Question

In an area where DDT has been used extensively, bird population declined because

• A. Birds stopped laying eggs
• B. Earthworms disappeared
• C. Cobras started feeding on birds
• D. Many birds eggs did not hatch

Answer 1

The correct option is D Many birds eggs did not hatch

Dichlorodiphenyltrichloroethane or DDT is a crystalline, colourless and odourless compound which is used as an insecticide. DDT on runoff from the fields reach the water bodies and gets accumulated in the bodies of fishes. When fishes are eaten by birds, it gets accumulated in the body of birds and hence, in this way it enters the food chain. With each successive trophic level, concentration of DDT increases and this is known as biomagnification.

High concentration of DDT disturbs the calcium metabolism of birds and reptiles and causes thinning of egg shells. and premature breaking. This leads to decline in their population. Very high concentrations of DDT can result in failure of hatching of eggs.

So, the correct answer is 'Many birds eggs did not hatch'.