UPSC Prelims PYQ 2010 — Chlorinated hydrocarbon pesticide biomagnification

A pesticide which is a chlorinated hydrocarbon is sprayed on a food crop. The food chain is: Food crop → Rat → Snake → Hawk

In this food chain, the highest concentration of the pesticide would accumulate in which one of the following?

Food crop
Rat
Snake
Hawk

Explanation

Option (d) is correct

Chlorinated hydrocarbons such as DDT are persistent organic pollutants. They are not easily metabolised or excreted and therefore accumulate in the fatty tissues of organisms. As these substances move along a food chain, their concentration increases at each successive trophic level. This process is known as biomagnification. In the given food chain, the hawk occupies the highest trophic level. Consequently, it accumulates the maximum concentration of the pesticide.

Diagram illustrating biomagnification of DDT in aquatic food chain, showing increasing concentration levels from water to large fish. Color-coded pyramid segments represent water, producers, zooplankton, small fish, and large fish, with a red arrow indicating DDT magnification from 1 to 10,000,000 times.