The process by which concentration of toxic substances add in each successive member in food chain .this is called biological magnification.
The process in which non- biodegradable substances accumulated in larger and larger concentration as it pass from one tropic level to other along a food chain is known as biological magnification.
A process in which concentration of harmful chemical increase in proceeding level in food chain
Biomagnification, also known as bioamplification or biological magnification, is the increasing concentration of a substance, such as a toxic chemical, in the tissues of organisms at successively higher levels in a food chain.

It is increase in the concerntration of chemicals and pesticides in each trophic level. As we move forward in the food cycle the concerntration of the chemicals increases hence, first trophic level has the lowest concerntration and last trophic level has the highest concerntration of chemicals.