What is Biological Magnification?

There are certain chemicals known as DDT which are not soluble in water. The water consists of 1 part of pesticide per billion parts of water. But they are soluble in the fat. The organisms present in the water absorb them in fat and they aggregate there in high concentrations. The zooplankton which acts on many aquatic phytoplankton cells has pesticide in their tissues. Their levels are not static. They keep on changing with as high as 1 part pesticide per million parts of the fat. There are certain fishes which feed on the zooplankton and have further higher levels of pesticide which range around 5 parts per million. The birds which feed on fishes have further higher levels of pesticide which range around 3000 parts per million. This increase in the level of pesticides at the higher trophic levels in the food pyramids is referred as the biological magnification. These high concentrations have an adverse effect on the predator birds and lead to the defective egg shell production in multiple birds. The shell of the eggs is very thin and can be broken by the bird’s weight. The developing embryos are also adversely affected. So, the numbers of birds are decreased. The herbivorous animals feed on the pesticide rich vegetation. The humans feed on their meat and milk and take pesticides in their tissues.