Alien species invasion leads to extinction of indigenous species' - Justify this statement by considering two animals as examples.

Explanation

Eg 1. : The Nile perch introduced into Lake Victoria in east Africa lead to the extinction of more than 200 species of cichlid fish in the lake.
Eg 2.: The invasive weed species like carrot grass (Parthenium), water hyacinth (Eicchornia) and Lantana posed threat to our native species.
Eg 3. : The illegal introduction of African cat fish (Clariasgariepinus) posed threat to indigenous cat fishes in our rivers.
Detailed Answer:
New species entering the geographical region are known as alien species. Introduction of alien species causes significant loss to the biological community. Some of the species are able to establish the area. Such successful exotic species eliminate the native species to the point of extinction. And so alter the habitat that many native species are no longer able to persist. For example- Introduction of Nile perch into Lake Victoria disturbed the ecosystem of lake by eliminating several native species of small cichlid fishes. When the toxic species of water hyacinth were introduced in India it caused huge water pollution and occupied all the water bodies.