) Darwin (D) Marie Curie One of the following traits cannot be inherited. This one is : (A) colour of eyes (B) colour of skin (C) size of body (D) nature of hair Only one of the following characteristic of the parents can be inherited by their children. This one is : (A) deep scar on chin (B) snub nose (C) technique of swimming (D) cut nose Which of the following statement is incorrect with respect to variations ? (A) all variations in a species have equal chance of survival (B) change in genetic composition results in variations (C) selection of variations by environmental factors forms the basis of evolutionary process (D) variations are the minimum in asexual reproduction One of the following traits of the parents cannot be passed on to their future generations. This trait is : (A) cleft chin (B) pointed chin (C) scarred chin (D) broad chin Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution, this means that: (A) reptiles have evolved from birds (B) there is no evolutionary connection between reptiles and birds (C) feathers are homologous structures in both the organisms (D) birds have evolved from reptiles Select the incorrect statement from the following : (A) frequency of certain genes in a population changes over several generations resulting in evolution (B) reduction in the weight of an organism due to starvation is genetically controlled (C) low weight parents can have heavy weight progeny (D) traits which are not inherited over generations do not cause evolution.

106 24.

25.

26.

27.

28.

29.

30.

10th Class Biology New species may be formed if : (i) DNA undergoes significant changes in germ cells (ii) chromosome number changes in the gamete (iii) there is no change in the genetic material (iv) mating does not take place (A) (i) and (ii) (B) (i) and (iii) (C) (ii), (iii) and (iv) (D) (i), (ii) and (iii) According to the evolutionary theory, formation of a new species is generally due to : (A) sudden creation by nature (B) accumulation of variations over several generations (C) clones formed during asexual reproduction (D) movement of individuals from one habitat to another. Some of the important fossils which have been studied are those of organisms X, Y and Z. X were marine arthropods which were common between 400 to 600 million years ago. Y were the invertebrate animals (molluscs) with a flat, coiled, spiral shell which lived in the sea about 180 million years ago. Z are the extinct carnivorous or herbivorous reptiles which appeared on the earth about 250 million years ago and became extinct about 65 million years ago. What are X, Y and Z ? The farmers have been cultivating a food plant X for over two thousand years and have produced as many as five entirely different looking vegetables A, B, C, D and E from it. (a) What could the plant X be ? (b) What are A, B, C, D and E ? (c) What is the process of evolution involved in this example known as ? There are five animals A, B, C, D and E. The animal A uses its modified forelimbs for flying. The animal B uses its forelimbs for running whereas the animal C uses its forelimbs for grasping. The animal D can live on land as well as in water and uses its forelimbs to prop up the front end of its body when at rest. The animal E which respires by using spiracles and tracheae uses wings for flying but its wings are analogous to the modified forelimbs of animal A. (a) What could the animals A, B, C, D and E be ? (b) Why are the forelimbs of animals A, B, C and D called homologous organs ? (c) What does the existence of homologous organs in animals A, B, C and D tell us about their ancestors? (d) Why are the modified forelimbs of animal A and the wings of animal E called analogous organs ? (e) State whether animals A and E have a common ancestor or not. X, Y, and Z are three animals. The animal X can fly but animal Y can only run on ground or walls. The forelimbs of animals X and Y have the same basic design but they are used for different purposes such as flying and running respectively. The animal Z became extinct a long time ago. The study of fossils of Z tells us that it had some features like those of X and some like those of Y. In fact, Z is said to form a connecting link in the evolutionary chain of X and Y. (a) What could the animals X, Y and Z be ? (b) What name is given to the forelimbs like those of X and Y which have the same basic design but different functions ? (c) Name one feature in which Z resembled X. (d) Name one feature in which Z resembled Y. (e) Which is the correct evolutionary chain involving X, Y and Z : X  Z  Y or Y  Z  X? A population of red beetles lives in green bushes in a garden. Once during the process of breeding, a green beetle is produced. (a) State whether the change in colour of beetle is a process of evolution or not. (b) Can the new colour of green beetle be passed on to its next generations ? (c) What will be the advantage (if any) of the green colour to the beetle ? (d) State whether the production of green colour involved a change in genetic material or not.

Heredity & Evolution

1.

107

Which of the following may be used to obtain an F2 generation ? (A) allowing flowers on a parent plant to be self-pollinated (B) allowing flowers on an Fi plant to be self-pollinated (C) cross-pollinating an F! plant with a parent plant (D) cross-pollinating two parent plants

2.

The following results were obtained by a scientist who crossed the Fj generation of pure-breeding parents for round and wrinkled seeds. Dominant trait

Recessive trait

No. of F 2 offspring

Round seeds

Wrinkled seeds

7524

From these results, it can be concluded that the actual number of round seeds he obtained was: (A) 1881 3.

5.

6.

9.

(B) stereotype

(C) phenotype

(A) vegetative reproduction

(B) asexual reproduction

(C) sexual reproduction

(D) budding

(D) genotype

A cross between a tall plant (TT) and short plant (tt) resulted in progeny that were all tall plants because: (A) tallness is the dominant trait

(B) shortness is the dominant trait

(C) tallness is the recessive trait

(D) height of plant is not governed by gene T or t

The number of pair(s) of sex chromosomes in the zygote of humans is : (B) two

(C) three

(D) four

In peas, a pure tall plant (TT) is crossed with a pure short plant (tt). The ratio of pure tall plants to pure short plants in F2 generation will be : (A) 1 : 3

8.

(D) 5643

The exchange of genetic material takes place in :

(A) one 7.

(C) 2508

The visible characteristic in an organism is known as : (A) prototype

4.

(B) 22572

(B) 3 :1

(C) 1 :1

(D) 2 :1

The two versions of a trait (character) which are brought in by the male and female gametes are situated on : (A) copies of the same chromosome

(B) sex chromosomes

(C) two different chromosomes

(D) any chromosomes

Select the statements that describe characteristics of genes : (i) genes are specific sequence of bases in a DNA molecule (ii) a gene does not code for proteins (iii) in individuals of a given species, a specific gene is located on a particular chromosome

10th Class Biology

108 (iv) each chromosome has only one gene (A) (i) and (ii) 10.

11.

12.

13.

(B) (i) and (iii)

(C) (i) and (iv)

(D) (ii) and (iv)

Select the group which shares the maximum number of common characters : (A) two individuals of a species

(B) two species of a genus

(C) two genera of a family

(D) two genera of two families

A trait in an organism is influenced by : (A) paternal DNA only

(B) maternal DNA only

(C) both maternal and paternal DNA

(D) neither by paternal nor by maternal DNA.

In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosomes is/are : (i) large chromosome

(ii) small chromosome

(iii) Y chromosome

(iv) X chromosome

(A) (i) and (ii)

(B) (iii) only

(C) (iii) and (iv)

(D) (ii) and (iv)

A person first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea p l a n t s having wrinkled-green seeds and found that only A-B type of seeds were produced in the F1 generation. When F1 generation pea plants having A-B type of seeds were cross-bred by self- pollination, then in addition to the original round-yellow and wrinkled-green seeds, two new varieties A-D and C-B type of seeds were also obtained. (a) What are A-B type of seeds ? (b) State whether A and B are dominant traits or recessive traits. (c) What are A-D type of seeds ? (d) What are C-B type of seeds ? (e) Out of A-B and A-D types of seeds, which one will be produced in (i) minimum numbers, and (ii) maximum numbers, in the F2 generation ?

14.

The person A has only B chromosomes in all its gametes. On the other hand, another person C has chromosome D in half of gametes and chromosome E in the other half of gametes. When chromosomes B and D combine during fertilisation, a female zygote results. On the other hand, of B and E chromosomes produces a male zygote. (a) What are chromosomes (i) B (ii) D, and (iii) E ? (b) Out of B, D and E, which two chromosomes are of the same type ? (c) Which chromosome is smaller in size ? (d) What is the general name of chromosomes such as B and E ? (e) Out of the two persons A and C, which one is (i) male, and (ii) female ?

15.

Mendel first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea plants having wrinkled-green seeds and found that only round-yellow seeds were produced in the F1 generation. When Ft generation pea plants having round-yellow seeds were cross-bred by self pollination, then peas having round- yellow seeds, round green seeds, wrinkled-yellow seeds and wrinkled-green seeds were produced. Mendel collected a total of 2160 seeds. (a) What will be the number of

Heredity & Evolution

109

(i) round green seeds (ii) wrinkled green seeds (iii) round yellow seeds, and (iv) wrinkled-yellowseeds? (b) Which ‘ratio’ as established by Mendel have you made use of in answering the part (a) above ? 16.

Pure-bred round-yellow pea seeds have genotype RRYY and the pure-bred wrinkled-green pea seeds have genotype rryy. Keeping this in mind, write the phenotypes of the following genotypes of hybrid pea seeds : (a) Rryy

17.

(b) rrYy

19.

20.

(d) RrYy

(e) RRyy

The organs which perform different functions but have the same basic structure are known as : (A) homologous organs

18.

(c) rrYY

(B) analogous organs

(C) homolytic organs

(D) analytic organs

The organs which perform similar functions but have different basic structure are called : (A) asymmetric organs

(B) analogous organs

(C) homologous organs

(D) homophonic organs

Wing of an insect and forelimb of a bird are : (A) analogous organs

(B) analeptic organs

(C) homologous organs

(D) homophobic organs

If the fossil of an organism is found in the deeper layers of earth, then we can predict that: (A) the extinction of organism has occurred recently (B) the extinction of organism has occurred thousands of years ago (C) the fossil position in the layers of earth is not related to its time of extinction (D) time of extinction cannot be determined.

21.

The presence of which of the following types of organs in two animals indicates that they are not derived from a common ancestor ? (A) homologous organs (B) excretory organs

22.

(C) digestive organs

(D) homologous organs

(B) cabbage

(C) spinach

(D) kale

(C) a reptile

(D) an ave

The fossil trilobite was originally : (A) an arthropod

25.

(B) respiratory organs

One of the following has not been produced from wild cabbage by the process of artificial selection. This one is : (A) kohlrabi

24.

(D) reproductive organs

The presence of which of the following types of organs in two organisms indicates that they are derived from the same ancestor ? (A) analogous organs

23.

(C) analogous organs

(B) an invertebrate

One pair of organs in the following animals are not homologous. This is : (A) forelimbs in humans and lizard

(B) forelimbs in lizard and frog

(C) wings in butterfly and bat

(D) wings in bat and bird

110

10th Class Biology

OUR ENVIRONMENT

CHAPTER

5 1.

2.

3.

4.



Classification of wastes



Coal



Water Management



Petroleum



Wild life sanctuaries

Green Chemistry



Balance in Ecosystem

 

Science towards a global village

Environmental Science • Living organisms live in different surroundings. • Plants, animals, human beings survive with the interaction between them and the non-living things like air, water and land. • Human beings depend on the resources of nature. • These resources improve the life style of human beings. • Environmental science can be defined as the study of organisms in relation to their surroundings. Pollutants and Pollution • Unplanned and vast misuse of natural resources like water, forest produce, land and mineral resources has led to an imbalance in nature and release of many harmful substances in the atmosphere. • Mankind is greatly influenced by the surrounding in view of the problem of over Population, environmental pollution, human survival, pest control and conservation of natural resources. • Human activities related to livelihood and welfare generates waste. All wastes are pollutants. • Air, land and water surroundings are affected due to improper disposal of wastes. • Any undesirable change in the physical, chemical or biological characteristics of air, land and water that affect human life adversely is called pollution. • A substance released into the environment due to natural or human activity which affects adversely the environment is called pollutant. Eg. Sulphurdi oxide, carbon-monoxide, lead, mercury, etc. Classification of wastes • Wastes are classified into (i) Bio – degradable wastes and (ii) Non - bio- degradable wastes • Substances that are broken down by biological process of biological or microbial action are called bio-degradable waste. e.g. wood, paper and leather. • Substances that are not broken down by biological or microbial action are called non-biodegradable wastes. e.g. Plastic substances and mineral wastes. Methods adopted for disposal of harmful waste materials i) Land Fills : There are permanent storage facilities in secured lands for military related liquid and radioactive waste materials. High level radioactive wastes are stored in deep underground storage. ii) Deep well injection: It involves drilling a well into dry porous material below ground water. Hazardous waste liquids are pumped into the well. They are soaked into the porous material and made to remain isolated indefinitely. iii) Incineration: The burning of materials is called incineration. Hazardous bio-medical wastes are usually disposed of by means of incineration. Human anatomical wastes, discarded medicines, toxic drugs, blood pus, animal wastes, microbiological and bio-technological wastes etc., are called bio-medical wastes.

