Question 41·200 Super-Hard SAT Reading Questions·Information and Ideas

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Ecologists have sometimes attributed the unexpectedly high genetic diversity of moth populations on isolated urban green roofs to yearly influxes of adults from large ground-level parks. In a three-year study, however, researchers found that although every roof supported only a small number of moths, each roof’s population retained a distinctive pattern of gene variants while exhibiting nearly as much overall diversity as park populations. The team also observed newly hatched larvae—which remain on the plants where eggs are laid—on roofs several weeks before monitoring recorded any adult moths dispersing from parks. Population models predict that complete isolation over this interval would sharply reduce diversity in such small groups, whereas extensive migration would make the groups genetically similar. Taken together, the findings suggest that _____

Which choice most logically completes the text?

For an inference question, identify every important observation and any general rule the passage provides. Then test each option against the full set of evidence: the correct choice should reconcile the findings without contradicting a stated principle or introducing an unsupported explanation.

Hints

Hint 1
Consider the timing
Compare when the rooftop larvae appeared with when adult moths were observed leaving the parks.
Hint 2
Test both migration extremes
Ask whether complete isolation or extensive migration would produce populations that are both highly diverse and genetically distinctive.
Hint 3
Account for every finding
The best answer must explain the larvae as well as both features of the genetic evidence.

Step-by-step

Step 1
Interpret the larvae evidence
The larvae were found before monitoring detected adult moths leaving the parks. Because larvae remain where their eggs are laid, this timing supports the inference that moths were already reproducing on the roofs.
Step 2
Apply the population models
Complete isolation would sharply reduce the small groups’ genetic diversity, but extensive migration would eliminate their distinctive genetic patterns. Neither extreme matches the observations.
Step 3
Combine the findings
Local reproduction explains the early larvae, and occasional migration explains how the groups can retain substantial diversity without becoming genetically alike. Therefore, choice D is the most logical completion.

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SAT Reading: Information and IdeasAdvancedCoreInferences about a study

Question 41·200 Super-Hard SAT Reading Questions·Information and Ideas

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