Class 10 Science · Chapter 5

Life Processes

266 Class 10 Science questions on Life Processes from the NCERT textbook, NCERT Exemplar and CBSE board papers 2024–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 5 of 14

1. Q81 Exemplar · Short Answer Questions
   Match the ​words of ​Column (A) ​with that of ​Column ​(B)
   Show answer

   (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii). That is, phloem carries out the translocation of food, the nephron carries out excretion, veins carry deoxygenated blood, and platelets bring about the clotting of blood.

   Step-by-step solution →
2. Q82 Exemplar · Short Answer Questions
   Differentiate ​between an artery and ​a ​vein.
   Show answer

   Arteries carry blood away from the heart under high pressure and have thick walls; veins bring it back, with thin walls and valves.

   An artery carries blood away from the heart to the organs, while a vein collects blood from the organs and carries it back to the heart; this is the difference that defines them. An artery usually carries oxygenated blood and a vein deoxygenated blood, but the pulmonary artery and the pulmonary vein are exceptions. Because blood enters an artery straight from the contracting ventricle at high pressure, an artery has a thick, muscular and elastic wall and a narrow lumen, and the blood in it flows rapidly and in spurts so that a pulse can be felt; a vein has a thin, much less muscular wall and a wide lumen, and its blood flows slowly and smoothly at low pressure with no pulse. Arteries have no valves along their length, only the semilunar valves where they leave the heart, whereas veins have valves at intervals that prevent the blood from flowing backwards. Arteries are mostly deep-seated in the body, while many veins lie close to the surface.

   Step-by-step solution →
3. Q83 Exemplar · Short Answer Questions
   What are ​the adaptations ​of ​leaf for ​photosynthesis?
   Show answer

   A broad, thin lamina, chloroplast-rich palisade cells, stomata with air spaces and a network of veins suit the leaf for photosynthesis.

   A leaf is adapted for photosynthesis in several ways. Its lamina is broad and flat and the leaves are arranged so as not to shade one another, giving the largest possible area for absorbing light and exchanging gases. The lamina is very thin, so that light reaches every layer and carbon dioxide has only a short distance to diffuse. The cuticle and epidermis are thin and transparent, so light passes through them to the palisade mesophyll just beneath, whose closely packed cells carry the greatest number of chloroplasts and so lie where the light is strongest. The lower epidermis has numerous stomata with guard cells that regulate them, through which carbon dioxide enters and oxygen leaves, and behind them the spongy mesophyll is loosely packed with large intercellular air spaces and moist cell walls, so that carbon dioxide reaches and dissolves at every cell. A dense network of veins brings water and minerals to the mesophyll through the xylem and carries the food made away through the phloem, and also keeps the lamina spread out.

   Step-by-step solution →
4. Q84 Exemplar · Short Answer Questions
   Why is ​small ​intestine in ​herbivores ​longer than ​in carnivores?
   Show answer

   Plant cellulose is hard to digest and needs time and surface, but flesh digests quickly, so herbivores need a longer small intestine.

   Because of the food each animal eats. A herbivore lives on grass and leaves, whose cells are enclosed in walls of cellulose, and cellulose is very difficult to digest; no mammal makes cellulase of its own, so herbivores depend on microorganisms in the gut that ferment it slowly. A slow digestion needs the food to be held for a long time and needs a large inner surface to absorb the sugars released, and a long small intestine provides both. A carnivore eats flesh, which is protein and fat and is digested rapidly and almost completely by the animal's own pepsin, trypsin and lipase, so a long intestine would gain it nothing; it would also mean flesh standing and putrefying in a warm gut and extra weight to carry while hunting. The small intestine of a carnivore is therefore much shorter than that of a herbivore of similar size.

   Step-by-step solution →
5. Q85 Exemplar · Short Answer Questions
   What will happen if mucus is ​not secreted ​by ​the gastric ​glands?
   Show answer

   The acid and pepsin would attack the stomach lining, causing gastritis and then peptic ulcers.

   The stomach would begin to digest its own wall. The gastric glands secrete hydrochloric acid and the protein-digesting enzyme pepsin along with the mucus, and the lining of the stomach is itself living tissue made largely of protein. Normally the mucus, with the bicarbonate secreted into it, spreads as a slimy layer over the lining and keeps the acid and the enzyme away from the living cells, besides lubricating the food. If it were not secreted, the acid would corrode the lining and the pepsin would digest its protein. The wall would become inflamed, that is gastritis, and with continued exposure the lining would be eroded into open sores, that is peptic ulcers, which are painful and may bleed and in severe cases perforate the wall.

