Respiration in Organisms

Transcription

1 SOME IMPORTANT POINTS FOR REVISION FOR CLASS 7 SA 2 EXAM (05 CHAPTERS) 1. Breathing is a part of respiration. Respiration in Organisms 2. All organisms are made of small microscopic units called cells. A cell is the smallest structural and functional unit of an organism. 3. Each cell of an organism performs certain functions such as nutrition, transport, excretion and reproduction. To perform these functions, the cell needs energy. The food has stored energy, which is released during respiration. 4. The process of breakdown of food in the cell with the release of energy is called cellular respiration. 5. All living organisms respire to get energy from food. During breathing, we breathe in air. You know that air contains oxygen. We breathe out air which is rich in carbon dioxide. The air we breathe in is transported to all parts of the body and ultimately to each cell. In the cells, oxygen in the air helps in the breakdown of food, and energy is released. 6. In the cell, the food (glucose) is broken down into carbon dioxide and water using oxygen along with release of energy. 7. When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration. Food respiration can also be broken down, without using oxygen. This is called anaerobic respiration. 8. There are some organisms such as yeast that can survive in the absence of air. They are called anaerobes. They anaerobes get energy through anaerobic respiration. In the absence of oxygen, glucose breaks down into alcohol and carbon dioxide, as given below: 9. Yeasts are single-celled organisms. They respire anaerobically and during this process yield alcohol. They are, therefore, used to make wine and beer. 10. Our muscle cells can also respire anaerobically, but only for a short time, when there is a temporary deficiency of oxygen. During heavy exercise, fast running, cycling, walking for many hours or heavy weight

2 lifting, the demand for energy is high. But the supply of oxygen to produce the energy is limited. Then anaerobic respiration takes places in the muscle cells to fulfill the demand of energy: 11. After heavy exercise we sometimes get muscle cramps. The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps. We get relief from cramps after a hot water bath or a massage. Hot water bath or massage improves circulation of blood. As a result, the supply of oxygen to the muscle cells increases. The increase in the supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water. 12. Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs. The taking in of air rich in oxygen into the body is called inhalation and inhalation giving out of air rich in carbon dioxide is known as exhalation. 13. The number of times a person breathes in a minute is termed as the breathing rate (both inhalation and exhalation take place). A breath means one inhalation plus one exhalation. 14. Whenever a person needs extra energy, he/she breathes faster. As a result more oxygen is supplied to our cells. It speeds up the breakdown of food and more energy is released. That is why we feel hungry after a physical activity. 15. We yawn when we are sleepy or drowsy in order to make available sufficient oxygen for our body. 16. On an average, an adult human being at rest breathes in and out times in a minute. During heavy exercise, the breathing rate can increase up to 25 times per minute. While we exercise, not only do we breathe fast, we also take deep breaths and thus inhale more oxygen. 17. Lungs are present in the chest cavity. This cavity is surrounded by ribs on the sides. A large, muscular sheet called diaphragm forms the floor of the chest cavity. Breathing involves the movement of the diaphragm and the rib cage. 18. Mechanism of breathing: - Normally we take in air through our nostrils. When we inhale air, it passes through our nostrils into the nasal cavity. From the nasal cavity, nasal cavity the air reaches our lungs through the windpipe. During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs. The lungs get filled with air. During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity and air is pushed out of the lungs.

3 19. Smoking damages lungs. Smoking is also linked to cancer. It must be avoided. 20. The air around us has various types of unwanted particles, such as smoke, dust, pollens, etc. When we inhale, the particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may get past the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body. When you sneeze, you should cover your nose so that the foreign particles you expel are not inhaled by other persons. 21. Model to show mechanism of breathing: Effect of exhaled air on lime water: - When air is blown into lime water, it turns milky. 23. Inhaled air contains, more oxygen used to create energy and less carbon dioxide than exhaled air which contains, more carbon dioxide produced as a waste product of energy production less oxygen as it has been used in respiration Gas exchange takes place by diffusion in the alveoli within the lungs. As a result the composition of inhaled and exhaled air is different. Upon inhaling, a person takes air into the respiratory system, and the air travels into the alveoli. Some air remains in the nasal cavity, trachea, bronchi and bronchioles to avoid creating a vacuum. The air stays in the respiratory passageways, and it cannot be used by the body. People inhale and exhale approximately 7 or 8 liters of air each minute or 11,000 liters per day. 5 percent of the volume of air is consumed each time a person inhales and is converted to carbon dioxide. Thus, a person uses around 550 liters of pure oxygen daily. 24. The normal amount of air breathed in and out at rest is called the tidal volume of air. The maximum amount of air a person can inhale and exhale is known as the vital capacity. A person normally does not use his entire vital capacity. When speaking or being active, a person takes in and lets out more air than the tidal volume. 25. At rest, the average adult inhales around 20 percent oxygen in the air and exhales about 15 percent oxygen 26. When inhaling, humans take in approximately 21 percent oxygen, 0.04 percent carbon dioxide and 79 percent nitrogen. On exhalation, humans give off approximately 16 percent oxygen, 4 percent carbon dioxide and 79 percent nitrogen. Exhaled air also contains water vapor. 27. Red blood cells travel by vein to the lung; they give of carbon dioxide and take in oxygen. 28. Animals such as elephants, lions, cows, goats, frogs, lizards, snakes, birds, have lungs in their chest cavities like the human beings.

4 29. Cockroach and small insects have small openings, called spiracles on the sides of their body. Insects have a network of air tubes called tracheae for gas exchange. Oxygen rich air rushes through spiracles into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body. Similarly, carbon dioxide from the cells goes into the tracheal tubes and moves out through spiracles. These air tubes or tracheae are found only in insects and not in any other group of animals. 30. Earthworms breathe through their skins. The skin of an earthworm feels moist and slimy on touching. Gases can easily pass through them. Though frogs have pair of lungs like human beings, they can also breathe through their skin, which is moist and slippery. 31. Whales and dolphins are not fish? They are mammals. People are mammals too. Mammals are the group of animals that breath air using lungs, give birth to live young (rather than laying eggs), and feed their young with mother s milk. Fish use their gills to take oxygen from the water that they live in. But people get the oxygen we need by breathing air, using our lungs. Whales and dolphins use their lungs to breathe air also. That s one reason why they come to the surface of the ocean. Sometimes they lie right at the surface of the water, with just a part of their back sticking out. Whales and dolphins don t have noses like you and me. Instead they have a hole called a blow hole on top of their heads. Sometimes when a whale breathes air out of its blow hole, it shows up as a spray or mist called a spout that can be seen many miles away. Blow holes are surrounded by muscles that keep the hole closed when the whale or dolphin is under water and open it when the

5 animal is at the surface and needs to breathe. The blowhole seals immediately after he breathes so that he won t get water in his lungs. 32. Gills in fish help them to use oxygen dissolved in water. Gills are projections of the skin. Gills are well supplied with blood vessels for exchange of gases. 33. Plants also respire for their survival. They also take in oxygen from the air and give out carbon dioxide. The exchange of gases takes place through tiny pores called stomata. In the cells oxygen is used to break down glucose into carbon dioxide and water as in other organisms. In plants each part can independently take in oxygen from the air and give out carbon dioxide. 34. Stomata are mainly found on the bottom of leaves to reduce dehydration. Stomata play an important role in photosynthesis as they allow the plant to absorb carbon dioxide from the environment. In exchange, stomata allow oxygen, which is a waste product of photosynthesis, to be released. In the process, water vapor is also lost as the internal parts of the leaves are exposed. To reduce exposure, stomata are found on the underside of the leaves. They are protected from the sun as excessive heat can increase the rate of water vapor leaving and thus wither the plant. Stomata also have guard cells around the epidermis that close when too much water is being lost. 35. Like all other living cells of the plants, the root cells also need oxygen to generate energy. Roots take up air from the air spaces present between the soil particles.

6 36. All living cells need air. In order for plants to be healthy, there needs to be a mixture of air and moisture in the soil. The correct balance of air to moisture is important because roots breathe air and the moisture surrounding the soil particles is part of the process that allow the roots to absorb both moisture and minerals for the plant's life processes. When a plant in a pot is overwatered, the excess water remains in the pot--completely saturating the plant's roots. Roots require air to thrive and survive. If their soil is filled with water, the tiny root hairs are unable to find any air in the soil and they drown. If the root hairs, which collect water and nutrients for the plant, are compromised--the entire plant is in jeopardy. 1. In cockroaches, air enters the body through (a) lungs (b) gills (c) spiracles (d) skin NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 2. During heavy exercise, we get cramps in the legs due to the accumulation of (a) carbon dioxide (b) lactic acid (c) alcohol (d) water

7 3. Normal range of breathing rate per minute in an average adult person at rest is: (a) 9 12 (b) (c) (d) During exhalation, the ribs (a) move outwards (b) move downwards (c) move upwards (d) do not move at all 5. Sometimes when we do heavy exercise, anaerobic respiration takes place in our muscle cells. What is produced during this process? (a) alcohol and lactic acid (b) alcohol and CO 2 (c) lactic acid and CO 2 (d) lactic acid only 6. Yeast is used in wine and beer industries because it respires (a) aerobically producing oxygen. (b) aerobically producing alcohol. (c) anaerobically producing alcohol. (d) anaerobically producing CO During the process of exhalation, the ribs move (a) down and inwards. (b) up and inwards. (c) down and outwards. (d) up and outward.

8 8. Breathing is a process that (a) provides O2 to the body. (b) breaks down food to release energy. (c) helps the body to get rid of CO2. (d) produces water in the cells. 9. Which of the following gives the correct combination of functions of breathing? (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iii) (d) (ii) and (iv) 10. Fish breathe with the help of gills which are richly supplied with blood vessels. The gills help the fish to (a) take in oxygen from air. (b) take in oxygen dissolved in water. (c) absorb nutrients present in water. (d) release waste substances in water. 11. Earthworms and frogs breathe through their skin because of which the skin of both the organisms is (a) moist and rough. (b) dry and rough. (c) dry and slimy. (d) moist and slimy. 12. The mountaineers carry oxygen with them because: (a) At an altitude of more than 5 km there is no air. (b) The amount of air available to a person is less than that available on the ground. (c) The temperature of air is higher than that on the ground. (d) The pressure of air is higher than that on the ground. 13. Fill in the blanks with suitable words. (a) The roots of a plant take up oxygen from the trapped between the particles. (b) Diaphragm forms the of the chest cavity. (c) Exchange of gases in the leaves take place with the help of. (d) Cockroaches breathe with the help of air tubes called.

