Calcium metabolism in birds gets disturbed due to effect of
A. Mercury
B. Cadmium
C. DDT
D. Lead
E. Copper

Hint: In birds about 99 % of the calcium is stored in bones and the remaining is in extracellular matter. It is one of the most important plasma constituents in birds and animals.

Complete Answer:
- Calcium is the nutrient which provides strength and stability to the bones and teeth. They play a major role in many biochemical reactions of the body. The control of calcium metabolism in birds is very efficient and closely regulated in a number of tissues initially in the parathyroid gland, intestine, kidney and bone.
- The hormones which are involved in the calcium regulation in birds are parathyroid hormone, calcitriol, estrogen and calcitonin. The important characteristics which are associated with calcium metabolism in birds include egg production. Calcium is the important plasma constituent in mammals and birds.
- Dichlorodiphenyltrichloroethane or DDT is a crystalline, odourless, colourless, compound which is mainly used as an insecticide. DDT when get runoff from the fields will reach the water bodies and get accumulated in the bodies of fishes. When the fishes which are living in these water bodies are eaten by birds , it gets accumulated in the body of birds and for this reason it gets incorporated with the food chain.
- In each trophic level the concentration of DDT increases and is known as biomagnifications. High concentration of DDT in the body of birds will affect their calcium metabolism and also it affect the reptiles also . this will cause the thinning of eggshells , and premature breaking of the shells. This may finally leads to decline in their number. So we can conclude that DDT will disturbs the calcium metabolism in birds.

So the correct answer for this question is option C, DDT.

Note: Birds require calcium to maintain their health. Calcium is important in maintaining the skeletal structure. It also helps in the functioning of the nervous system.