Some Astyanax mexicanus, a river-dwelling fish found in northeast Mexico, have colonized caves in the region. Although there is little...
GMAT Information and Ideas : (Ideas) Questions
Some Astyanax mexicanus, a river-dwelling fish found in northeast Mexico, have colonized caves in the region. Although there is little genetic difference between river and cave A. mexicanus and all members of the species can emit the same sounds, biologist Carole Hyacinthe and colleagues found that the context and significance of those sounds vary by location—e.g., the click that river-dwelling A. mexicanus use to signal aggression is used by cave dwellers when foraging—and the acoustic properties of cave fish sounds show some cave-specific variations as well. Hyacinthe and colleagues note that differences in sonic communication could accumulate to the point of inhibiting interbreeding among fish from different locations, suggesting that ______
Which choice most logically completes the text?
although A. mexicanus living in rivers are genetically similar to those living in caves, river fish rely on sonic communication less than cave fish do.
although A. mexicanus is a single species at present, it could be in the process of splitting into distinct populations with different characteristics.
although all A. mexicanus emit sounds, the fish living in rivers produce some sounds that the fish living in caves do not, and vice versa.
although A. mexicanus from different locations can interbreed currently, river fish and cave fish are sufficiently genetically distinct that they can be considered separate species.
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| 'Some Astyanax mexicanus, a river-dwelling fish found in northeast Mexico, have colonized caves in the region.' |
|
| 'Although there is little genetic difference between river and cave A. mexicanus and all members of the species can emit the same sounds,' |
|
| 'biologist Carole Hyacinthe and colleagues found that the context and significance of those sounds vary by location—e.g., the click that river-dwelling A. mexicanus use to signal aggression is used by cave dwellers when foraging—' |
|
| 'and the acoustic properties of cave fish sounds show some cave-specific variations as well.' |
|
| 'Hyacinthe and colleagues note that differences in sonic communication could accumulate to the point of inhibiting interbreeding among fish from different locations, suggesting that ______' |
|
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- The passage builds a logical progression: these fish are currently one species with similar genetics, but they're developing different communication patterns in different environments
- The key insight is that these communication differences could prevent interbreeding between populations
- The right answer should acknowledge their current status as one species while suggesting they could be diverging into distinct groups due to communication barriers
although A. mexicanus living in rivers are genetically similar to those living in caves, river fish rely on sonic communication less than cave fish do.
✗ Incorrect
- Claims river fish rely on sonic communication less than cave fish. This contradicts the passage, which shows both populations use sonic communication extensively.
although A. mexicanus is a single species at present, it could be in the process of splitting into distinct populations with different characteristics.
✓ Correct
- Acknowledges they're currently a single species and suggests they could be splitting into distinct populations. This perfectly captures the evolutionary implication the passage is building toward.
although all A. mexicanus emit sounds, the fish living in rivers produce some sounds that the fish living in caves do not, and vice versa.
✗ Incorrect
- Claims each population produces unique sounds the other doesn't. This directly contradicts the passage statement that 'all members of the species can emit the same sounds.'
although A. mexicanus from different locations can interbreed currently, river fish and cave fish are sufficiently genetically distinct that they can be considered separate species.
✗ Incorrect
- Claims they're already 'sufficiently genetically distinct that they can be considered separate species.' This contradicts the passage's clear statement that there is 'little genetic difference' between them.