Q. 7

Observe figure and answer the following questions.



i. What ecological term is used to describe the DDT accumulation at different trophic levels?

ii. List any one effect of DDT accumulation on birds

iii. Will DDT accumulation lead to eutrophication?

iv. Does it affect the BOD?

v. Name disease caused by accumulation of any heavy metal.

Answer :

i) The ecological term used to describe DDT accumulation at different trophic levels is Biomagnification.


The increase of concentration of toxic substances at successive trophic levels in the food chain is known as Biomagnification.


ii) High concentration of DDT in birds disturbs their metabolism resulting into thinning of their egg shells and their premature breaking. This causes a decline in the population of birds.


iii) Yes, DDT accumulation leads to eutrophication. Eutrophication is the natural aging of a water body due to its increased nutrient enrichment which increases its fertility. This causes increased growth of algae.


iv) Since DDT accumulation leads to eutrophication (increased life in water body) which ultimately results in increased Biological Oxygen Demand. Biological Oxygen Demand is the amount of dissolved oxygen used by microorganisms in the biological process of metabolizing organic matter in water.


v) There are numerous diseases caused by accumulation of any heavy metal. For example-


• Minamata Disease due to Mercury


• Black foot due to Arsenic


• Itai-Itai due to Cadmium


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