Question

Assertion (A): The natural aging of a lake may occur within 10 years
Reason (R): The aging of the lake depends on climate, size of the lake and other factors

• A. Both assertion and reason are true and reason is the correct explanation for the assertion
• B. Both assertion and reason are true but reason is not the correct explanation for the assertion
• C. Assertion is false but reason is true
• D. Both assertion and reason are false

Answer 1

The correct option is C Assertion is false but reason is true

Eutrophication is the process of aging of a water body (lake) due to excessive growth of algae, plants and other aquatic organisms.

Eutrophication is of two types:

• Natural: It takes place slowly at a rate which cannot be predicted in human lifetime. It may take thousands of years depending on climate, size of the lake and other factors. It is the process of addition and accumulation of nutrients to water bodies, resulting in changes to the species composition of the community.
• Accelerated: It is otherwise called cultural eutrophication. It occurs due to draining off sewage and run off from agricultural fields entering into the water bodies. It causes profuse growth of algae like cyanobacteria. It occurs at a faster rate. This occurs mainly as a result of nutrient enrichment with nitrates and phosphate. As the fertility (amount of nutrients) increases in water bodies, fish and other aquatic organisms get suffocated. They will die and the organic remains will accumulate at the bottom of the lake. With passage of time the lake grows shallower and warmer.

Hence, the assertion is false and the reason is true.