Question 47·200 Super-Hard SAT Reading Questions·Information and Ideas
Desert mosses can remain dry for months and resume photosynthesis soon after rain. Because mosses collected in the field often recover faster than mosses maintained in laboratories, some biologists have attributed the difference mainly to inherited adaptation. A research team tested this idea by dividing genetically identical shoots between two treatments: repeated drying and rewetting or continuously moist conditions. The repeatedly dried shoots later recovered faster, but the advantage largely disappeared after eight weeks of continuous moisture; new growth produced during that interval also recovered slowly. In a separate test, however, shoots from different sites retained distinct recovery rates even after receiving the same drying treatment.
Which choice best states the main idea of the text?
For a main-idea question describing multiple experiments, identify what each result establishes and then select the choice that accurately combines them without making a stronger causal claim than the evidence supports. Pay particular attention to whether the study distinguishes a reversible treatment effect from an inherited or permanent difference.
Hints
Use the experimental controls
Consider what researchers can conclude when genetically identical shoots receive different treatments.
Track changes over time
Ask what the fading of the recovery advantage indicates about whether the treatment's effect is permanent.
Include the final comparison
Determine how the result involving shoots from different sites qualifies the conclusion from the first experiment.
Step-by-step Explanation
Interpret the identical-shoot experiment
Because the shoots in the first experiment were genetically identical, their different recovery rates must have resulted from the different moisture treatments rather than from genetic differences.
Determine whether the treatment effect was permanent
The recovery advantage largely disappeared after the repeatedly dried shoots spent eight weeks in continuous moisture, and new growth produced during that period recovered slowly. This shows that the effect of moisture history was reversible rather than permanent.
Account for the separate site comparison
Shoots from different sites still had distinct recovery rates after receiving the same drying treatment. This finding indicates that recent moisture treatment alone cannot explain all the observed variation, though it does not establish that the remaining differences are necessarily genetic.
Synthesize the findings
The best main idea must incorporate both results: recent conditions can reversibly affect recovery, and more persistent differences remain among mosses from different sites.