Environmental Issues Out of Syllabus

Biomagnification is a phenomenon through which certain pollutants get accumulated in tissues in increasing concentrations at successive trophic levels along the food chain. Many pesticides such as DDT, have a long life. Thus, they get incorporated in food chain and get magnified at higher levels.

Biological Oxygen Demand (BOD) is the amount of $\mathrm{O}_2$ (in milligrams), required to decompose organic matter present in one litre of water which is heavily polluted. Increase in BOD value causes sharp decline in dissolved oxygen in water, hence, indicating that the water is polluted.