Water Pollution

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

Biochemical Oxygen Demand (BOD) may not be a good index for pollution in water bodies receiving effluents from?

1. domestic sewage

2. dairy industry

3. petroleum industry

4. sugar industry

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

1.	increased population of aquatic organisms due to minerals
2.	drying of the lake due to algal bloom
3.	increased population of fish due to lots of nutrients
4.	mortality of fish due to lack of oxygen

The highest DDT concentration in aquatic food chain shall occur in?

1. phytoplankton

2. seagull

3. crab

4. eel

A species that was introduced for ornamentation but has become a troublesome weed in India:

1. Parthenium hysterophorus

2. Eichhornia crassipes

3. Prosopis juliflora

4. Trapa Spinosa

Which one of the following statements is not correct?

1.	The amount of some toxic substances of industrial wastewater increases in the organisms at successive trophic levels.
2.	The micro-organisms involved in biodegradation of organic matter in a sewage-polluted water body consume aquatic organisms.
3.	Algal blooms caused by excess of organic matter in water improve water quality and promote fisheries.
4.	Water hyacinth grows abundantly in eutrophic water bodies and lead to an imbalance in the ecosystem dynamics of the water body.

Which of the following statements is correct?

1.	Algal Bloom decreases fish mortality.
2.	Eutrophication refers to increase in domestic sewage and waste water in lakes.
3.	Biomagnification refers to increase in concentration of the toxicant at successive trophic levels.
4.	Presence of large amounts of nutrients in water restricts 'Algal Bloom'.