Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with any three examples.

When alien species are introduced deliberately or unintentionally or any purpose to a new environment, some of them may turn to be invasive or destruction causing for the indigenous species over there.

Example:

• Introducing Nile perch into Lake Victoria in East Africa caused the extinction of more than 200 species of cichlid fish in the lake.

• Illegal introduction of the African catfish Clarias gariepinus for aquaculture purpose is posing a great threat to indigenous catfishes in our rivers.

• Carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia) are among the invasive weed species which are a great threat to the native species.