Life Processes — Class 10 Science practice questions

Question 1

Ravi is a 10-year-old boy who loves playing football. His coach notices that during intense exercise, Ravi breathes much faster and his heart beats more quickly. After the match, Ravi complains that his leg muscles feel sore and tired. His mother, a doctor, explains that during heavy exercise the body has to work harder to keep all the organs supplied with what they need to stay alive.

Based on the above passage, answer the following questions:
(a) Why does Ravi breathe faster during intense exercise?
(b) Why does his heart beat faster during exercise?
(c) Ravi's leg muscles feel sore after the match. Name the substance responsible for this soreness and write the equation for the reaction that produces it. OR (c) Name the life process that provides energy to Ravi's muscles during the match. State the type of respiration that occurs in muscles during intense exercise and give ONE reason why it occurs.

Accepted Answer

(a) During intense exercise, the muscles of Ravi's body respire faster to produce more energy. This leads to a greater production of carbon dioxide (CO₂) in the blood. The increased CO₂ level is detected by the brain, which sends signals to the diaphragm and intercostal muscles to contract and relax more rapidly. This results in faster breathing so that more oxygen is taken in and more carbon dioxide is expelled from the body. [1 mark]

(b) During exercise, the muscles require a greater supply of oxygen and glucose to carry out respiration and produce energy. The heart beats faster to pump more oxygenated blood to the working muscles and to carry away the increased amount of carbon dioxide produced. This ensures a continuous and sufficient supply of oxygen and nutrients to all organs during physical activity. [1 mark]

(c) The substance responsible for the soreness in Ravi's leg muscles is lactic acid. During intense exercise, the supply of oxygen to the muscles becomes insufficient. The muscles then carry out anaerobic respiration (without oxygen) to meet the urgent energy demand. In this process, glucose is incompletely broken down to produce lactic acid instead of carbon dioxide and water.

The equation for this reaction is:

Glucose → Lactic acid + Energy
C₆H₁₂O₆ → 2C₃H₆O₃ + Energy

The accumulation of lactic acid in the muscles causes soreness and fatigue. [2 marks]

OR

(c) The life process that provides energy to Ravi's muscles during the match is Respiration. During intense exercise, the oxygen supplied to the muscles through the blood is not sufficient to meet the high energy demand. Therefore, the type of respiration that occurs in muscles during intense exercise is Anaerobic respiration (respiration without oxygen). It occurs because the rate of oxygen supply to the muscle cells becomes less than the rate at which energy is needed, so the cells temporarily shift to anaerobic breakdown of glucose to produce energy rapidly. [2 marks]

Question 2

A student noticed that the leaves of a plant placed near a sunny window appeared greener and healthier than the leaves of the same plant kept in a dark corner of the room. She also noticed that the plant near the window had soil that needed watering more frequently. Her teacher told her that both observations are connected to the same process happening inside the leaves.

In the context of the above observation, answer the following questions:

(a) Name the process the teacher is referring to. Where exactly in the leaf cell does this process occur?

(b) The student placed a variegated leaf (partially green, partially white) under sunlight for a few hours, then tested it for starch. Which parts of the leaf — the green parts or the white parts — would give a positive starch test? Give one reason.

(c) Explain why the soil near the sunny window dried out faster. Your answer must include the name of the process responsible AND state any two factors that affect the rate of this process.

Accepted Answer

(a) The process the teacher is referring to is Photosynthesis. [½ mark]
Photosynthesis occurs in the chloroplasts present in the cells of the leaf. [½ mark]

(b) Only the green parts of the leaf would give a positive starch test. [½ mark]
Reason: The white parts of a variegated leaf lack chlorophyll. Since chlorophyll is essential for trapping sunlight and carrying out photosynthesis, no glucose (and therefore no starch) is produced in the white regions. [½ mark]

(c) The soil near the sunny window dried out faster because the plant absorbs more water from the soil and loses it through the leaves by the process of Transpiration. [½ mark]
Transpiration is the process by which plants lose water in the form of water vapour through tiny pores called stomata present on the surface of leaves.
Two factors that increase the rate of transpiration:
(i) Higher light intensity (sunlight near the window increases stomatal opening, allowing more water vapour to escape). [½ mark]
(ii) Higher temperature (near the sunny window, temperature is higher, which increases the rate of evaporation of water from leaf surfaces). [½ mark]
[Award any two valid factors — e.g. low humidity, wind/air movement also accepted.]

