Question

Draw a food chain/web and use the illustration to explain biomagnifications

Answer 1

Fig:- Food chain showing biomagnification in which the higher is the trophic level, the higher is the toxicity, or higher is the presence of toxic substances in the animal.

Explanation:-

Bio-magnification in a food chain:-

Bio-magnification is the gradual increase of toxic materials in the food chain.

In this process substances like pesticides from the agricultural land or heavy metals from industrial wastes or toxins from the other resources enter the lake or soil or water bodies along with the rain water. In an aquatic ecosystem like lake they enter the water and are taken up by the aquatic plants or phyto-planktons and get accumulated in these plants which are called producers, when these plants are taken up by small fishes which are called primary consumers the pollutant travels through the food chain to the next trophic level, when the small fishes are taken by large fishes along with food the pollutants goes up into the secondary consumer to the next trophic level, when these large fishes are taken by hawks or large birds which are the tertiary consumers the pollutants travel to the next trophic level.

So as the trophic level increases in a food chain the accumulation of these toxic materials in the body of animals keeps increasing.

Here in this case initially the producers who are aquatic plants had 0.04 ppm of DDT in them (usually the presence of toxic material is measured in ppm that is parts per million), when these plants are taken by the primary consumer who are small fishes the amount of DDT increased to 0.23 ppm, and when these small fishes are taken by large fishes the level of toxin increased to 2.07 ppm in the next trophic level, which is higher than the previous level. When these large fishes are taken by hawks the large birds who occupy the topmost position in this food chain the level of DDT became 13.8 ppm. So the higher the trophic level in a food chain higher is the bio-magnification level, that is higher the presence of toxic substances in to layers or at higher trophic levels in a food chain in the ecosystem.

So the toxic substances become more concentrated in the in the tissues or internal organs of animals as they goes up in the food chain.

bio-magnification causes various deadly diseases like cancer in human beings, in case or aquatic organisms they accumulate in vital organs and affect their reproduction and developmental process, for example in case of sea birds eggs are produced with thinner shells,by which during incubation period bird may crush the eggs instead of incubating them.

It is also responsible for destruction of coral reefs which support many marine lives. bio-magnification adversely affects the ecosystem.