Question

With the help of a flow chart, show the phenomenon of biomagnifications of DDT in an aquatic food chain.

Answer 1

The increased concentration of toxic materials at each trophic level of a food chain is called biomagnification or biological concentration.
When the agricultural fields are sprayed with dichlorodiphenyltrichloroethane (DDT), it is carried into water bodies with low concentrations. It gets accumulated by the zooplankton and its concentration goes on increasing at each trophic level in a food chain from small fish to large fish and birds.

Answer 2

A few toxic substances, such as DDT, can undergo biological magnification (biomagnification) in the aquatic food chain. Biomagnification refers to an increase in concentration of the toxicant at successive trophic levels. This happens because a toxic substance accumulated by an organism cannot be metabolised or excreted, and is thus passed on to the next higher trophic level. The figure shows biomagnification of DDT in an aquatic food chain. In this manner, the concentration of DDT is increased at successive trophic levels; say, if it starts at 0.003 ppb (ppb = parts per billion) in water, it can ultimately reach 25 ppm (ppm = parts per million) in fish-eating birds through biomagnification.