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Class 12th Biology 2015 Set1 Delhi Board Paper Solution

Question 22

Many plant and animal species are on the verge of their extinction because of loss of forest land by indiscriminate use by the humans. As a biology student what method would you suggest along with its advantages that can protect such threatened species from getting extinct ?


"Determination of Biological Oxygen Demand (BOD) can help in suggesting the quality of a water body." Explain.


As a biology student, I would suggest the below given method that can protect these threatened species from becoming extinct:

Ex situ conservation - The threatened species of plants and animals are taken out of their habitats and are kept in special settings such as zoological parks, botanical gardens and wildlife parks.

Nowadays, the gametes of endangered species can be preserved by methods such as cryopreservation and can be fertilised in vitro followed by propagation through tissue culture methods. Similarly, seeds can be preserved in seed banks. This method is an off-site conservation method.




Biological Oxygen Demand (BOD) is the amount of dissolved oxygen required by the aerobic organisms to break down the organic material present in the water body at a certain temperature over a certain period of time. Natural water bodies contain a certain level of organic substances that are acted upon and decomposed by microbes.

Determining the BOD of the water body establishes the amount of organic content in it. Presence of more organic wastes increase the biological activity, thus leading to algal blooms. High BOD value indicates more microbial activity, indicating that the water body is polluted.