   Step-by-step solution →
6. Q86 Exemplar · Short Answer Questions
   What is ​the significance ​of ​emulsification ​of ​fats?
   Show answer

   Bile salts break fat globules into tiny droplets, greatly increasing the surface exposed to lipase and so speeding up fat digestion.

   Fats are insoluble in water and reach the small intestine as large globules, while lipase, the enzyme that digests them, is water soluble and can act only at the surface where water meets fat. Bile salts from the liver break these large globules into a great many tiny droplets and keep them dispersed in the watery contents; this is emulsification, and it is a purely physical change, since bile contains no enzyme. Its significance is that it enormously increases the surface of fat exposed to the enzyme, so that lipase can act on far more fat at once and the rate of fat digestion rises greatly. Dividing one globule into a thousand equal droplets, for instance, makes the surface ten times as large without changing the amount of fat. The emulsion also keeps the fat from running together again, and the bile, being alkaline, neutralises the acid food from the stomach and provides the alkaline medium the pancreatic enzymes need. Lipase then converts the fats into fatty acids and glycerol, which the villi can absorb.

   Step-by-step solution →
7. Q87 Exemplar · Short Answer Questions
   What ​causes ​movement of ​food ​inside ​the alimentary ​canal?
   Show answer

   Peristalsis, a wave of contraction in the involuntary smooth muscle of the canal wall, pushes food along.

   The movement of food inside the alimentary canal is caused by peristalsis. The wall of the canal contains two layers of involuntary smooth muscle, an outer one whose fibres run lengthwise and an inner one whose fibres run round the tube. Behind the mass of food the circular muscle contracts and narrows the tube, while ahead of it the circular muscle relaxes and the longitudinal muscle contracts so that the tube widens; this point of constriction travels steadily along the canal as a wave and pushes the food ahead of it, helped by the mucus that lubricates the lining. Peristalsis begins in the oesophagus the moment food is swallowed and continues all along the canal to the anus, and being involuntary it goes on without our control.

   Step-by-step solution →
8. Q88 Exemplar · Short Answer Questions
   Why ​does ​absorption of digested ​food occur ​mainly in ​the small ​intestine?
   Show answer

   The small intestine completes digestion, and its villi, thin walls, blood supply and length ensure thorough absorption.

   Because the small intestine is the only part of the canal where all the conditions for absorption are met at once. Digestion is completed there, bile, pancreatic juice and intestinal juice together breaking carbohydrates down to glucose, proteins to amino acids and fats to fatty acids and glycerol, and only molecules as small as these can be absorbed. Its inner lining is thrown into folds and bears millions of finger-like villi, each covered with microvilli, so the absorbing surface is enormous. The wall of a villus is only one cell thick, and inside each villus is a dense network of blood capillaries together with a lacteal, so that glucose and amino acids pass into the blood and fatty acids and glycerol into the lymph and are carried away at once, keeping the concentration gradient steep. Finally, the small intestine is the longest part of the canal and the food is moved through it slowly, so it stays in contact with this surface long enough for absorption to be practically complete.

   Step-by-step solution →
9. Q89 Exemplar · Short Answer Questions
   Match Group (A) with Group (B)
   Show answer

   (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii). That is, autotrophic nutrition is shown by the green plant, heterotrophic nutrition by the deer, parasitic nutrition by the leech, and digestion in food vacuoles by Paramecium.

   Step-by-step solution →
10. Q90 Exemplar · Short Answer Questions
    Why is the rate ​of breathing ​in aquatic ​organisms ​much faster ​than in terrestrial ​organisms?
    Show answer

    Water holds far less oxygen than air, so aquatic organisms must pass much more water over their gills, breathing faster.

    Because the medium they breathe holds far less oxygen. A litre of air contains about $210$ mL of oxygen, while a litre of water holds only about $5$ to $8$ mL of dissolved oxygen, roughly thirty times less; oxygen also diffuses much more slowly through water than through air. Since the oxygen collected is the volume of medium passed over the respiratory surface multiplied by its oxygen content, an aquatic organism has to sweep a far larger volume of water across its gills to obtain the same amount of oxygen, and it does this by breathing much faster than a terrestrial organism.

    Step-by-step solution →
11. Q91 Exemplar · Short Answer Questions
    Why is blood ​circulation ​in ​human ​heart called ​double circulation?
    Show answer

    Blood passes through the heart twice in one complete round of the body: once on the lung circuit, once on the body circuit.

