Assertion (A) : Accumulation of harmful chemicals is maximum in the organisms at the highest trophic level of a food chain.

Reason (R) : Harmful chemicals are sprayed on the crops to protect them from diseases and pests.

options

1. (A) and (R) are true and (R) is the reason for (A).
2. (A) and (R) are true and (R) is not the reason for (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.

(A) and (R) are true and (R) is not the reason for (A).

Reason —

• Assertion (A) is true because this happens due to biological magnification, where harmful chemicals such as pesticides or insecticides enter the food chain and their concentration increases at each successive trophic level. Thus, the organisms at the highest trophic level (like hawks or humans) accumulate the maximum amount of these toxic substances in their bodies.

• Reason (R) is also true because pesticides and insecticides are sprayed on crops to kill pests and prevent plant diseases. These chemicals, however, get absorbed by plants and enter the food chain when animals or humans consume these plants.

Both Assertion (A) and Reason (R) are true, but Reason (R) only gives the cause of entry of harmful chemicals into the food chain; it does not directly explain why their accumulation is maximum at the highest trophic level.

Hence, (A) and (R) are true and (R) is not the reason for (A).