9 14. Pick the odd-one-out from each of the groups given below on the basis of respiratory organs. Give reason for your answer. (a) cockroach, grasshopper, snail, ant (b) lizard, cow, earthworm, snake (c) crocodile, whale, dolphin, fish (d) snake, tadpole, crow, goat 15. Match the items in Column I with those in Column II: Column I (a) Yeast (b) Diaphragm (c) Skin (d) Leaves (e) Fish (f) Frog Column II (i) Earthworm (ii) Gills (iii) Alcohol (iv) Chest cavity (v) Stomata (vi) Lungs and skin (vii) Tracheae 16. There are some sentences given below related to respiration in organisms. Write one word answer against each description. (i) The air tubes of insects - (ii) Skeletal structures surrounding chest cavity - (iii) Muscular floor of chest cavity - (iv) Tiny pores on the surface of leaf - (v) Small openings on the sides of the body of an insect - (vi) The respiratory organs of human beings - (vii) The openings through which we inhale - (viii) An anaerobic organism - (ix) An organism with tracheal system 17. Which gas present in air is essential for aerobic respiration? What is the role of oxygen during respiration? 18. On an average, an adult human being at rest breathes times per minute. The breathing rate, however, may differ under different conditions. Arrange the following activities given in the box in order of increasing breathing rates and give reason for your answer. sleeping, cycling, brisk walk, watching T.V. 19. Whenever we feel drowsy or sleepy, we start yawning. Does yawning help us in anyway?

10 20. Insects and leaves of a plant have pores through which they exchange gases with the atmosphere. Can you write two points of differences between these pores with respect to their position, number and extension into the body? 21. Paheli participated in a 400 m race competition held at her school and won the race. When she came home she had mixed feelings of joy and pain as she had cramps in her leg muscles. After a massage she was relieved of the pain. Answer the following questions related to the situation. (a) What can be the possible reasons for the pain in her legs? (b) Why did she feel comfortable after a massage? 22. Observe the figures given below and answer the following. (a) Which of the figures A or B indicates the process of inhalation and which the process of exhalation? (b) In the figure label the arrows and indicate the direction of (i) movement of air (ii) movement of diaphragm (iii) movement of ribs 23. Match the names of organisms in Column I with their organs of breathing given in Column II. Transportation in Animals and Plants and Plants 1. All organisms need food, water and oxygen for survival. They need to transport all these to various parts of their body. Further, animals need to transport wastes to parts from where they can be removed. 2. Blood is the fluid which flows in blood vessels. It transports substances like digested food from the small intestine to the other parts of the body. It carries oxygen from the lungs to the cells of the body. It also transports waste for removal from the body. 3. Blood is a liquid, which has cells of various kinds suspended in it. The fluid part of the blood is called plasma. One type of cells are the red blood cells (RBC) which contain a red pigment called haemoglobin. The blood also has white blood cells (WBC) which fight against germs that may enter our body. Another type of cells called platelets are also present in the blood which help in blood clotting.

11 4. Haemoglobin bind with oxygen and transports it to all the parts of the body and ultimately to all the cells. It will be difficult to provide oxygen efficiently to all the cells of the body without haemoglobin. The presence of haemoglobin makes blood appear red. 5. Two types of blood vessels are present - the arteries and the veins. Arteries carry oxygen-rich blood from the heart to all parts of the body. Since the blood flow is rapid and at a high pressure, the arteries have thick elastic walls. Veins are the vessels which carry carbon dioxide-rich blood from all parts of the body back to the heart. The veins have thin walls. There are valves present in veins which allow blood to flow only towards the heart. 6. Schematic diagram of circulation: - 7. The pulmonary artery carries blood from the heart, so it is called an artery and not a vein. It carries carbon dioxide-rich blood to the lungs. Pulmonary vein carries oxygen-rich blood from the lungs to the heart. 8. Arteries s divide into smaller vessels. On reaching the tissues, they divide further into extremely thin tubes called capillaries. The capillaries join up to form veins which empty into the heart. 9. The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it. The heart is located in the chest cavity with its lower tip slightly tilted towards the left. The heart is roughly the size of our fist. To avoid the blood rich in oxygen and the blood rich in carbon dioxide from mixing with each other, the heart has four chambers. The two upper chambers are called the atria and the two lower chambers are called the ventricles. The partition between the chambers helps to avoid mixing up of blood rich in oxygen with the blood rich in carbon dioxide.

12 10. Functioning of the circulatory system: As the heart pumps, the arteries expand and contract, this is the pulse. So, the pulse is simply the expansion of the arteries. This expansion is caused by an increase in blood pressure pushing against the elastic walls of the arteries each time our heart beats. 12. The number of beats per minute is called the pulse rate. A resting pulse rate person, usually has a pulse rate between 72 and 80 beats per minute. 13. The walls of the chambers of the heart are made up of muscles. These muscles contract and relax rhythmically. This rhythmic contraction followed by its relaxation constitutes a heartbeat. Heartbeat can be felt

13 by placing hand over the left hand side of the chest. The doctor feels the heartbeats with the help of an instrument called a stethoscope. 14. A stethoscope is a device which amplifies the sound of the heart. It consists of a chest piece that carries a sensitive diaphragm, two ear pieces and a tube joining the parts. Doctors can get clues about the condition of your heart by listening through a stethoscope. 15. Each heart beat generates one pulse in the arteries and the pulse rate per minute indicates the rate of heartbeat. 16. The rhythmic beating of the various chambers of the heart maintains circulation of blood and transport of substances to the different parts of the body. 17. Animals such as sponges and Hydra do not posses any circulatory system. The water in which they live brings food and oxygen as it enters their bodies. The water carries away waste materials and carbon dioxide as it moves out. Thus, these animals do not need a circulatory fluid like the blood. 18. Carbon dioxide is removed as waste from the body through the lungs during exhalation. Undigested food is removed during egestion. 19. When our cells perform their functions, certain waste products are released. These are toxic and hence need to be removed from the body. The process of removal of wastes produced in the cells of the living organisms is called excretion. The excretion parts involved in excretion forms the excretory system (The kindeys, ureters, bladder and urethra form the excretory system).

14 20. The blood capillaries in the kidneys help in the removal of waste which is present in the blood. When the blood reaches the two kidneys, it contains both useful and harmful substances. The useful substances are absorbed back into the blood. The wastes dissolved in water are removed as urine. From the kidneys, the urine goes into the urinary bladder through tube-like ureters. It is stored in the bladder and is passed out through the urinary opening at the end of a muscular tube called urethra. 21. An adult human being normally passes about L of urine in 24 hours, and the urine consists of 95% water, 2.5 % urea and 2.5% other waste products. 22. We sweat on a hot summer day. The sweat contains water and salts. When we sweat, it helps to cool our body. 23. Aquatic animals like fishes, excrete cell waste in gaseous form (ammonia) which directly dissolves in water. Some land animals like birds, lizards, snakes excrete a semi-solid, white coloured compound (uric acid). The major excretory product in humans is urea. 24. In the event of kidney failure, waste products start accumulating in the blood. Such persons cannot survive unless their blood is filtered periodically through an artificial kidney. This process is called dialysis. 25. Plants take water and mineral nutrients from the soil through the roots and transport it to the leaves. The leaves prepare food for the plant, using water and carbon dioxide during photosynthesis. 26. Food is the source of energy and every cell of an organism gets energy by the breakdown of glucose. The cells use this energy to carry out vital activities of life. Therefore food must be made available to every cell of an organism. 27. Plants absorb water and minerals by the roots. The roots have root hair. The root hair increase the surface area of the root for the absorption of water and mineral nutrients dissolved in water. The root hair is in contact with the water present between the soil particles. Plants have pipe-like vessels to transport water and nutrients from the soil. The vessels are made of special cells, forming the vascular tissue. The vascular tissue for the transport of water and nutrients in the plant is called the xylem. The food has to be transported to all parts of the plant. This is done by the vascular tissue called the phloem. Thus, xylem and phloem transport substances in plants.

15 28. A tissue is a group of tissue cells that perform specialized function in an organism. 29. For very short distances water can move from one cell to another. In the same way water reaches xylem vessels of the root from the soil. 30. Plants release a lot of water by the process of transpiration. Plants absorb mineral nutrients and water from the soil. Not all the water absorbed is utilized by the plant. The water evaporates through the stomata present on the surface of the leaves by the process of transpiration. The evaporation of water from leaves generates a suction pull which can pull water to great heights in the tall trees. Transpiration also cools the plant. NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 1. The muscular tube through which stored urine is passed out of the body is called (a) kidney (b) ureter (c) urethra (d) urinary bladder 2. They are pipe-like, consisting of a group of specialised cells. They transport substances and form a two-way traffic in plants. Which of the following terms qualify for the features mentioned above? (a) Xylem tissue (b) Vascular tissue (c) Root hairs (d) Phloem tissue

16 3. The absorption of nutrients and exchange of respiratory gases between blood and tissues takes place in (a) veins (b) arteries (c) heart (d) capillaries 4. In which of the following parts of human body are sweat glands absent? (a) Scalp (b) Armpits (c) Lips (d) Palms 5. In a tall tree, which force is responsible for pulling water and minerals from the soil? (a) Gravitational force (b) Transportation force (c) Suction force (d) Conduction force 6. Aquatic animals like fish excrete their wastes in gaseous form as (a) Oxygen (b) Hydrogen (c) Ammonia (d) Nitrogen 7. In plants, water is transported through (a) Xylem (b) Phloem (c) Stomata (d) Root hair

17 8. Water absorption through roots can be increased by keeping the plants (a) in the shade (b) in dim light (c) under the fan (d) covered with a polythene bag 9. Fill in the blanks. (i) The blood from the heart is transported to all parts of the body by the. (ii) Haemoglobin is present in cells. (iii) Arteries and veins are joined by a network of. (iv) The rhythmic expansion and contraction of the heart is called. (v) The main excretory product in human beings is. (vi) Sweat contains water and. (vii) Kidneys eliminate the waste materials in the liquid form called. (viii) Water reaches great heights in the trees because of suction pull caused by. 10. Match structures given in Column I with functions given in Column II. Column I (i) Stomata (ii) Xylem (iii) Root hairs (iv) Phloem Column II (a) Absorption of water (b) Transpiration (c) Transport of food (d) Transport of water (e) Synthesis of carbohydrates 11. Why is transport of materials necessary in a plant or in an animal? Explain. 12. What will happen if there are no platelets in the blood? 13. What are stomata? Give two functions of stomata. 14. Does transpiration serve any useful function in the plants? Explain. 15. What are the components of blood? 16. Why is blood needed by all the parts of a body? 17. What makes the blood look red?

