Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

4. Both A and B.

Explanation:

The excessive use of fertilizers has many serious disadvantages like it kills the microorganism of the soil which decreases the fertility of the soil. Nitrate rich water is unfit for drinking and is rather difficult to treat. When nitrate rich water is carried off into surface water bodies such as ponds, rivers, and lakes it proliferates (accelerates) the growth of Algae. These Algae consume dissolved oxygen from water and thus deplete the water of its oxygen content leading to the death of useful aquatic life, such as fish. Such an increase in the growth of Algae in the lakes, ponds etc. resulting in the reduction of oxygen content in water is called as eutrophication.