Sample 1Easy
The 'Evil Quartet' is the name given to the four major causes of
- A
global warming
- B
ozone depletion
- C
water pollution
- D
the loss of biodiversity
Show the answer
The answer is D.The Evil Quartet describes the four major causes of biodiversity loss: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions.
- A.
Global warming is caused by greenhouse gases, not the four causes named here.
- B.
Ozone depletion is caused mainly by CFCs.
- C.
Water pollution is not what the term describes.
NCERT: Class 12 Biology, Chapter 13 (Biodiversity and Conservation), Causes of Biodiversity Losses
Sample 2Medium
A food-web sketch of Lake Victoria in East Africa has a 'before' panel with more than 200 species of cichlid fish and an 'after' panel in which a large predatory fish, the Nile perch, has been added and the cichlid boxes are crossed out. Which cause of biodiversity loss does the sketch show?
- A
Alien species invasion
- B
Habitat loss and fragmentation
- C
Over-exploitation by humans, as with Steller's sea cow
- D
Co-extinction of a host and its parasite
Show the answer
The answer is A.Alien species invasion is one of the 'evil quartet' of causes of biodiversity loss. The Nile perch introduced into Lake Victoria led to the extinction of an ecologically unique assemblage of more than 200 cichlid species.
- B.
The lake habitat was not cleared or broken up; a new predator was introduced.
- C.
The cichlids were lost to an introduced predator, not to human harvesting.
- D.
Co-extinction is the loss of an obligately associated species, not predation by an introduced fish.
NCERT: Class 12 Biology, Chapter 13
Sample 3NEET level
Assertion (A): The introduction of the Nile perch into Lake Victoria in East Africa led to the extinction of more than 200 species of cichlid fish in the lake. Reason (R): Every alien species introduced into a new area becomes invasive.
- A
Both A and R are true and R is the correct explanation of A
- B
Both A and R are true but R is not the correct explanation of A
- C
A is true but R is false
- D
A is false but R is true
Show the answer
The answer is C.The Nile perch introduced into Lake Victoria eventually led to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish, so A is true. Only some introduced species turn invasive and cause decline or extinction of indigenous species, so the claim that every alien species does is false.
- A.
R is false: not every introduced species becomes invasive.
- B.
R is false, so it cannot be a true statement that fails to explain A.
- D.
A is true: the Nile perch drove over 200 cichlid species to extinction.
NCERT: Class 12 Biology, Chapter 13 (Biodiversity and Conservation), Causes of biodiversity losses