Question

A crane had a DDT level of 5ppm in its body. What would happen to the population of such birds?

Answer 1

The term biomagnification is used when harmful and unwanted chemicals accumulate inside the body of living organisms and the chemicals accumulated increase at each trophic level. The wastes (such as chemicals from industries and agricultural activities) are dumped into the water bodies. Most of them are toxic and are consumed by marine organisms or primary producers and thus, enter the food chain.

Complete answer:
Due to biomagnification, the accumulated non-metabolized chemicals are maximum at the highest trophic level. This is because; an organism at a higher trophic level consumes many organisms of lower trophic level having some harmful accumulated chemicals. The chemicals from these lower trophic level organisms are accumulated in the organism of higher trophic level. Thus, the presence of 5ppm in the crane’s body indicates the high biomagnification or concentration. This is because; it has consumed many such fishes in which DDT was present.

As we know, some of the toxic chemicals such as DDT are not metabolized by the body of living organisms. Most of the harmful, toxic chemicals are fat-soluble. Hence, cannot excrete out of the body of an organism. Thus, if these chemicals are accumulated inside the body of living organisms it may cause serious harm to the body and interferes with normal body processes.

The presence of a 5ppm DDT level in the crane’s body can stop the metabolism of calcium in its body. The deficiency of calcium causes the weakening of eggshells. There will be the premature breaking of eggs due to thinning of eggshells. This results in a significant decline population of cranes.

Note: Bioaccumulation is different from biomagnification. In bioaccumulation, the harmful chemicals are accumulated inside the body organism but it does not increase progressively at each trophic level. The accumulated chemicals remain in the body of an organism over its life span. The chemicals are more concentrated in older organisms as it is not excreted from the body.