18 18. Describe the function of the heart. 19. Why is it necessary to excrete waste products? 20. Draw a diagram of the human excretory system and label the various parts. 21. Veins have valves which allow blood to flow only in one direction. Arteries do not have valves. Yet the blood flows in one direction only. Can you explain why? 22. What is the special feature present in a human heart which does not allow mixing of blood when oxygenrich and carbon dioxide-rich blood reach the heart? 23. Name the organ which is located in the chest cavity with its lower tip slightly tilted towards the left. 24. Arrange the following statements in the correct order in which they occur during the formation and removal of urine in human beings. (a) Ureters carry urine to the urinary bladder. (b) Wastes dissolved in water is filtered out as urine in the kidneys. (c) Urine stored in urinary bladder is passed out through the urinary opening at the end of the urethra. (d) Blood containing useful and harmful substances reaches the kidneys for filtration. (e) Useful substances are absorbed back into the blood. 12. Paheli uprooted a rose plant from the soil. Most of the root tips, with root hairs got left behind in the soil. She planted it in a pot with new soil and watered it regularly. Will the plant grow or die? Give reason for your answer. 13. (a) Name the only artery that carries carbon dioxide-rich blood. (b) Why is it called an artery if it does not carry oxygen-rich blood? 14. Boojho s uncle was hospitalised and put on dialysis after a severe infection in both of his kidneys. (a) What is dialysis? (b) When does it become necessary to take such a treatment? 15. Name the process and the organ which helps in removing the following wastes from the body. (a) Carbondioxide (b) Undigested food (c) Urine (d) Sweat 16. While learning to ride a bicycle Boojho lost his balance and fell. He got bruises on his knees and it started bleeding. However, the bleeding stopped after some time. (a) Why did the bleeding stop? (b) What would be the colour of the wounded area and why? (c) Which type of blood cells are responsible for clotting of blood? 17. What is a stethoscope? What is its application?

19 18. Match the parts of the heart in Column I with the direction of flow of blood in Column II. Column I (i) Right ventricle (ii) Pulmonary veins (iii) Left atrium (iv) Pulmonary arteries (v) Left ventricle (vi) Right auricle Column II (a) Pushes blood into the pulmonary artery. (b) Take deoxygenated blood from the heart to lungs. (c) Receives blood from different parts of the body. (d) Bring oxygenated blood from lungs to the heart. (e) Pushes blood into the aorta. (f) Receives deoxygenated blood from the pulmonary veins. 19. Read the following terms given below. root hairs, xylem, urethra, arteries, kidneys, veins, atria, capillaries, heart, ureter, phloem, urinary bladder. Group the terms on the basis of the categories given below. (a) Circulatory system of animals. (b) Excretory system in human. (c) Transport of substances in plants. 20. Fill in the blanks of the following paragraph using just two words arteries and veins. (a) carry oxygen-rich blood from the heart to all parts of the body and (b) carry carbon dioxide-rich blood from all parts of the body back to the heart. (c) have thin walls and (d) have thick elastic walls. Blood flows at high pressure in (e). Valves are present in (f) which allow blood to flow only towards the heart. (g) divide into smaller vessels. These vessels further divide into extremely thin tubes called capillaries. The capillaries join up to form (h). 21. While learning to ride a bicycle Boojho lost his balance and fell. He got bruises on his knees and it started bleeding. However, the bleeding stopped after some time. (a) Why did the bleeding stop? (b) What would be the colour of the wounded area and why? (c) Which type of blood cells are responsible for clotting of blood? 22. What is a stethoscope? What is its application?

20 Reproduction in Plants 1. To produce its kind is a characteristic of all living organisms. 2. The production of new individuals from their parents is known as reproduction. 3. There are different modes of reproduction in plants: - (i) Asexual reproduction: - Plants can give rise to new plants without seeds or spores. (ii) Sexual reproduction: - New plants are obtained from seeds. 4. Vegetative propagation is a type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds. Since reproduction is through the vegetative parts of the plant, it is known as vegetative propagation. 5. Natural vegetative propagation can take place from the following parts of a plant: 1. Roots 2. Stem 3. Leaves Vegetative propagation by roots: - Examples, sweet potato, dahlia. Vegetative propagation by stem: - Examples, potato, ginger, turmeric. Vegetative propagation by leaves: - Example, bryophyllum.

21 6. Following are some of the advantages of vegetative propagation: - (i) The new plants produced by vegetative propagation are exactly like the parent plant i.e. the new plants possess all characteristics of the parent plant. (ii) The plants produced by vegetative propagation grow rapidly. (iii) Desired varieties and qualities of fruits and plants can be produced by vegetative propagation. (iv) Those plants can also be produced by vegetative propagation which do not produce seeds or which cannot produce viable seeds. (v) The desirable characters of a variety can be preserved indefinitely through vegetative reproduction. 7. Plants such as cacti produce new plants when their parts get detached from the main plant body. Each detached part can grow into a new plant. 8. Artificial vegetative propagation is the deliberate production of new plants from parts of old plants by humans. This can be done by following three methods: 1. Cutting 2. Layering 3. Grafting Cutting: - This method is commonly used in rose and sugar cane. In this method one year old stem of root is cut from a distance of 20 to 30 cm. and is buried in the moist soil in natural position. After sometime, roots develop from this cutting and it grows into a new plant. Layering: - This method of asexual reproduction is also used in the production of plants such as Bougainvillea, jasmine, guava, strawberries, lemon, China rose etc. This method of vegetative propagation is used in those plants whose soft branches occur near the ground such as jasmine plant. In this method, a branch of the plant which is near to the ground is pulled towards the ground and a part of this branch is covered with moist soil leaving the tip of this branch above the ground. After sometime, roots develop from that part of the branch which was buried in the soil.

22 Grafting: - The plant of which the root system is taken is called stock, while the other plant of which the shoot is selected is known as scion or graft. This method of propagation is used in mango, apple, rose, banana, pear, grape, pineapple and peach. In this method of vegetative propagation the stems of two different plants are joined together so as to produce a new plant containing the characters of both plants. Out of the two plants one plant has a strong root system while the other has a better flower or fruit yield. 9. Budding in Yeast: - Most yeasts reproduce asexually by a process called budding. First, it produces a small protuberance on the parent cell that grows to a full size and forms a bud. The nucleus of the parent cell splits into a daughter nucleus and migrates into the daughter cell. The bud detaches from the mother s body by forming a constriction at the base. Budding will repeat to form a chain of bud cells. The daughter cell produced during the budding process is generally smaller than the mother cell. 10. Fragmentation may be defined as the process of breaking up of parent animal into small parts, each of which can grow into a new complete individual. This process of asexual reproduction is found in planaria, spirogyra and hydra.

23 11. Spore formation: - The spores are asexual reproductive bodies. When spores are released they keep floating in the air. As they are very light they can cover long distances. Each spore is covered by a hard protective coat to withstand unfavourable conditions such as high temperature and low humidity. So they can survive for a long time. Under favourable conditions, a spore germinates and develops into a new individual. Plants such as moss and ferns also reproduce by means of spores. 12. The flowers are the reproductive parts of a plant. The stamens are the male reproductive part and the pistil is the female reproductive part. 13. The flowers which contain either only the pistil or only the stamens are called unisexual flowers. The flowers which contain both stamens and pistil are called bisexual flowers. Corn, papaya and cucumber produce unisexual flowers, whereas mustard, rose and petunia have bisexual flowers. Both the male and the female unisexual flowers may be present in the same plant or in different plants. 14. Anther contains pollen grains which produce male gametes. A pistil consists of stigma, style and ovary. The ovary contains one or more ovules. The female gamete or egg is formed in an ovule. In sexual reproduction a male and a female gamete fuse to form a zygote. 15. Generally pollen grains have a tough protective coat which prevents them from drying up. Since pollen grains are light, they can be carried by wind or water. Insects visit flowers and carry away pollen on their

24 bodies. Some of the pollen lands on the stigma of a flower of the same kind. The transfer of pollen from the anther to the stigma of a flower is called pollination. 16. If pollination the pollen lands on the stigma of the same flower it is called self-pollination. When selfpollination the pollen of a flower lands on the stigma of another flower of the same plant, or that of a different plant of the same kind, it is called cross-pollination. 17. The cell which results after fusion of fusion the gametes is called a zygote. The process of fusion of male and female gametes (to form a zygote) is called fertilization. The zygote develops into an embryo. 18. After fertilisation, the ovary grows into a fruit and other parts of the flower fall off. The fruit is the ripened ovary. The seeds develop from the ovules. The seed contains an embryo enclosed in a protective seed coat. Some fruits are fleshy and juicy such as mango, apple and orange. Some fruits are hard like almonds and walnuts.

