Self-paced
Ornithologist: Support The curvature of the claws of modern tree-dwelling birds enables them to perch in trees. ███ █████ ██ █████████████ ███ ████████ █████ ████████ █████████ ████ ███████ █████████ ████ ████ ████ ███████ ███ ████████ ██ █████ ██ ████ ██████ ██████████ ████████████ ███ ████████ █ █████████████ █████████
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Ornithologist's Argument
The ornithologist concludes that Archeopteryx probably lived in trees. This is supported by an analogy to modern tree-dwelling birds, whose curved claws let them perch in trees. Archeopteryx also had curved claws, so according to the ornithologist, Archeopteryx must also have been able to perch in trees.
However, there's an important gap in this argument. The ornithologist's evidence shows that Archeopteryx probably could live in trees, but the conclusion is that Archeopteryx probably did live in trees. To get there, the ornithologist has to assume that Archeopteryx’s ability to perch in trees indicates Archeopteryx having actually spent time in trees.
Paleontologist's Argument
In response, the paleontologist concludes that being able to perch in trees doesn't actually support Archeopteryx being tree-dwelling. To back up this claim, the paleontologist introduces a competing analogy. The paleontologist compares Archeopteryx to chickens, which are able to perch in trees, and yet live mostly on the ground.
9.
Which one of the following ██ ██ ██████████ ██ █████ ███ ███████████████ █████████ ████████
a
Modern tree-dwelling birds ███ ███ ██████ ███████████ ██ █████████████
Whether or not modern tree-dwelling birds directly descended from Archeopteryx isn’t relevant to whether Archeopteryx actually spent time in trees.
b
Archeopteryx made use ██ ███ █████████ ██ ███ ██████
In other words, Archeopteryx truly spent time perching in trees, enabled by its curved claws. This is necessary to assume, because if Archeopteryx didn’t use its claws to perch in trees, then its claws don’t support the theory that it was tree-dwelling.
c
There have never ████ █████████████ █████ ███████ ██████ ██████
The ornithologist treats curved claws as being sufficient to show that Archeopteryx lived in trees. Whether or not curved claws are a necessary condition to be tree-dwelling birds is a separate question; curved claws could be sufficient without being necessary.
d
Archeopteryx was in ████ ███ ████████ ████████ █████████
The ornithologist’s argument just concerns Archeopteryx’s behavior, so it’s totally irrelevant whether there were unknown earlier birdlike creatures.
e
The curvature of ███ █████ ██ ███ ████ █████████ ████████ ███ ███ █████ ████ ████████████ ███ ██████████████
Whether or not there’s other evidence of Archeopteryx living in trees isn’t necessary to support the ornithologist’s theory that Archeopteryx lived in trees. If anything, making this assumption would weaken the ornithologist's argument: more evidence is better than less evidence, after all.