112 5.

6.

7.

8.

10th Class Biology Solid waste management – Management of non-hazardous wastes i) Reuse and recycling technique : The separating out of materials such as rubber, glass, paper and scrap metal from refuse and reprocessing them for reuse is named as reclamation of waste or recycling. ii) Paper : (54% recovery) Can be repulped and reprocessed into recycled paper, cardboard and other products. iii) Glass : (20% recovery) Can be crushed, remelted and made into new containers or crushes used as a substitute for gravel or sand in construction materials such as concrete and asphalt. iv) Food waste and yard wastes (leaves, grass etc.,) can be composted to produce humus soil conditioner. Water management • Due to increasing demands for water and reduced availability of fresh ground water resources, urgent measures have to be taken to conserve each and every drop of water that is available. • More than any other environmental factors, the availability of water determines the location and activities of human beings. Sources of water • Water in India is of two kinds. Salt water and fresh water. Fresh water is obtained from rain water, surface water and ground water. • The main sources of water are rain and snow which form a part of the hydrological cycle. i) Surface water : India is blessed with a number of rivers, lakes, streams and ponds. ii) Ground water : Aquifers are under ground reserves of fresh water. In the water table, water that percolates into the ground through porous rocks is ground water. These porous rocks are saturated with water to a certain level. The upper layer of water level is the water table. The ground water is important for plant growth, man also taps this water through tube wells and bore wells. Scanty rainfall and unnecessary felling of trees affect the ground water level. Fresh water management i) Seeding clouds Seeding clouds with dry ice or potassium iodide particles sometimes can initiate rain if water laden clouds and conditions that favour precipitation are present. ii) Desalination: (Reverse osmosis) • Desalination of ocean water is a technology that has great potential for increasing fresh water. • Desalination is more expensive than most other sources of fresh water. • In desalination, the common methods of evaporation and recondensation are involved. iii) Dams, reservoirs and canals Dams and storage reservoirs tap runoff water in them and transfer the water from of excess to areas of deficit using canals and underground pipes. iv) Water shed management • The management of rainfall and resultant run-off is called water shed management. • Water shed is an area characterized by construction of small dams to hold back water which will provide useful wildlife habitat and stock watering facilities. v) Rain water harvesting • Rain water harvesting essentially means collecting rain water from the roof of building or courtyards and storing it underground for later use. • The main idea in harvesting rain water is to check the run-off water. • The rain water that falls on the roofs of buildings or in courtyards is collected through pipes and stored in underground tanks of the buildings fitted with motor for lifting water for use. • The process of rain water harvesting is not only simple but also economically beneficial. • It helps in meeting the increased demand for water, particularly in urban areas and prevent flooding of living areas.

Our Environment

Wetland conservation It preserves natural water storage and acts as aquifer recharge zones. vii) Domestic conservation As an individual, everyone can reduce the water loss by taking shower, using low-flow taps, using recycled water for lawns, home gardens, vehicle washing and using water conserving appliances. viii) Industrial conservation Cooling water can be recharged and waste water can be treated and reused. Wild life • All non-domesticated and non-cultivated biota found in natural habitat are termed ‘wildlife’. It includes all the natural flora and fauna of a geographic region. • There are approximately 400 varieties of reptiles, 200 varieties of amphibians, 3000 varieties of fishes, 3000 species of birds 20,000 species of flowering plants and 4100 species of mammals found in our country according to the latest census estimate. • It is essential to protect and conserve wildlife because they have aesthetic, ecological, educational, historical and scientific values, a good biotic diversity is essential for ecological balance. • Wildlife also adds aesthetic value and from this, eco-tourism is being promoted in a big way by several countries. • Wildlife and their products could be of great economic value if utilized properly. The invulnerable plants could yield products of immense medicinal value in future. • Wildlife also forms as store of vast genetic diversity which could be properly used with advances in genetic engineering. Wild Life sanctuaries • Wildlife sanctuary is an area constituted by competent authority in which hunting or capturing of animals is prohibited except by or under control of the highest authority responsible for management of the area. • Wildlife sanctuaries were established in India in the pursuit of conserving wildlife which was suffering due to ecological imbalance caused by human activities. • There are 89 National parks, 500 wildlife sanctuaries, 27 Tiger reserves, 200 Zoos and 13 Biosphere reserves in the country covering an area of 1.6 lakh sq.km. Ecosystem • A community of organisms that interact with one another and with the environment is called an ecosystem. • The Ecosystem is of two types, namely aquatic and terrestrial. • There are four major components, namely: (i) Abiotic factors (ii) Producers (iii) Consumers (iv) Decomposers. • Producers, consumers and decomposers are biotic factors. • Abiotic factors : It includes light, temperature, hydrogen ion concentration, inorganic substances like CO2, H2, O2, N2, PO4, CO3 and S and organic substances like carbohydrates, proteins and lipids. • Biotic factors : It includes producers and consumers. Producers are the water living plants like hydrilla, Vallisneria etc., and phytoplankton like Chlamydomonas, Volvox and Spirogyra. • Primary consumers or herbivores : Zooplanktons like insects, larvae of Dragon-fly consume the phytoplanktons. • Secondary Consumers: These are certain fishes, frogs, water beetles etc., which feed on the primary consumers in the pond. • Tertiary Consumers : These are big fishes and kingfisher that feed on small fishes. • Decomposers : Several bacteria and fungi form the decomposers in the pond. vi)

9.

10.

11.

113

10th Class Biology

114 12.

Flow of energy in Ecosystem

13.

Balance in ecosystem • A balanced ecosystem is an ecological community together with its environment and functioning as a complex unit. • An ecosystem maintains the balance between the number of resources and the number of users or the balance between prey and predators. Eg: Hawks & mice, Monkeys and banana trees. Food chain and Food web • Various organisms are linked by food chains in which the food energy is passed from one organism to another in a linear fashion. • Food chain of a grassland ecosystem. Grass Frog Snake Eagle  Grass hopper    (Producers) (Herbivores) (Primary (Secondary (Teritary consumer) consumer) consumer) • Food web: The food chains are interlinked to form food webs, So every component of the ecosystem is connected to one another. Maintenance of Ecosystem • Killing animals, cutting down the trees, polluting land, air and water disturb the balance in nature. • In order to maintain the eco-balance in an ecosystem, there should be recycling of nutrients, minerals, and water. • Careful use of natural resources will maintain the eco-balance. • Eco-balance or ecological balance is the maintenance of balance between living components and its resources of an ecosystem, so that it remains a stable environment community for the better functioning of the organisms. Bio – Geo Chemical Cycles • In an ecosystem, the energy from the sun, fixed by the plants, is transferred to herbivores and carnivores i.e. the energy flows in one direction only. • Minerals required in the ecosystem are continuously absorbed by the plants and transferred to animals. • Minerals are returned to the soil by the decomposition of dead and decaying materials by saprophytic organisms such as bacteria and fungi. Coal • Coal is a compost primarily of carbon along with variable quantities of other elements chiefly sulphur, hydrogen, oxygen and nitrogen. • Coal is a fossil fuel and is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide sources of CO2 emissions. • Gross CO2 emission from coal usage is high and more than those from petroleum and about double the amount from natural gas. • Coal is obtained through mining or in open pits. • Coal is primarily used as a solid fuel to produce electricity and heat through combustion. • When coal is heated in air, coal burns and produces mainly carbon-di-oxide gas. • Coal is processed in industry to get some useful products such as coke, coal tar and coal gas. Environmental effects of coal burning i) Generation of waste products which contain mercury, uranium, thorium, arsenic and other heavy metals, which are harmful to human health and environment. ii) Sulphur particles present in the coal will cause acid rain..

14.

15.

16.

17.

18.

Our Environment

19.

20.

21.

22.

23.

115

iii) Interference with ground water and water table levels. iv) Contamination of land and water ways. v) Dust nuisance. vi) Release of CO2, a green house gas, which causes climate change and global warming. vii) Coal is the largest contributor to the man-made increase of CO2 in the air. Petroleum • Petroleum or crude oil is a naturally occurring, toxic, flammable liquid consisting of a complex mixture of hydrocarbons and other organic compounds that are found beneath the earth’s surface. • Petroleum was formed from organisms living in the sea. After the death of those organisms, their bodies settled at the bottom of the sea and were covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas. • Many useful substances are obtained from petroleum and natural gas. These are used in the manufacture of detergents, fibers (polyester, nylon, acrylic etc.), polythene and other plastic substances. Hydrogen gas, obtained from natural gas, is used in the production of fertilizers (urea). • Due to its great commercial importance, petroleum is also called ‘Black Gold’. Environmental effects of Petroleum extraction 1. Crude oil (refined fuel) spills from tanker ship and accidents have damaged natural ecosystem. 2. Oil Spills at sea are generally causing more damage than those on land. This can kill sea birds, mammals, shellfish and other organisms, because of their lateral spreading on water surface. 3. A tar ball is a blob of oil which has been weathered after floating on the ocean. Tar balls are aquatic pollutants in most of the seas. Alternatives to petroleum – based vehicle fuels 1. Internal combustion engines (Bio-fuel or combustion hydrogen) 2. Electricity (for e.g. all electric (or) hybrid vehicles), Compressed air or fuel cells (hydrogen fuel cells). 3. Compressed natural gas used by natural gas vehicles. Green Chemistry • Green chemistry is the design of chemical products and processes to reduce or eliminate the use and generation of hazardous substances. • The concept of green chemistry was introduced in 1995. • The Green Chemistry Institute was recently created and the Presidential Green Chemistry challenge awards were established in 1999. • Greener reaction conditions for an old synthesis e.g. replacement of an organic solvent with water or the use of no solvent at all) • A greener synthesis for an old chemical (e.g. a synthesis which uses biomass rather than petrochemical feed stock or the use of catalytic rather than stoichiometric reagents). • The synthesis of a new compound that is less toxic but has the same desirable properties as an existing compound. (e.g. a new pesticide that is toxic only to target organisms and bio-degrades to environmentally benign substances) • Green chemistry / technology has been developed in almost all branches of chemistry including organic, biochemistry, inorganic, polymer, toxicology, environmental, physical, industrial etc. The Principles of Green Chemistry • It is better to prevent waste generation than to treat or clean up waste after it is generated. • Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment. • Chemical products should be designed to preserve efficacy of function while reducing toxicity.

10th Class Biology

116 24.

25.

26.

Products produced by the process of green chemistry • Lead free solders and other product alternatives to lead additives in paints and the development of cleaner batteries. • Bio-plastics: Plastics made from plants including corn, potatoes or other agricultural products. • Flame resistant materials. • Halogen free flame retardants. e.g. silicon based materials can be used. Future products • A raw material feedstock should be renewable rather than depleting whenever technically and economically practical. • Catalytic reagents are superior to stoichiometric reagents. • Green Chemistry is applicable to all aspects of the product life cycle as well. Finally, the definition of green chemistry includes ‘The term “hazardous”. It is important to note that green chemistry is a way of dealing with risk reduction and pollution prevention. PVC and Lead • New lead free solders with lower heat requirements are being developed. Beware of Green washing • Green chemistry is not a panacea. We must be vigilant in making sure that what is called • “Green Chemistry” really pushes towards a more sustainable world or not. Science today towards a global vilage • Global village is the term used to mean that world had shrunk into a village by means of different media types, most especially the world wide web, making • It is easy to pass across messages (like news) thereby making the world become a single village where people can easily contact each other quicker. What is global village? • A term that compares the world to a small village, where fast and modern communication allows news to reach quickly. • The use of electronics for faster communication is a global village concept. What is the global electronic village? • Global electronic village (GEV) is a term used to refer to a village without borders; it refers to connecting people around the world technologically through Information Communication Technologies (ICTS). • The term global village was coined by Marshall McLuhan. He emphasized that “this forces us to become more involved with one another from countries around the world and be more aware of our global responsibilities”. • The concept of global village has implications for forming new sociological structures within the context of culture.

