Question 83·Medium·Command of Evidence
The saguaro cactus (Carnegiea gigantea) produces large white flowers that open shortly after sunset and close the following midday. Although daytime-active bees have traditionally been viewed as the saguaro’s primary pollinators, a 2023 field study led scientists to hypothesize that night-flying moths contribute more to the plant’s reproductive success than bees do.
Which finding, if true, would most directly support the scientists’ hypothesis?
For SAT “support the hypothesis” questions, first restate the hypothesis in your own words, paying attention to what is being compared (here, moths vs. bees) and what the outcome is (here, reproductive success like fruit set). Then scan the options for evidence that directly measures that same outcome under different conditions that isolate the variable of interest (moths present vs. absent while bees are still present). Prefer experimental results that report clear changes in the key outcome over indirect clues like behavior, timing, or physical traits, which may sound related but don’t actually prove the hypothesis.
Hints
Clarify what the hypothesis is comparing
Underline the key comparison in the hypothesis: it isn’t just about which insect visits more often, but about which group, moths or bees, contributes more to reproductive success of the cactus.
Focus on reproductive outcomes, not just behavior
Ask yourself which answer choices actually measure how well the cactus reproduces (such as fruit or seeds), instead of only describing insect behavior, timing, or flower traits.
Look for an experiment that isolates moths’ effect
Is there a choice where moths are added or removed while bees are still allowed, so you can see what extra effect moths have on reproduction beyond what bees already do?
Check for a clear, strong difference
Among the choices that involve reproduction, look for one that shows a large, clear change in reproductive success when moths are not present.
Step-by-step Explanation
Restate the hypothesis in simple terms
The scientists hypothesize that night-flying moths contribute more to the saguaro cactus’s reproductive success than bees do. In other words, the cactus should produce more successful offspring (fruit/seeds) thanks to moths than thanks to bees.
Identify what kind of evidence would be strongest
To directly support this hypothesis, we want evidence that:
- Measures the cactus’s reproductive success (for example, fruit set or seed production), and
- Compares conditions where moths are present vs. absent, while bees are still allowed, so we can see if moths add something important beyond what bees do.
Screen answer choices for direct tests of reproductive success
Now look at the answer choices and ask for each one:
- Does it measure fruit set or another direct reproductive outcome?
- Does it clearly show what happens when moths are prevented or allowed, especially compared with bees alone? Choices that only describe behavior (when they visit, how much pollen they carry, or flower scent) are indirect and do not directly prove higher reproductive success.
Match the best evidence to the hypothesis
One choice describes an experiment where moths are blocked from the flowers at night but bees can still visit during the day, and then shows that fruit set drops by about 80 percent compared with unmanipulated flowers. This directly measures reproductive success and shows that bees alone cannot maintain normal fruit production, so moths are crucial and contribute more than bees. Therefore, the correct answer is: “When moths are prevented from accessing saguaro flowers at night but bees can visit freely during the day, the plants’ fruit set drops by about 80 percent compared with unmanipulated flowers.”