Question 3

Read the following passage and answer the questions that follow:

A school student, Priya, was investigating digestion. She set up three test tubes as follows:

• Test tube P: 2 mL starch solution + 1 mL saliva → kept at 37°C for 10 minutes
• Test tube Q: 2 mL starch solution + 1 mL water → kept at 37°C for 10 minutes
• Test tube R: 2 mL starch solution + 1 mL saliva → kept at 0°C for 10 minutes

After 10 minutes, she added a few drops of iodine solution to each test tube and recorded the colour change.

(a) What colour change will Priya observe in test tube P? Give a reason.
(b) What colour change will Priya observe in test tube Q? Name the enzyme responsible for the reaction (or absence of it) in test tube P.
(c) Test tube R also turned blue-black after adding iodine, even though saliva was present. Explain why digestion of starch did not occur in test tube R. What does this tell us about the nature of the enzyme in saliva?

Accepted Answer

(a) Test tube P will NOT turn blue-black — it will remain orange-brown (the original colour of iodine solution). [½ mark]
Reason: Salivary amylase (an enzyme present in saliva) acts on starch and breaks it down into simpler sugars (maltose). Since starch is no longer present in test tube P, iodine does not give the blue-black colour. [½ mark]

(b) Test tube Q will turn blue-black. [½ mark]
This is because no enzyme was added to test tube Q (only water was added). Starch remains undigested and unchanged. Iodine reacts with starch to give the characteristic blue-black colour.
The enzyme responsible for starch digestion in test tube P is salivary amylase (also called ptyalin). [½ mark]

(c) At 0°C, the enzyme salivary amylase is inactive. Enzymes work only within a narrow optimum temperature range (approximately 37°C for human enzymes). At 0°C (very low temperature), the kinetic energy of the enzyme and substrate molecules is greatly reduced, so the enzyme cannot bind effectively to its substrate (starch). As a result, starch is not broken down, and iodine turns the solution blue-black. [1 mark]
This tells us that salivary amylase is a thermolabile (temperature-sensitive) biological catalyst — its activity depends critically on temperature. Enzymes are denatured or rendered inactive outside their optimum temperature range. [1 mark]

Question 4

A 14-year-old student, Riya, participated in a 400-metre race. After finishing the race, she noticed that she was breathing very rapidly and her leg muscles felt painful and fatigued. Her biology teacher explained that during intense exercise, the body undergoes specific physiological changes to meet increased energy demands.

Read the information above and answer the following questions:

(a) Name the two types of respiration that can occur in human muscle cells. Which one occurred in Riya's leg muscles during the race? [1]

(b) Write the chemical equation for the process that occurred in Riya's leg muscles. Why does this process cause pain and fatigue? [1]

(c) Why was Riya breathing so rapidly after the race? How does rapid breathing help her body recover? Explain with reference to the substance responsible for pain in her muscles. [2]

Accepted Answer

(a) The two types of respiration that can occur in human muscle cells are:
(i) Aerobic respiration — occurs when sufficient oxygen is available.
(ii) Anaerobic respiration — occurs when oxygen supply is insufficient.

During the race, Riya's leg muscles underwent anaerobic respiration, because the demand for oxygen by the rapidly contracting muscles exceeded the supply that the circulatory and respiratory systems could deliver.

