UPSC Prelims 2019 CSAT Paper II · Q43 of 79 Comprehension medium

Passage

Passage - 2 Most invasive species are neither terribly successful nor very harmful. Britain's invasive plants are not widespread, not spreading especially quickly, and often less of a nuisance than vigorous natives such as bracken. The arrival of new species almost always increases biological diversity in a region; in many cases, a flood of newcomers drives no native species to extinction. One reason is that invaders tend to colonise disturbed habitats like polluted lakes and post-industrial wasteland, where little else lives. They are nature's opportunists.

Which one of the following is the most logical and rational inference that can be made from the above passage ?

  1. (a) Invasive species should be used to rehabilitate desert areas and wastelands of a country.
  2. (b) Laws against the introduction of foreign plants are unnecessary.
  3. (c) Sometimes, the campaigns against foreign plants are pointless. ✓ UPSC's answer
  4. (d) Foreign plants should be used to increase the biodiversity of a country.

Why the answer is (c)

• The passage states that most invasive species are neither terribly successful nor very harmful and often cause less nuisance than vigorous native plants like bracken.

• It notes that the arrival of new species almost always increases biological diversity and rarely drives native species to extinction.

• The text explains that invaders tend to colonise disturbed habitats, such as polluted lakes and post-industrial wastelands, where little else lives.

• Since these species are opportunists in already degraded environments and do not significantly harm native biodiversity, opposing them in such contexts yields little benefit.

• Therefore, the most logical inference is that campaigns against foreign plants are sometimes pointless, as they do not address a significant ecological threat in these specific scenarios.

Why the other options are wrong

(a) Invasive species should be used to rehabilitate desert areas and wastelands of a country.
The passage describes invasive species as opportunists in disturbed habitats but does not recommend their active use for rehabilitation, which is a prescriptive action not supported by the text.
(b) Laws against the introduction of foreign plants are unnecessary.
The passage argues that most invasive species are not harmful, but it does not conclude that all laws against foreign plants are unnecessary, as some may still be harmful or successful.
(d) Foreign plants should be used to increase the biodiversity of a country.
While the passage mentions that new species increase biodiversity, it does not advocate for the deliberate use of foreign plants for this purpose, making this a prescriptive rather than a logical inference.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2019, held on 2 June 2019. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

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