Class 10 Science · Chapter 5
Life Processes
431 Class 10 Science questions on Life Processes from the NCERT textbook, NCERT Exemplar and CBSE board papers 2018–2026, each with its answer and a step-by-step solution.
NCERT exercises
NCERT Exemplar exercises
CBSE Class 10 Science previous year papers, with answers →
Questions · page 14 of 22
- Q261 CBSE 2024During respiration, exchange of gases occurs in :
- (a)Alveoli
- (b)Bronchi
- (c)Larynx
- (d)Trachea
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(a) Alveoli - Q262 CBSE 2024In plants, waste products like resins and gums are stored in :
- (a)leaves that fall off
- (b)old xylem
- (c)phloem
- (d)cellular vacuoles
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(b) old xylem - Q263 CBSE 2024The opening and closing of stomatal pore in the leaves of a plant is due to :
- (a)diffusion of carbon dioxide in and out of the guard cells.
- (b)movement of water in and out of the guard cells.
- (c)high pressure of gases inside the guard cells.
- (d)stimulus of light in the guard cells.
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(b) movement of water in and out of the guard cells. - Q264 CBSE 2024For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Assertion (A): In the human heart ventricles have thicker muscular walls than atria.
Reason (R): Ventricles have to pump the blood into various organs.
- (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
- (c)Assertion (A) is true, but Reason (R) is false.
- (d)Assertion (A) is false, but Reason (R) is true.
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(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). - Q265 CBSE 2024For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Assertion (A): Most of the plants close their stomata at night.
Reason (R): Closing of stomata helps to conserve water as large amount of water evaporates from the leaves.
- (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
- (c)Assertion (A) is true, but Reason (R) is false.
- (d)Assertion (A) is false, but Reason (R) is true.
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(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). - Q266 CBSE 2024Two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below :
Assertion (A): The rate of breathing in aquatic organisms is much faster than in terrestrial organisms.
Reason (R): The amount of oxygen dissolved in water is very high as compared to the amount of oxygen in air.
- (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
- (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
- (c)Assertion (A) is true, but Reason (R) is false.
- (d)Assertion (A) is false, but Reason (R) is true.
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(c) Assertion (A) is true, but Reason (R) is false. - Q267 CBSE 2024Two statements are given — one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (a), (b), (c) and (d) as given below.
Assertion (A): In humans, the inner lining of the small intestine has finger-like projections called villi which are richly supplied with blood vessels.
Reason (R): Villi increase the surface area for the absorption of digested food.
- (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
- (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
- (c)Assertion (A) is true, but Reason (R) is false.
- (d)Assertion (A) is false, but Reason (R) is true.
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(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). - Q268 CBSE 2024State one role of each of the following in human digestive system :
- (i)Hydrochloric acid
- (ii)Villi
- (iii)Anal Sphincter
- (iv)Lipase
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HCl makes the stomach acidic for pepsin, villi increase absorption, the anal sphincter controls the exit of waste, and lipase digests emulsified fats.
(i) Hydrochloric acid: Creates an acidic medium in the stomach which facilitates the action of the protein-digesting enzyme pepsin. (ii) Villi: These finger-like projections of the inner lining of the small intestine increase the surface area for absorption of digested food, which their blood vessels carry to the cells of the body. (iii) Anal sphincter: Regulates the exit of the waste material from the body through the anus. (iv) Lipase: This enzyme of pancreatic juice breaks down emulsified fats into fatty acids and glycerol in the small intestine. - Q269 CBSE 2024
- (i)Give reason why herbivorous animals have longer, small intestine than carnivorous animals ?
- (ii)Although ‘Pepsin’ and ‘Trypsin’ are both protein digesting enzymes yet they differ from each other. Justify this statement by giving one difference between them.
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Herbivores digest cellulose in a longer small intestine; pepsin acts in the acidic stomach, trypsin in the alkaline small intestine.