(b) The chemical equation for anaerobic respiration in human muscle cells is:

Glucose → Lactic acid + Energy
C₆H₁₂O₆ → 2C₃H₆O₃ + Energy

This process causes pain and fatigue because lactic acid (a by-product) accumulates in the muscle tissue. The build-up of lactic acid lowers the pH of the muscle cells, interfering with enzyme function and muscle contraction, which results in a painful, fatigued feeling.

(c) Riya was breathing rapidly after the race because her body had accumulated an 'oxygen debt' — the lactic acid produced during anaerobic respiration in the muscles needs to be broken down, and this breakdown requires extra oxygen. The brain detects the elevated carbon dioxide and lactic acid levels in the blood and sends signals to increase the rate and depth of breathing.

Rapid breathing helps her recover by supplying the additional oxygen needed to oxidise the accumulated lactic acid. The lactic acid is carried by the blood to the liver, where, in the presence of this extra oxygen, it is converted back to glucose (and ultimately to carbon dioxide and water). As the lactic acid is removed from the muscles, the pain and fatigue gradually disappear. This process of repaying the oxygen debt restores the muscles to their normal state.

Question 5

Riya is a student who recently learned about how plants make food. She sets up an experiment: she takes two potted plants of the same species — Plant A is kept in a well-lit room near a window, and Plant B is kept inside a dark cupboard. After 48 hours, she tests a leaf from each plant for starch using iodine solution. The leaf from Plant A turns blue-black, while the leaf from Plant B does not change colour.

[Diagram: Cross-section of a leaf showing upper epidermis, palisade mesophyll cells, spongy mesophyll cells with air spaces, lower epidermis, and a stoma with two guard cells]

Study the diagram of a leaf cross-section given below and answer the questions that follow.

[Diagram: Cross-section of a leaf showing upper epidermis, palisade mesophyll cells, spongy mesophyll cells with air spaces, lower epidermis, and a stoma with two guard cells]

(a) Name the green-coloured pigment present in the palisade mesophyll cells that is essential for photosynthesis. In which cell organelle is this pigment found?

(b) Why did the leaf from Plant B not show a blue-black colour with iodine solution?

(c) Write the overall chemical equation for photosynthesis. Also name ONE raw material used in photosynthesis and state where the plant absorbs it from.

Accepted Answer

(a) The green-coloured pigment is chlorophyll. It is found in the chloroplast. [½ + ½ = 1 mark]

(b) Plant B was kept in complete darkness. Sunlight (light energy) is an essential raw material for photosynthesis. Without light, the plant could not carry out photosynthesis and therefore could not produce glucose, which is converted to starch for storage. Since no starch was present in the leaf, iodine solution did not turn blue-black. [1 mark]

(c) Overall chemical equation for photosynthesis:

6CO₂ + 6H₂O →(Sunlight / Chlorophyll)→ C₆H₁₂O₆ + 6O₂

Any ONE raw material and its source (any one of the following):

(i) Carbon dioxide (CO₂) — the plant absorbs it from the atmosphere through tiny pores called stomata present on the surface of leaves.

OR

(ii) Water (H₂O) — the plant absorbs it from the soil through the roots and it is transported up to the leaves through the xylem vessels.

[1 mark for balanced equation + 1 mark for raw material with source = 2 marks]

Question 6

Riya is a 14-year-old student who recently ran a 400-metre race at her school sports day. After finishing, she noticed her heart was beating very fast, she was breathing rapidly, and her leg muscles were aching and felt stiff. Her friend, who is a regular runner, recovered much faster and did not feel the same muscle pain.

Based on the above scenario, answer the following questions:

(a) Why does Riya's heart beat faster immediately after the race? [1 mark]

(b) Riya's leg muscles started to ache during the race. Name the process responsible for this and write the chemical equation for it. [1 mark]

(c) Why did Riya's friend, who exercises regularly, recover faster and experience less muscle pain? Explain with reference to the process of respiration that takes over during recovery. [2 marks]

Accepted Answer

(a) During intense physical activity such as running, the muscles require more oxygen and glucose to produce energy. The heart beats faster to pump more oxygenated blood to the working muscles at a higher rate, meeting their increased demand for oxygen and removal of carbon dioxide.

