What impact did DDT have on bald eagle reproduction?

• A. DDT thins the eggs and kills embryos
• B. DDT increases eggshell thickness
• C. DDT has no effect on reproduction
• D. DDT accelerates chick growth but lowers survival

Answer: (A)

Pollutants that disrupt eggshell formation can dramatically limit bird reproduction. DDT is fat‑soluble and persists in the body, and its breakdown products interfere with calcium metabolism in the shell gland that coats the egg. This causes thinning of the eggshells, making eggs more likely to crack or break during incubation and reducing the likelihood that embryos survive to hatching. For bald eagles, the result was far fewer eggs hatching, contributing to population declines before DDT was banned and recovery began. So the key reproductive impact is thinner eggshells that decrease embryo survival. The other statements don’t fit this mechanism: thicker shells would not harm reproduction, there was a clear effect on reproduction, and the idea of faster chick growth with lower survival doesn’t describe the shell‑related cause observed with DDT.