from the surface of the Earth. The absorption of radiation results in the heating up of the atmosphere. Hence, greenhouse gases are essential for maintaining the temperature of the Earth for the sustenance of life. In the absence of greenhouse gases, the average temperature of the Earth will decrease drastically, making it uninhabitable. As a result, life on Earth would be impossible.
Q: 18. A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.
The amount of dissolved oxygen present in water is limited. The abundance of phytoplanktons causes depletion of this dissolved oxygen. This is because phytoplanktons are degraded by bacteria present in water. For their decomposition, the require a large amount of oxygen. Hence, they consume the oxygen dissolved in water As a result; the BOD level of water drops below 6 ppm, inhibiting the growth of fish and causing excessive fish-kill.
Q: 19. How can domestic waste be used as manure?
Depending upon the nature of the waste, domestic waste can be segregated into two categories i.e., biodegradable and non-biodegradable. Biodegradable waste such as leaves, rotten food, etc. should be deposited in landfills, where they get decomposed aerobically and anaerobically into manure. Non-biodegradable waste (which cannot be degraded) such as plastic, glass, metal scraps etc. should be sent for recycling.
Q: 20. For your agricultural field or garden, you have developed a compost-producing pit. Discuss the process in the light of bad odour, flies, and recycling of wastes for a good produce.
It is essential to take proper care of the compost-producing pit in order to protect ourselves from bad odour and flies.
It should be kept covered to minimize bad odour and prevent flies from entering it.
The recyclable waste should not be dumped in the compost-producing pit. It should be sent to the industries through vendors for recycling.