Which of the following factors are responsible for the loss of biodiv…

The correct answer is Option (3) → B, C and D only

The accelerated loss of species today is due to human activities. Four major causes make up “The Evil Quartet”: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions.

(A) Migration — Incorrect. The movement of animals from place to place is not a cause of the loss of biodiversity. It is not one of the four causes. When habitats are broken into small pieces, it is the animals with migratory habits that suffer.

(B) Over-exploitation — Correct. When human need turns into greed, a species is harvested faster than it can replace itself. Steller’s sea cow and the passenger pigeon were lost this way.

(C) Fragmentation — Correct. Habitat loss and fragmentation is the most important cause. Large habitats are broken into small pieces. Mammals and birds that need large territories decline.

(D) Co-extinctions — Correct. When a species becomes extinct, the species that depend on it also die out. A host fish and its parasites, and a plant and its pollinator, are examples.

NCERT Extract:
Loss of Biodiversity – “… Causes of biodiversity losses: The accelerated rates of species extinctions that the world is facing now are largely due to human activities. There are four major causes (‘ The Evil Quartet ’ is the sobriquet used to describe them).”
Loss of Biodiversity – “… 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.”
Loss of Biodiversity – “… Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due to overexploitation by humans.”
Loss of Biodiversity – “… (iv) Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.”