On the basis of the above passage, the following assumptions have been made : 1. Global warming is a frequently occurring natural phenomenon. 2. The impending global warming will not adversely affect small mammals. 3. Humans are responsible for the loss of the Earth's natural resilience. Which of the above assumptions is/are valid ?
- (a) 1 and 2 only
- (b) 3 only ✓ UPSC's answer
- (c) 2 and 3 only
- (d) 1, 2 and 3
Why the answer is (b)
• Assumption 1 is invalid because the passage mentions a specific instance of rapid warming 13,000 years ago but does not provide evidence that global warming is a 'frequently occurring' phenomenon.
• Assumption 2 is invalid because the passage states that modern ecosystems are not adapting as easily as in the past due to the decline in energy flow, implying that current environmental changes (including warming) do adversely affect small mammals.
• Assumption 3 is valid because the passage explicitly attributes the 'enormous drop in biomass and energy flow' and the resulting lack of adaptation to 'human-made changes to the environment' from the last quarter of the nineteenth century.
• Therefore, only Assumption 3 is supported by the text, making option (b) the correct answer.
Why the other options are wrong
- (a) 1 and 2 only
- Includes Assumption 1, which is not supported by the text, and Assumption 2, which contradicts the passage's statement that modern ecosystems are struggling to adapt.
- (c) 2 and 3 only
- Includes Assumption 2, which is incorrect because the passage indicates that modern ecosystems are not adapting as easily as they did in the past.
- (d) 1, 2 and 3
- Includes Assumptions 1 and 2, both of which are unsupported or contradicted by the passage, alongside the valid Assumption 3.
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.