Question

If a water body is contaminated with toxicant, its biomagnification will be more marked in
A. Plankton
B. Small fish
C. Birds
D. Water

Answer 1

Hint: Biomagnification leads to the accumulation of toxicants like pesticides (e.g.: DDT) from subsequent trophic levels in an ecosystem.

Complete answer: It is generally found that the level of toxicant keeps increasing as the food chain progresses to further higher trophic levels.
This signifies that organisms belonging to the T2 trophic level (primary consumers) will have more toxicants than T1 trophic level (producers); T3 (secondary consumers) will have more than T2 (primary consumers) and so on.

The highest concentrations will hence be observed in the top carnivore. This is due to the fact that the consumers at each successive trophic level keep consuming more than the previous level in order to meet the energy requirements. This entire process is what we know as biomagnification.
So, planktons will have the least amount of toxicants while birds being in the highest trophic level, in this case, will have the most amount of toxicants. The given image shows the biomagnification of DDT:

Therefore, the correct answer is option C. Birds.

Note: Accumulation of pesticides like DDT in some species of birds have disturbed the calcium metabolism in them, resulting in thinning of eggshells; this has been a threat to their numbers in recent years.