25 19. SEED DISPERSAL:- Plants make seeds that can grow into new plants, but if the seeds just fall to the ground under the parent plant, they might not get enough sun, water or nutrients from the soil. Because plants cannot walk around and take their seeds to other places, they have developed other methods to disperse (move) their seeds. The most common methods are wind, water, animals and explosion. Seeds are dispersed away from each other and from the parent plant so that there is less competition. (i) Winged seeds such as those of drumstick and maple and, light seeds of grasses or hairy seeds of aak (Madar) and hairy fruit of sunflower get blown off with the wind to faraway places. (ii) Some seeds are dispersed by water. These fruits or seeds usually develop floating ability in the form of spongy or fibrous outer coat as in coconut. (iii) Some seeds are dispersed by animals, especially spiny seeds with hooks which get attached to the bodies of animals and are carried to distant places. Examples are Xanthium) and Urena. (iv) Some seeds are dispersed when the fruits burst with sudden jerks. The seeds are scattered far from the parent plant. This happens in the case of castor and balsam. Coconut Lotus Mangroove

26 20. Seed dispersal helps the plants to (i) prevent overcrowding, (ii) avoid competition for sunlight, water and minerals and (iii) invade new habitats. NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 1. Which of the following parts of a plant take part in sexual reproduction? (i) Flower (ii) Seed (iii) Fruit (iv) Branch Choose the correct answer from below. (a) (i) and (ii) (b) (i), (ii) and (iii) (c) (iii) and (iv) (d) (ii), (iii) and (iv) 2. Lila observed that a pond with clear water was covered up with a green algae within a week. By which method of reproduction did the algae spread so rapidly? (a) Budding (b) Sexual reproduction (c) Fragmentation (d) Pollination 3. Seeds of drumstick and maple are carried to long distances by wind because they possess (a) winged seeds (b) large and hairy seeds (c) long and ridged fruits (d) spiny seeds 4. The eye of the potato plant is what (a) the root is to any plant. (b) the bud is to a flower. (c) the bud is to Bryophyllum leaf. (d) the anther is to stamen. 5. The ovaries of different flowers may contain (a) only one ovule (b) many ovules (c) one to many ovules (d) only two ovules

27 6. Which of the following statements is/are true for sexual reproduction in plants? (i) Plants are obtained from seeds. (ii) Two plants are always essential. (iii) Fertilization can occur only after pollination. (iv) Only insects are agents of pollination. Choose from the options given below. (a) (i) and (iii) (b) (i) only (c) (ii) and (iii) (d) (i) and (iv) 7. Pollination refers to the (a) transfer of pollen from anther to ovary. (b) transfer of male gametes from anther to stigma. (c) transfer of pollen from anther to stigma. (d) transfer of pollen from anther to ovule. 8. The reproductive part of a plant is the (a) leaf (b) stem (c) root (d) flower 9. The process of fusion of the male and the female gametes is called (a) fertilization (b) pollination (c) reproduction (d) seed formation 10. Mature ovary forms the (a) seed (b) stamen (c) pistil (d) fruit

28 11. A spore producing plant is (a) rose (b) bread mould (c) potato (d) ginger 12. Bryophyllum can reproduce by its (a) stem (b) leaves (c) roots (d) flower 13. Pick the odd one out from the following on the basis of mode of reproduction and give reason for it. Sugarcane, Potato, Rice, Rose 14. Fungus, moss and fern reproduce by a common method of asexual reproduction. Name the method. 15. One morning as Paheli strolled in her garden she noticed many small plants which were not there a week ago. She wondered where they had come from as nobody had planted them there. Explain the reason for the growth of these plants. 16. When you keep food items like bread and fruits outside for a long time especially during the rainy season, you will observe a cottony growth on them. (a) What is this growth called? (b) How does the growth take place? 17. Coconut is a large and heavy fruit. How is it adapted for dispersal by water? 18. Match items in Column I with those in Column II: Column I (a) Bud (b) Eyes (c) Fragmentation (d) Wings (e) Spores Column II (i) Maple (ii) Spirogyra (iii) Yeast (iv) Bread mould (v) Potato (vi) Rose 19. Boojho had the following parts of a rose plant a leaf, roots, a branch, a flower, a bud and pollen grains. Which of them can be used to grow a new rose plant?

29 20. Fill in the blanks: (a) Production of new individuals from the vegetative part of parent is called. (b) A flower may have either male or female reproductive parts. Such a flower is called. (c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as. (d) The fusion of male and female gametes is termed as. (e) Seed dispersal takes place by means of, and. 21. Describe the different methods of asexual reproduction. Give examples. 22. Explain what you understand by sexual reproduction. 23. State the main difference between asexual and sexual reproduction. 24. Sketch the reproductive parts of a flower. 25. Explain the difference between self-pollination and cross-pollination. 26. How does the process of fertilization take place in flowers? 27. Describe the various ways by which seeds are dispersed. 28. In the diagram given below label the parts marked (a), (b) and (c): There are some statements given below which describes functions of certain parts of a flower. Identify the parts. (a) The part which contains pollen grains - (b) The part where the female gamete is formed - (c) The female reproductive part where pollen grains germinate - (d) The colourful part of flower which attracts insects 30. Fill in the blanks with correct terms. The male and female gametes fuse to form a (a) during the process of (b). This grows into an (c) which is enclosed within a seed. After fertilization the ovules develop into (d) and the ovary develops into a (e).

30 31. Write how the following seeds are dispersed. (a) Seeds with wings. (b) Small and light seeds. (c) Seeds with spines/hooks. 32. In the diagram of a bisexual flower given below5, draw the missing part and label the parts marked (a), (b) and (c). Also label the missing part that you draw. Soil 1. Soil is one of the most important natural resources. It supports the growth of plants by holding the roots firmly and supplying water and nutrients. It is the home for many organisms. Soil is essential for agriculture. 2. Polythene bags and plastics pollute the soil. They also kill the organisms living in the soil. Other substances which pollute the soil are a number of waste products, chemicals and pesticides. 3. The use of polythene bags and plastics should be banned. Waste products and chemicals should be treated before they are released into the soil. The use of pesticides should be minimized. 4. The rotting dead matter in the soil is called humus. 5. The soil is formed by the breaking down of rocks by the action of wind, water and climate. This process is called weathering. The weathering nature of any soil depends upon the rocks from which it has been formed and the type of vegetation that grows in it. 6. A vertical section through different layers of the soil is called the soil profile. Soil is composed of distinct layers. These layers are referred to as horizons. Each layer differs in feel (texture), colour, depth and chemical composition. 7. Soil profile: - (I) The uppermost horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more water. It is called the topsoil or the il A-horizon. This provides shelter for many living organisms such as worms, rodents, moles and beetles. The roots of small plants are embedded entirely in the topsoil. (II) The next layer has a lesser amount of humus but more of minerals. This layer is generally harder and more compact and is called the B-horizon or the middle layer. (III) The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices. Below this layer is the bedrock, bedrock which is hard and difficult to dig with a spade.

31 8. The mixture of rock particles and humus is called the soil and humus is called and humus is called the soil the soil. The soil is classified on the basis of the proportion of particles of various sizes: - (i) If soil contains greater proportion of big particles it is called sandy soil sandy soil. (ii) If the proportion of fine particles is relatively higher, then it is called clayey soil clayey soil. (iii) If the amount of large and clayey soil fine particles is about the same, then the soil is called loamy. 9. Sandy soils tend to be light, well aerated and rather dry. Sand particles are quite large. They cannot fit closely together, so there are large spaces between them. These spaces are filled with air (sand is well aerated). Water can drain quickly through the spaces between the sand particles. 10. Clay particles, being much smaller, pack tightly together, leaving little space for air. Unlike sandy soil, water can be held in the tiny gaps between the particles of clay. So clay soils have little air. But they are heavy as they hold more water than the sandy soils. 11. The best topsoil for growing plants is loam. Loamy soil Loamy soil is a mixture of sand, Loamy soil clay and another type of soil particle known as silt. Silt occurs as a deposit in river beds. The size of the silt particles is between those of sand and clay. The loamy soil also has humus in it. It has the right water holding capacity for the growth of plants. 12. Some soil properties: - (i) Soil texture can influence whether soils are free draining, whether they hold water and how easy it is for plant roots to grow. (ii) Soil structure describes the way the sand, silt and clay particles are clumped together. Organic matter (decaying plants and animals) and soil organisms like earthworms and bacteria influence soil structure. Clays, organic matter and materials excreted by soil organisms bind the soil particles together to form aggregates. Soil structure is important for plant growth, regulating the movement of air and water, influencing root development and affecting nutrient availability.

32 (iii) Soil porosity refers to the pores within the soil. Porosity influences the movement of air and water. Healthy soils have many pores between and within the aggregates. Poor quality soils have few visible pores, cracks or holes. (iv) Soil colours range from black to red to white. Sometimes it can even be blue! Soil colour mostly comes from organic matter and iron. Topsoil is often dark because of organic matter. An even, single colour indicates the soil is well drained. In contrast, rusty spots and grey patches (sometimes even a light blue in colour) indicate poor drainage. (v) Soil consistence refers to the ease with which an individual ped can be crushed by the fingers. Soil consistence, and its description, depends on soil moisture content. (vi) The most important effect of ph in the soil is on ion solubility, which in turn affects microbial and plant growth. A ph range of 6.0 to 6.8 is ideal for most crops because it coincides with optimum solubility of the most important plant nutrients. Some minor elements (e.g., iron) and most heavy metals are more soluble at lower ph. This makes ph management important in controlling movement of heavy metals (and potential groundwater contamination) in soil. 13. Finding percolation rate of water in soil (An activity): - Approx. 5 cm. diameter PVC pipe is taken and cut into 20 cm long piece. At the place where the soil is collected, the pipe is placed about 2 cm deep in the ground. 200 ml water is poured in the pipe slowly. The time is noted when we start pouring water. When all the water has percolated leaving the pipe empty, the time is noted again. We should be careful not to let the water spill over or run down on the outside of the pipe while pouring. The rate of percolation is calculated by using the following formula: For example, suppose that for a certain sample, it took 20 minutes for 200 ml to percolate. So, 14. Moisture in the soil (An activity): - A boiling tube is taken. Two spoonfuls of a soil sample is put in it. It is heated on a flame. On heating, water in the soil evaporates, moves up and condenses on the cooler inner walls of the upper part of the boiling tube. On a hot summer day, the vapour coming out of the soil, reflect the sunlight and the air above the soil seems to shimmer.