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

Which of these is a pollutant? ( Mercury, Lead, Sulphur dioxide, All) Which of the following is non bio-degradable? ( Mineral wastes, Leather, Wood, Rubber) In recycling of paper there is _________ % recovery. ( 64, 54, 20, 30) Toxic drugs are disposed by __________. ( Land fills, Incineration, Deep well injection, Recycling) Hazardious waste liquids are disposed by ________. ( Land fills, Incineration, Deep well injection, Recycling )

Our Environment 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.

23. 24. 25.

117

Food waste and yeard wastes can be __________ to produce humus soil conditioner. ( Composted, Incinerated, Biotechnologically treated , None ) Recycled glass can be used as a substitute for ( Scrap metal, Asphalt, Concrete, Gravel or sand ) Which of the following is not a source of fresh water? ( Rain water, Brackish water, Surface water, Ground water ) The main sources of water are rain and snow which form a part of the _________ cycle. ( Biogeochemical cycle, Ecological cycle, Hydrological cycle, Photosynthetic cycle ) The chemical used in seed clouding is ( Potassium iodide, Sodium iodide, Potassium chloride, Photosynthetic cycle ) Wetland conservation preserves natural water storage and acts as _______ zones. ( Aquifer recharge, Precipitation, Surface water, Both ) What are the methods that help in tapping run - off water? ( Dams and reservoirs, Rain water harvesting, Water shed management, All ) The approximate number of varieties of reptiles in our country is ( 100, 200, 300, 400) Number of biosphere reserves in our country is: ( 23, 13, 27, 17 ) With respect to Kanha National park, pick the odd one out. ( Deer, Wild dog, Sloth bear, Chital ) Wild peacocks are found in ( Mudumalia wildlfe sanctuary, Viralimalai, Slopes of western ghats, Vandalur ) Bharatpur Bird Sanctuary has _________ species of birds. ( 274, 374, 474, 574 ) An example of a producer in pond ecosystem is ( Vallisnaria, Clamydomonas, Volvox, Spirogyra ) Which particles present in coal cause acid rain? ( Potassium, Thorium, Sulphur, Lead ) Which of the following is generated from coal? ( Mercury, Uranium, Thorium, All ) Which of the following is not a property of petroleum? ( Ionizing , Naturally occurring, Toxic, Flammable ) ________ is a complex mixture of hydrocarbons and other organic compounds found beneath the Earth’s surface. ( Urea, PVC, Petroleum, None ) Which of the following is not a green chemistry product? ( Bio Plastics, Lead free solders, Flame resistant materials , Hydrogen free flame retardants) Which of the following is a tertiary consumer? ( Eagle, King fisher, Shark, All ) The branch of science that design chemical products and processes to reduce or eliminate the use and gneration of hazardous substances ( Organic Chemistry, Inorganic Chemistry, Green Chemistry, Blue Chemistry)

10th Class Biology

118

WORKSHEET 2 1.

2.

3.

4.

5.

Match the column I with Column II.

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

Land fills Deep well injection Incineration Recycling

Reclamation of waste Burning of materials Hazardous liquid waste Bacteria

Match the column I with Column II.

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

Seeding clouds Desalination Domestic Conservation Vitamin K

Cooling water is recharged Dry ice or potassium iodide Evaporation and re condensation Water conserving appliances

Match the column I with Column II.

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

Fish Amphibians Flowering plants Mammals

4, 100 3, 000 200 20, 0000

Match the column I with Column II.

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

National Parks Wildlife sanctuaries Tiger reserves Zoos

27 500 89 200

Match the column I with Column II.

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

Indira Gandhi Wildlife Sanctuary Kalakkadu Wildlife Sanctuary Gulf of Mannar Marine National Park Anamalai Wildlife Sanctuary

Elephant Slopes of western Ghats Lion tailed Macaque Coral reefs

Our Environment 6. Match the column I with Column II.

7.

8.

9.

10.

11.

12.

119

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

374 species of birds Royal Bengal Tiger Bandhpur National Park Manas Wildlife Sanctuary

West Bengal Assam Rajasthan Karnataka

Match the column I with Column II.

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

Indian Bison Chital Indian Darters Hispid Hare

Corebett National Park Bharathpur Bird Sanctuary Manas Wildlife Sanctuary Bandhipur National Park

Match the column I with Column II.

Column-I

Column-II

A. B. C. D.

P. Q. R. S.

Zooplankton Secondary Consumers Tertiary consumers Decomposers

Big fishes Larvae of dragon fly Fungi Water beetles

Assertion (A): Indira Gandhi wildlife sanctuary is located in the western ghats. Reasoning (R): Mukkurthi National Park is located in the Nilgiris. Choose the correct option (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): Oil spills at sea are causing more damage than those on land. Reasoning(R): Oil spills spread laterally on the water surface. Choose the correct answer (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): Global village compares the world to a village. Reasoning(R): Global electronic village refers to connecting people around the world technologically through information communication technologies. Choose the correct answer (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): Sulphur dioxide, carbon-monoxide, lead, mercury are pollutants. Reasoning(R): They are the substances released into the environment due to natural or human activity which affects adversely the environment. Choose the correct answer (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. .

120 10th Class Biology 13. Assertion (A): Wood, paper and leather are bio-degradable wastes. Reasoning (R): They cannot be broken down by biological or microbial action. Choose the correct option (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. . 14. Assertion (A): Plastic substances and mineral wastes are non-bio-degradable. Reasoning (R): As these substances cannot be broken down by biological or microbial action, they are called non-biodegradable. Choose the correct option (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. 15. Assertion (A): Hazardous waste liquids are pumped into the well by incinearation. Reasoning (R): The burning of materials is called incineration. Choose the correct option (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. . 16. Assertion (A): Killing animals, cutting down the trees, polluting land, air and water disturb the balance in nature. Reasoning (R): In order to maintain the eco-balance in an ecosystem, there should be no recycling of nutrients, minerals, and water. Choose the correct option (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. 17. Assertion (A): In an ecosystem, the energy cannot be tranferred from carnivores to herbivores, or herbivores to plants or plants to the sun. Reasoning (R): In an ecosystem, the energy from the sun, fixed by the plants, is transferred to herbivores and carnivores i.e. the energy flows in one direction only. Choose the correct option (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. 18. Say true or false. i) In deep well injection, hazardous liquid wastes are isolated permanently ii) The main sources of water are rain and ice, which form a part of the hydrological cycle iii) Biotic factors include organic substances like carbohydrates, proteins and lipids iv) In bio-geo chemical cycles, energy flows in multiple directions.

Our Environment

I. 1. 2. 3. 4. 5. 6. 7. 8. 9. II. 10.

11.

12. 13. 14.

15. 16. 17. 18.

19.

121

Spot the mistakes in the given statements and correct them. a) All wastes are pollutants. b) Air, land and water surroundings are affected due to improper disposal of wastes. a) High level radioactive wastes are stored in deep underground storage. b) Hazardous waste liquids are soaked into non porous materials. a) Seed clouding can initiate rain if water laden clouds and conditions that favour evaporation are present. b) Desalination is reverse osmosis a) Dams and reserviors transfer water through areas of deficit using canals and underground pipes. b) Water shed provides water for constructions. a) Wildlife includes some of the natural flora and fauna of geographic region. b) Large scale destruction of wildlife leads to ecological balance. a) Number of species of birds in India is 2000. b) Number of varieties of amphibians in India is 200. a) Volvox is a water living plant. b) Zooplanktons are primary consumers of the pond ecosystem. a) Minerals are continuouosly absorbed by plants. b) Minerals are returned to soil by tertiary consumers. a) Green chemistry has been developed in bio chemistry toxicology, physical chemistry, etc. b) Coal and petroleum are synthesized using green chemistry. Fill up the blanks a) __________ science is te study of organisms in relation to surroundings. b) Undesirable change in the physical, chemical or biological characteristics of air, land and water that affect human life adversely is called ___________. a) A substance released due to natural or human activity and affects the environment adversely is called ________ b) The wastes are classified into ________ and ___________. a) Separation of materials from refuse and reprocessing them for reuse is called _______. b) The type of water found in India are _________ and _________. a) In the water table, water that percolates into the ground through porous rocks is called ________ b) The upper layer of water level is called ________. a) __________ preserves natural water storage and acts as aquifer recharge zones. b) _________ is done by collecting rainwater through pipes and storing in underground tanks fitted with motor for lifting water for use. a) All non - domesticated and non - cultivated biota found in natural habitat are termed ________. b) Wild life sanctuaries were established in India covering an area of _______ sq. km a) The India’s first national park is _________. b) Gir National Park is located in _________ state. a) The examples of water living plants are _____________. b) The two examples of phytoplankton are _________ and ___________. a) ________ is an ecological community together with its environment and functioning as a complex unit. b) ________ is the maintenance of balance between living components and the resources of an ecosystem. a) Gross CO2 emission from coal is more than that from ________ and about double the amount from _______ b) Every component of the ecosystem is connected to one another in a _______.

122 10th Class Biology 20. a) the methods adopted for disposal of harmful waste material are____, _________ and ______. b) Wild life sanctuaries were established in India in the pursuit of ___________. 21. a) In an ecosystem, the energy flow is always __________. b) Minerals required in the ecosystem are continuously absorbed by the _______and transferred to ________. 22. a) Due to its great commercial importance, petroleum is also called ________. b) ___________is the design of chemical products and processes to reduce or eliminate the use and generation of hazardous substances. III. PICK THE OUT ONE OUT 23. Coke, Coal tar, Coal gas, Acrylic 24. Sulphurdioxide, Oxygen, Carbon-monoxide, lead 25. Wood, Plastic, leather, paper 26. Land Fills , Constructing dams, Deep well injection, Incineration. 27. Tube wells, Rivers, Lakes, Streams 28. Seeding clouds, Deep well injection, Desalination, Rain water harvesting 29. Light, hydrilla, Sun, Water 30. Pick the odd one out with respect to primary producers. Hydrilla, Vallisneria, Spirogyara, Insects. 31. No Killing, No Polluting land, No planting of trees, No polluting water 32. Fossil fuel, Compost, Formed from organisms living under sea, Gross CO2 emission 33. Introduced in 1995, Black gold, Better to prevent waste generation, Bio plastics 34. Rivers, Lakes, Streams, Aquifers.

CHAPTER

6 1.

MANAGEMENT OF NATURAL RESOURCES    

Forests and wildlife Water for all Dams Pollution of river water

  

Rain water harvesting Coal and Petroleum The three R’s to Save the Environment

Introduction Anything in the environment ‘which can be used’ is called a ‘natural resource’. Some of our important natural resources are : Forests and Wildlife, Water, Coal and Petroleum. A system of controlling the use of natural resources in such a way as to avoid their wastage and to use them in the most effective way, is called management of natural resources. The natural resources are a ‘tool’ of development for human beings but it should be ‘sustainable development’. The development which meets the current basic human needs and also preserves the resources for the needs of future generations, is called sustainable development. And to protect the environment from harm or destruction is said to ‘conserve’ the environment. In this chapter we will describe how to use our natural resources so as to achieve sustainable development as well as to conserve our environment. Why do We Need to Manage Our Resources All the things which we use such as food, clothes, furniture, fuels, vehicles, water, etc., are obtained from the resources on this earth. We need to manage our natural resources because of the following reasons: 1. The resources of the earth are limited. Because of the rapid increase in human population, the demand for resources is increasing day by day. The proper management can ensure that the natural resources are used judiciously so that they fulfil the needs of present generation and also last for the generations to come. 2. The proper management of natural resources takes into consideration long-term perspective and prevents their exploitation to the hilt for short-term gains. 3. The proper management can ensure equitable distribution of natural resources so that all the people can benefit from the development of these resources. 4. The proper management will take into consideration the damage caused to the environment during the ‘extraction’ or ‘use’ of the natural resources and find ways and means to minimise this damage. For example, if some forest trees have to be cut for various purposes, then the damage to the environment can be minimised by planting new saplings in place of cut down trees.

2.

