Male túngara frogs make complex calls to attract mates, but their calls also attract frog-biting midges, insects that feed on...
GMAT Information and Ideas : (Ideas) Questions
Male túngara frogs make complex calls to attract mates, but their calls also attract frog-biting midges, insects that feed on the frogs' blood. Researchers Ximena Bernal and Priyanka de Silva wondered if the calls alone are sufficient for midges to locate the frogs or if midges use carbon dioxide emitted by frogs as an additional cue to their prey's whereabouts, like mosquitoes do. In an experiment, the researchers placed two midge traps in a túngara frog breeding area. One trap played recordings of túngara frog calls and the other released carbon dioxide along with playing the calls. Bernal and de Silva concluded that carbon dioxide does not serve as an additional cue to frog-biting midges.
Which finding from the experiment, if true, would most directly support Bernal and de Silva's conclusion?
Only a small number of midges were found in the traps, though the majority were found in the trap that played calls and released carbon dioxide.
Midges entered the trap that released carbon dioxide and played calls only during or immediately after periods of carbon dioxide release.
More midges were found in the trap that only played calls than in the trap that played calls and released carbon dioxide.
The trap that released carbon dioxide and played calls attracted few midges when carbon dioxide concentrations were low but attracted many midges when carbon dioxide concentrations were high.
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| 'Male túngara frogs make complex calls to attract mates, but their calls also attract frog-biting midges, insects that feed on the frogs' blood.' |
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| 'Researchers Ximena Bernal and Priyanka de Silva wondered if the calls alone are sufficient for midges to locate the frogs or if midges use carbon dioxide emitted by frogs as an additional cue to their prey's whereabouts, like mosquitoes do.' |
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| 'In an experiment, the researchers placed two midge traps in a túngara frog breeding area.' |
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| 'One trap played recordings of túngara frog calls and the other released carbon dioxide along with playing the calls.' |
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| 'Bernal and de Silva concluded that carbon dioxide does not serve as an additional cue to frog-biting midges.' |
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Part B: Provide Passage Architecture & Core Elements
Main Point: Researchers determined that frog-biting midges rely solely on frog calls to locate their prey, not on carbon dioxide as an additional cue.
Argument Flow: The passage establishes that frog calls create a problem by attracting dangerous midges along with mates. Researchers questioned whether midges use multiple cues (calls plus CO2) like mosquitoes do. They tested this by comparing traps with different combinations of attractants and concluded that CO2 doesn't help midges locate frogs.
Step 2: Interpret the Question Precisely
What's being asked? We need to identify which experimental finding would most directly support the researchers' conclusion.
What type of answer do we need? A specific experimental result that would logically lead to concluding that CO2 is not an additional cue for midges.
Any limiting keywords? 'Most directly support' means we need the finding that provides the strongest evidence for their conclusion, not just any supporting evidence.
Step 3: Prethink the Answer
- If the researchers concluded that CO2 does NOT serve as an additional cue, then the experimental results should show that adding CO2 to the calls didn't improve the trap's effectiveness
- We'd expect to see that the calls-only trap performed just as well as, or even better than, the calls + CO2 trap
- The key logic: If CO2 were truly helpful to midges, then Trap 2 (calls + CO2) should have caught more midges than Trap 1 (calls only)
- Since they concluded CO2 doesn't help, the results must have shown either equal performance or better performance from the calls-only trap
- So the right answer should show that the calls-only trap was more effective than the calls + CO2 trap
Only a small number of midges were found in the traps, though the majority were found in the trap that played calls and released carbon dioxide.
✗ Incorrect
- This says most midges were found in the trap with calls + CO2
- This would actually contradict the researchers' conclusion by suggesting CO2 does help attract midges
Midges entered the trap that released carbon dioxide and played calls only during or immediately after periods of carbon dioxide release.
✗ Incorrect
- This describes midges entering the calls + CO2 trap specifically during CO2 release periods
- This would suggest that CO2 timing matters, which implies CO2 IS serving as a cue
- This contradicts rather than supports their conclusion
More midges were found in the trap that only played calls than in the trap that played calls and released carbon dioxide.
✓ Correct
- This shows the calls-only trap outperformed the calls + CO2 trap
- Perfectly matches our prethinking: if CO2 doesn't help, then adding it shouldn't improve trap performance
- Directly supports the conclusion that CO2 is not an additional cue
The trap that released carbon dioxide and played calls attracted few midges when carbon dioxide concentrations were low but attracted many midges when carbon dioxide concentrations were high.
✗ Incorrect
- This shows that CO2 concentration levels affected trap performance
- If CO2 concentration mattered for catching midges, then CO2 would indeed be serving as a cue
- This contradicts the researchers' conclusion