Q. No.Eutrophication of water bodies leading to the killing of fishes is mainly due to non-availability of:
1. Food
2. Light
3. Essential minerals
4. Oxygen
An increase in the concentration of the toxicant at successive trophic levels is known as:
1. Biomagnifications
2. Biodeterioration
3. Biotransformation
4. Biogeochemical cycling
Which one of the following is a wrong statement?
| 1. | Most of the forests have been lost in tropical areas |
| 2. | Ozone in upper part of atmosphere is harmful to animals |
| 3. | Greenhouse effect is a natural phenomenon |
| 4. | Eutrophication is a natural phenomenon in freshwater bodies |
In an area where DDT had been used extensively, the population of birds declined significantly because:
1. Birds stopped laying eggs
2. Earthworms in the area got eradicated
3. Cobras were feeding exclusively on birds
4. Many of the birds laid eggs, but the eggs did not hatch
When domestic sewage mixes with river water:
| 1. | The increased microbial activity releases micro-nutrients such as iron. |
| 2. | The increased microbial activity uses up dissolved oxygen. |
| 3. | The river water is still suitable for drinking as impurities are only about 0.1%. |
| 4. | Small animals like rats will die after drinking river water. |
Biochemical Oxygen Demand (BOD) in river water:
| 1. | remains unchanged when algal bloom occurs |
| 2. | has no relationship with the concentration of oxygen in the water |
| 3. | gives a measure of Salmonella in the water |
| 4. | increases, when sewage gets mixed with river water |
DDT residues are rapidly passed through food chain causing biomagnification because DDT is:
1. lipo soluble
2. moderately toxic
3. non-toxic to aquatic animals
4. water soluble
A lake near a village suffered heavy mortality of fish within a few days. Consider the following reasons for this:
| 1. | Lots of urea and phosphate fertilizer were used in the crops in the vicinity. |
| 2. | The area was sprayed with DDT by an aircraft. |
| 3. | The lake water turned green and stinky |
| 4. | Phytoplankton populations in the lake declined initially, thereby, greatly reducing photosynthesis. |
Which two of the above were the main causes of fish mortality in the lake?
1. 2, 3
2. 3, 4
3. 1, 3
4. 1, 2
Which one of the following is not a bioindicator of water pollution?
1. Sludge-worms
2. Blood-worms
3. Stone files
4. Sewage fungus
In which one of the following the BOD (Biochemical Oxygen Demand) of sewage (S), distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE) have been arranged in ascending order?
1. SE < S < PE < DE
2. SE < PE < S <DE
3. PE < S < SE < DE
4. S < DE < PE <SE
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