Question

Difficulty: MediumEvaluating Counterarguments and Rebuttals

Consider the following passage:

For decades, marine ecologists maintained that coral bleaching was a uniformly catastrophic event resulting from the irreversible expulsion of endosymbiotic dinoflagellates (zooxanthellae) under thermal stress. However, recent empirical research has given rise to the Adaptive Bleaching Hypothesis (ABH), which posits that bleaching allows host corals to recombine with alternative, thermo-tolerant algal clades, thereby enhancing heat resilience.

Opponents of ABH contend that this mechanism cannot serve as an effective long-term evolutionary adaptation. They observe that corals hosting thermo-tolerant Clade D zooxanthellae exhibit significantly reduced calcification rates and impaired reproductive output compared to those dominated by sensitive Clade C algae. Consequently, critics argue that any temporary thermal tolerance is offset by severe fitness costs that undermine reef structure over time.

Nevertheless, proponents of ABH have effectively rebutted this objection by demonstrating that the observed metabolic trade-off is both transient and context-dependent. Longitudinal surveys reveal that following acute thermal anomalies, corals temporarily retaining Clade D algae experience dramatically lower mortality rates than non-bleached controls. More importantly, as ambient seawater temperatures return to seasonal baselines, corals systematically reshuffle their symbiont populations, re-establishing dominance of high-growth Clade C algae. Thus, the short-term calcification penalty functions not as an evolutionary dead end, but as a crucial survival strategy that preserves host viability until optimal environmental conditions recur.

Based on the passage above, evaluate whether the following statement is True or False:

The proponents neutralize the critics' counterargument by establishing that the growth penalty incurred by hosting Clade D algae is temporary rather than persistent.

Answer: Answer

Answer

True. Proponents successfully neutralize the counterargument by showing that the metabolic penalty of hosting thermo-tolerant algae is transient, as corals revert to high-growth algae once thermal stress subsides.
The passage explicitly describes how proponents of the Adaptive Bleaching Hypothesis respond to the critics' counterargument concerning reduced calcification rates. The proponents show that the metabolic penalty is short-term ('transient and context-dependent') because corals reshuffle their symbionts back to dominant Clade C algae when baseline temperatures return, thereby neutralizing the argument that ABH causes long-term structural harm.

Step-by-Step Solution

1
Identify the critics' counterargument in the passage
Critics argue that hosting Clade D algae reduces calcification and reproduction, creating severe long-term fitness costs that undermine reef structure.
Understanding the specific mechanism of the objection is necessary to evaluate the logic of the response.
2
Analyze how the proponents respond to this objection
Proponents demonstrate that the trade-off is transient; once temperatures normalize, corals reshuffle back to high-growth Clade C algae.
Evaluating a rebuttal requires determining whether and how it addresses the core premise of the counterargument.
3
Compare the proponents' logic to the given statement
The statement accurately reflects the passage logic: proponents neutralize the counterargument by proving the growth penalty is temporary rather than persistent.
Verifying alignment between the text evidence and the evaluation statement ensures correct true/false classification.

Key Concept

Evaluating Counterarguments and Rebuttals
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