PrepTest 149, Section 3, Question 10
The prehistoric fish Tiktaalik is the earliest known(49 more words not shown)
The statements above, if true,(8 more words not shown)
- ATiktaalik likely used(6 more words not shown)
- BTiktaalik's fingers were(15 more words not shown)
- CTiktaalik is not(8 more words not shown)
- DNo fish without(9 more words not shown)
- EThe evolutionary significance(15 more words not shown)
Reading the argument
A fish with fingers sounds unusual. But we're told prehistoric fish varied so much that this feature wouldn't have made Tiktaalik stand out at the time.
Its importance comes from a different comparison: what likely happened later. If Tiktaalik was an ancestor of many land animals with fingers, a feature that initially looked like just another variation could become an important development in their evolution. Looking ordinary among its contemporaries doesn't erase that later significance.
What we’re looking for
For the supported statement, I'd expect something about that limit on judging importance from the creatures alive at the same time. We can use the connection the passage gives us without filling in a complete history of Tiktaalik's life or descendants.
Working the answers
- A
We aren't told what Tiktaalik itself used its fingers for. It might have remained in the water while later descendants used related features on land. The proposed ancestry doesn't establish how this particular animal moved.
- B
Calling the fingers important doesn't make them the only important feature. Other aspects of Tiktaalik's anatomy might also have mattered to later land animals. The passage doesn't evaluate every feature or exclude other contributions.
- C
Being an ancestor of land animals wouldn't prevent Tiktaalik from also being an ancestor of surviving fish. Descendant groups could take different paths. The passage doesn't tell us whether any modern fish descend from it, so we can't rule that out.
- D
Nothing makes fingers necessary for every possible way a fish could move on land. A fish might, for example, move by flopping without using fingers. We don't have to establish a particular real-world example; the passage simply gives no universal restriction of the kind D states.
- ECorrect
Comparison with contemporary fish wouldn't make Tiktaalik look especially unusual, yet its likely relationship to later land animals makes its fingers significant. The comparison by itself therefore doesn't supply the information that establishes the evolutionary importance described. We need the later-development perspective as well. E stays with that limitation instead of inventing an unmentioned use of the fingers or an exclusive family tree.
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