    Because in one complete round of the body the blood passes through the heart twice. On the pulmonary circuit, deoxygenated blood goes right atrium $\to$ right ventricle $\to$ pulmonary artery $\to$ lungs, where it is oxygenated, and returns by the pulmonary veins to the left atrium. On the systemic circuit it goes left atrium $\to$ left ventricle $\to$ aorta $\to$ body tissues, where it gives up its oxygen, and returns by the venae cavae to the right atrium. Two circuits, each beginning and ending at the heart, mean two passages through the heart for every single circuit of the body, and a complete septum keeps the oxygenated and deoxygenated blood from mixing while this happens. Hence the name double circulation.

    Step-by-step solution →
12. Q92 Exemplar · Short Answer Questions
    What ​is ​the ​advantage ​of having ​four chambered ​heart?
    Show answer

    A complete septum keeps oxygenated and deoxygenated blood apart, so tissues get fully oxygenated blood for a high rate of aerobic respiration.

    The four chambers, separated by a complete septum, keep oxygenated and deoxygenated blood from mixing: the right atrium and right ventricle carry only deoxygenated blood to the lungs, and the left atrium and left ventricle carry only oxygenated blood to the body. The advantages that follow are that the body always receives fully oxygenated blood, so oxygen is delivered to the tissues as efficiently as possible and they can respire aerobically at a high rate; that this supports the high, continuous energy demand of warm-blooded animals such as birds and mammals, which must spend energy all the time to keep their body temperature constant; and that the delicate low-pressure lung circuit and the high-pressure body circuit can each be driven at the pressure that suits it. In a three-chambered heart the single ventricle mixes the two bloods, so the blood sent to the body carries less oxygen than it could.

    Step-by-step solution →
13. Q93 Exemplar · Short Answer Questions
    Mention ​the ​major events during ​photosynthesis
    Show answer

    Chlorophyll absorbs light energy, which is converted to chemical energy with splitting of water, and carbon dioxide is then reduced to carbohydrate.

    The three major events are: (i) absorption of light energy by chlorophyll; (ii) conversion of that light energy into chemical energy, together with the splitting of water molecules into hydrogen and oxygen, the oxygen being released as a by-product; and (iii) reduction of carbon dioxide to carbohydrate, using the hydrogen and the chemical energy obtained in the previous event. These events need not take place one immediately after another, since the energy and hydrogen produced in light can be used later; overall, $6{\text{CO}}_2+6{\text{H}}_2\text{O}\underset{\text{chlorophyll}}{\overset{\text{sunlight}}{\to }}{\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2$.

    Step-by-step solution →
14. Q94 Exemplar · Short Answer Questions
    In ​each of the following ​situations ​what happens ​to the rate ​of photosynthesis?

    1. (a)Cloudy days
    2. (b)​No rainfall in the area
    3. (c)Good manuring in ​the area
    4. (d)Stomata get blocked due to ​dust
    Show answer

    Photosynthesis decreases on cloudy days, with no rainfall and when stomata are blocked, and increases with good manuring.

    (a) The rate decreases, because clouds cut down the light intensity and light is what chlorophyll absorbs to drive the process. (b) The rate decreases: less water reaches the leaf, and to conserve it the plant closes its stomata, which also shuts out the carbon dioxide, so the fall is sharp. (c) The rate increases, because manure supplies minerals such as nitrogen and magnesium that the plant needs to make chlorophyll and enzymes, giving greener, healthier leaves. (d) The rate decreases, because dust plugging the stomata prevents carbon dioxide from diffusing into the leaf, and a thick layer shades it as well.

    Step-by-step solution →
15. Q95 Exemplar · Short Answer Questions
    Name ​the energy currency ​in ​the living organisms. ​When and ​where is ​it produced?
    Show answer

    ATP (adenosine triphosphate) is the energy currency; it forms during respiration in the cytoplasm and mitochondria, and in chloroplasts during the light reaction.

    The energy currency of living organisms is ATP, adenosine triphosphate. It is produced during cellular respiration, that is whenever glucose and other food molecules are broken down, and in green plants also during the light reaction of photosynthesis. It is produced in the cytoplasm, where glycolysis yields a small amount of it; chiefly in the mitochondria, where pyruvate is completely oxidised in the presence of oxygen, which is why mitochondria are called the powerhouse of the cell; and, in green plants, in the chloroplasts while light is available. Energy is stored by adding a phosphate group to ADP, $\text{ADP}+{\text{P}}_i+\text{energy}\to \text{ATP}$, and released again when that terminal bond is broken, giving about $30.5$ kJ per mole.