Forests and Wildlife A large area of land on which trees and other plants grow naturally is called a forest. And the wild animals (like lion, tiger, elephants, deer, snakes, etc.) and birds which live in a forest, are called wildlife. The ‘plants’ and ‘animals’ of a forest are called ‘flora’ and ‘fauna’ respectively. Due to the presence of a large number of species, forests are said to be ‘biodiversity hotspots’. One of the main aim of the management of forests and wildlife is to conserve the biodiversity which we have inherited. This is because the loss of biodiversity leads to the loss of ecological stability of the forest ecosystem. We will now discuss the various stakeholders in the management of forests and their aspirations. A person with an interest or concern in something is called a stakeholder. When we consider the management of forests, we find that there are four stakeholders in it. These are : 1. The people who live in and around the forest and are dependent to some extent on forest produce to lead their life. 2. The Forest Department of the Government which owns the forest land and controls the resources from the forest.

10th Class Biology

124 3.

The industrialists who use various forest products for their factories, such as wood for making paper and furniture, and tendu leaves for making bidis, etc. 4. The forest and wildlife activists who want to see the forests in their pristine form (original condition). We will now describe what each of these stakeholder groups needs or gets out of the forests. The people who live in villages around the forests take firewood from the forest trees. They usually lop the branches of the trees and pluck their leaves but do not cut down the whole trees. They take bamboo from the forest to make their huts and baskets for collecting and storing food materials. The local people take wood for making agricultural implements and gather fruits, nuts and medicinal herbs from the forest. They also collect green fodder and graze their cattle in the forest. On the whole, people living near the forests usually use the resources of the forests in a way that much damage is not done to the environment. In fact, the people living near forests had developed practices to ensure that the forest resources were used in a sustainable manner. So, the damage caused to forests cannot be attributed to only the local people living around the forests. The Forest Department has a major stake in the resources of forests and wildlife because it is a good source of revenue for the Government. Most of the forest revenue comes from the sale of cut down forest trees for timber. In order to plant trees for timber such as pine, teak, and eucalyptus, etc., huge areas of forests are cleared of all vegetation. This destoys a large amount of biodiversity in the area which harms the environment. The management of protected forest areas by keeping the local people out completely has some ill effects too. This will become clear from the following example. The great Himalayan National Park is a protected forest area which contains alpine meadows that were earlier grazed by outside sheep in summer. So, nomadic shepherds drove their flock of sheep up from the valley to this area every summer. After the formation of Himalayan National Park, the grazing by sheep was not allowed. This has a harmful effect on the growth of vegetation because, without regular grazing by sheep, the grass first grows very tall and then falls over, preventing fresh growth from below. The developmental projects like building roads through the forest area and construction of dams are also damaging the forests. Even the large inflow of tourists to the forests for observing wildlife, building resthouses for tourists within the forest and dumping of waste materials by the tourists in the forest, are damaging the forest environment. Industrialists have a major vested interest in forest resources. They consider the forests as merely a source of raw material for their industry. Some of the major industries which are based on forest produce are : Timber industry, Paper manufacturing industry, Lac industry and Sports equipment industry. In fact, most of the deforestation is caused by industrial needs. It is true that wood from the forest trees is needed for manufacturing various types of goods required for development but at the same time efforts should be made to make up the loss of trees cut down from the forest. This can be done by planting saplings in the forest in place of cut down trees. It should be noted that the destruction of forests affects not just the availability of forest products but also the quality of soil and the sources of water. A major programme called silviculture has been started to replenish the forests by growing more trees and plants. Thus, silviculture is a major programme started to replenish depleting forests. The silviculture programme has many advantages : (i) It produces a large quantity of raw materials for industry (ii) It increases the area of earth under forests (iii) It maintains a perfect water cycle in nature (iv) It prevents soil erosion (v) It prevents floods There are certain people who are not dependent on the forests in any way but who want forests and wildlife to be conserved to prevent undue damage to the environment.

Management of Natural Resources

125

They started by working for the conservation of large wild animals such as tigers, lions, elephants, and rhinoceros but they now recognise the need to preserve forests as well. This is because without preserving forests, we cannot conserve wildlife. We will now give two instances where ordinary people have played a great role in the conservation of forests by preventing them from being cut down mdiscriminately. (i) The Case of Khejri Trees There is a Bishnoi community in Rajasthan state of our country for whom conservation of forests and wildlife has been a religious belief. In 1731, Amrita Devi Bishnoi led a group of 363 persons who sacrificed their lives for the protection of khejri trees in khejrali village near Jodhpur in Rajasthan. This shows the determination of some people to work for the conservation of their natural environment. The Government has recently instituted an ‘Amrita Devi Bishnoi National Award for Wildlife Conservation’ in the memory of Amrita Devi Bishnoi. (ii) The Chipko Andolan Another example of the contribution of common people towards the conservation of forests is the Chipko Andolan. The Chipko Andolan originated from an incident in a remote village called ‘Reni’ in Garhwal, high up in the Himalayas in the early 1970s. A logging contractor had been allowed to cut down trees in a forest close to a village. The people of the village did not want this forest to be cut down because it would have spoiled their healthy environment. One day, when the men folk of the village were out for work, the contractor’s workers came in the forest to cut down the trees. In the absence of men, the women of the village reached the forest quickly and clasped the tree trunks with their arms, preventing the workers from cutting down the trees. The forest trees were thus saved. The Chipko Movement quickly spread across all the communities and helped in the conservation of forests. Participation of Local People in the Management of Forests People’s participation in the management of forests can help in increasing forest produce as well as in their conservation. An example of how local people’s participation in the management of forests led to the revival of degraded forests is like this : In 1972, the West Bengal Forest Department formulated a novel scheme to revive the degraded sal forests by involving the local people. A beginning was made in the Arabari forest range of Midnapore district. A far-sighted forest officer A.K. Banerjee involved the villagers of the area around the forest in the protection of 1272 hectares of badly degraded sal forest. In return for help in protecting the forest, the villagers were given employment in both silviculture and harvesting operations of the forest, 25 per cent of the final harvest produce, and were allowed to collect firewood and fodder from the forest area on a nominal payment. With the active and willing participation of local people living around the forest, the degraded sal forest of Arabari became thick and green within ten years. This is how participation of local people can lead to efficient management of forests. Conservation of Wildlife The large scale poaching of wild animals residing in the forests by man is a serious threat to the survival of many animal and bird species. This also disturbs the food chains in which these animals occur resulting in undesirable consequences for the whole ecosystem. This point will become more clear from the following example. Snake is a wild animal. The skin of snakes is in great demand for making fancy leather goods, so the snake skin sells at a high price in the market. Now, to make some easy money, some people kill the snakes mdiscriminately in large numbers to obtain their skin. This large scale killing of snakes disrupts the food chains in which snakes occur and creates an imbalance in nature. For example, snake is a friend of the farmer in the sense that it eats vermins like rats and mice which are pests and damage the crops. Now, when the snakes are killed in large numbers to obtain their skin, the population of snakes is reduced greatly. Now, due to the lesser number of ‘predator’ snakes, the population of pests like rats and mice in crop-fields increases. The increased number of rats and mice in the fields damages the standing crops leading to loss in the production of food-grains.

10th Class Biology

126

It is very important to conserve wildlife to maintain the ecological balance in nature and to preserve the gene pool. Some of the measures to be taken for the conservation of wildlife are given below: 1. Laws should be made to impose a total ban on poaching or capturing of any animal or bird belonging to an endangered species. The poaching of an endangered species of animals and birds should be made a punishable offence. Such laws should not remain on paper only, they should be enforced strictly. 2. Even if some type of wild animals and birds are in abundance today, their indiscriminate killing should not be allowed by the forest authorities. 3. The natural habitats of wild animals and birds should be preserved by establishing National Parks and Sanctuaries throughout the country. 4. The Government Department connected with the conservation of wildlife should conduct a periodic survey in all the forests, National Parks and Sanctuaries to have a knowledge of the population of all species of wild animals and birds, so that these animals can be helped in the times of distress like floods and famines. 5. Special attention should be paid to the conservation of endangered species of wild animals and birds to prevent their extinction altogether. 6. The unauthorised felling of forest trees for timber trade and fuel-wood should be curbed immediately. This is because depletion of forests destroys the natural habitat of wild animals and birds, and exposes them to the cruelty of man as well as nature. 7. In the case of Government authorised felling of forest trees, for every acre of forest cut down, an equal area of land should be planted with saplings of trees to make up for the loss in the long run.

3.

Water for all Water is the basic necessity for all forms of life, human beings, other animals as well as plants. Some parts of our country have good resources of water whereas other parts suffer from chronic water shortage. The regions having good availability of water are flourishing because they have good crops but the regions having shortage of water are in the thick of poverty because of poor crop growth. It is, therefore, necessary to have proper management of available water resources so that there is an equitable distribution of water for all the people in all the parts of the country. The various sources of water which are available to us are: Rains, Rivers, Lakes, Ponds, Wells, Oceans and Glaciers. We will discuss the management of water from some of these sources of water in detail. Let us start with rains. Rain is a very important source of water. Rains in India are largely due to monsoon which lasts for a few months. This means that most of the rainwater falls on the earth in a few months of the year. This rainwater fills the lakes and ponds, and also flows into rivers. Some rainwater also seeps into the ground and becomes available as ground water. Though most of the parts of our country get a good rainfall during monsoon but due to the loss of vegetation cover, much water does not seep into the ground, it rather flows into rivers. Ramwater is stored in lakes for use over a long period of time. There are some natural lakes in our country. Some artificial lakes have also been made at various places to store rainwater to meet the increasing demand for water. In fact, many cities of our country depend on such lakes for their water supply during the year. Despite good rains, we are not able to meet the demand for water of all the people because : (i) our population is increasing rapidly. (ii) due to lack of sufficient vegetation cover on ground, only a little rain water seeps into the ground and gets stored as ground water. (iii) the high yielding varieties of crops require much more water for irrigation. (iv) discharge of untreated sewage and industrial wastes into rivers and lakes reduces the availability of usable water. (v) the changing life-style of people, especially in urban areas, is consuming more water.

Management of Natural Resources

127

Rivers are another important source of water. Rivers get their water supply from the melting of snow lying on the peaks of snow mountains as well as from rains. The management of river-water is done by constructing dams on rivers.

4.

Dams In order to make proper use of river water, dams are constructed across the rivers to regulate the flow of water. In our country dams have been built across many rivers. The large reservoir of a dam stores a huge amount of water. This stored water is then allowed to flow downstream at the desired rate. Bhakra Dam is one such dam which has been built across the river Satluj in the state of Punjab in our country. Dams built across the rivers are big storehouses of river water. Dams are useful for the society in the following ways: Water from a dam is used for irrigation in fields through a network of canals. Dams ensure round the year water supply to the crop fields and help raise agricultural production. For example, Indira Gandhi Canal originating from Bhakra Dam has brought greenery to considerable areas of Rajasthan.

Water from a dam is supplied to the people in towns and cities through pipelines after suitable treatment. In this way, construction of dams ensures continuous water supply in the region. The falling water from the dam is used for generating electricity. The water rushing down the dam turns turbines which run electric generators. The electricity thus produced is called hydroelectricity. The construction of high-rise dams for the management of river water and generation of electricity has certain problems associated with it. The public opposition to the construction of large dams on rivers is mainly due to the following three problems likely to be created by them : (i) Social Problems Due to the construction of high-rise dams, a large number of human settlements are submerged in the water of large reservoir formed by the dam and many people are rendered homeless. This creates a social problem. It is, therefore, necessary that all the people who are displaced from the dam site are given adequate compensation by the Government for rehabilitation so as to start their life afresh. (ii) Environmental Problems The construction of high-rise dams on the rivers contributes to deforestation and loss of biodiversity. This is because a vast variety of flora and fauna get submerged in the water of large reservoir formed by the dam and disturb the ecological balance. (iii) Economic Problems Some people say that the construction of high-rise dams involves the spending of huge amount of public money without the generation of proportionate benefits. On the other hand, others say that there can be no real progress without building dams because they allow us to manage our water resources properly and at the same time give us much needed electricity. So, whether the construction of dams on rivers is an economic problem or not is a debatable question.

10th Class Biology

128

The opposition to the construction of Tehri Dam on the river Ganga and raising the height of Sardar Sarovar Dam on the river Narmada are due to such problems. We have all heard about the protests by the Narmada Bachao Andolan against the raising of height of Sardar Sarovar Dam. So, before taking a decision to construct high-rise dams on rivers, or raising the height of existing dams, it is necessary to consider its long term effects on social life and environment carefully.

5.

