Toxic chemicals introduced into the environment eventually enter food chains and food webs. In 1972, DDT (a chemical used to control mosquitoes) was banned in the United States because of its deleterious effects on the food chain and web. The processes that proved DDT to be hazardous also have shown that other substances, like heavy metals, are harmful to food chains and webs. Explain why heavy metals can have such far-reaching effects. Your answer should include the terms bioaccumulation, persistence, and biological magnification.

The danger of DDT and similar chemicals, like heavy metals, is their tendency to increase as they carried through the food chain. Persistence is a function of the stable chemical structure of a substance. Therefore, heavy metals will remain static in the environment for a long time without breaking down. Bioaccumulation is a function of this persistence. Because heavy metals do not break down, they remain stored in the fatty tissue of the organisms that ingested them. Biological magnification is the idea that animals higher on the food chain tend to store greater concentrations of heavy metals than animals at lower trophic levels.