Q. 28

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Answer :

a. Habitat loss and fragmentation are responsible for biodiversity loss.

i. Habitat loss: The most dramatic examples of habitat loss come from tropical rain forestsThe Amazon rainforest (called the “lungs of the planet”) is being cut and cleared for cultivation of soya beans and for conversion into grasslands for raising beef.


ii. Fragmentation: When large-sized habitats are broken or fragmented due to human settlements, building of roads, digging of canals, etc., the population of animals requiring large territories and some animals with migratory habitats declines.


b. The two different ways of biodiversity conservation are:


i. Ex situ: In this conservation threatened organism are taken out from the natural habitat and placed in special setting with care and protected. Example- zoological park, botanical garden.


ii. In situ conservation: In this conservation threatened organisms are conserved in their natural habitat. Example-national parks, biosphere reserves.


OR


a. Chlorofluorocarbons (CFCs) released from the refrigerators air conditioners deplete the ozone in the stratosphere.


UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules. Ozone acts as a shield and protects the earth from the harmful UV rays of the sun.


CFCs depletes ozone layer causing UV rays to reach to earth which damages DNA causing mutation, skin cancer, inflammation of cornea, cataract, aging of skin, snow blindness.


b. Biomagnification is the increasing concentration of a substance, such as a toxic chemical, in the tissues of tolerant organisms at successively higher levels in a food chain. The concentration of DDT is increased at successive trophic levels; say if it starts at 0.003 ppb (ppb = parts per billion) in water, it can ultimately can reach 25 ppm (ppm = parts per million) in fish-eating birds, through biomagnification.


High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshell and their premature breaking, eventually causing decline in bird populations.



Figure 5.Flowchart depicting biomagnification of DDT in aquatic food chain.


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