Biological magnification

7/8/2015 CBSE

Biological magnification: -
�To protect the
crops from the several diseases and pests, a large number of pesticides are
used. These pesticides reach the soil and are absorbed by plants with water and
minerals from the soil. Due to rain, these chemicals can also enter water
sources and into the body of aquatic plants and animals.
As a result, chemicals
enter the food chain. Since these chemicals cannot be decomposed, they keep on
accumulating at each trophic level. The maximum concentration is accumulated at
the top carnivore's level. This increase in the concentration of pollutants or
harmful chemicals with an increase in the trophic level is called biological

For example, high DDT concentrations were found in a pond. The
producers (phytoplankton) were found to have 0.04 ppm concentration of DDT.
Since many types of phytoplankton were eaten by zooplankton (consumers), the
concentration of DDT in the bodies of zooplankton was found to be 0.23 ppm.
Small fish that feed on zooplankton accumulate more DDT in their body. Thus,
large fish (top carnivore) that feed on several small fish have the highest
concentration of DDT.

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