(i) Herbivores eat grass, which is rich in cellulose, and cellulose takes a long time to digest. A longer small intestine keeps the food in the gut for longer, allowing the cellulose to be digested; meat is easier to digest, so carnivores have a shorter small intestine. (ii) Pepsin is secreted by the gastric glands of the stomach and acts in the stomach in an acidic medium, provided by hydrochloric acid, whereas trypsin is secreted by the pancreas and acts in the small intestine in an alkaline medium. Any one of these differences, in the site of secretion, the site of action or the medium, answers the question. - Q270 CBSE 2024Photosynthesis takes place in the leaves and the food prepared by it reaches other parts of the plants. Name the process involved and explain it.Step-by-step solution →
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Translocation: sucrose made in leaves is loaded into the phloem using ATP and carried by pressure to roots, fruits, seeds and buds.
The process is translocation — the transport of the soluble products of photosynthesis from the leaves to other parts of the plant. It takes place in the sieve tubes of the phloem, with the help of adjacent companion cells, in both upward and downward directions. Material like sucrose is loaded into the phloem using energy from ATP; this raises the osmotic pressure of the tissue, so water moves into it, and the pressure pushes the material to tissues with less pressure, such as roots, fruits, seeds and growing buds. Unlike transport in the xylem, translocation uses energy, and it moves food according to the plant's needs. - Q271 CBSE 2024Two test tubes A and B are taken, each containing one mL of starch solution. Add 1 mL of saliva to test tube ‘A’ only and leave both the test tubes undisturbed for a few minutes. Now add a few drops of dilute iodine solution to both the test tubes.
- (a)Which one of the two test tubes shows change in colour ? Write the changed colour observed in this test tube.
- (b)What can we conclude from this activity ?
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Test tube B turns blue-black as its starch remains; saliva contains amylase, which breaks starch into sugar, so digestion starts in the mouth.
(a) Test tube B shows the change in colour: it turns blue-black, because its starch is still present. Test tube A does not turn blue-black, because its starch has been broken down. (b) Saliva contains the enzyme salivary amylase, which breaks down starch, a complex molecule, into simple sugar; the digestion of starch therefore begins in the mouth. - Q272 CBSE 2024Name the blood vessel which brings blood to the kidneys. Why is nephron called a basic filtration unit of kidney ? Write the role of tubular part of nephron in urine formation.Step-by-step solution →
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The renal artery brings blood to the kidneys; blood is filtered in each nephron's glomerulus, and the tubule selectively reabsorbs useful substances.
The renal artery brings blood to the kidneys. The nephron is called the basic filtration unit because each kidney is made of large numbers of nephrons, and in each one blood is filtered through the glomerulus, a cluster of very thin-walled capillaries, into the cup-shaped Bowman's capsule. The tubular part selectively reabsorbs useful substances such as glucose, amino acids, salts and a major amount of water back into the blood, so that what remains flows on as urine. - Q273 CBSE 2024Write two roles each of
- (i)bile juice and bile salts and
- (ii)pancreatic enzymes in the process of digestion.
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Bile makes the food alkaline and its salts emulsify fats; pancreatic trypsin digests proteins and lipase breaks down emulsified fats.
(i) Bile juice and bile salts: (1) Bile juice makes the acidic food coming from the stomach alkaline, so that the pancreatic enzymes can act. (2) Bile salts break large fat globules into smaller globules (emulsification), which increases the efficiency of the fat-digesting enzyme. (ii) Pancreatic enzymes: (1) Trypsin digests proteins. (2) Lipase breaks down emulsified fats. - Q274 CBSE 2024We need to water the soil in plants on a regular basis. But it ultimately reaches the leaves of the plant. Explain how this takes place.Step-by-step solution →
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Water enters the roots and rises through the xylem, pushed by root pressure and mainly pulled by transpiration pull from the leaves.
Water reaches the leaves through the xylem, whose vessels and tracheids in the roots, stem and leaves are interconnected to form a continuous water-conducting channel. Two forces move it. (1) Root pressure: root cells in contact with the soil actively take up ions, so water moves from the soil into the root; the steady entry of water into the root xylem pushes a column of water upwards (this is more important at night). (2) Transpiration pull: water evaporates from the leaf cells and is lost as vapour through the stomata; this creates a suction that pulls water up the xylem from the roots to the leaves. During the day, when the stomata are open, transpiration pull is the main driving force. - Q275 CBSE 2024Sometimes while running, the athletes suffer from muscle cramps. Why ? How is the respiration in this case different from aerobic respiration ?Step-by-step solution →
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Lack of oxygen makes pyruvate form lactic acid, which causes cramps; unlike aerobic respiration, it releases much less energy.
