Water flowing around an obstruction creates vortices (patterns of swirls) of varying size; by detecting the vortices, fish can determine...
GMAT Information and Ideas : (Ideas) Questions
Water flowing around an obstruction creates vortices (patterns of swirls) of varying size; by detecting the vortices, fish can determine the size and position of the obstruction. Testing by Yuzo R. Yanagisuru, Otar Akanyeti, and James C. Liao using models of three head shapes—narrow (low ratio of width to length), intermediate, and wide (high ratio of width to length)—showed that for medium-sized vortices, fish with wide heads would be least able to distinguish between vortices and general turbulence in the water. A second research team has therefore hypothesized that in low-visibility conditions, wider-headed fish will be less likely than narrower-headed fish to detect obstructions.
Which finding, if true, would most directly support the second research team's hypothesis?
A study using obstructions that created medium-sized vortices in low-visibility conditions found that the bristlemouth (Chaetostoma yurubiense), which has a relatively wide head, bumped into more than half of the obstructions.
A study using obstructions that created medium-sized vortices in low-visibility conditions found that some specimens of dusky smooth-hound (Mustelus canis), which has a relatively narrow head, bumped into the obstructions more often than other specimens of the same fish did.
A study using obstructions that created medium-sized vortices in low-visibility conditions found that the wider-headed bristlemouth (Chaetostoma yurubiense) bumped into obstructions more often than the narrower-headed dusky smooth-hound (Mustelus canis) did.
A study using obstructions that created medium-sized vortices in low-visibility conditions found that the narrower-headed dusky smooth-hound (Mustelus canis) bumped into the obstructions just as often as the wider-headed bristlemouth (Chaetostoma yurubiense) did.
Step 1: Decode and Map the Passage
Part A: Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| Water flowing around an obstruction creates vortices (patterns of swirls) of varying size; by detecting the vortices, fish can determine the size and position of the obstruction. |
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| Testing by Yuzo R. Yanagisuru, Otar Akanyeti, and James C. Liao using models of three head shapes—narrow (low ratio of width to length), intermediate, and wide (high ratio of width to length)—showed that for medium-sized vortices, fish with wide heads would be least able to distinguish between vortices and general turbulence in the water. |
|
| A second research team has therefore hypothesized that in low-visibility conditions, wider-headed fish will be less likely than narrower-headed fish to detect obstructions. |
|
Part B: Passage Architecture & Core Elements
Main Point: Research showing that wide-headed fish struggle to distinguish vortices from turbulence has led to a hypothesis that these fish will be worse at detecting obstructions in low-visibility conditions.
Argument Flow: The passage establishes how fish use vortices to detect obstructions, then presents research showing wide-headed fish are worse at this task, which leads to a hypothesis about their performance in low-visibility conditions.
Step 2: Interpret the Question Precisely
What's being asked? Which finding would most directly support the second research team's hypothesis?
What type of answer do we need? Evidence or a study result that would provide support for the hypothesis that wider-headed fish are less likely than narrower-headed fish to detect obstructions in low-visibility conditions.
Any limiting keywords? 'most directly support' - we need the strongest, most direct evidence.
Step 3: Prethink the Answer
- The hypothesis is that in low-visibility conditions, wider-headed fish will be less likely than narrower-headed fish to detect obstructions. To support this, we need evidence showing:
- A study conducted in low-visibility conditions
- A comparison between wider-headed and narrower-headed fish
- Results showing wider-headed fish performed worse at detecting obstructions
- So the right answer should show wider-headed fish failing to detect obstructions more often than narrower-headed fish in low-visibility conditions.
A study using obstructions that created medium-sized vortices in low-visibility conditions found that the bristlemouth (Chaetostoma yurubiense), which has a relatively wide head, bumped into more than half of the obstructions.
✗ Incorrect
- Reports that a wide-headed fish bumped into more than half the obstructions but only provides data about wide-headed fish with no comparison to narrow-headed fish
- Cannot support the hypothesis because it lacks the crucial comparison element
A study using obstructions that created medium-sized vortices in low-visibility conditions found that some specimens of dusky smooth-hound (Mustelus canis), which has a relatively narrow head, bumped into the obstructions more often than other specimens of the same fish did.
✗ Incorrect
- Only discusses narrow-headed fish and variation within that species
- Provides no information about wide-headed fish performance
- Cannot support a hypothesis that requires comparing the two head types
A study using obstructions that created medium-sized vortices in low-visibility conditions found that the wider-headed bristlemouth (Chaetostoma yurubiense) bumped into obstructions more often than the narrower-headed dusky smooth-hound (Mustelus canis) did.
✓ Correct
- Directly compares wider-headed and narrower-headed fish in the required conditions
- Shows wider-headed fish bumped into obstructions more often than narrower-headed fish
- Perfectly demonstrates worse performance by wide-headed fish in detecting obstructions
A study using obstructions that created medium-sized vortices in low-visibility conditions found that the narrower-headed dusky smooth-hound (Mustelus canis) bumped into the obstructions just as often as the wider-headed bristlemouth (Chaetostoma yurubiense) did.
✗ Incorrect
- Shows both fish types performed equally (bumped into obstructions just as often)
- Actually contradicts the hypothesis rather than supporting it