33 15. Absorption of water by soil (An activity): - A plastic funnel is taken. A filter paper (or a piece of newspaper sheet) is taken, folded and placed it as shown in the figure. 50g of dry, powdered soil is weighed and poured into the funnel. A certain amount of water is measured in a measuring cylinder and poured drop by drop on the soil. A dropper can be used for this purpose. (Do not let all the water fall at one spot.) The water is poured all over the soil. The water is poured till it starts dripping. On subtracting the amount of water left in the measuring cylinder from the amount we started with gives the amount of water retained by the soil. The results are recorded in the following manner: Weight of soil = 50g Initial volume of water in the measuring cylinder = U ml Final volume of water in the measuring cylinder = V ml Volume of water absorbed by the soil = (U V) ml Weight of water absorbed by the soil = (U V) g (1 ml of water has weight equal to 1 g) This activity is repeated with different soil samples. 16. Soil is affected by wind, rainfall, temperature, light and humidity. These are some important climatic factors which affect the soil profile and bring changes in the soil structure. The climatic factors, as well as the components of soil, determine the various types of vegetation and crops that might grow in any region. (i) Clayey and loamy soils are both suitable for growing cereals like wheat, and gram. Such soils are good at retaining water. (ii) For paddy, soils rich in clay and organic matter and having a good capacity to retain water are ideal. (iii) For lentils (masoor) and other pulses, loamy soils, which drain water easily, are required. (iv) For cotton, sandy loam or loam, which drain water easily and can hold plenty of air, are more suitable. 17. The removal of land surface by water, wind or ice is known as erosion. Plant roots firmly bind the soil. In the absence of plants, soil becomes loose. So it can be moved by wind and flowing water. Erosion of soil is more severe in areas of little or no surface vegetation, such as desert or bare lands. So, cutting of trees and deforestation should be prevented and effort should be made to increase the green areas.

34 NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 1. In addition to the rock particles, the soil contains (a) air and water (b) water and plants (c) minerals, organic matter, air and water (d) water, air and plants 2. The water holding capacity is the highest in (a) sandy soil (b) clayey soil (c) loamy soil (d) mixture of sand and loam 3. The microorganisms present in the soil require moisture (water) and nutrients for growth and survival. Choose from the options below the habitat (place) where the soil has plenty of water and nutrients. (a) Desert (b) Forest (c) Open field (d) Cricket ground 4. Availability of water and minerals in the soil for maximum absorption by roots is in the (a) B-horizon (b) C-horizon (c) A-horizon (d) surface of soil 5. Soil conservation measures are mainly aimed at protecting which of the following? (a) Plants (b) Top soil (c) Sub soil (d) Soil organisms 6. Read the following statements with reference to soil. (i) Weathering is a very fast process of soil formation. (ii) Percolation of water is faster in sandy soils. (iii) Loamy soil contains only sand and clay. (iv) Top soil contains the maximum amount of humus. Choose the correct statements from the above. (a) (ii) and (iv) (b) (i) and (iii) (c) (ii) and (iii) (d) (i) and (ii) 7. Soil has particles of different sizes. Arrange the words given below in increasing order of their particle size. Rock, Clay, Sand, Gravel, Silt 8. Read the following statements and give the appropriate terms for each of them. (a) The process of breakdown of rocks by the action of wind, water, sunlight. (b) Removal of top soil during heavy rains or strong winds. (c) Accumulation of wastes in the soil generated by human activity which alter the features of soil. (d) The process of movement of water into deeper layers of soil.

35 9. Is it a good practice to remove grass and small plants that are growing in an open, unused field? Give reason to support your answer. 10. A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper. He could not dig beyond a depth of 5 feet. Provide a suitable scientific explanation. 11. Locate the following zones in the diagram of soil profile given below: - Top soil, Subsoil, C-horizon, Bedrock 12. Rajasthan is a desert state in India. Once while travelling to Rajasthan by train, Boojho observed several streams and rivulets of rain water during the journey but to his surprise he did not see streams of water in the desert region even during rains. Help Boojho find a suitable explanation for this. 13. Match the animals in Column I with their natural place of dwelling (habitat) in Column II. 14. Continuously water-logged soils are disadvantageous for plant growth. Why? 15. Why is soil erosion relatively less in dense forests as compared to barren, open fields? 16. Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently. Give reasons. 17. In towns and cities, generally, the bore wells have to be dug very deep to get water as compared to bore wells dug in villages. Give suitable reasons.

36 18. Unscramble the following jumbled words related to soil. 19. How can a farmer convert acidic soil to neutral soil? 20. Match the items in Column I with those in Column II: Column I (i) A home for living organisms (ii) Upper layer of the soil (iii) Sandy soil (iv) Middle layer of the soil (v) Clayey soil 21. Explain how soil is formed. 22. How is clayey soil useful for crops? 23. List the differences between clayey soil and sandy soil. Column II (a) Large particles (b) All kinds of soil (c) Dark in colour 24. Sketch the cross section of soil and label the various layers. (d) Small particles and packed tight (e) Lesser amount of humus 25. Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 ml of water to percolate through the soil sample. Calculate the rate of percolation. 26. Explain how soil pollution and soil erosion could be prevented. Motion and Time 1. The distance covered by an object in a unit time as the speed of speed the object. 2. When we say that a car is moving with a speed of 50 kilometres per hour, it implies that it will cover a distance of 50 kilometres in one hour. However, a car seldom moves with a constant speed for one hour. In fact, it starts moving slowly and then picks up speed. So, when we say that the car has a speed of 50 kilometres per hour, we usually consider only the total distance covered by it in one hour. We do not bother whether the car has been moving with a constant speed or not during that hour. The speed calculated here is actually the average speed of the car. 3. Speed is the total distance covered divided by the total time taken. 4. If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform. On the other hand, an object moving along a straight line with a constant speed is said to be in uniform motion. 5. Our ancestors noticed that many events in nature repeat themselves after definite intervals of time. For example, they found that the sun rises everyday in the morning. The time between one sunrise and the next was called a day. Similarly, a month was measured from one new moon to the next. A year was fixed as the time taken by the earth to complete one revolution of the sun. 6. A simple pendulum consists of a small metallic ball or a piece of stone suspended from a rigid stand by a thread. The metallic ball is called the bob of the pendulum.

37 One of the most well-known periodic motions is that of a simple pendulum. The first figure given above shows the pendulum at rest in its mean position. When the bob of the pendulum is released after taking it slightly to one side, it begins to move to and fro [Refer the second figure]. The to and fro motion of a simple pendulum is an example of a periodic or an oscillatory motion. The pendulum is said to have completed one oscillation when oscillation its bob, starting from its mean position O, moves to A, to B and back to O. The pendulum also completes one oscillation when its bob moves from one extreme position A to the other extreme position B and comes back to A. The time taken by the pendulum to complete one oscillation is called its time period. 7. The basic unit of time is a second. Its second symbol is s. Larger units of time are minutes (min) and hours (h). 8. Unit of speed: - Since the speed is distance/time, the basic unit of speed is m/s. Of course, it could also be expressed in other units such as m/min or km/h. 9. Many time measuring devices were used in different parts of the world before the pendulum clocks became popular. Sundials, water clocks and sand clocks are some examples of such devices. Different designs of these devices were developed in different parts of the world A speedometer is an instrument that indicates the speed of a vehicle, usually combined with a device known as an odometer that records the distance traveled. 12. DISTANCE-TIME GRAPH: - (I) The table shown below gives the odometer reading at different times of the journey: -

38 Time (AM) Odometer reading Distance from the starting point 8:00 AM km 0 km 8:30 AM km 20 km 9:00 AM km 40 km 9:30 AM km 60 km 10:00 AM km 80 km The table shown above gives the information about the distance moved by the bus only at some definite time intervals. On the other hand, from the distance-time graph we can find the distance moved by the bus at any instant of time. Suppose we want to know how much distance the bus had travelled at 8:15 AM. We mark the point corresponding to the time (8:15 AM) on the x-axis. Suppose this point is A. Next we draw a line perpendicular to the x-axis (or parallel to the y-axis) at point A. We then mark the point, T, on the graph at which this perpendicular line intersects it. Next, we draw a line through the point T parallel to the x-axis. This intersects the y-axis at the point B. The distance corresponding to the point B on the y-axis, OB, gives us the distance in km covered by the bus at 8:15 AM. (II) Boojho and Paheli found out the distance travelled by a car and the time taken by it to cover that distance. Their data was made into a tabular form. S. No. Time Distance min 1 km 3 2 min 2 km 4 3 min 3 km 5 4 min 4 km 6 5 min 5 km

39 NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 1. Which of the following cannot be used for measurement of time? (a) A leaking tap. (b) Simple pendulum. (c) Shadow of an object during the day. (d) Blinking of eyes. 2. Observe the figure given below: - The time period of a simple pendulum is the time taken by it to travel from (a) A to B and back to A. (b) O to A, A to B and B to A. (c) B to A, A to B and B to O. (d) A to B.