Pollution of River Water The water in most of our rivers is highly polluted. The pollution of river water is caused by the dumping of untreated sewage and industrial wastes into it. For example, the river Ganga which flows for over 2500 kilometres from Gangotri in the Himalayas to Ganga Sagar in the Bay of Bengal is being turned into a dirty water drain by the discharge of untreated sewage and industrial wastes emanating from more than a hundred towns and cities which lie along its way. In addition to sewage and industrial wastes, the pollution of river Ganga is also caused by other human activities like bathing, washing of clothes, immersion of ashes of the dead and dumping of unburnt corpses in its water. The industries also discharge chemical effluents into the river water. The toxicity of these chemical effluents kills the fish in many parts of the river. The contamination of river water can be usually found from two factors: (i) the presence of coliform bacteria in river water, and (ii) measurement of pH of river water. Coliform is a group of bacteria found in human intestines. The presence of coliform in the river water indicates its contamination by diseasecausing micro-organisms. This is because though coliform itself is harmless but its presence in river water indicates that other, more harmful, intestinal bacteria might also be present. The pH of river water is measured by using universal indicator paper. If the pH of river water is found to be below 7, then the river water will be acidic and hence polluted. A multicrore ‘Ganga Action Plan’ (GAP) project was launched in 1985 to clean the river Ganga and make its water pollution free. Wells and tube-wells are yet another source of water. Some of the rainwater which falls on earth seeps through the soil and goes down under the surface of the earth. Ultimately this water is stopped by some hard rocks and collects there. This underground water is taken out by digging a ‘well’ into the ground. This is called well water. Such wells are a common sight in village areas. The deep tube-wells called ‘bore-wells’ are also dug into the earth which are much deeper than the ordinary wells and their water is drawn out by using water pumps. This water is used for the irrigation of crops and for drinking purposes. When too much water is pumped out through deep tube-wells then the water table gets lowered too much. This lowering of water table decreases the amount of available underground water. In order to maintain the water table at a proper depth, it is necessary to ensure better percolation of rainwater into the soil. A scheme called ‘rainwater harvesting’ is recommended to stop flowing rainwater and make it percolate into the soil more efficiently.

6.

Rainwater Harvesting The people in rural India have used a large number of water collecting methods to capture as much rainwater as possible which had fallen on their land. Some of the methods used for water harvesting by the rural people were: Digging of small pits and lakes; Building of small earthen dams; Construction of dykes; Construction of sand and limestone reservoirs; and setting up of roof-top water collecting units. All these methods of collecting and saving rain water have recharged the depleting groundwater levels.

Management of Natural Resources

129

Rainwater harvesting is an age-old practice in India. Water-harvesting techniques used depend on the location where it is to be used. Some of the ancient ‘water harvesting structures’ used in different rural regions of our country are given below: Region

Ancient water harvesting structure

1.

Rajasthan

Khadin, Tanks, Nadis

2.

Maharashtra

Bandharas, Tals

3.

Madhya Pradesh and Uttar Pradesh

Bhundhis

4.

Bihar

Ahars and Pynes

5.

Himachal Pradesh

Kulhs

6.

Jammu region

Ponds

7.

Tamil Nadu

Eris (Tanks)

8.

Kerala

Surangams

9.

Karnataka

Kattas

We will now describe a traditional rainwater harvesting system for agriculture called khadin which is used in Rajasthan. The main feature of khadin system of rainwater harvesting is a very long earthen embankment called ‘bund’ built across the lower edge of the sloping farmland. The rainwater from catchment area flows down the slopes and stopped by the bund to form a reservoir. The excess water flows across the bund through sluiceways provided for this purpose and goes into shallow wells dug behind the bund. The rainwater which collects in the reservoir formed by the bund, and in the well, seeps slowly into the land. This water-saturated land is subsequently used* for growing crops. Please note that the main purpose of water harvesting is not to hold rainwater on the surface of the earth but to make rainwater percolate under the ground so as to recharge ‘groundwater’. The various advantages of water stored in the ground are as follows : (i) The water stored in ground does not evaporate. (ii) The water stored in ground spreads out to recharge wells and provides moisture for crops over a wide area. (iii) The water stored in ground does not promote breeding of mosquitoes (unlike stagnant water collected in ponds or artificial lakes). (iv) The water stored in ground is protected from contamination by human and animal wastes. (v) The water stored in ground is utilised for the benefit of local population. Rainwater harvesting in rural areas not only increases the agricultural production and income of the farmers but also mitigates the effect of droughts and floods, and increases the life of downstream dams and reservoirs. Rainwater Harvesting in Urban Areas (City Areas) In rural areas, most of the ground has open soil due to which rainwater can seep into the ground naturally to make up for the loss in groundwater due to excessive use. In urban areas, however, most of the ground is covered with buildings, concrete pavements and metalled roads due to which only very little rainwater seeps into the ground naturally. Most of the rainwater which falls in cities flows into dirty water drains and goes away. So, rainwater harvesting is necessary in city areas. Rainwater harvesting by making

10th Class Biology

130

more water percolate into the ground is usually done in those areas of a city where tube-wells for supplying water are located. This is to make sure that the tube-wells will never go dry. The rainwater harvesting from open spaces around the buildings in a city is done by constructing percolation pits covered with concrete slabs having holes in them, and connected to a recharge well through a pipe.

Rainwater harvesting in open spaces around buildings to recharge groundwater. The recharge well is about 1 metre in diameter and 3 metres deep. The rainwater falling in the open spaces around buildings goes into the percolation pit through the holes in its concrete slab cover. After filtration in percolation pit, rainwater enters the recharge well through the outlet pipe and gradually seeps into the soil. Please note that the purpose of recharge well is to collect the vast amount of water falling on the ground quickly when it rains and then make it seep into soil gradually. This groundwater can then be taken out through tube-wells as and when required. The advantage of rainwater harvesting is that it increases the availability of groundwater and helps in overcoming water shortage.

7.

Coal and Petroleum Coal and petroleum are called fossil fuels. Coal and petroleum are the natural resources which are important ‘sources’ of energy for us. Coal is used as a fuel as such in homes and in industry, or it is used to generate electricity at Thermal Power Plants. Petroleum products such as petrol and diesel are used as fuels in transport to run scooters, motorcycles, cars, buses, trucks, trains, ships and aeroplanes. Kerosene and LPG obtained from petroleum are used as domestic fuels for cooking food, etc. Since the industrial revolution, we have been using increasing amounts of energy to meet our basic needs and for the manufacture of goods upon which our life depends. ‘All these energy needs have so far been met mostly by coal and petroleum reserves of the earth. Coal and Petroleum in the Earth are Limited Coal and petroleum were formed from the degradation of biomass of plants and animals respectively, buried deep under the earth millions of years ago. We obtain coal from the ‘coal mines’ dug into the earth and petroleum is obtained by digging ‘oil wells’ deep in the earth. The crude petroleum oil obtained from oil wells is then separated into fuels such as LPG, petrol, diesel and kerosene. We have been using coal and petroleum resources at such a rapid rate in the past that they will get exhausted in the near future. It has been estimated that at the present rate of consumption, the known petroleum reserves of the earth will last us for just about 40 years more and the coal will last for about another 200 years only. Once exhausted, coal and petroleum will not be available to us in near future. It is, therefore, necessary to

Management of Natural Resources

131

conserve coal and petroleum resources of the earth by reducing their consumption so that they may last for as long as possible. Steps to Reduce the Consumption of Coal and Petroleum Coal is used mainly to produce electricity. So, if we can save electricity, then the consumption of coal will be automatically reduced. Similarly, the petroleum products kerosene and LPG are used for cooking food, and petrol and diesel are used as fuel in motor vehicles, so if we can save on kerosene, LPG, petrol and diesel, then the consumption of petroleum will also get reduced. Some of the steps which can be taken to conserve energy resources are as follows : 1. Switch off the lights, fans, television and other electrical appliances when not needed. This will save a lot of electricity. 2. Use energy efficient electrical appliances to save electricity. This can be done by using Compact Fluorescent Lamps and fluorescent tube-lights instead of traditional filament-type electric bulbs (because CFL and tube-lights consume much less electric energy as compared to filament-type electric bulbs for producing the same amount of light). 3. Use stairs to climb at least up to three floors of a building instead of taking a lift. This will save electricity. 4. Pressure cookers should be used for cooking food to save fuels like kerosene and LPG. 5. Good quality stoves should be used to burn fuels like kerosene and cooking gas so as to obtain maximum heat. 6. Solar cookers should be used to cook food whenever possible. 7. The use of biogas as domestic fuel should be encouraged in rural areas. 8. Bicycles should be used for covering short distances to save precious fuel like petrol. 9. Public transport system in the cities should be improved so that people do not commute in their personal vehicles. This will save a lot of petrol and diesel. 10. Fuel efficient engines of motor vehicles should be designed to reduce the consumption of petrol and diesel. Pollution Caused by Burning Coal and Petroleum Based Fuels Since coal and petroleum have been formed from biomass, therefore, in addition to carbon and hydrogen, they also contain nitrogen and sulphur elements. When coal, and petroleum based fuels are burnt, the products of combustion are : Carbon dioxide, Water, Sulphur dioxide and Nitrogen oxides. And if combustion takes place in an insufficient supply of air, then some carbon monoxide is also produced. Out of all the products of combustion of these fuels, only water is harmless and does not affect the environment. All other products are harmful and hence pollute the environment. For example : (i) Sulphur dioxide attacks the lungs causing bronchitis and other diseases. Sulphur dioxide also dissolves in rainwater making it acidic. The acid rain thus produced damages trees, plants, aquatic organisms, buildings and metal structures. (ii) Just like sulphur dioxide, nitrogen oxides attack the breathing system and also cause acid rain. (iii) Carbon monoxide is a very poisonous gas. If carbon monoxide gets into our blood stream, it stops red blood cells from carrying oxygen from lungs to the rest of the body causing suffocation. Too much carbon monoxide causes death. (iv) Though carbon dioxide is not a poisonous gas but it is a greenhouse gas which traps sun’s heat energy falling on the earth. The burning of more and more of fossil fuels is increasing the amount of carbon dioxide in the atmosphere causing increased greenhouse effect leading to global warming. From the above discussion we conclude that : We need to use fossil fuels (coal and petroleum) judiciously because: (i) fossil fuels left in the earth are limited which will get exhausted soon, and (ii) the products of combustion of fossil fuels pollute the environment.

10th Class Biology

132

8.

The three R’s to Save the Environment The excessive and indiscriminate use of various types of natural resources is spoiling our healthy environment day by day. We can save our environment by practising three R’s: Reduce, Recycle and Reuse. This is explained below. 1. Reduce Reduce means that we use less of the natural resources by cutting down on those practices which lead to their wastage. For example, we can reduce the wastage of electricity by switching off unnecessary lights and fans. Saving electricity means that we are reducing the use of coal. We can reduce the wastage of water by repairing the leaking taps. We can reduce the use of LPG by making use of solar cooker for cooking food. We can reduce the use of petrol by walking or cycling for short distances. And we can reduce the use of water resources and fertilisers by preventing the wastage of food. 2. Recycle Recycling means that we should collect the used and discarded items of paper, plastic, glass and metals, and send them to the respective industries for making fresh paper, plastic, glass or metal objects. In order to recycle materials, we should first segregate our domestic wastes properly so that the materials which can be recycled do not get dumped alongwith other household wastes which are to be thrown away. 3. Reuse Reuse means that, if possible, we should use the same things again. For example, the plastic jars in which we buy various food items like jams and pickles, etc., can be used later on for storing things like salt, spices, sugar, tea-leaves and pulses, etc. And paper envelopes can be reversed inside out and used again. The process of ‘reuse’ is better than that of ‘recycling’ because some energy is used to recycle old objects but no energy is required during reuse. The items which can be reused are, however, very limited.

WORKSHEET 1 1.

2. 3.

4.

5. 6.

