UPSC Prelims 2000 · General Studies

Question 126: Environment and Ecology

Within biological communities, some species are important in determining the ability of a large number of other species to persist in the community. Such species are called

aKeystone species

bAllopatric species

cSympatric species

dThreatened species

AnswerThe answer is (a).

A keystone species has an effect on its community far greater than its numbers would suggest; if it is removed, many other species decline or disappear. Examples include sea otters and sea stars. Allopatric species live in different geographical areas, sympatric species in the same area, and threatened species are those at risk of extinction.

Why each option is right or wrong

(a) Right: keystone species determine whether many others persist.
(b) Allopatric species are those living in different geographical areas.
(c) Sympatric species are those living in the same area.
(d) Threatened species are those at risk of extinction.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.