AP BIOLOGY

Detailed explanation-1: -Biomagnification is a process causing the concentration of a substance (crosses) to increase at higher levels of the food chain. In this scenario, a pond has been contaminated with toxic waste. Further up the food chain, the concentration of the contaminant increases, sometimes resulting in the top consumer dying.

Detailed explanation-2: -High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshell and their premature breaking, eventually causing a decline in bird populations.

Detailed explanation-3: -When an animal consumes food having DDT residue, the DDT accumulates in the tissue of the animal by a process called bioaccumulation. The higher an animal is on the food chain (e.g. tertiary consumer such as seals), the greater the concentration of DDT in their body as a result of a process called biomagnification.

Detailed explanation-4: -The biomagnification of DDT in the aquatic food chain from 0.003ppb in water to fish-eating birds would be 25ppm. Biomagnification is the process by which the concentration of toxic substances increases with each trophic level in the food chain.

Detailed explanation-5: -The concentration of DDT starts at 0.003 ppb (parts per billion) in the water. When it moves up in each tropical level, its concentration increases through biological magnification and reaches up to 25 ppm (parts per million) in fish-eating birds. Hence, the correct answer is option (C).