Question 144·Hard·Command of Evidence
Ecologists Maria Lopez and Tariq Singh surveyed wild bee populations on 30 commercial farms. They recorded both the total length of hedgerows (dense rows of shrubs and trees that provide nesting sites) bordering each field and the yearly amount of insecticide applied. Bee abundance was strongly and positively correlated with hedgerow length but showed no meaningful connection to insecticide use. Lopez and Singh therefore argued that habitat availability, rather than chemical exposure, is the dominant factor limiting bee abundance on these farms.
Which finding, if true, would most directly strengthen Lopez and Singh’s conclusion?
For strengthen-a-conclusion questions, restate the conclusion as a specific comparison (here: hedgerow habitat matters more than insecticides for abundance). Then pick the choice that most directly produces the predicted pattern (e.g., bees still abundant under high insecticide when habitat is strong) while rejecting choices that add confounds or suggest the alternative cause is actually driving the result.
Hints
Clarify the claim you need to support
What do Lopez and Singh say is the dominant factor limiting bee abundance, and what do they say is not dominant?
Look for a decisive pattern
What would it look like if insecticides weren’t the main limiter—especially in cases where insecticide use is very high?
Stay with the same variables
Which choices discuss bee abundance in relation to hedgerow length and insecticide use on farms like the ones surveyed?
Avoid weakening evidence
Eliminate any choice that suggests insecticides drive abundance when other factors are held constant, or that makes the hedgerow effect ambiguous by introducing confounding.
Step-by-step Explanation
Identify the researchers’ conclusion
Lopez and Singh claim that habitat availability (hedgerows) is the dominant factor limiting bee abundance on these farms, and that insecticide exposure is not the main driver.
Predict what would strengthen that conclusion
A strong strengthening finding would show that bees can still be abundant when insecticide use is high as long as habitat (hedgerows) is extensive. That pattern supports the idea that insecticides are not the dominant limiting factor.
Eliminate choices that weaken or muddy the causal story
Be careful with choices that:
- Suggest insecticides do reduce abundance when other factors are held constant.
- Introduce a confounding pattern (for example, hedgerow length and insecticide use moving together), which makes it harder to claim habitat is the true driver.
Choose the finding that most directly supports habitat over insecticides
The statement that bee abundance stays high on farms with extensive hedgerows even when insecticide application exceeds recommended maximums most directly supports the conclusion that habitat availability, rather than chemical exposure, is the dominant limiting factor.