(i) Biological magnification or Biomagnification refers to the increase in concentration of the toxicant at successive trophic levels.

(ii) This caused due to the inability of the organisms to metabolise or excrete the particular toxic substance and hence it keeps on accumulating at each level.

(iii) As the biomass passes forward in the food chain, the toxicant concentration in the body of organisms increases at each trophic level.

(iv) E.g. Accumulation of DDT, mercury.