The Bishnoi community of Rajasthan is associated with the conservation of : (A) coal and petroleum (B) forests and wildlife (C) water resources (D) abiotic environment The Chipko Andolan is associated with : (A) Tigers (B) Turtles (C) Trees (D) Tomatoes Amrita Devi Bishnoi was associated with: (A) preventing the custom of child marriage in Rajasthan (B) campaign to save the girl child (C) conservation of cultural heritage of Rajasthan (D) conservation of forests and wildlife One of the following is not a direct stakeholder in the management (or conservation) of forests. This is: (A) the people “who have paper mills. (B) the people who run the forest department (C) the people who campaign for the conservation of forests (D) the people who live in urban areas The river water is said to be polluted with acidic wastes if the pH of river water is: (A) zero (B) above 7 (C) below 7 (D) exactly 7 The major programme started to replenish the damaged forests is called : (A) horticulture (B) tissue culture (C) agriculture (D) silviculture

Management of Natural Resources 7. 8. 9. 10. 11.

12. 13. 14. 15.

133

With which tree Amrita Devi Bishnoi is associated ? (A) khajoor (B) khejrali (C) khejri (D) keekar One of the following does not contribute in producing acid rain. This one is : (A) sulphur dioxide (B) carbon dioxide (C) nitrogen oxides (D) carbon monoxide The poisonous gas which reduces the oxygen-carrying capacity of blood to a large extent is : (A) SO2 (B) NO (C) CO (D) CO2 Which of the following is not an ancient water harvesting structure ? (A) kattas (B) sargam (C) kulhs (D) surangams Snakes are killed in large numbers because : (A) they are very poisonous (B) they kill rats (C) their skin is expensive (D) they damage the crops Which of the following is not a fossil fuel ? (A) LPG (B) natural gas (C) biogas (D) CNG Which of the following is not a natural resource ? (A) soil (B) water (C) electricity (D) natural gas The most rapidly dwindling natural resource in the world is: (A) water (B) soil (C) sunlight (D) forests Which of the following is not a natural resource ? (A) snake (B) wind (C) wooden house (D) mango tree

WORKSHEET 2 1.

2.

3.

4.

5. 6.

7.

The three R’s which can help us to conserve natural resources for long term use are : (A) recycle, regenerate, reuse (B) reduce, regenerate, reuse (C) reduce, reuse, redistribute (D) reduce, recycle, reuse The main reason for the abundant coliform bacteria in the water of river Ganga is : (A) immersion of ashes of the dead into the river (B) washing of clothes on the banks of river (C) discharge of industrial wastes into river water (D) disposal of unburnt corpses into river water The pH of a sample of water collected from a river is found to be in the range of 3.5 to 4.5. The most likely reason for this is the waste being discharged into the river from a : (A) soap and detergent manufacturing factory (B) car battery manufacturing factory (C) alcohol manufacturing factory (D) plastic cups moulding factory Which of the following statement is incorrect ? (A) economic development is linked to environmental conservation (B) sustainable development meets the current basic human needs and also preserves resources for future generations (C) sustainable development does not take into consideration the viewpoints of all stakeholders (D) sustainable development is a long planned and persistent development Arabari forest of Bengal is dominated by : (A) Teak (B) Sal (C) Bambooo (D) Mangroove Groundwater will not be depleted due to : (A) process of afforestation (B) establishing thermal power plants (C) process of deforestation (D) cultivation of high yielding varieties of crops Ahars, Kattas, Bhundhis and Khadins are the modes of : (A) grain storage (B) soil conservation (C) water harvesting (D) cold storage

134 8. 9.

10. 11.

12.

13.

14.

15.

10th Class Biology Which of the following combination of terms has no fossil fuel ? (A) wind, ocean, coke (B) kerosene, tide, wind (C) wood, wind, sun (D) petrol, wood, sun The use of one of the following is eco-friendly. This one is : (A) cars for transportation (B) polybags for shopping (C) windmills for generating power (D) dyes for colouring clothes Khadins are used in Rajasthan to: (A) hold water for irrigation (B) recharge groundwater (C) promote soil erosion (D) trap wild animals In a village, farmers started cultivating crops all around a lake which was always filled with water. They added lot of materials W to the soil in their fields to increase the yield of crops. Soon they found that the whole surface of water in the lake was covered with a green layer made up of tiny organisms X. After some time, the fish present in the lake started dying in large numbers because they could not get sufficient Y due to a process Z which had occurred in lake water and drained out all the Y present in the water of lake. (A) What do you think materials W are ? (B) Name (z) X, and (ii) Y. (C) What is the process Z known as ? (D) What happens during the process Z which uses up all the Y present in lake water ? (E) What does this example tell us about the use of materials like W ? There were lot of organisms A in the crop fields in an area. These organisms used to feed on organisms B also present in the crop fields but which damaged the standing crops. One day some people arrived in the fields and killed all the organisms A so that they could remove their C for making fancy items which were in great demand. Due to large scale killing of A, the population of B increased too much damaging all the crops in the area and causing a famine-like situation. Apart from A, there is another organism D which can also kill and eat B. Name A, B, C and D. There are two important fuels A and B both of which are extracted from deep inside the earth. Fuel A is a thick, dark, foul smelling liquid whereas fuel B is a black solid. Combustion of both the fuels produces products, C, D, E and F. The product C makes the rainwater only slightly acidic but it is mainly responsible for causing global warming. The product D is neither acidic nor basic. It is harmless and does not affect the environment in any way. Both E and F attack breathing system of humans and are mainly responsible for causing acid rain. In addition to combustion of fuels A and B, the product F is also formed when lightning occurs in the sky. (A) What are (i) fuel A, and (ii) fuel B ? (B) Name (i) C (ii) D (iii) E, and (iv) F (C) What is the process of formation of F during lightning known as ? (D) Which fuel is supposed to be exhausted sooner : A or B ? (E) Which fuel is mostly used for generating electricity at thermal power plants ? A man bought a device X which could cook pulses, vegetables and rice without using any fuel like wood, coal, kerosene or LPG, etc. This device did not work at night. It also took a lot of time for cooking. (A) Name the device X. (B) What is the source of energy which cooks food in this device ? (C) What is the name of the process which traps energy in this device ? (D) State one advantage (other than saving on fuel) of using such a device for cooking food. A person buys two electrical devices P and Q for lighting purposes in his house. The device P consumes only 5 units of electricity in a month but device Q consumes 15 units of electricity in a month when used for the same number of hours daily. The device Q wastes a lot of electricity by radiating energy C but P does not do so. (A) What type of device is (i) P, and (ii) Q ? (B) Name one component which is present in Q but not in P. (C) Name the energy C. (D) Which device is more energy efficient: P or Q ? (E) Which fossil fuel is most likely to be conserved if all of us switch over to devices like P ?

ANSWERS & KEY

LIFE PROCESSES WORKSHEET-1

17.

B

18.

D

1.

B

2.

B

19.

A

20.

A

3.

C

4.

C

21.

C

22.

D

5.

B

6.

D

23.

A

24.

B

7.

C

8.

D

25.

B

26.

D

9.

D

10.

B

27.

C

28.

A

11.

B

12.

C

29.

A

30.

B

13.

B

14.

D

15.

C

16.

A

17.

A

WORKSHEET-2

WORKSHEET-4 1.

B

2.

C

3.

A

4.

D

5.

B

6.

D

7.

B

8.

D

9.

C

10.

B

3.

C

5.

C

6.

A

11.

B

12.

B

7.

C

8.

A

13.

C

14.

C

9.

B

10.

D

15.

B

16.

C

11.

D

12.

C

17.

B

18.

D

13.

C

14.

A

15.

B

16.

C

1.

A

2.

D

17.

B

18.

C

3.

B

4.

A

19.

D

20.

C

5.

B

6.

B

21.

C

22.

B

7.

A

8.

A

23.

C

24.

C

9.

B

10.

B

25.

D

26.

B

11.

A

12.

B

27.

A

28.

B

13.

C

14.

D

29.

A

30.

A

WORKSHEET-5

WORKSHEET-6

WORKSHEET-3

1.

B

2.

D

1.

C

2.

B

3.

D

4.

D

3.

C

4.

C

5.

C

6.

A

5.

D

6.

D

7.

C

8.

C

7.

C

8.

B

9.

A

10.

B

9.

A

10.

B

11.

C

12.

C

11.

C

12.

C

13.

D

14.

C

13.

A

14.

A

15.

B

16.

A

COMPETITIVE WORKSHEET

17.

Statement (b) is incorrect.

1.

A–Q;B–S;C –R;D–P

Correction:

2.

A–S;B–Q;C–Q;D–R

3.

A–P;B–Q;C–S;D–P

4.

Both the statements are incorrect.

The translocation of food and other substances takes place in the sieve tubes (sieve tubes are one of the constituents of the phloem which act as pipe line from leaves to the other parts of the plant) with the help of companion cells both in upward and downward directions.

Correction: a)

b)

5.

6.

7.

The process of acquiring oxygen through breathing and making it available for cells 18. is called Transportation Respiration is the process by which food and water are carried from one organ to the other.

19.

3

Statement (a) is incorrect.

20.

1

Correction: Angiosperms like Monotropa lack chlorophyll and have mycorrhizal roots and absorbs nourishments from the humus through their mycorrhizal roots.

21.

4

22.

1

23.

1

Statement (b) is incorrect.

24.

4

Correction: Food we eat contain starch which is the source of energy.

25.

a)

Parasites

b)

Hosts

Both statements are incorrect.

26.

a)

Non living organic matter.

b)

Defensive

a)

Pseudopodia

b)

Intracellular digestion.

a)

Oxidized

b)

Adenosine triphosphate.

a)

Aerobic respiration and Anaerobic respiration.

b)

The liberated electrons.

a)

Fermentation.

a) b)

With the formation of pyruvic acid, glycolysis comes to an end. The second step of aerobic respiration occurs in mitochondira.

27.

28.

Statement (b) is incorrect. Correction:

29.

Respiration in frog occurs through both lungs and skin. 16.

Correction: Lymph is also called Tissue fluid .

Correction:

8.

Statement (b) is incorrect.

Statement (b) is incorrect.

30.

Correction: Rings of cartilage are present in the throat which keep the air passage open and 31. prevent it from collapsing. 32.

33.

b)

Body surface.

a)

ATP

b)

Mucous

a)

Rings of Cartilage.

b)

Alveoli

a)

Leaves, Roots

b)

Vessels and Tracheids

34.

35.

36.

37.

38.

39.

40.

41.

a)

Suction

b)

Translocation ; phloem

a)

In amoeba and paramoecium, useful substances are distributed by a process called _________.

b)

Oxygen enters amoeba through_____.

a)

Diffusion.

b)

Cell membrane

a)

Uricotelic

b)

Plasma

a)

Co-ordination.

b)

Brain and photoreceptors.

a)

Nerve impulses.

b)

Immediate.

a)

Hormones.

b)

Bio catalysts.

a)

Nutrition

b)

Energy

42.

Playing

43.

Deer

44.

O2

45.

Green plants

46.

Mycorrhizal roots.

47.

Human beings

48.

Oesophagus.

49.

Gills

50.

Kidneys

51.

The digestion that takes place in the space or lumen of alimentary canal i.e outside the cell it is called as extracellular digestion.

54.

X is lymphatic capillaries; Y is lymph vessels.

55.

Lymph or tissue fluid is similar to the plasma of blood but it is colourless and contains less protein. Lymph drains into lymphatic capillaries from the intercellular spaces, which join to form large lymph vessels that finally open into veins. Lymph carries digested and absorbed fat, from intestine and drains excess fluid from extra cellular space back into the blood.

56.

Muscular activities like running to catch a ball, involves many other forms of co-ordination, such as those which increase the rate of breathing and heart beat to adjust blood pressure, remove extra heat from body and maintaining sugar and salt levels in the blood.

57.

Plant cells change the shape by changing the amount of water in them resulting in swelling or shrinking and therefore the leaves in touch-menot plant shrinks.

58.

a)

The roots of coconut tree are seen away from the plant for want of water.

b)

The pollen tubes towards ovule.

a)

The life process includes the activities performed by the different organs to maintain the body.

b)

Nutrition, Respiration, Transportation, Excretion

59.

60.

a) Chlorophyll 6CO2  12 H 2 O   C6 H12 O6  6 H 2O Sunlight

 Glu cos e 

b) 61.

Heart and Blood vessels

The raw materials and other necessary items required for photosynthesis are Sunlight, Water, CO2 and Chlorophyll. Sunlight - energy from the sun ;

52.

A = Lime water ; B = Sugar + Water + Yeast

Water - plant absorbs water from the soil through roots.

53.

(i)

Xylem transports water with dissolved minerals absorbed from the soil.

