Causes of biodiversity losses:
(i)Habitat loss and fragmentation.
(ii) Over-exploitation.
(iii)Alien species invasions.
(iv)Co-extinctions.
Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.Another example is the case of a co-evolved plant pollinator mutualism where extinction of one invariably leads to the extinction of the other.