Q. Consider the following statements:

1. All alien species turn invasive, and cause decline or extinction of indigenous species.
2. The Nile perch introduced in East Africa led to extinction of cichlid fish.
3. Parthenium, Lantana and Clarias gariepinus are examples of invasive weed species.

Which of the above is / are correct?
Answer: Only 1 and 2
Notes: When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive, and cause decline or extinction of indigenous species. The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake. Examples include environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia). The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers.

This question is part of UPSC Daily 20 MCQ Series Course on GKToday Android app.