This set of Class 12 Biology Chapter 16 Multiple Choice Questions & Answers (MCQs) focuses on “Environmental Issues” for NEET Preparation.
1. What should be the amount of BOD in the drinking water?
a) More than 1 ppm
b) Less than 1 ppm
c) 5 ppm
d) 10 ppm
Explanation: The amount of biological oxygen demand in pure drinking water should be less than 1 ppm. Less amount of BOD means more amount of dissolved oxygen (DO) is present in water. This DO is essential for the proper growth of organisms.
2. What amount of BOD indicates high water pollution?
Explanation: BOD is the dissolved oxygen is utilized by microbes in decomposing the organic wastes of water. When the amount of BOD is more than equal to 4000mg/liter, it indicates high water pollution.
3. What amount of BOD indicates low water pollution?
Explanation: Biological Oxygen Demand (BOD) is the dissolved oxygen. It is utilized for decomposing the organic wastes of water by the microbes. When the amount of BOD is 1500mg/liter, it indicates low water pollution.
4. How much amount of dissolved oxygen does gravely polluted water consists of?
a) 20 ppm
b) 8 ppm
c) Above 4 ppm
d) Below 4 ppm
Explanation: The water with the maximum amount of pollution is known as gravely polluted water. The dissolved oxygen does gravely polluted water is below 4 ppm. Very few aquatic animals can survive in this water.
5. What is the reason for the increase in the BOD?
a) Planting trees
b) Collecting of sewage water
c) Dumping of sewage in the water
d) Cleaning of water
Explanation: BOD is the dissolved oxygen is utilized by microbes in decomposing the organic wastes of water. The BOD increases when a large amount of sewage is dumped into the water. This lowers the dissolved oxygen content in water.
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