(b) The process responsible for muscle ache is Anaerobic Respiration (in muscles).

Chemical equation:

Glucose → Lactic acid + Energy

C₆H₁₂O₆ → 2C₃H₆O₃ + Energy

During intense exercise, when oxygen supply to muscles is insufficient, muscles respire anaerobically, producing lactic acid. The accumulation of lactic acid causes the sensation of pain and stiffness in the muscles.

(c) Riya's friend recovers faster because her body, trained through regular exercise, is more efficient at switching back to aerobic respiration once the exercise stops. During recovery, the lactic acid that accumulated in the muscles is broken down through aerobic respiration using the extra oxygen that continues to be breathed in deeply after the race.

Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

A trained person has a stronger heart, better lung capacity, and more efficient blood circulation, so oxygen is delivered to muscles more quickly. The lactic acid is oxidised completely, reducing muscle pain and speeding up recovery. In contrast, Riya's untrained body takes longer to clear the lactic acid, resulting in prolonged aching.

Question 7

A doctor examines two patients, Ravi and Priya, who both complain of fatigue and breathlessness. Blood tests reveal the following:

| Parameter | Ravi | Priya | Normal Range |
|-----------|------|-------|---------------|
| Haemoglobin (g/dL) | 14.5 | 7.2 | 12–16 |
| Blood Glucose (mg/dL) | 180 | 90 | 70–110 |
| Urine Test | Glucose present | Normal | No glucose |

Based on the data above, answer the following questions:

(a) Which patient is likely suffering from anaemia? Give one reason based on the data. [1]
(b) Which patient shows signs of a malfunction in a life process other than respiration? Name that life process and the organ most likely responsible. [1]
(c) Explain why Ravi's cells may still experience a shortage of energy despite his haemoglobin level being normal. Relate your answer to how glucose is used in cellular respiration. [2]

Accepted Answer

(a) Priya is suffering from anaemia. Her haemoglobin level (7.2 g/dL) is well below the normal range of 12–16 g/dL. Since haemoglobin is the pigment in red blood cells that carries oxygen to body tissues, a deficiency reduces the oxygen supply to cells, causing fatigue and breathlessness. [1 mark]

(b) Ravi shows signs of a malfunction in the life process of nutrition (specifically, regulation of glucose metabolism). The organ most likely responsible is the pancreas, which produces the hormone insulin that enables body cells to absorb and utilise glucose from the blood. In Ravi's case, inadequate insulin action leads to high blood glucose (180 mg/dL) and its spillover into urine (glycosuria), indicating diabetes mellitus. [1 mark]

(c) Although Ravi's haemoglobin is normal, his cells experience an energy shortage because glucose — the primary fuel for cellular respiration — cannot enter the cells properly without effective insulin action. Cellular respiration is the process by which glucose is broken down (oxidised) to release energy in the form of ATP:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

Even though glucose is present in high amounts in Ravi's blood, it remains outside the cells because insulin is absent or ineffective. The cells are therefore 'starved' of their energy substrate. Unable to carry out aerobic respiration efficiently, cells may switch to incomplete breakdown pathways that yield far less ATP — resulting in persistent fatigue and weakness despite normal oxygen-carrying capacity. [2 marks — 1 mark for linking insulin/glucose entry to cells; 1 mark for explaining the role of glucose in cellular respiration and consequence of its absence inside the cell]

Question 8

Read the following passage and answer the questions that follow:

Rahul is a 14-year-old boy who has been diagnosed with a condition called 'achlorhydria' — a rare disorder in which the stomach lining fails to secrete hydrochloric acid (HCl). His doctor explains that as a result, certain digestive enzymes cannot function in the stomach, proteins remain largely undigested there, and the food that passes into the small intestine is not properly acidified. The doctor also notes that Rahul is more prone to bacterial infections in his gut than a healthy person.

