In a mountain meadow, alpine gentian flowers generally open shortly before bees become active. On mornings following cold nights, the flowers often begin opening before the air warms appreciably; after mild nights, opening more closely tracks morning warming. Botanist Nadiya Shah hypothesizes that the flowers switch between two cues: after a cold night, they use the polarization pattern of dawn light to anticipate suitable conditions, whereas after a mild night, they respond directly to rising temperature. Shah’s team independently varied overnight temperature, dawn-light polarization, and morning air temperature.
Which result from the team’s study would provide the strongest support for Shah’s hypothesis?
For evidence questions involving a conditional hypothesis, translate each condition into a separate prediction and identify which variables must be controlled to test it. Then compare every choice against the complete pattern, giving preference to evidence that isolates both proposed effects rather than merely showing a difference in degree or supporting only one part of the claim.
Hints
Separate the conditions
Write down which cue the hypothesis assigns to flowers after a cold night and which cue it assigns after a mild night.
Look for controlled comparisons
To determine whether one cue affects opening, compare treatments that differ in that cue while the other cue is held constant.
Test the complete pattern
The strongest evidence should address the effects of both manipulated cues under both overnight-temperature conditions, rather than supporting only one part of the hypothesis.
Step-by-step Explanation
Identify both parts of the hypothesis
Shah proposes that the flowers use dawn-light polarization to initiate opening after cold nights but respond directly to rising temperature after mild nights.
Determine the necessary comparisons
To isolate each cue, the study should vary polarization while holding morning warming constant and vary morning warming while holding polarization constant. The effect of each manipulation should depend on the preceding night’s temperature.
Evaluate the complete pattern
The strongest result shows that changing polarization delays opening after cold nights but not after mild nights. It also shows the complementary pattern: delaying warming affects opening after mild nights but not after cold nights. Together, these controlled comparisons directly support a switch between cues.