40 3. The correct symbol to represent the speed of an object is (a) 5 m/s (b) 5 mp (c) 5 m/s -1 (d) 5 s/m 4. Boojho walks to his school which is at a distance of 3 km from his home in 30 minutes. On reaching he finds that the school is closed and comes back by a bicycle with his friend and reaches home in 20 minutes. His average speed in km/h is (a) 8.3 (b) 7.2 (c) 5 (d) A car moves with a speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. The total distance covered by the car is: (a) 100 km (b) 25 km (c) 15 km (d) 10 km 6. An oscillating pendulum is shown below: - Time taken by the bob to move from A to C is t 1 and from C to O is t 2. The time period of this simple pendulum is (a) (t 1 + t 2 ) (b) 2 (t 1 + t 2 ) (c) 3 (t 1 + t 2 ) (d) 4 (t 1 + t 2 )

41 7. Two students were asked to plot a distance-time graph for the motion described by Table A and Table B. The graph given above is true for (a) both A and B. (b) A only. (c) B only. (d) neither A nor B. 8. A bus travels 54 km in 90 minutes. The speed of the bus is (a) 0.6 m/s (b) 10 m/s (c) 5.4 m/s (d) 3.6 m/s 9. Which of the following distance-time graphs shows a truck moving with speed which is not constant?

42 10. The distance-time graph for the motion of two vehicles A and B is shown below. Which one of them is moving faster? 11. If Boojho covers a certain distance in one hour and Paheli covers the same distance in two hours, who travels in a higher speed? 12. The average age of children of Class VII is 12 years and 3 months. Express this age in seconds. 13. A spaceship travels 36,000 km in one hour. Express its speed in km/s. 14. The odometer of a car reads km when the clock shows the time 08:30 AM. What is the distance moved by the car, if at 08:50 AM, the odometer reading has changed to km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also. 15. Complete the data of the table given below with the help of the distance-time graph given below the table:

43 16. Given below is the distance-time graph of the motion an object: - (i) What will be the position of the object at 20s? (ii) What will be the distance travelled by the object in 12s? (iii) What is the average speed of the object? 17. Show the shape of the distance-time graph for the motion in the following cases: (i) A car moving with a constant speed. (ii) A car parked on a side road. 18. A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum? 19. The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train. 20. Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school. 21. Starting from A, Paheli moves along a rectangular path ABCD as shown in given below. She takes 2 minutes to travel each side. Plot a distance-time graph and explain whether the motion is uniform or nonuniform.

44 22. Boojho goes to the football ground to play football. The distance time graph of his journey from his home to the ground is as given below: - (a) What does the graph between point B and C indicate about the motion of Boojho? (b) Is the motion between 0 to 4 minutes uniform or nonuniform? (c) What is his speed between 8 and 12 minutes of his journey?

45 SOME IMPORTANT POINTS FOR REVISION FOR CLASS 7 (03 CHAPTERS) 1. Light travels along straight lines. Light 2. Any polished or a shiny surface changes the direction of light that falls on it. This change of direction by any polished or a shiny surface is called reflection of light. 3. When a lighted candle is placed in front of a plane mirror, it appears as if a similar candle is placed behind the mirror. The candle, which appears behind the mirror, is the image of the candle formed by the mirror. The candle itself is the object. 4. An image formed by a plane mirror is erect and of the same size as the object. 5. An image which can be obtained on a screen is called a real image. 6. An image which cannot be obtained on a screen is called a virtual image. 7. The image formed by a plane mirror is erect, virtual, and is of the same size as the object. The image is at the same distance behind the mirror as the object is in front of it. 8. In an image formed by a mirror, the left side of the object is seen on the right side in the image, and right side of the object appears to be on the left side in the image. 9. If the reflecting surface of a spherical mirror is concave, it is called a concave mirror. If the reflecting surface is convex, then it is a convex mirror. A Concave and a Convex mirror 9. The word AMBULANCE is written as shown below on the vehicle: - When the driver of a vehicle ahead of an ambulance looks in her/his rear view mirror, s/he can read AMBULANCE written on it and give way to it. It is the duty of every one of us to allow an ambulance to pass without blocking its way. 10. Image formed by a convex mirror is erect, virtual and smaller in size than the object. 11. In the side mirror of a scooter or a car the images of all the objects appear smaller than the objects themselves.

46 12. The curved shining surface of a spoon acts as a mirror. (i) Image from the outer side of a spoon: - The image will be erect and larger in size. (ii) Image from the inner side of a spoon: - The image will be inverted and smaller in size. The inner surface of a spoon acts like a concave mirror, while its outer surface acts like a convex mirror. 13. A concave mirror can form a real and inverted image. When the object is placed very close to the mirror, the image formed is virtual, erect and magnified. 14. Doctors use concave mirrors for examining eyes, ears, nose and throat. Concave mirrors are also used by dentists to see an enlarged image of the teeth. The reflectors of torches, headlights of cars and scooters are concave in shape. 15. Convex mirrors can form images of objects spread over a large area. So, these help the drivers to see the traffic behind them. 16. A magnifying glass is actually a type of a lens. Lenses are widely used in spectacles, telescopes and microscopes. 17. Those lenses which feel thicker in the middle than at the edges are convex lenses. Those which feel thinner in the middle than at the edges are concave lenses. A convex lens and concave lens 18. A convex lens converges (bends inward) the light generally falling on it. Therefore, it is called a converging lens. On the other hand, a concave lens diverges (bends outward) the light and is called a diverging lens.

47 19. A convex lens can forms real and inverted image. When the object is placed very close to the lens, the image formed is virtual, erect and magnified. When used to see objects magnified, the convex lens is called a magnifying glass. 20. A concave lens always forms erect, virtual and smaller image than the object. 21. White light is composed of seven colours. These are red, orange, yellow, green, blue, indigo and violet. 22. Some uses of convex lens: - (i) The lens in the human eyes is a biconvex lens. So the most common use of the lens is that it helps us to see. (ii) Another common example of the use convex lens is a magnifying glass. When an object is placed in front of it at a distance shorter than the focal length of the lens, it produces a magnified and erect image of the object on the same side as the object itself. (iii) It is used to correct hypermetropia or long-sightedness. (iv) It is used in cameras because it focuses light and produces a clear and crisp image. (v) It is also used in other magnifying devices such as microscopes and telescopes. 23. Despite being less useful than convex lenses, concave lenses have several uses, including in eyeglasses and contacts, flashlights, peepholes, binoculars, telescopes, and in photography. NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 1. Boojho and Paheli were given one mirror each by their teacher. Boojho found his image to be erect and of the same size whereas Paheli found her image erect and smaller in size. This means that the mirrors of Boojho and Paheli are, respectively (a) plane mirror and concave mirror. (b) concave mirror and convex mirror. (c) plane mirror and convex mirror. (d) convex mirror and plane mirror. 2. Which of the following can be used to form a real image? (a) Concave mirror only. (b) Plane mirror only. (c) Convex mirror only. (d) Both concave and convex mirrors

48 3. If an object is placed at a distance of 0.5 m in front of a plane mirror, the distance between the object and the image formed by the mirror will be (a) 2 m (b) 1 m (c) 0.5 m (d) 0.25 m 4. You are provided with a concave mirror, a convex mirror, a concave lens and a convex lens. To obtain an enlarged image of an object you can use either (a) concave mirror or convex mirror. (b) concave mirror or convex lens. (c) concave mirror or concave lens. (d) concave lens or convex lens. 5. A rainbow can be seen in the sky (a) when the sun is in front of you. (b) when the sun is behind you. (c) when the sun is overhead. (d) only at the time of sun rise. 6. An erect and enlarged image can be formed by (a) only a convex mirror. (b) only a concave mirror. (c) only a plane mirror. (d) both convex and concave mirrors. 7. You are provided with a convex mirror, a concave mirror, a convex lens and a concave lens. You can get an inverted image from (a) both concave lens and convex lens. (b) both concave mirror and convex mirror. (c) both concave mirror and convex lens. (d) both convex mirror and concave lens.

49 8. An image formed by a lens is erect. Such an image could be formed by a (a) convex lens provided the image is smaller than object. (b) concave lens provided the image is smaller than object. (c) concave lens provided the image is larger than object. (d) concave lens provided the image is of the same size. 9. A virtual image larger than the object can be produced by a (a) concave lens (b) concave mirror (c) convex mirror (d) plane mirror 10. David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be (a) 3 m (b) 5 m (c) 6 m (d) 8 m 11. The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be (a) 1 m/s (b) 2 m/s (c) 4 m/s (d) 8 m/s 12. The image formed by a lens is always virtual, erect and smaller in size for an object kept at different positions in front of it. Identify the nature of the lens. 13. State the characteristics of the image formed by a plane mirror. 14. What is a virtual image? Give one situation where a virtual image is formed. 15. Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings. 16. State two differences between a convex and a concave lens. 17. Give one use each of a concave and a convex mirror. 18. Which type of mirror can form a real image?

50 19. Which type of lens forms always a virtual image? 20. Fill in the blanks: (a) An image that cannot be obtained on a screen is called. (b) Image formed by a convex is always virtual and smaller in size. (c) An image formed by a mirror is always of the same size as that of the object. (d) An image which can be obtained on a screen is called a image. (e) An image formed by a concave cannot be obtained on a screen. (f) The inner surface of a steel spoon acts as a mirror. (g) The outer surface of a flat steel plate acts as a mirror. (h) The outer shining surface of a round bottom steel bowl acts as a mirror. (i) The inner surface of the reflector of a torch acts as a mirror. 21. What type of mirror is used as a side mirror in a scooter? Why is this type of mirror chosen? 22. Boojho made light from a laser torch to fall on a prism. Will he be able to observe a band of seven colours? Explain with a reason. 23. The side mirror of a scooter got broken. The mechanic replaced it with a plane mirror. Mention any inconvenience that the driver of the scooter will face while using it? 24. The concave reflecting surface of a torch got rusted. What effect would this have on the beam of light from the torch? 25. An erect and enlarged image of an object is formed on a screen. Explain how this could be possible. 26. Two different type of lenses are placed on a sheet of newspaper. How will you identify them without touching? 27. A shopkeeper wanted to fix a mirror which will give a maximum view of his shop. What type of mirror should he use? Give reason. 28. The distance between an object and a convex lens is changing. It is noticed that the size of the image formed on a screen is decreasing. Is the object moving in a direction towards the lens or away from it? 29. Suppose we wish to obtain the real image of a distant tree. Explain two possible ways in which we can do it. 30. It was observed that when the distance between an object and a lens decreases, the size of the image increases. What is the nature of this lens? If you keep on decreasing the distance between the object and the lens, will you still able to obtain the image on the screen? Explain. 31. You are given three mirrors of different types. How will you identify each one of them?

