Answer :

Example of Alien species invasion

Nile Perch , introduced into lake Victoria ( in East Africa) , led to extinction of Cichlid fish (more than 200 species) in the lake
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Introduction of African cat fish (Clarias gariepinus) , for aquaculture, posing threat to indigenous catfish
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Introduction of carrot grass (Parthenium) / Lantana / Water hyacinth (Eicchornia) ,which are invasive weed , that pose threat to native species.
Causes of biodiversity loss
(i) Habitat loss and fragmentation
(ii) Over exploitation
(iii) Co-extinction