(a) Name the enzyme secreted by the stomach that acts on proteins. Why is HCl essential for its action?

(b) The partially undigested protein (polypeptide) now enters the small intestine. Name ONE enzyme secreted by the pancreas that continues protein digestion here.

(c) Explain TWO consequences — other than incomplete protein digestion — that Rahul would face because of the absence of HCl in his stomach.

Accepted Answer

(a) The enzyme secreted by the stomach that acts on proteins is **pepsin**. HCl is essential because pepsin is secreted in an inactive form called **pepsinogen**. HCl converts pepsinogen into its active form, pepsin. Additionally, HCl provides the strongly acidic medium (low pH) that pepsin requires to function — pepsin can only break down proteins in an acidic environment (pH ≈ 2). Without HCl, pepsinogen remains inactive and no protein digestion occurs in the stomach. [1 mark]

(b) The pancreas secretes **trypsin** (also accept: chymotrypsin / pancreatic protease), which continues the digestion of polypeptides into shorter peptides in the small intestine. [1 mark]

(c) Any TWO of the following consequences [1 mark each]:

(i) **Increased risk of gut infections:** HCl in the stomach normally kills most bacteria and pathogens that enter with food. In the absence of HCl, the stomach does not provide this antibacterial barrier, so harmful microorganisms survive and pass into the intestine, making Rahul more prone to infections. [1 mark]

(ii) **Impaired activation of other gastric processes / delayed emptying:** The acidic chyme entering the small intestine normally triggers the release of secretin (a hormone) from the intestinal wall, which in turn stimulates the pancreas to release sodium bicarbonate to neutralise the acid. Without acidic chyme, this hormonal signal is weakened, disrupting the coordination of digestive secretions. [1 mark]

(iii) **Deficiency in iron absorption:** HCl helps convert dietary iron from its ferric form (Fe³⁺) to the ferrous form (Fe²⁺), which is the absorbable form. Without HCl, iron absorption is significantly reduced, potentially leading to anaemia in Rahul. [1 mark]

(Accept any two well-explained consequences with correct reasoning. Award 1 mark per consequence only if the explanation of the mechanism/reason is included — a bare statement alone earns 0.)

Question 9

Which of the following correctly pairs a digestive secretion with the organ that produces it in the human alimentary canal?

Accepted Answer

Option (A) is correct.

Explanation: Bile is a digestive secretion produced by the liver and stored in the gall bladder; it is released into the small intestine where it emulsifies fats. The remaining options are incorrectly paired: pepsin is secreted by the gastric glands of the stomach, not the pancreas; salivary amylase is produced by the salivary glands, not the stomach; and trypsin is secreted by the pancreas, not the small intestine. Therefore, only the pair Bile — Liver is correct.

Question 10

In the human digestive system, when food components are completely broken down by the end of digestion in the small intestine, amino acids, glucose, and fatty acids with glycerol are the final products of which of the following groups of nutrients respectively?

Accepted Answer

Option (A) is correct.

Explanation: During digestion, each class of macronutrient is broken down into its specific monomeric units by the enzymes of the digestive system. Proteins are hydrolysed by proteases (such as pepsin in the stomach and trypsin in the small intestine) to yield amino acids. Carbohydrates are broken down by amylases and other carbohydrases to yield glucose. Fats are hydrolysed by lipases (aided by bile salts) to yield fatty acids and glycerol. The question asks for the nutrients whose final products are amino acids, glucose, and fatty acids with glycerol respectively — these correspond to Proteins, Carbohydrates, and Fats in that order.

Question 11

Assertion (A): Herbivores have a longer small intestine than carnivores.
Reason (R): Cellulose, which forms the cell walls of plant cells, is difficult to digest and requires a longer digestive tract for complete breakdown.

Accepted Answer

Option (A) is correct.

