Class 10 Science - Chapter Our Environment NCERT Solutions | What is biological magnification? Will t

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Question 6

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer

Some toxic substances chemicals and large number of pesticides like D.D.T (Dichloro- diphenyl- trichloroethane) are non- biodegradable. When the concentration of these chemicals and pesticides increases at each trophic level of the food chain, this phenomenon is known as biological magnification or biomagnifications. They are non- biodegradable substances, so they do not decompose then they get accumulated in the environment and affect each of the trophic level. And, our body get directly affected at some stage of trophic level or mostly human beings are on the top level because we consume most of the chemicals in our body.

The level of biological magnification will be different at the different trophic levels. The concentration of the biomagnification got increased with the increase in trophic levels. For example:- biomagnification of pesticide D.D.T in aquatic food chain;

        Water           ←         Zooplankton         ←       Small fishes       ←     Large fishes        ←      Fish eating birds
(DDT 0.003ppm)           (DDT 0.04 ppm)               (DDT 0.5 ppm)             (DDT 2 ppm)                   (DDT 5 ppm)

In the above example, when the pesticides are sprayed on the agricultural fields then they are carried out by running off water into the aquatic bodies in the pond or lakes etc. The pesticide DDT get accumulate into the water and then in the zooplanktons, the concentration of DDT goes on increasing with each trophic level in the food chain. The fish eating birds have the higher concentration of biomagnification, which affects the egg shells due to the effect on calcium metabolism. Egg shell becomes thin and breaks at the premature stage. Then mercury discharge into the ponds, rivers or lakes that is changed by the bacteria into the toxic forms which is very harmful, absorbes by the fishes and they may get killed.

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