    Step-by-step solution →
16. Q96 Exemplar · Short Answer Questions
    What ​is ​common ​for cuscuta, ​ticks ​and ​leeches?
    Show answer

    All three are parasites: each lives on a host and takes ready-made food from it.

    All three are parasites: they show parasitic nutrition. Each lives on the body of another living organism, called the host, and takes ready-made food from it, harming the host without killing it outright. Cuscuta, or amarbel, has no chlorophyll and so cannot make its own food; it twines over a host plant and pushes haustoria into its stem to draw out food and water. Ticks attach to the skin of cattle and other animals and suck their blood, and leeches attach by a sucker and do the same. Since none of the three can make its own food, all three are heterotrophs of the parasitic kind.

    Step-by-step solution →
17. Q97 Exemplar · Short Answer Questions
    Explain ​the role ​of ​mouth ​in ​digestion of food.
    Show answer

    The mouth chews food into small pieces, mixes it with saliva into a bolus, and starts starch digestion with salivary amylase.

    The mouth begins both the mechanical and the chemical digestion of food. Food is taken in, and the teeth cut, tear and grind it into small pieces, which greatly increases the surface area available to the digestive enzymes that will act on it later. The salivary glands pour in saliva, and the muscular tongue mixes it thoroughly through the food; the mucus of saliva moistens and lubricates the food so that the tongue can roll it into a soft ball, the bolus, that is easily swallowed, and the tongue also bears the taste buds. Saliva contains the enzyme salivary amylase, or ptyalin, which breaks starch down into the sugar maltose, $\text{starch}\stackrel{\text{salivary amylase}}{\to }\text{maltose}$; this is the only chemical digestion that occurs in the mouth, and it is why chewed bread or rice starts to taste sweet. The bolus is then swallowed into the oesophagus.

    Step-by-step solution →
18. Q98 Exemplar · Short Answer Questions
    What ​are the functions ​of ​gastric glands present ​in the wall ​of the ​stomach?
    Show answer

    They secrete gastric juice: hydrochloric acid for acidity and killing germs, pepsin to digest proteins, and mucus to protect the stomach lining.

    The gastric glands in the wall of the stomach secrete gastric juice, which has three components, each with its own function. (i) Hydrochloric acid makes the contents of the stomach strongly acidic, which provides the medium the enzyme pepsin needs in order to act, and it also kills the bacteria and other germs that enter with the food. (ii) Pepsin, a protein-digesting enzyme, begins the digestion of proteins by breaking them into shorter fragments called peptones, $\text{proteins}\stackrel{\text{pepsin}}{\to }\text{peptones}$. (iii) Mucus coats the inner lining of the stomach and protects it from being damaged by the acid and from being digested by the pepsin. The three work as one system: the acid makes the enzyme effective and the mucus makes the acid safe.

    Step-by-step solution →
19. Q99 Exemplar · Short Answer Questions
    Match ​the ​terms in ​Column ​(A) ​with those ​in Column ​(B)
    Show answer

    (a)-(i), (b)-(iv), (c)-(ii), (d)-(iii). That is, trypsin is secreted by the pancreas, amylase by the saliva, bile by the liver and pepsin by the gastric glands. Bile and the liver pair first because bile is the only entry that is not an enzyme and the liver the only gland that secretes none; pepsin pairs with the gastric glands because it works only in the acidic medium they provide; trypsin pairs with the pancreas because no other listed source can supply it; and amylase, which the pancreas also secretes, is then left with saliva, where salivary amylase begins the digestion of starch in the mouth.

    Step-by-step solution →
20. Q100 Exemplar · Short Answer Questions
    Name ​the correct ​substrates for the following enzymes

    1. (a)​Trypsin
    2. (b)Amylase
    3. (c)​Pepsin
    4. (d)​Lipase
    Show answer

    Trypsin and pepsin act on proteins, amylase on starch, and lipase on emulsified fats.

    (a) Trypsin acts on proteins, in particular on the partly digested proteins or peptones that reach the small intestine, breaking them down into peptides and amino acids. (b) Amylase acts on starch, breaking it down into the sugar maltose. (c) Pepsin acts on proteins, breaking them down into peptones in the acidic medium of the stomach. (d) Lipase acts on fats, and specifically on emulsified fats, the fine droplets that bile salts have made from large fat globules, breaking them down into fatty acids and glycerol.

    Step-by-step solution →