Biologist Valentina Gómez-Bahamón and her team have investigated two subspecies of the fork-tailed flycatcher bird that live in the same...
GMAT Information and Ideas : (Ideas) Questions
Biologist Valentina Gómez-Bahamón and her team have investigated two subspecies of the fork-tailed flycatcher bird that live in the same region in Colombia, but one subspecies migrates south for part of the year, and the other doesn't. The researchers found that, due to slight differences in feather shape, the feathers of migratory forked-tailed flycatcher males make a sound during flight that is higher pitched than that made by the feathers of nonmigratory males. The researchers hypothesize that fork-tailed flycatcher females are attracted to the specific sound made by the males of their own subspecies, and that over time the females' preference will drive further genetic and anatomical divergence between the subspecies.
Which finding, if true, would most directly support Gómez-Bahamón and her team's hypothesis?
The feathers located on the wings of the migratory fork-tailed flycatchers have a narrower shape than those of the nonmigratory birds, which allows them to fly long distances.
Over several generations, the sound made by the feathers of migratory male fork-tailed flycatchers grows progressively higher pitched relative to that made by the feathers of nonmigratory males.
Fork-tailed flycatchers communicate different messages to each other depending on whether their feathers create high-pitched or low-pitched sounds.
The breeding habits of the migratory and nonmigratory fork-tailed flycatchers remained generally the same over several generations.
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| 'Biologist Valentina Gómez-Bahamón and her team have investigated two subspecies of the fork-tailed flycatcher bird that live in the same region in Colombia' |
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| 'but one subspecies migrates south for part of the year, and the other doesn't.' |
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| 'The researchers found that, due to slight differences in feather shape, the feathers of migratory forked-tailed flycatcher males make a sound during flight that is higher pitched than that made by the feathers of nonmigratory males.' |
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| 'The researchers hypothesize that fork-tailed flycatcher females are attracted to the specific sound made by the males of their own subspecies' |
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| 'and that over time the females' preference will drive further genetic and anatomical divergence between the subspecies.' |
|
Part B: Provide Passage Architecture & Core Elements
Main Point: Researchers have discovered that feather differences create distinct sounds in two fork-tailed flycatcher subspecies and hypothesize that female mate preferences based on these sounds will drive continued evolutionary divergence.
Step 2: Interpret the Question Precisely
What's being asked? Which finding would most directly support the researchers' hypothesis about female preference driving further divergence.
What type of answer do we need? Evidence that would strengthen or validate the specific hypothesis presented - that females prefer sounds from their own subspecies and this preference leads to increasing divergence over time.
Any limiting keywords? 'Most directly support' - we need evidence that provides the strongest, most direct validation of their hypothesis.
Step 3: Prethink the Answer
- The researchers' hypothesis has two connected parts: (1) females are attracted to sounds made by males of their own subspecies, and (2) this preference will drive further genetic and anatomical divergence over time
- To most directly support this hypothesis, we need evidence showing that the predicted divergence is actually happening
- Since the hypothesis specifically claims that female preference will drive 'further' divergence 'over time,' the strongest support would be evidence showing progressive change across generations - the sound differences becoming more pronounced as time passes, which would demonstrate the ongoing divergence the researchers predict
The feathers located on the wings of the migratory fork-tailed flycatchers have a narrower shape than those of the nonmigratory birds, which allows them to fly long distances.
- Explains that wing feather shape differences help migratory birds fly long distances
- While this provides a functional explanation for why the feather differences exist, it doesn't address the researchers' hypothesis about female preference driving further divergence
Over several generations, the sound made by the feathers of migratory male fork-tailed flycatchers grows progressively higher pitched relative to that made by the feathers of nonmigratory males.
- Shows that over several generations, the sound difference between migratory and non-migratory males is becoming progressively greater
- This directly demonstrates the 'further divergence' that the hypothesis predicts should result from female mate preferences
Fork-tailed flycatchers communicate different messages to each other depending on whether their feathers create high-pitched or low-pitched sounds.
- Indicates that the birds communicate different messages through different pitch sounds
- This explains a function for the sound differences but doesn't show evidence of increasing divergence over time
The breeding habits of the migratory and nonmigratory fork-tailed flycatchers remained generally the same over several generations.
- States that breeding habits remained the same across generations
- This would actually work against the hypothesis, since unchanging breeding patterns wouldn't support the idea of ongoing divergence