Single correct option
The passage below is followed by four summaries. Choose the option that best captures the essence of the passage.
Contrary to the assumption that coral reefs are simply passive structures battered by rising ocean temperatures, recent research has documented several reef populations that have shifted their heat tolerance within a few generations, apparently by favouring symbiotic algae strains better suited to warmer water. This adaptive capacity is real but limited: the pace of warming in many regions now appears to be outstripping the rate at which such shifts can occur, meaning the mechanism offers a partial buffer rather than a guarantee of long-term reef survival.
Contrary to the assumption that coral reefs are simply passive structures battered by rising ocean temperatures, recent research has documented several reef populations that have shifted their heat tolerance within a few generations, apparently by favouring symbiotic algae strains better suited to warmer water. This adaptive capacity is real but limited: the pace of warming in many regions now appears to be outstripping the rate at which such shifts can occur, meaning the mechanism offers a partial buffer rather than a guarantee of long-term reef survival.
- A. Coral reefs are entirely immune to the effects of ocean warming because of their ability to shift symbiotic algae strains.
- B. Coral reefs can adaptively increase heat tolerance across generations by favouring hardier algae strains, but this capacity is limited and may not keep pace with current warming rates.
- C. All coral reef populations have already successfully adapted to rising ocean temperatures.
- D. Ocean warming has had no measurable effect on coral reef populations to date.
Show answer and solution
Answer: (B) Coral reefs can adaptively increase heat tolerance across generations by favouring hardier algae strains, but this capacity is limited and may not keep pace with current warming rates.
The passage makes a balanced claim: adaptation is real (algae-strain shifting) but 'limited,' with warming potentially 'outstripping' adaptive pace. Option B reflects both the reality and the limitation. A and C overstate the adaptive capacity as complete or universal; D contradicts the passage's premise that warming is an active threat being partially, not fully, countered.
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