The Assertion is true: herbivores possess a longer small intestine than carnivores because plant-based food is harder to digest than animal protein. The Reason is also true: cellulose, which forms the cell walls of plant cells, is difficult to digest and demands a prolonged digestive process. The Reason is the correct explanation of the Assertion, since it is precisely the presence of hard-to-digest cellulose in plant food that necessitates a longer digestive tract in herbivores to ensure complete breakdown and maximum absorption of nutrients.

Question 12

A student lists the steps involved in the digestion of food by Amoeba. Which of the following gives the CORRECT sequence of these steps?
(i) Digestive enzymes break down complex food molecules into simpler ones inside the food vacuole
(ii) Pseudopodia extend and surround the food particle
(iii) Simpler molecules are absorbed into the cytoplasm by diffusion
(iv) A food vacuole is formed enclosing the food particle
(v) Undigested waste is expelled through the cell surface

Accepted Answer

Option (A) is correct.

Explanation: Amoeba carries out holozoic nutrition in a fixed sequence. First, pseudopodia extend and surround the food particle (ii) — this is ingestion. The pseudopodia then fuse, enclosing the particle to form a food vacuole (iv). Digestive enzymes are secreted into this food vacuole and break down complex food molecules into simpler ones (i) — this is digestion. The simpler molecules are then absorbed into the cytoplasm by diffusion (iii) — this is absorption. Finally, undigested waste is expelled through the cell surface (v) — this is egestion. The correct sequence is therefore (ii) → (iv) → (i) → (iii) → (v).

Question 13

Assertion (A): In single-celled organisms such as Amoeba, the food is taken in by the process of endocytosis.
Reason (R): Single-celled organisms have a large surface area relative to their volume, which allows them to exchange materials directly with the environment without the need for a specialized digestive system.

Accepted Answer

Option (b) is correct.

The Assertion is true: Amoeba ingests food by endocytosis (specifically phagocytosis), in which the cell membrane folds around food particles to form a food vacuole. The Reason is also true: single-celled organisms possess a large surface area relative to their volume, which enables direct exchange of gases, nutrients, and waste products with the surrounding environment, making a specialised digestive system unnecessary. However, the Reason does not explain the Assertion. Endocytosis is a membrane-mediated mechanism of food ingestion and is not caused by the high surface area to volume ratio; the two statements describe independent biological facts, where the surface area to volume ratio explains efficiency of material exchange across the cell surface, not the specific mechanism by which food is engulfed.

Question 14

Assertion (A): The left ventricle of the human heart has thicker walls than the right ventricle.
Reason (R): The left ventricle pumps oxygenated blood to all parts of the body through the aorta, requiring greater force and higher pressure than the right ventricle which pumps blood only to the lungs.

Accepted Answer

Option (A) is correct.

Both the Assertion and the Reason are true, and the Reason is the correct explanation of the Assertion. The left ventricle does indeed have thicker muscular walls than the right ventricle — this is an established anatomical fact. The Reason correctly identifies the cause: the left ventricle must pump oxygenated blood through the aorta into the systemic circulation, supplying every organ and tissue in the body, which demands significantly greater force and pressure. The right ventricle, by contrast, pumps deoxygenated blood only to the lungs through the pulmonary artery — a shorter distance requiring considerably less pressure. This greater mechanical demand on the left ventricle directly results in the development of thicker, more muscular walls. Thus, R is the correct and complete explanation of A.

Question 15

Assertion (A): In single-celled organisms, all life processes are carried out by that single cell.
Reason (R): Single-celled organisms have a higher surface area to volume ratio, which allows efficient exchange of materials with the environment without the need for specialised organs.

Accepted Answer

Option (A) is correct.

