What is the “evil quartet” ?

The evil quartet is the four major causes for species extinction in the world. They are :
i. Habitat loss and fragmentation :
a) Deforestation leads to species extinction.
b) Conversion of forest land to agriculture land.
Eg: Amazon rain forest
ii. Over exploitation : When need turns to greed it leads to over exploitation.
Eg: Steller’s sea cow, passenger pigeon.
iii. Invasion of alien species : When alien species are introduced into a habitat, they establish themselves and eliminate native species.
iv. Co extinction : In an obligate association between a plant and an animal, if plant becomes extinct then animal also becomes extinct.
Eg: Plant-pollinator association