Question

Match column I with column II and choose the correct option.

Column I	Column II
A. Fragmentation of large habitats	1. Nile perch
B. Species turn invasive and cause extinction of indigenous species	2. Host and parasite
C. Mutual extinction	3. Steller’s sea cow
D. Over-exploitation	4. Affects animals requiring large territories

• A. A-1, B-2, C-3, D-4
• B. A-4, B-3, C-2, D-1
• C. A-4, B-1, C-3, D-2
• D. A-4, B-1, C-2, D-3

Answer 1

The correct option is D A-4, B-1, C-2, D-3

Our planet Earth is endowed with enormous and rich biodiversity (a variety of life forms). But unfortunately, this biological wealth is rapidly declining due to human activities.

There are four major causes for the accelerated rates of species extinctions. These four major causes are often referred to as 'Evil Quartet'.

These include habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinction.

Habitat loss and fragmentation - This is the most important cause of loss of biodiversity.

For example, there is a huge habitat loss in the tropical rain forests. These forests which once covered more than 14 percent of the earth’s land surface, now cover no more than 6 per cent.
The destruction of these forests is happening at a very fast rate.

The Amazon rainforest (‘lungs of the planet’) is home to millions of species. It is highly unfortunate that these forests are cleared for cultivating soya beans or getting converted to grasslands for raising beef cattle.

Destruction of such large habitats leads to fragmentation. Birds (especially migratory birds) and mammals that require large territories are affected by fragmentation of large habitats.

Over-exploitation - Overuse of natural resources by humans leads to overexploitation of resources.

For example: Steller’s Sea cow of Russia was overexploited by humans as a result of which they became extinct.

Alien species invasions - Certain alien species introduced into a habitat either purposefully or unintentionally turn invasive and cause decline or extinction of indigenous species.

For example, nearly 200 species of cichlid species became extinct due to the introduction of the Nile perch (an alien species in this context) into Lake Victoria in east Africa.

Co-extinctions - When certain species become extinct, then the plant and animal species associated with it also become extinct. For example, when host fish get extinct then the parasites depending on this fish also get extinct. This is called co-extinction.