Life Processes CBQs — CBSE Class 10 (2027) with step-wise solutions

Sample Life Processes CBQs

1. Question 1MCQ1 mark
   Patient X was suffering from a pancreatic condition due to which the pancreas was not functioning adequately. Which of the following is a doctor likely to suggest to such an individual?
   • including a large amount of protein in the diet
   • eating a diet with low-fat content
   • eating only carbohydrates
   • including only liquid foods
   Show step-wise solution

   1. [1 mark] Pancreas secretes lipase (digests fats) along with amylase, trypsin. If pancreas malfunctions, fat digestion is impaired ⟹ low-fat diet recommended.

   Answer: (b) eating a diet with low-fat content

2. Question 2Assertion-Reason1 mark
   Two statements are given - one labelled Assertion (A) and the other labelled Reason (R). Read the statements carefully and choose the option that correctly describes statements A and R. Assertion (A): Warm-blooded animals have their left and right side of the heart separated for more efficient supply of oxygen to the body. Reason (R): Warm-blooded animals need high energy to maintain their body temperatures.
   • Both A and R are true and R is the correct explanation for A.
   • Both A and R are true but R is not the correct explanation for A.
   • A is true but R is false.
   • A is false but R is true.
   Show step-wise solution

   1. [1 mark] Correct option: (1) Both A and R are true and R is the correct explanation for A. Keeping a constant body temperature demands a high rate of respiration, which needs an efficient oxygen supply - and that is exactly what a fully separated heart provides by keeping oxygenated and deoxygenated blood apart.

   Answer: Both A and R are true and R is the correct explanation for A.

3. Question 3Short answer2 marks
   A plant X was enclosed in a glass jar with some lizards. A similar plant Y was enclosed in another glass jar but without lizards. Both jars are kept under the same light conditions for a few hours. Which plant is likely to photosynthesize more and why?
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   1. [1 mark] Lizards respire and release CO2 inside the jar, increasing CO2 concentration around plant X.
   2. [1 mark] Higher CO2 availability + adequate light ⟹ higher rate of photosynthesis in X compared to Y (which has limited CO2 in the closed jar).

   Answer: Plant X — higher CO2 from lizard respiration boosts photosynthesis.

4. Question 4Case study4 marks
   Not all plants carry out photosynthesis by the same mechanism. In most plants, photosynthesis depends directly on the gaseous carbon dioxide that diffuses into the leaf through the stomata. However, some plants - such as pineapple - have the ability to store carbon dioxide in the vacuoles of the leaf cells as part of a complex carbon compound. This complex compound is transported to the chloroplasts and releases carbon dioxide when required, for photosynthesis to occur. This special photosynthesis mechanism is believed to have evolved as an adaptation to conserve water for survival in dry conditions. (a) Which process in the plants does this photosynthesis mechanism minimise to help the plant survive in dry conditions? (b) How is the ability to store carbon dioxide as a complex compound likely to help minimise the process referred to in (a)? (c) When are such plants likely to take in carbon dioxide from the environment?
   Show step-wise solution

   1. [1 mark] (a) transpiration
   2. [2 marks] (b) Since stored carbon dioxide can be used, stomata need not be open for photosynthesis to occur during the day. Keeping the stomata closed during the day helps to minimise water loss due to transpiration.
   3. [1 mark] (c) during the night

   Answer: (a) transpiration; (b) stored CO₂ lets the stomata stay shut by day, cutting water loss; (c) at night.

5. Question 5Long answer5 marks
   Aditi planned an experiment in her school laboratory to test whether carbon dioxide is needed for photosynthesis. She took two healthy potted plants of the same kind and size and kept both in a dark room for three days. She then placed each plant on a separate glass plate and covered it with a bell jar, sealing the rim of each jar to its plate with petroleum jelly. Under jar A she placed a watch glass containing potassium hydroxide solution; under jar B she placed nothing extra. Both set-ups were kept in bright sunlight for six hours. One leaf from each plant was then decolourised in alcohol over a water bath and tested with iodine solution. (a) Why were the plants kept in the dark for three days first? [1 mark] (b) What is the role of the potassium hydroxide solution, and why was the rim of each jar sealed? [1 mark] (c) Predict the result of the iodine test on the leaf from each plant. [1 mark] (d) What conclusion can Aditi draw? [1 mark] (e) Why was the set-up with jar B needed? [1 mark]
   Show step-wise solution

   1. [1 mark] (a) To destarch the leaves: in the dark the stored starch is used up, so any starch found later must have been made during the experiment.
   2. [0.5 mark] (b) Potassium hydroxide absorbs carbon dioxide, so the air around plant A has no carbon dioxide.
   3. [0.5 mark] (b) Sealing the rim with petroleum jelly makes the jar airtight, so outside air containing carbon dioxide cannot enter.
   4. [1 mark] (c) The leaf from plant A does not turn blue-black (no starch), while the leaf from plant B turns blue-black (starch present).
   5. [1 mark] (d) Plant A could not make starch without carbon dioxide, so carbon dioxide is necessary for photosynthesis.
   6. [1 mark] (e) Jar B is the control: it is identical except that carbon dioxide is present, so the difference in results can be due only to carbon dioxide.

   Answer: (a) Destarching; (b) potassium hydroxide absorbs carbon dioxide, seal keeps outside air out; (c) A no starch, B starch; (d) carbon dioxide is necessary; (e) B is the control.

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