SAT Reading & Writing · Command of Evidence (textual)
Freshwater stickleback fish in many separate lakes have independently evolved reduced pelvic armor, and researchers have traced much of…
Freshwater stickleback fish in many separate lakes have independently evolved reduced pelvic armor, and researchers have traced much of this repeated pattern to changes near a single gene called Pitx1. A textbook states that this finding proves evolution always produces identical genetic changes when the same trait evolves repeatedly. Which finding would most directly undermine the textbook's claim?
Answer and explanation
Answer: D: While many populations show changes near the same gene region, the specific genetic changes involved are not identical across all populations, and some populations achieve reduced pelvic armor…
"Always... identical" is an absolute claim, and D directly supplies the counterevidence: genetic routes to the same trait vary across populations, some sharing the same gene region without identical changes, others using different genetic paths altogether. A restates the basic repeated-pattern finding without addressing whether the underlying genetics are identical. C and B are background facts about the species and trait function that don't bear on genetic mechanism.
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