Biological Magnification

Prepared by: Reo Paolo M. Uri

An understanding of the food  chain  and food web well will help present the use of pesticides which has damaged many of our wildlife. An example is DDT, a chemical used for killing insects. DDT sprayed on insects contaminants plants. From the plants, the chemical passes on to the herbivores and then to the carnivores, including humans. Some may be absorbed by the fish and then by the birds that eat the fish. The organisms in the last trophic level recieve the highest amount of DDT. This phenomenon is what we call biological magnification. It is the transfer of toxins from thetrophic level to another. Biological magnification happens because organisms cannot metabolize the poisons. As an result, 100% of these poison is returned and absorbed by the tissues of organisms and is not eliminated.

DDT has been found to prevent eggs from hatching. It also has many harmful side effects. IT cause genetic abnormalities, cancer and disorders of the central nervous system like hallucinations, convulsions and paralysis.

There are other ecological poisons released by humans to the environment. These include radioactive isotopes from fallout of atomic bombs testings and waste from nuclear reactors; metals like mercury and lead, which may come from broken thermometers; industrial wastes; gasoline additives; and agricultural fungicides. All these poisons remain in the biosphere and accumulate there as more are released to the einvironment.

A very seriuos mercury poisoning called Minamata disease happened in Japan in the 1950's. Industrial wastes contained mercury dumped into Minamata bay. Mercury was absorbed by the phythoplanktons (tiny floating plants) which were eaten by the fish which were eaten by the Japanese villagers. The fish contained about 50 parts per million (ppm) of mercury which is the equivalent of about 0.00s percent mercury. The villagers which ate the contaminated fish held over 100 ppm of the poison in their bodies. As a consequence, the victims suffered symptoms of mercury poisoning- blurred vision numbed muscles, impaired speech, and ultimately, death.

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