During running the muscles use energy so fast that the oxygen reaching the muscle cells falls short. Pyruvate, formed from glucose, is then converted into lactic acid instead of being broken down in the mitochondria, and the build-up of lactic acid in the muscles causes the cramps. This respiration differs from aerobic respiration: it takes place when oxygen is lacking, whereas aerobic respiration uses oxygen; pyruvate is converted into lactic acid, a three-carbon molecule, instead of being broken down in the mitochondria into carbon dioxide and water; and it releases much less energy than aerobic respiration. - Q276 CBSE 2024Name the type of nutrition exhibited by Amoeba. Explain how food is taken in and digested by this organism.Step-by-step solution →
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Amoeba is holozoic: pseudopodia surround food to form a food vacuole, where enzymes digest it and the undigested part is thrown out.
Amoeba shows holozoic nutrition (a heterotrophic mode). It takes in food with the help of pseudopodia — temporary finger-like extensions of the cell surface — which surround the food particle and fuse over it, forming a food vacuole. Inside the food vacuole, digestive enzymes break the complex food into simpler substances, which diffuse into the cytoplasm and are used by the cell. The undigested material is moved to the surface of the cell and thrown out. - Q277 CBSE 2024Write the other name given to lymph. State its two functions.Step-by-step solution →
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Lymph is also called tissue fluid; it carries absorbed fat from the intestine and drains excess fluid from the tissue spaces into the blood.
Lymph is also called tissue fluid. Its two functions: (1) it carries digested and absorbed fat from the intestine; (2) it drains excess fluid from the spaces between the cells (the extracellular spaces) back into the blood, since the lymph vessels finally open into larger veins. - Q278 CBSE 2024Mention the pathway of urine in our body starting from the organ of its formation to its excretion. What will happen if the tubular part of the nephron does not work properly?Step-by-step solution →
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Urine passes from kidneys through ureters, bladder and urethra; if the tubules fail, useful substances and water are lost in the urine.
Pathway of urine: kidneys (urine is formed) → ureters → urinary bladder (urine is stored) → urethra (urine is passed out). If the tubular part of the nephron does not work properly, selective reabsorption of glucose, amino acids, salts and water will not take place. These useful substances and a large amount of water will be lost in the urine, and the body will lose nutrients and water and may become dehydrated. - Q279 CBSE 2024Give reason for the following:
- (a)Fine hair and mucus are present in the nasal passage.
- (b)Rings of cartilage are present in the throat.
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Nasal hair and mucus trap dust and germs and filter the air; cartilage rings keep the air passage from collapsing.
(a) The fine hairs and the mucus lining the nasal passage filter the air we breathe in: dust particles and germs are trapped by the hairs and stick to the mucus, so cleaner air goes on to the lungs. (b) The rings of cartilage in the throat support the air passage and ensure that it does not collapse, so air can pass freely to and from the lungs. - Q280 CBSE 2024(i) Why is respiratory pigment needed in multicellular organisms with large body size ? (ii) Give reasons for the following :
- (a)Rings of cartilage are present in the throat.
- (b)Lungs always contain a residual volume of air.
- (c)The diaphragm flattens and ribs are lifted up when we breathe in.
- (d)Walls of alveoli contain an extensive network of blood vessels.
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Haemoglobin carries oxygen in large bodies; cartilage keeps the airway open; residual air allows exchange; ribs and diaphragm enlarge the chest; capillaries exchange gases.
(i) In a large body, diffusion alone cannot deliver oxygen to all parts of the body. A respiratory pigment (haemoglobin in human beings, which has a very high affinity for oxygen) takes up oxygen from the air in the lungs and carries it to the tissues that are deficient in oxygen. (ii) (a) The rings of cartilage ensure that the air-passage does not collapse. (b) The residual air gives sufficient time for oxygen to be absorbed and for carbon dioxide to be released. (c) Lifting the ribs and flattening the diaphragm makes the chest cavity larger, so air is sucked into the lungs and fills the expanded alveoli. (d) The network of blood vessels allows the exchange of gases: oxygen from the alveolar air is taken up by the blood and carried to all the cells, and carbon dioxide brought by the blood is released into the alveoli.