$A$ lake which is rich in organic waste may result in

What is the gradual increase in the concentration of toxicants at successive trophic levels called?

Observe the 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 a disease caused by the accumulation of any heavy metal.

The 'Itai-itai' disease is caused by the poisoning of which of the following?

The accelerated aging of a lake by biological enrichment of its water is known as:

Assertion $(A)$: Pollution is always caused by human activities.
Reason $(R)$: Pollution is not different from contamination.