51 32. Observe the figures given below carefully: - The given figures show the path of light through lenses of two different types, represented by rectangular boxes A and B. What is the nature of lenses A and B? 33. State the correct sequence (1-7) of colours in the spectrum formed by the prisms A and B, shown in the figure given below: Match the items given in Column I with one or more items of Column II. Column I (a) A plane mirror (b) A convex mirror (c) A convex lens (d) A concave mirror (e) A concave lens Column II (i) Used as a magnifying glass. (ii) Can form image of objects spread over a large area. (iii) Used by dentists to see enlarged image of teeth. (iv) The image is always inverted and magnified. (v) The image is erect and of the same size as the object. (vi) The image is erect and smaller in size than the object.

52 1. 22 March is celebrated as the world water day. Water: A Precious Resource 2. We celebrate water day every year to attract the attention of everybody towards the importance of conserving water. 3. The amount of water recommended by the United Nations for drinking, washing, cooking and maintaining proper hygiene is a minimum of 50 litres per person per day. This amount is about two and a half buckets of water per person per day. 4. Earth appears blue from space. About 71% of the earth s surface is covered with water. Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in the atmosphere. 5. Freshwater makes up a very small fraction of all water on the planet. While nearly 71 percent of the world is covered by water, only 2.5 percent of it is fresh. The rest is saline and ocean-based. And the water available for use is roughly 0.006% of all water found on the earth. 6. Water on the earth has been maintained for millions of years by various processes which make the water cycle. The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.). Plants also lose water to the air (this is called transpiration). The water vapor eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater. But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water. 7. When water circulates through the water cycle it can be found in all the three forms, i.e., solid, liquid and gas at any given time somewhere on the earth. The solid form, snow and solid ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers. Liquid water Liquid is present in oceans, lakes, rivers, and even underground. The gaseous form is the gaseous water vapour present in the air around us. The continuous cycling of water among its three forms keeps the total amount of water on the earth constant even when the whole world is using it. 8. Most towns and cities have water supply system maintained by the civic bodies. The water is drawn from nearby lakes, rivers, ponds or wells. The water is supplied through a network of pipes. 9. Many villages do not have such a water supply system. There people fetch water directly from the sources. Often women and children have to walk several kilometres to fetch water. The children suffer a lot. They cannot attend school regularly since they spend hours in fetching water.

53 10. A large number of people draw water from wells, tube wells or hand pumps. 11. Groundwater is the water found underground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations of soil, sand and rocks called aquifers. 12. Water table may be at a depth of less than a metre or may be several metres below the ground. The water found below the water table is called groundwater. The rainwater and water from other sources such as rivers and ponds seeps through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. The groundwater thus gets recharged by this process. 13. At places underground, the groundwater is stored between layers of hard rock below the water table. This is known as an aquifer. Water in the aquifers can be usually pumped out with the help of tube wells or hand pumps. 14. Water drawn from under the ground gets replenished by seepage of rainwater. The water table does not get affected as long as we draw as much water as is replenished by natural processes. 15. Water table may go down if the water is not sufficiently replenished. This may happen due to many reasons. Increase in population, deforestation, decrease in the effective area for seepage of water, industrial and agricultural activities are some common factors affecting water table. Scanty rainfall is another factor that may deplete the water table. 16. Some sources of water: Increasing population creates demand for construction of houses, shops, offices, roads and pavements. This decreases the open areas like parks, and playgrounds. This, in turn, decreases the seepage of rainwater into the

54 ground. A pukka floor does not allow water to seep in easily, while in a grass lawn water seeps through in no time. A huge amount of water is required for construction work. Often groundwater is used for this purpose. 18. With the increasing population, number of industries is increasing continuously. Water used by most of the industries is drawn from the ground. 19. Population pressure on agriculture forces increasing use of groundwater day by day. This also results in depletion of water table. 20. When the civic authorities supply water through pipes not all of it may reach the destination. Water supply pipes can be seen leaking at several places, and a lot of water gushing out of the pipes. It is the responsibility of the civic authorities to prevent such wastage of precious water. 21. All of us, knowingly or unknowingly, waste water while brushing teeth, shaving, bathing, washing and during many other activities. Leaking taps is another source of huge water wastage. 22. Most of the water that we get as rainfall just flows away. This is a waste of precious natural resource. The rainwater can be used to recharge the groundwater. This is referred to as water harvesting or rainwater harvesting. 23. Bawri/Baori (Stepwell) was the traditional way of collecting water. 24. A farmer using water in the field can also use water economically. Maybe you have heard of drip irrigation. Drip irrigation is a technique of watering plants by making use of narrow tubings which deliver water directly at the base of the plant. 25. Some ways to conserve water: - Some ways to conserve water in kitchen (i) When washing dishes by hand, fill the sink basin or a large container and rinse when all of the dishes have been soaped and scrubbed. (ii) Don t let the faucet run while you clean vegetables. In-fact, clean them in the pan of clean water. (iii) Always have the bottle of clean water in the refrigerator; This will help in reducing the running tap water. (iv) Turn off water faucets tightly so they don t drip. (v) When you wash dishes by hand don t leave the water running for rinsing. (vi) Mop the floor instead of washing. Some ways to conserve water in bathroom (i) Don t take lengthy showers. Though it may be comforting but it may lead to wastage of water. (ii) Avoid flushing the toilet unnecessarily. Dispose of tissues, insects and other such waste in the trash rather than the toilet. (iii) Don t let water run while shaving or washing your face. Brush your teeth first while waiting `for water to get hot, then wash or shave after filling the basin.

55 (iv) Keep a bucket in the shower to catch water as it warms up or runs. Use this water to flush toilets or water plants. (v) Check faucets and pipes for leaks (vi) If you re taking a shower, don t waste cold water while waiting for hot water to reach the shower head. Catch that water in a container to use on your outside plants or to flush your toilet. Some ways to conserve water outside (i) Water your lawn and garden in the morning or evening when temperatures are cooler to minimize evaporation. (ii) Collect the water you use for rinsing fruits and vegetables, and then reuse it to water houseplants. (iii) Collect water from your roof using a rainwater tank to water your garden. (iv) Rather than following a set watering schedule, check for soil moisture two to three inches below the surface before watering. (v) Water only when necessary. More plants die from over-watering than from under-watering. (vi) Wash your pets outdoors in an area of your lawn that needs water. 26. Effect of water scarcity on plants: - (i) The first obvious effect of water stress is wilting because turgor pressure, which inflates plant cells and keeps them erect, is lost. Without this force, the cells inside plant leaves begin collapsing, giving them a limp appearance. As wilting increases, plant cells fully deflate, causing their deaths. (ii) When water levels are low due to water stress, photosynthesis can slow or even stop, causing internal food supplies vital to other processes to diminish or disappear -- yellowing may also occur if photosynthesis stops completely. (iii) Transpiration maintains turgor in plants, keeping cells evenly filled with water. When transpiration is stopped or slowed, the plant begins to die from lack of nutrients, usually from the top down. The green character of the planet shall be lost. This may mean the end of all life, for a world without plants shall mean no food, no oxygen, not enough rain, and innumerable other problems. NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 1. The total water (a) in the lakes and rivers of the world remains constant. (b) under the ground remains constant. (c) in the seas and oceans of the world remains constant. (d) of the world remains constant.

56 2. Which of the following does not show water shortage? (a) Taps running dry. (b) Long queues for getting water. (c) Marches and protests for demand of water. (d) A family gets three buckets of water per person per day. 3. Seas and oceans are full of water on earth. However, a very small percentage of water present on earth is available for us. This percentage is roughly (a) 0.006%. (b) 0.06%. (c) 0.6%. (d) 6%. 4. Which of the following are not the liquid forms of water? (i) Snow (ii) Lake water (iii) River water (iv) Water vapour (v) Ice Choose the correct combination from the options below. (a) (i), (iv) and (v) (b) (i) and (ii) (c) (ii) and (iii) (d) (iv) only 5. A man digging the ground near a water body found that the soil was moist. As he kept digging deeper and deeper he reached a level where all the spaces between particles of soil and gaps between rocks were filled with water. The upper limit of this layer is called (a) water level. (b) water table. (c) ground water. (d) water limit.

57 6. On which of the following day is World Water Day observed? (a) 22 March (b) 14 November (c) 2 October (d) 21 December 7. The amount of water recommended by the United Nations for drinking, washing, cooking and maintaining proper hygiene per person per day is a minimum of (a) 5 litres (b) 15 litres (c) 30 litres (d) 50 litres 8. Every Drop Counts is a slogan related to (a) counting of drops of any liquid. (b) counting of water drops. (c) importance of water. (d) importance of counting. 9. Water cycle does not involve which of the following? (a) Evaporation (b) Condensation (c) Formation of clouds (d) Rainwater harvesting 10. Which of the following inhibits the seepage of rainwater into ground? (a) A pukka floor (b) Playground (c) Grass lawn (d) Forest land

58 11. Some definitions are given below which can be corrected by changing one word. Correct them. (a) Aquifer is ground water stored between layers of hard rock above the water table. (b) The process of evaporation of water in the ground is called infiltration. (c) The evaporation of water from oceans and its arrival back into oceans is called vapour cycle. 12. What is the source of water in each of the following? (a) Wells (b) Ground (c) Atmosphere 13. Fill in the blanks in the given passage. The rainwater and from other sources such as rivers and ponds seeps through the and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called. 14. Fill in the blanks and complete the story selecting words from the box given here. cold, demand, leaders, dry, hot, scarcity, workers, wet, oceans, harvesting, rivers Rajasthan is a and dry place. The challenge of natural of water was met by a successful experiment. A band of social had transformed a area into a green place. They have revived five dried-up by constructing water structures. 15. Place the following statements in a proper order to form a meaningful paragraph. (a) Which in turn decreases the seepage of rain water into the ground. (b) This decreases the open areas like park, and playgrounds. (c) Increasing population creates demand for construction of houses, shops, offices, roads and pavements. (d) This results in depletion of water table and creates scarcity of more water. 16. How can you observe the three forms of water in (i) nature and (ii) at home? 17. A list of jumbled words are given here. Write the correct form of each word. (a) WASHFERRET (b) CHARREGE (c) QUIFERA (d) WOSN

59 18. From where do the following usually get water? In which form is water present in them? (a) Clouds (b) Plants (c) Mountain tops (d) Aquifer 19. What is ground water? What are the sources of water which are fed by ground water? 20. Water is very precious for all the living beings. What will happen in future if we do not save water now? 21. Match Column I with Column II: Make a sketch showing groundwater and water table. Label it. 23. Which one of the following is not responsbile for water shortage? (i) Rapid growth of industries (ii) Increasing population (iii) Heavy rainfall (iv) Mismanagement of water resources 24. Fill in the blanks with the appropriate answers: (a) People obtain groundwater through and. (b) Three forms of water are, and. (c) The water bearing layer of the earth is. (d) The process of water seepage into the ground is called. 25. Explain the factors responsible for the depletion of water table. 26. You have been asked to maintain a garden. How will you minimize the use of water? 27. There are ten tube wells in a lane of fifty houses. What could be the long term impact on the water table? 28. Explain how groundwater is recharged?

