Question 162·Hard·Command of Evidence
Entomologist Dr. Kamala Singh investigated why populations of the desert wildflower Mentzelia noctis have declined sharply over the past 60 years. Comparing preserved herbarium specimens collected in the 1950s with flowers gathered in 2020, she found that the older specimens bore large clumps of pollen grains from night-flying bats, whereas the modern specimens carried only a few isolated pollen grains typically transported by moths. On the basis of this observation, Singh concluded that bat visitation to M. noctis flowers has drastically decreased, leading to reduced pollination and subsequent population decline.
Which finding, if discovered, would most strongly support Singh’s conclusion?
For SAT Reading & Writing “support the claim” questions, first restate the claim (or conclusion) in your own words so you know exactly what needs support. Then scan the answer choices and ask: “Does this directly make that claim more believable?” Prefer evidence that is specific, directly about the main subject (here, bat visitation in the flower’s habitat), and shows a clear change or relationship over time. Quickly eliminate choices that discuss side topics (like other species or general conditions) or that merely describe change without tying it strongly to the claim you’re testing.
Hints
Clarify what needs support
Focus on what Singh is claiming: is she mainly talking about weather, plant timing, moths, or bat visitation and pollination?
Look for direct rather than indirect evidence
Ask yourself which choice gives the most direct, specific information about how bat activity in the flower’s habitat has changed over time, not just any environmental or biological change.
Eliminate off-topic changes
If an answer describes a change in something other than bats—such as rainfall, flowering time, or other insects—consider whether that actually proves that bat visitation has decreased, or just shows a different kind of change.
Step-by-step Explanation
Restate the scientist’s conclusion
First, put Singh’s conclusion into your own words. She believes that:
- Night-flying bats used to visit M. noctis flowers often.
- Now, bats visit those flowers much less.
- This drop in bat visitation has led to less pollination and a decline in the wildflower’s population.
The key idea to test is: bat visitation to these flowers has drastically decreased (which then affects pollination).
Identify what kind of evidence would support the conclusion
To support this conclusion, we want evidence that makes it more believable that bat visitation has really decreased.
The strongest evidence would:
- Directly show a big decline in bat presence or activity in the same habitat as the flowers over time, or
- Show something closely tied to bat pollination of M. noctis getting much rarer.
Evidence that focuses on other changes (weather, timing, other insects) without showing a bat decline is weaker or off-topic.
Check why the other options are weaker
Now quickly evaluate why each of the other choices does not strongly support the idea that bat visitation has drastically decreased:
- A) Rainfall change of less than 5% is small and about weather, not specifically bats.
- B) Earlier flowering time shows a change in the plant’s schedule, but it doesn’t show that bats are visiting less. Bats might adjust too.
- C) More moths might even suggest alternative pollinators, not a loss of bats. It doesn’t confirm that bats are visiting less.
None of these give direct evidence of a large drop in bat activity in the flower’s habitat.
Select the option that most directly shows bat activity declined
The remaining option describes nocturnal acoustic surveys over the same 60-year period showing a 90% decrease in bat echolocation calls within the wildflower’s habitat. Echolocation calls are how bats navigate and locate food, so far fewer calls strongly suggest far fewer bats are active there.
This is direct, quantitative evidence that bat activity—and therefore likely bat visitation to M. noctis flowers—has drastically decreased in that area, which most strongly supports Singh’s conclusion. So the correct answer is: “Nocturnal acoustic surveys from 1960 to 2020 show a 90% decrease in the number of bat echolocation calls within the wildflower’s habitat.”