Biological magnification is an aspect of food chain in which harmful chemicals enter the food chains and are passed from one trophic level to another getting concentrated at each level.
Man being omnivorous, eats fish, meat as well as vegetables. Being a powerful and intelligent animal, he is very rarely eaten up by other animals. He disposes his dead ones in such a way that scavengers do generally not consume them. Thus he is at the top of most food chains. He is only a consumer.
It is seen that through the food chain some harmful chemicals enter our bodies. The pesticides and insecticides are used to protect crops from diseases and pests.These chemical enter the soil and gradually either enter the water table or get absorbed by plants along with water and mineral salts.Thus,they enter the food chain at the producer level.These plants are consumed by organisms which in turn consumed by others and so on. At each trophic level these harmful chemicals get more and more concentrated and ultimately reach our bodies. Humans have higher concentration of these chemicals than organisms lower in the food chain. The organisms which is onthe extreme right of the food chain, has the maximum concentration of the harmful chemical in its body. The process of concentration of harmful chemicals such as pesticides, at each successive step in a food chain is called biological magnification.