60 29. Complete the following chart by writing appropriate words in the boxes marked (a) to (e). Forests: Our Lifeline 1. The forests serve as green lungs and water purifying systems in nature. 2. Once inside a forest everyone should keep quiet because noise could disturb the animals living in the forest. 3. Sudden sound of birds and animals may be a type of warning call to alert other animals about the presence of strangers or animals of prey. 4. Animals like boar, bison, jackals, porcupine, and elephants live in the deeper areas of the forest. 5. Forest provides a home for many animals and plants. 6. Plywood, fuel wood, boxes, paper, matchsticks, furniture, gum, oils, spices, fodder for animals and medicinal plants are some of the products which we get from the forest. 7. Nobody need plant trees inside a forest. In nature trees produce enough seeds. The forest floor provides favourable conditions for them to germinate and develop into seedlings and saplings. Some grow up into trees. He added that branchy part of a tree above the stem is known as the crown of the tree. 8. In the forest most plant and animal life is not found on the forest floor, but in the leafy world known as the canopy. The canopy, which may be over 100 feet (30 m) above the ground, is made up of the overlapping branches and leaves.

61 9. Canopy - A tree s upper branches are called the crown. The canopy is a horizontal layer of tree crowns making up the top layer of a forest. The fast growing trees can grow taller than others around and are called dominant. Dominant trees form an upper canopy. Trees with crowns making up most of the canopy may be called co-dominant. 10. Understory - The understory includes the shorter trees in the forest, especially the trees and shrubs growing between the forest canopy and the forest floor.. Some are young trees, but others are trees that are just growing slowly because they don t get much light filtering through the dense canopy. These may be called suppressed trees. The understory also has bushes and other plants, as well as snags (dead trees that are still standing). Giant and tall trees constituted the top layer followed by shrubs and tall grasses, and herbs formed the lowest layer. 11. All animals, whether herbivores or carnivores, depend ultimately on plants for food. Organisms which feed on plants often get eaten by other organisms, and so on. For example, grass is eaten by insects, which in turn, is eaten by the frog. The frog is consumed by snakes. This is said to form a food chain: Grass insects frog snake eagle. Many food chains can be found in the forest. All food chains are linked. If anyone food chain is disturbed, it affects other food chains. Every part of the forest is dependent on the other parts. If we remove one component, say trees, all other components would be affected.

62 12. Mushroom and other micro-organisms thriving in the forest feed upon the dead plant and animal tissues and convert them into a dark coloured substance called humus. The micro-organisms which convert the dead plants and animals to humus are known as decomposers. 13. Nothing goes waste in a forest. Dead animals become food for vultures, crows, jackals and insects. On decomposition, the humus ensures that the nutrients of the dead plants and animals are released into the soil. From there, these nutrients are again absorbed by the roots of the living plants. 14. Plants release oxygen through the process of photosynthesis. The plants help to provide oxygen for animal respiration. They also maintain the balance of oxygen and carbon dioxide in the atmosphere. That is why forests are called lungs. 15. Trees take in water from their roots and release water vapour into the air through evaporation. 16. Some people belonging to different tribes live in forest. The forest provides them with food, shelter, water and medicines. They have traditional knowledge about many medicinal plants in the forest. 17. The dense bushes and the tall grass provide animals with the food and shelter. They also protect them from carnivores that live in the forest. 18. The forest officers could recognize the presence of some animals in the forest by their droppings and footprints. 19. Several beetles and grubs feed on the animal droppings, and seedlings can also be found sprouting from the droppings. These seedlings are of the herbs and shrubs. The animals also disperse the seeds of certain plants and help the forest to grow and regenerate. The decaying animal dung provides nutrients to the seedlings to grow. 20. By harbouring greater variety of plants, the forest provides greater opportunities for food and habitat for the herbivores. Larger number of herbivores means increased availability of food for a variety of carnivores. The wide variety of animals helps the forest to regenerate and grow. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the forest is a dynamic living entity full of life and dynamic living entity vitality. 21. The forest also acts as a natural absorber of rainwater and allows it to seep. It helps maintain the water table throughout the year. Forests not only help in controlling floods but also help maintain the flow of water in the streams so that we get a steady supply of water. On the other hand, if trees are not present, rain hits the ground directly and may flood the area around it. Heavy rain may also damage the soil. Roots of trees normally bind the soil together, but in their absence the soil is washed away or eroded. 22. The weather of the village surrounded by forest will be pleasant. Due to the surrounding forest, there will be good rainfall. The air also would remain cool. Noise pollution too would be less because the forest absorbs the noise of the nearby highway. 23. Construction of roads, buildings, industrial development, increasing demand of wood, overgrazing of animals and indiscriminate felling of trees would create pressure on the forests and the forests would start vanishing. 24. Forests provide us with oxygen. They protect soil and provide habitat to a large number of animals. Forests help in bringing good rainfall in neighbouring areas. They are a source of medicinal plants, timber and many other useful products. We must preserve our forests.

63 25. What would happen if forests disappear? (i) If forests disappear, the amount of carbon dioxide in air will increase, resulting in the increase of earth s temperature. (ii) In the absence of trees and plants, the animals will not get food and shelter. (iii) In the absence of trees, the soil will not hold water, which will cause floods. (iv) Deforestation will endanger our life and environment. 1. Which of the following serve as green lungs? (a) Green pigment of the plants (b) Forests (c) Kitchen gardens (d) Green house gases NOW TRY TO ANSWER THE FOLLOWING QUESTIONS 2. Boojho visited a forest near his town with his classmates and his teacher. As they were entering the forest, their class teacher told them not to make noise in the forest as noise could disturb the (a) birds (b) animals (c) both birds and animals (d) plants 3. Which among the following forest animals is the smallest? (a) Fox (b) Boar (c) Bison (d) Porcupine 4. Which of the following has the strongest stem? (a) A tree (b) A creeper (c) A climber (d) A bush

64 5. Which of the following is not prepared from the wood obtained from forest? (a) Paper (b) Thermocol (c) Matchsticks (d) Plywood 6. Which of the following is not the name of a tree? (a) Teak (b) Sal (c) Porcupine (d) Kachnar 7. Pick the option which gives the names of a tree and an animal, respectively from the following. (a) semal, hornbill (b) sal, khair (c) chinkara, blue bull (d) neem, palash 8. Which of the products is not obtained from a forest? (a) Honey (b) Catechu (c) Gum (d) Ginger 9. The branchy part of a tree above the stem is known as (a) crown (b) canopy (c) sapling (d) humus 10. Forests are not responsible for (a) providing medicinal plants. (b) maintaining the flow of water into the streams. (c) creating flood conditions. (d) absorbing rainwater and maintaining water table.

65 11. Which of the following is not a forest product? (a) Gum (b) Plywood (ci) Sealing wax (d) Kerosene 12. Which of the following statements is not correct? (a) Forests protect the soil from erosion. (b) Plants and animals in a forest are not depedent on one another. (c) Forests influence the climate and water cycle. (d) Soil helps forests to grow and regenerate. 13. Micro-organisms act upon the dead plants to produce (a) sand (b) mushrooms (c) humus (d) wood 14. Fill in the blank: (a) The insects, butterflies, honeybees and birds help flowering plants in. (b) A forest is a purifier of and. (c) Herbs form the layer in the forest. (d) The decaying leaves and animal droppings in a forest enrich the. 15. Why should we worry about the conditions and issues related to forests far from us? 16. Explain why there is a need of variety of animals and plants in a forest. 17. Explain how animals dwelling in the forest help it grow and regenerate. 18. Explain how forests prevent floods. 19. What are decomposers? Name any two of them. What do they do in the forest? 20. Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere. 21. Explain why there is no waste in a forest. 22. List five products we get from forests? 23. Paheli while moving in a forest observed that there was no noise pollution, though lots of heavy vehicles were passing from the nearby highway. Explain why?

66 24. Paheli wrote a food chain in the following way: frog eagle insects grass snake The chain is not in the correct order. Help her to write the food chain correctly. 25. Give names of any four birds which you expect to see in a forest. 26. A bunch of seedlings were seen sprouting on a heap of animal dropping in a forest. How do you think is the seedling benefited from the animal dung? 27. Deforestation may lead to floods. Why? 28. Name any four useful products other than wood, which we get from forests. 29. People say that nothing goes waste in a forest. Can you explain, how? 30. Give any four factors which are responsible for the destruction of forests. 31. All the needs of animals living in a forest are fulfilled. Justify this statement in a few sentences. 32. Forests are our lifeline. Write five sentences on this topic. 33. Match Column I with Column II: -