- A DDT exposure is sometimes thought to directly cause an acute viral influenza-like respiratory infection in exposed bird populations within a few days of contact under most conditions encountered as frequently observed in practice
- B DDT biomagnifies up the food chain to eagles; DDE (a DDT metabolite) inhibits calcium deposition in eggshells, causing thin, fragile eggshells that crack during incubation, leading to reproductive failure and population decline
- C DDT exposure is sometimes thought to cause a slow, progressive, largely irreversible loss of feathers spreading across the body plumage of affected adult birds in many documented cases according to conventional understanding
- D DDT exposure has sometimes been thought through limited field studies to be largely harmless to most wild bird populations studied worldwide to date in routine practice overall in most cases under typical conditions according to standard textbooks
Correct answer: B. DDT biomagnifies up the food chain to eagles; DDE (a DDT metabolite) inhibits calcium deposition in eggshells, causing thin, fragile eggshells that crack during incubation, leading to reproductive failure and population decline
Explanation: DDT biomagnification: plankton (0.000003 ppm) → small fish (0.5 ppm) → large fish (2 ppm) → osprey/eagle (25 ppm). DDE (persistent DDT metabolite) inhibits calcium-transporting carbonic anhydrase enzyme in the bird's shell gland, reducing CaCO3 deposition. Thin eggshells crack during incubation. Bald eagle, peregrine falcon, osprey, brown pelican declined severely. DDT ban (1972 in USA) allowed recovery. Rachel Carson's Silent Spring (1962) raised public awareness.
Concept context
Pollution, global warming, ozone depletion, deforestation, and sustainability. Important for NEET and general awareness.