Botany - Environmental Issues Question with Solution | TestHub

The concentration of DDT gets increased at successive trophic levels. If it starts at 0.003 ppb (ppb-parts per billion) in water, it can ultimately reach 25 ppm (ppm-parts per million) in fish-eating birds, through biomagnification.

High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshells and their premature breaking, eventually causing a decline in bird populations.
This increase in the accumulation of toxic substances in the food pyramids is called "Biological magnification".