CBSE Class 10 Science 2018 · Paper 31(B) · Question 18

Life Processes 5 marks Medium

(a)Why do fishes die when taken out of water ?
(b)Leaves of a healthy potted plant were coated with Vaseline. Will this plant remain healthy for long ? Give reason to justify your answer.
(c)If a plant is releasing $CO_{2}$ and taking in $O_{2}$ during the day, does it mean that there is no photosynthesis occurring ? Give reason for your answer.

Answer

Fish gills cannot absorb oxygen from air; Vaseline blocks the stomata so the plant dies; photosynthesis still occurs but is slower than respiration.

(a) Fishes respire through gills, which take in the oxygen dissolved in water. Out of water the gills cannot take in oxygen from the air (their thin filaments collapse and dry up), so the fish cannot respire and dies. (b) No, the plant will not remain healthy for long. The Vaseline covers the stomata, so the exchange of gases stops: carbon dioxide cannot enter the leaves, photosynthesis stops and the plant cannot make its food. Transpiration also stops, so the upward pull of water and minerals slows down. The plant will weaken and die. (c) No, it does not mean that there is no photosynthesis. Respiration goes on all the time, and during the day the

CO_{2}

released in respiration is taken up in photosynthesis. A plant that still releases

CO_{2}

and takes in

O_{2}

in the day is photosynthesising more slowly than it respires (as in dim light): photosynthesis is occurring, but it uses up only part of the

CO_{2}

produced in respiration.

🔒 Step-by-step solution

From the board paper

CBSE Class 10 Science 2018 · Paper 31(B), Question 18 — all 27 questions with answers →

CBSE Class 10 Science 2018 · Paper 31(B) · Question 18

Answer

From the board paper

More questions from Life Processes