CO2 - assimilated from the atmosphere through leaves containing small pores called stomata.

(ii)

Phloem transports products of photosynthesis (food) from the leaves to the parts of the plant.

Chlorophyll - the gr een pigments in the chloroplasts, an organelle of the cells of leaf.

62.

63.

66. Parasitic plants have some special roots, which penetrate the host plants and absorb food from the phloem, water and minerals from xylem. These roots are called haustoria. (e.g.: 67. Cuscutta and Viscum). a)

b)

64.

65.

The gastro intestinal tract (alimentary canal) is a long muscular tube, about 9 mts in length and it commences from the 68. mouth and ends in the anus. The mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus are the 69. parts of the alimentary canal.

Food contains a number of nutrient molecules needed for building up of new body tissues, repairing damaged tissues and sustained chemical reaction. Substance that is used in respiration is known as respiratory substrate. Respiratory substrates are of three kinds viz., carbohydrates, fats and proteins.

70.

Transpiration helps in the absorption and upward movement of water and mineral dissolved in it from roots to the leaves. It also helps in temperature regulation. In the spring, sugar stored in root or stem tissue would be transported to the buds, which need energy to grow. i) True

ii) True

iii) True

iv) False

v) True The uriniferous tubules reabsorb the substances required in the body from that filterate and the final urine product contains mostly water and nitrogenous waste products. The movements that plants show are : i)

Movement independent of growth. Eg: Touch – me – not plant

ii)

Movement dependent growth. Eg:

Phototropism, hydrotropism, etc.

CONTROL AND COORDINATION WORKSHEET-1

4.

A–Q;B–R;C–P

1.

C

2.

B

5.

A–Q;B–R;C–P

3.

C

4.

A

6.

A–R;B–Q;C–S;D–P

5.

D

6.

A

7.

A–R;B–Q;C–P

7.

C

8.

D

9.

A

10.

A

8.

A–P;B–Q;C–R

11.

A

12.

A

9.

A–P;B–Q;C–R

13.

B

14.

A

10.

A–P;B–R;C–Q

15.

A

16.

A

11.

A–Q;B–R;C–P

17.

A

18.

B

12.

A – Q, R ; B – P, Q

19.

A

20.

A

13.

A – R, ; B – P, C – Q

21.

B

22.

D

14.

Statement (b) is incorrect.

23.

D

24.

A

25.

A

WORKSHEET-2 1.

B

2.

B

3.

B

4.

A

5.

B

6.

C

7.

B

8.

B

9.

D

10.

A

11.

B

12.

A

13.

C

14.

A

15.

D

Correction: Medullated nerve cells are enclosed by Myelin sheath. 15.

Both statements are incorrect. Correction:

16.

a)

Motor areas are responsible for the initiation of voluntary activities takes place.

b)

Association areas are responsible for complex functions like intersensory associations, memory and communication.

Statement (b) is incorrect. Correction: Thalamusis the major conducting centre for sensory and motor signalling.

WORKSHEET-3 17.

Both the statements are incorrect.

1.

A

2.

A

3.

A

4.

A

Correction:

5.

A

6.

D

a)

7.

C

8.

B

The outer region of the cerebrum is called Grye matter.

9.

A

10.

C

b)

11.

B

12.

D

The inner region of the cerebrum is called White matter.

13.

A

COMPETITIVE WORKSHEET 1.

A–S;B–R;C–Q;D–P

2.

A – Q ; B – R; C – P

3.

A–R;B–P;C–Q

18.

Both the statements are incorrect. Correction: a)

The middle covering of CNS is thin and vascularised and is called Arachnoid membrane.

b)

19.

Both statements are incorrect. Correction: a) b)

20.

27.

Alpha cells produce a hormone called glucagon

b)

Beta cells produce insulin and amylin.

Both statements are incorrect.

a)

Testosterone stimulates the growth of reproductive organs and the production of male sex cell, the sperms.

b)

Progesterone maintains pregnancy and regulates menstrual cycle.

Thalamus is the major conducting centre for sensory and motor signaling.

Both statements are incorrect. 28.

a)

Excess production of STH causes gigantism in children.

b)

Less production of STH causes dwarfism 29. in children.

ICSH in male produces testosterone

b)

LH in female produces oestrogen and progosterone

Both the statements are incorrect. Correction:

Both statements are incorrect.

a)

Statement (a) is incorrect. Correction: Meosis bring change in structure and number of chromosmes.

Correction:

22.

a)

Correction:

Hypothalamus controls body temperature, urge eat and drink.

Correction:

21.

Correction:

The innermost cover of CNS is a very thin delicate membrane and is closely applied on the outer surface of brain and spinal cord and it is called Piameter.

30.

a)

Meosis – I is called Reduction.

b)

Meosis – II is called Mitosis.

Both the statements are incorrect. Correction:

Statement (b) is incorrect.

a)

The point of contact between the homologous pair of chromosomes are called Chiasmata.

b)

The exchange of segments of chromatids between homologous chromosomes, is called crossing over.

Correction: Less production of ADH results in Diabetes insipidus. 23.

Both statements are incorrect. Correction:

24.

a)

Hyperthyroidism is due to excess secretion of thyroxine.

b)

Hypothyroidism is due to less secretion of thyroxine.

Statement (b) is incorrect. Correction: Alpha cells of Islets of Langerhans produces Glucagon.

25.

31.

1

32.

1

33.

1

34.

2

35.

2

36.

A – Unipolar neuron ; B – Myelinated or Medullated or White neurons ; C – NonMyelinated or Non-Medullated or Grey neurons.

Statement (b) is incorrect. Correction: Glucagon is secreted when glucose 37. level in blood is low.

26.

Both statements are incorrect.

P) White neurons – brain.

Cerebral cortex of our

Q) Grey neurons – cerebrum

White

matter

of

R) Unipolar neurons nervous tissue

–

HOW DO ORGANISMS

Embr yonic

REPRODUCE

S) Bipolar neurons – Sensory hair cells of the sense organs like rods and cones of retina T) Multipolar neuron cortex

–

Cerebral

WORKSHEET-1 C

2.

B

3.

C

4. A – Fore brain ; B – Mid Brain ; C – Hind Brain 7. ; D – Cerebrum; E – Thalamus ; F – 10. Hypothalamus ;

D

5.

B

6.

D

C

8.

D

9.

D

D

11.

D

12.

C

G – Cerebellum ; H – Pons ; I – Medulla oblongata.

13.

C

14.

A

15.

A

16.

D

17.

D

18.

C

39.

X – Cerebrum ; Y – Cerebral aqueduct ; Z – Medulla oblongata

19.

D

20.

C

21.

B

40.

Cerebrum is the seat of consciousness, intelligence, memory, imagination and reasoning. Hence, the cerebrum of her brain have got affected due to the accident.

22.

D

23.

D

24.

B

25.

(a)

A is Leishmania, B is Plasmodium, C is Amoeba and D is Paramecium

(b)

Organism A (Leishmania) has a whip-like structure called flagellum at its one end

(c)

Female Anopheles mosquito

(d)

(i) Binary fission (ii) Multiple fission

(e)

In pond water

(a)

X is yeast and Y is Hydra

(b)

Fermentation

Ram – Cerebellum

(c)

Fungi

Rahim – Pons

(d)

Y has tentacles

Anthony – Medulla oblongata

(e)

Y is multicellular whereas X is unicellular

(a)

Bread mould ; Rhizopus

(b)

Spores of bread mould plant are always present around us. One such spore landed on moist slice of bread and finding the conditions favourable (presence of moisture, nutrients and warmth, etc.) grew into bread mould

38.

41.

42.

43.

1.

Specific areas of cerebrum are associated with specific functions. Thus there is a centre for hearing, another for seeing, another for tasting, another for smelling, another for speaking and so on. A damage in a specific centre of cerebrum will deprive the particular faculty from doing its 26. functions. Thus, cerebrum of his brain have got damaged badly.

Head – (A) pituitary gland (B) pineal gland Neck – (C) thyroid gland (D) parathyroid gland

27.

Thorax – (E) thymus gland 44.

A and B are the correct statements and C and D are incorrect statements.

45.

All the above are the functions of thyroxine.

46.

Thyroxine.

(c)

Hyphae

47.

A = Cretinism ; B = Myxoedema ; C = Simple goitre

(d)

Sporangia ; Spores

(e)

Spore formation

Grave’s disease is due to the excess production of thyroxine. It is also called exophthalmic goiter.

(f)

Bacteria

(g)

Ferns and Mosses

48.

28.

29.

30.

31.

32.

33.

34.

35.

(a) Bryophyllum (b) Buds (c) Begonia(d) Money plant (e) Buds.

(a)

Callus

(b)

Tissue culture

(c)

Agar

(d)

Plant hormones

1.

(D)

2.

(A)

3.

(D)

(e)

Dahlia and Carnation

4.

(B)

5.

(C)

6.

(D)

(f)

Micropropagation

7.

(A)

8.

(D)

9.

(C)

10.

(C)

11.

(A)

12.

(D)

13.

(D)

14.

(B)

15.

(C)

16.

(C)

17.

(B)

18.

ABCD/SRQP

19.

ABCD/QPSR

20.

ABCD/RPSQ

21.

ABCD/SPQR

22.

(C)

(B)

25.

(A)

26.

Statement (B) is incorrect.

27.

Statement (B) is incorrect.

28.

Both the statements are incorrect.

29.

Statement (A) is incorrect.

(a) Grafting (b) Stock (c) Scion (d) Cambium layer (e) Because the layer Z (called cambium layer) in the stem is responsible for growth (f) Apple, peach, apricot and pear trees (g) It enables us to combine the most desirable characteristics of the two plants in fruits (a) Cuttings method (b) The cutting should have one (or more) bud on it (c) Sugar cane and Banana plants (d) By using the cuttings method, we can produce many new plants from just one plant quickly, without waiting for flowers and seeds (e) Asexual method of reproduction ; Because new plants are produced from a single parent plant without the involvement of sex cells (or gametes) of the plant (f) clones

WORKSHEET-2

(a) Layering (b) Slender branches (Thin 30. branches) (c) Jasmine and China rose (d) Lemon and Guava (e) Strawberry (a) Planaria (Flatwor m) (b) Hydra (c) Regeneration (d) Simple multicellular organisms (e) No ; Because dog is a complex multicellular organism

23.

Both statements are incorrect.

WORKSHEET-3

1. (B)

2. (B)

3. (B)

4. (B)

5. (B)

6. (A)

7. (B)

8. (C)

9. (D)

10. (D)

11. (D)

12. (C)

13. (B)

14. (A)

15. (B)

16. (D)

17. (C)

18. (D)

19. (C)

20. (C)

21. (B)

(a) Spirogyra (b) Green (c) Fragmentation 22. (B) (d) The binary fission in Amoeba is a 25. (A) reproduction process which takes place in unicellular organisms ; Fragmentation in alga is a reproduction process which takes place in simple multicellular organisms (e) Sea anemone

23. (A)

24. (A)

(a) Stem tubers (b) Potato tuber (c) Eyes or Buds (d) No ; Even cut pieces of X can be planted in the soil to obtain new plants provided each cut piece has an eye or bud on it (e) Vegetative propagation by tubers (f) The vegetative propagation method of growing new plants from tubers like X is much faster than the production of new plants from their seeds

24.

(A)

26.

(a) (i) Menstruation (ii) Periods (b) 10 to 12 years ; Puberty (c) 28 days; About 3 to 5 days (d) That the reproductive system of human female has started working (e) Beginning of pregnancy (f) About 45 to 50 years

11.

D

12.

C

13.

C

14.

C

15.

A

16.

D

17. (D)

18. (C)

19. (C)

20. (C)

21. (B)

22. (D)

23. (C) 24. (D) 25. (D) 27. (a) (i) Ovary (ii) Ovum (or Egg) (b)Fallopian tube ; Oviduct (c) (i) Testis (if) 26. (a) A is carpel (or pistil); Stigma, Style and Ovary (b) Ovary (c) B is stamen ; Anther Sperm (d) Sperm duct; Vas deferens (e) (i) (d)Pollen grains (e) (i) B (ii) A Zygote (Fertilised egg) (ii) Embryo (iii) Uterus (or Womb) (iv) (i) Y is male (if) X is female 27. (a)A are pollen grains; Cross-pollination (b) Pollen tube (c) C is male gamete (d) D is 28. (a) Zygote (b) Placenta (c) Umbilical cord female gamete (ovum or egg) ; E is ovule (e) F (d) From mother’s blood to embryo : Oxygen is fertilised egg (zygote) and Nutrients ; From embryo to mother’s blood

29.