The Assertion is true: in single-celled organisms such as Amoeba and Paramecium, all life processes — nutrition, respiration, excretion, and reproduction — are carried out by that single cell itself. The Reason is also true: because a single-celled organism has a high surface area to volume ratio, the entire cell surface is available for exchange of gases, nutrients, and waste products directly with the surrounding environment, making specialised organs unnecessary. R is the correct explanation of A, since it is precisely this favourable surface area to volume ratio that allows one cell to efficiently perform all life functions without requiring a division of labour among organ systems.

Question 16

Consider the following statements about the mode of nutrition in a mushroom and select the one which is NOT correct:

Accepted Answer

Option (C) is correct.

Explanation: Mushrooms are fungi that obtain nutrition by the saprophytic mode of heterotrophic nutrition. They secrete digestive enzymes outside their body onto dead or decaying organic matter, breaking it down extracellularly, and then absorb the soluble products of digestion through their body surface. Forming pseudopodia to engulf solid food particles is a characteristic feature of Amoeba, which follows holozoic nutrition — it does not apply to fungi or mushrooms in any way. Statements (A), (B), and (D) are therefore all correct descriptions of the mushroom's mode of nutrition, while Statement (C) is not correct for a mushroom.

Question 17

Assertion (A): Leaves appear green because they reflect green light and absorb red and blue wavelengths for photosynthesis.
Reason (R): Chlorophyll is the primary pigment responsible for trapping light energy during photosynthesis, and it absorbs light mainly in the red and blue regions of the visible spectrum.

Accepted Answer

Option (A) is correct.

The Assertion is true — leaves appear green because chlorophyll reflects green light while absorbing red and blue wavelengths, which are utilised in photosynthesis. The Reason is also true — chlorophyll is the primary photosynthetic pigment and it absorbs light energy predominantly in the red (≈ 680 nm) and blue (≈ 430 nm) regions of the visible spectrum. The Reason directly explains the Assertion: it is precisely because chlorophyll absorbs red and blue light and reflects green light that leaves appear green. Therefore, R is the correct explanation of A.

Question 18

A lion hunts and kills a deer, then swallows large chunks of meat which are broken down step by step inside its body before the nutrients are absorbed into the blood. Which of the following terms CORRECTLY describes this mode of heterotrophic nutrition?

Accepted Answer

Option (A) is correct.

Explanation: Holozoic nutrition is the mode of heterotrophic nutrition in which an organism ingests solid or liquid food, digests it internally through a series of steps (ingestion → digestion → absorption → assimilation → egestion), and absorbs the simpler products into the blood. The lion ingests large chunks of meat and breaks them down step by step inside its body before absorbing nutrients — this exactly matches holozoic nutrition. Saprophytic nutrition involves secreting digestive enzymes outside the body and absorbing the products (as in fungi), parasitic nutrition involves feeding on a living host without killing it, and autotrophic nutrition involves synthesising food from inorganic substances using light or chemical energy — none of these apply to the lion's feeding process.

Question 19

Which of the following correctly describes what happens to guard cells when a stoma opens?

Accepted Answer

Option (B) is correct.

Explanation: When water enters the guard cells by osmosis, they become turgid (swollen with water). Because the inner wall of each guard cell (facing the stomatal pore) is thicker than the outer wall, the cells cannot expand uniformly — they bend outward. This bending of the two guard cells away from each other widens the gap between them, so the stoma opens. Loss of water (not gain) causes the guard cells to become flaccid and the stoma to close.

Question 20

Assertion (A): The walls of the left ventricle of the human heart are thicker than the walls of the right ventricle.
Reason (R): The left ventricle pumps blood to the lungs, which requires greater force.

Accepted Answer

Option (C) is correct.

The Assertion is true: the left ventricle does have thicker, more muscular walls than the right ventricle. However, the Reason is false. The left ventricle pumps oxygenated blood to the entire body through the aorta, which requires much greater force and pressure to push blood over a long distance. It is the right ventricle that pumps blood to the lungs (a shorter distance, lower pressure). Therefore, R is not the correct explanation of A — in fact, R states the opposite of what is true.

Life Processes: Class 10 Science Practice Questions

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