Read the following statements about the causes of loss of biodiversity:
A. Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species.
B. When large habitats are broken up into small fragments, it is mainly mammals and birds requiring small territories that are badly affected.
C. Over-exploitation of natural resources happens when ‘need’ turns to ‘greed’, as in the over-harvesting of many marine fish populations.
D. Certain animals with migratory habits are badly affected when large habitats are broken up into small fragments due to human activities.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A, C and D only
The book lists four major causes of the loss of biodiversity: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions. Habitat loss is the most important of them.
Statement A: Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species. — True. A habitat need not vanish to cause harm. Pollution that degrades a habitat also threatens the species living in it.
Statement B: When large habitats are broken up into small fragments, it is mainly mammals and birds requiring small territories that are badly affected. — False. Fragmentation hurts the mammals and birds that need large territories. A small fragment cannot meet their needs, so their populations decline. Animals with small territories can still live in a small patch.
Statement C: Over-exploitation of natural resources happens when ‘need’ turns to ‘greed’, as in the over-harvesting of many marine fish populations. — True. Humans have always used nature for food and shelter. When this use goes beyond need, it becomes over-exploitation. Steller’s sea cow and the passenger pigeon were lost this way, and many marine fish are over-harvested today.
Statement D: Certain animals with migratory habits are badly affected when large habitats are broken up into small fragments due to human activities. — True. Migratory animals need large, connected areas to move through. When a habitat is broken into pieces, their routes are cut, and they are badly affected.
NCERT Extract:
Loss of Biodiversity – “… Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species. When large habitats are broken up into small fragments due to various human activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to population declines. (ii) Over-exploitation: Humans have always depended on nature for food and shelter, but when ‘need’ turns to ‘greed’, it leads to over-exploitation of natural resources. Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due to overexploitation by humans. Presently many marine fish populations around the world are over harvested, endangering the continued existence of some commercially important species.”