30.

: Wastes (e) S (umbilical cord) is tied and then 28. cut; To separate the new born baby from the mother 29. (a) Follicles (b) Ovulation (c) 28 days (d) Conception (or Pregnancy) (e) About nine months (f) Menstruation (g) Hormones 30. (a) Sperm ducts (or Vas deferens) (b) Sperms (c) Testes (d) Egg cell (or Ovum) (e) Vasectomy

31.

(a) Oviducts (or Fallopian tubes) (b) Ovum (or Egg cell) Ovary (d) Sperms (e) Tubectomy

32.

(a) Condom (b) Sperms (c) Diaphragm (or Cap) (d) Barrier methods (e) X

33.

(a) Syphilis and Gonorrhoea (b) AIDS (c) HIV (d) By sexual contact with an infected person (e) B (AIDS) A is ovum (or egg cell); B is sperm ; C is zygote (fertilised egg); D is uterus ; E is embryo ; F is foetus; Y is male; X is female

HEREDITY & EVOLUTION WORKSHEET-1

(a) Hormones (b) Oral pills (c) Spermicides (d) 1. 2. Vaginal pills (e) Chemical methods COMPETITIVE WORKSHEET

(a) Copper-T and IUCD (b) Uterus (or Womb) (c) No

Sexual reproduction B

3.

Genes

4.

Tt

5.

False

7.

Pea plants

1.

D

2.

C

3.

C

6.

Baby boy

4.

D

5.

C

6.

B

8.

Black hair

7.

C

8.

A

9.

D

9.

10.

C

(a) pairs (b) recessive ; dominant (c) free; attached (d) 23; 46 (e) same (f) sex ; female ; male

10.

Tall plants : Tt and TT ; Short plants : tt

11.

Equal chance of having blood group O or blood group B

12.

Monohybrid cross

13.

(a) tt (b) TT (c) (i) tt (ii) TT

14.

(a) (i) 23 (ii) 46 (b) 3 tall plants and 1 dwarf plant

15.

(a) 46 (b) 23 (c) 23 (d) 46 (e) 46

16.

(a) Genes (b) Chromosomes

17.

No, because mother has a pair of X chromosomes. All new born babies will inherit an X chromosome from mother regardless of whether they are baby boys or baby girls.

18.

(a) Green seed ; Yellow is dominant; Green is recessive (b) Wrinkled seed ; Round is dominant; Wrinkled is recessive

19.

(C)

20.

(A)

21.

22.

(A)

23.

(C)

24. (D)

25.

(B)

26.

(B)

27.

(C)

28.

(C)

29.

(A)

30.

(C)

31.

(D)

32.

(B)

33.

(D)

34.

(C)

35.

(a) Brown (b) Blue (c) Brown

36.

(i) B (ii) A ; Dwarf pea plants do not appear in F1 generation

37.

(a) All tall plants (b) 3 :1 (c) Dwarf plants

38.

(a) Red colour (b) Rr

39.

The brown hair colour genes are dominant to the red hair colour genes ; The genotype of brown hair can be represented as BB and that of red hair as bb

40.

41.

42.

Possible genotypes are IA IB, IA I°, IBI° and I° I°. So, the possible phenotypes or blood groups are : AB, A, B and O

43.

No, the parents are not correct. The baby born to father having blood groups A and mother having blood group B can have any one of the four possible blood groups : A, B , AB and O.

44.

No (Case I : If father’s blood group A is dominant trait, his genotypes will be IAIA and IAI°; and mother’s blood group O being recessive trait, her genotype will be So, daughter can receive one recessive allele I° from father and another recessive allele I° from mother to have genotype I°I° and hence blood group O. Case II : If father’s blood group A is recessive trait, his genotype will be IAIA; and mother’s blood group O being dominant trait, her genotypes will be I°I° and I°IA. In this case, daughter can receive a dominant allele I° from mother and a recessive allele IA from father to have genotype I°IA and hence blood group O)

45.

(c) TtWW (Hint. T is the gene form for tallness, t for dwarfness, W for violet colour and w for white colour. T and W are dominant genes whereas t and w are recessive genes)

(C)

WORKSHEET-2 1.

Evolution

2.

False

3.

Homologous organs

4.

(a) Wings of bird and wings of bat (b) Wings of birds and wings of insect

5.

Wild cabbage

(a) Because black colour genes are dominant over brown colour genes (b) Three black mice and one brown mouse will be obtained in F2 generation ; It is a monohybrid cross

6.

(a) homologous ; analogous (b) stages (c) Homo sapiens (d) wild cabbage (e) Darwin

7.

(i) c (ii) b (iii) e (iv) a (v) d

(a) (i) e (blue colour) (ii) E (brown colour) (b) Brown eyes (c) ee (d) EE and Ee

8.

(B)

9.

(B)

10.

(B)

15.

(a) (i) 405 (ii) 135 (iii) 1215 (iv) 405 (b) Dihybrid ratio

16.

(a) Round-green (b) Wrinkled-yellow (c) Wrinkled-yellow (d) Round-yellow (e) Round-green

(B)

17.

(A)

18.

(B)

19.

(A)

26.

X : Trilobites; Y : Ammonites; Z : Dinosaurs

20.

(B)

21.

(C)

22.

(D)

27.

(a) Wild cabbage (b) Cabbage, Broccoli, Cauliflower, Kohlrabi and Kale (c) Artificial selection

23.

(C)

24.

(A)

25.

(C)

28.

(a) A: Bird; B: Lizard; C : Human ; D : Frog ; E : Insect (b) Because they have the same basic designbut perform different functions (c) They are derived from the same ancestor (d) Because they have different basic design but perform similar functions (e) No

11.

(B)

12.

(A)

14.

(C)

15.

(B)

16.

(B)

17.

(C)

18.

(B)

19.

(A)

20.

(C)

22.

(D)

23.

(B)

24.

(A)

25.

29.

30.

WORKSHEET-1 1.

All

2.

Mineral wastes

X : Bird ; Y : Lizard ; Z : Dinosaur (b) Homologous organs (c) Both Z and X had feathered wings like those of birds (d) Both Z and Y had tail like those-of reptiles (e) Y  Z X

3.

54

4.

Incineration

5.

Deep well injection

(a) Yes (b) Yes (c) The green colour of beetle allows it to mix up with green bushes and helps in its survival (because then it cannot be seen easily by the predators) (d) Yes

6.

Composted

7.

Gravel or sand

8.

Brackish water

9.

Hydrological cycle

10.

Potassium iodide

11.

Aquifer recharge

12.

All

13.

400

14.

13

15.

Sloth bear

16.

Viralimalai

17.

374

18.

Vallisnaria

19.

Sulphur

20.

All

1.

(B)

2.

(D)

3.

(C)

4.

(C)

5.

(A)

6.

(A)

7.

(C)

8.

(A)

9.

(B)

10.

(A)

11.

(C)

12.

(C)

13.

(a) Round yellow (b) A (round) and B (yellow) are dominant traits (c) Round-green (d) Wrinkled-yellow (e) (i) A-D (ii) A-B

14.

OUR ENVIRONMENT

(a) (i) X chromosomes (ii) X chromosome (iii) Y chromosome (b) B and D (both are X chromosomes) (c) E (d) Sex chromosomes (e) (i) C (ii) A

4.

21.

Ionizing

22.

Petroleum

23.

Hydrogen free flame retardants

24.

All

25.

Green Chemistry

5.

WORKSHEET-2 1.

A–S;B–R;C–Q;D–P

2.

A–Q;B–R;C –S;D–P

3.

A–Q;B–R;C –S;D–P

4.

A–R;B–Q;C–P;D–S

5.

A–P;B–R;C–S;D–Q

6.

A–R;B–P;C–S;D–Q

7.

A–S;B–P;C–Q;D–R

8.

A.

A–Q;B–S;C–P;D–R

9.

2

10. 1

11.

1

12.

1

13. 3

14.

1

15.

4

16. 3

17.

1

18.

i) iii)

False False

ii) iv)

False False

6.

7.

8.

9.

COMPETITIVE WORKSHEET 1.

2.

3.

Statement (a) is incorrect. Correction: A substance released into the environment due to natural or human activity which affects adversely the environment is called pollutant. Statement (b) is incorrect. Correction: Hazardous waste liquids are pumped into the well. They are soaked into the porous material and made to remain isolated indefinitely. Statement (a) is incorrect. Correction: Seeding clouds with dry ice or potassium iodide particles sometimes can initiate rain if water laden clouds and conditions that favour precipitation are present.

10. 11.

12. 13.

14.

Statement (b) is incorrect. Correction: Water shed provides useful wildlife habitat and stock watering facilities. Both statements are incorrect. Correction: a) Wildlife includes ALL the natural flora and fauna of geographic region. b) Large scale destruction of wildlife leads to ecological IMBALANCE. Statement (a) is incorrect. Correction: Number of species of birds in India is 20, 000. Statement (b) is incorrect. Correction: Zooplanktons are producers of the pond ecosystem. Statement (b) is incorrect. Correction: Minerals are returned to the soil by the decomposition of dead and decaying materials by saprophytic organisms such as bacteria and fungi. Statement (b) is incorrect. Correction: Lead free solders, Bioplastics, Flame resistant materials, Halogen free flame retardants, etc are synthesized using green chemistry. a) Environmental b) Pollution a) Pollutant b) Bio-degradable wastes and Non bio - degradable wastes a) Recycling b) Salt water and fresh water a) Ground water b) Water table a) Wetland conservation b) Rainwater harvesting.

15. 16. 17. 18. 19. 20.

21. 22. 23. 24. 25. 26. 27. 28. 29. 29. 30.

30. 31. 31. 32.

32. 33.

a) b) a) b) a) b) a) b) a) b) a)

Wild life. 1.6 lakh sq.km. Corbett National park Gujurat Hydrilla, Vallisneria Chlamydomonas, Volvox A balanced ecosystem Eco-balance. Petroleum ; Natural gas Food web Land fills, Deep well injection, Incineration b) Conserving wild life a) Unidirectional b) Plants and animals. a) Black Gold b) Green chemistry Acrylic Oxygen Plastic Constructing dams Tube wells Deep well injection Light, hydrilla, Sun, Water Hydrilla Pick the odd one out with respect to primary producers. Hydrilla, Vallisneria, Spirogyara, Insects. Insects No Killing, No Polluting land, No planting of trees, No polluting water No Planting trees. Fossil fuel, Compost, Formed from organisms living under sea, Gross CO2 emission Formed from organisms living under sea Introduced in 1995, Black gold, Better to prevent waste generation, Bio plastics

33. 34. 34.

Black Gold Rivers, Lakes, Streams, Aquifers. Aquifers

MANAGEMENT OF NATURAL RESOURCES WORKSHEET-1 1. (b)

2. (c)

3. (d)

4. (d)

5. (c)

6. (d)

7. (c)

8. (d)

9. (c)

10. (b)

11. (c)

12. (c)

13.(c)

14. (d)

15. (c)

WORKSHEET-2 1. (d)

2. (d)

3. (b)

4. (c)

5. (b)

6. (a)

7. (c)

8. (c)

9. (c)

10. (b)

11.

(a) Fertilisers (b) (i) Algae (ii) Oxygen (c) Eutrophication (d) When algae die, bacteria use all the oxygen dissolved in water to decompose dead algae (e) Excessive use of fertilisers in fields is not good for the environment

12.

A : Snakes ; B : Rats ; C : Skin ; D : Cat

13.

(a) (i) Petroleum (ii) Coal (b) (i) Carbon dioxide (ii) Water (iii) Sulphur dioxide (iv) Nitrogen oxides (c) Natural fixation of nitrogen (d) A (Petroleum) (e) B (Coal)

14.

(a) Solar cooker (b) Sun (c) Greenhouse effect (d) It does not cause air pollution

15.

(a) (i) Compact Fluorescent Lamp (CFL)(ri) Filament type bulb (or lamp) (b) Filament (c) Heat energy (d) P (e) Coal