Which of the following statements are correct?
I. The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of cichlid fish in the lake.
II. Steller’s sea cow and the passenger pigeon became extinct due to over-exploitation by humans.
III. Lantana and Eichhornia are invasive weeds in India.
IV. The African catfish Clarias gariepinus was legally introduced into our rivers for aquaculture purposes.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → I, II and III only
The four statements give NCERT’s examples of the causes of biodiversity loss: alien species invasions and over-exploitation.
I. The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of cichlid fish in the lake. — True. The Nile perch is an alien species in the lake, and it wiped out a unique group of cichlid fish there.
II. Steller’s sea cow and the passenger pigeon became extinct due to over-exploitation by humans. — True. Both are among the extinctions of the last 500 years caused by overexploitation by humans.
III. Lantana and Eichhornia are invasive weeds in India. — True. Both are invasive weed species, along with carrot grass (Parthenium), that damage the environment and threaten native species.
IV. The African catfish Clarias gariepinus was legally introduced into our rivers for aquaculture purposes. — False. NCERT calls it an illegal introduction. The catfish now threatens the indigenous catfishes in our rivers.
So statements I, II and III are correct.
NCERT Extract:
Loss of Biodiversity – “… Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due to overexploitation by humans. … 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.”