Which of the following examples illustrates an alien species invading a new ecosystem and resulting in biodiversity losses?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → All of the above.
Alien species are species brought into a new area, on purpose or by chance. Some of them become invasive: they spread fast and cause the decline or extinction of the native (indigenous) species. Alien species invasion is one of the four major causes of biodiversity loss (‘The Evil Quartet’).
Option (1) The introduction of Nile perch into Lake Victoria in East Africa. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The Nile perch introduced into Lake Victoria in east Africa led to the extinction of more than 200 species of cichlid fish in the lake.
Option (2) The introduction of water hyacinth into India. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. Water hyacinth (Eichhornia) is an invasive weed in India, along with carrot grass (Parthenium) and Lantana. It harms native species and the environment.
Option (3) The introduction of African catfish into Indian rivers. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The illegal introduction of the African catfish (Clarias gariepinus) for aquaculture threatens the native catfishes of Indian rivers.
NCERT Extract:
Loss of Biodiversity – “… (iii) Alien species invasions: 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. You must be familiar with the 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.”