PrepTest 150, Section 2, Question 13
Scientist: It seems likely that the earliest dinosaurs(53 more words not shown)
Each of the following, if(6 more words not shown)
- AEarly flying dinosaurs(8 more words not shown)
- BEarly flying dinosaurs(9 more words not shown)
- CEarly flying dinosaurs(14 more words not shown)
- DEarly flying dinosaurs(14 more words not shown)
- EEarly flying dinosaurs(13 more words not shown)
Reading the argument
Gliding down sounds like an easier starting point than launching yourself off the ground. But what evidence tells us that dinosaurs actually developed flight that way?
The scientist points to simple wings: enough for gliding, and an intermediate step toward larger wings. That gives the proposed sequence some plausibility. I'd still like evidence that those intermediate forms came first. For example, finding simple gliding wings in the fossil record before the more developed wings would support the proposed history.
What we’re looking for
This is a strengthen EXCEPT question. Four answers will add support; we want the one that doesn't. The useful evidence could support the gliding route or make the competing running-start route less plausible.
Working the answers
- ACorrect
A nest at the base of a tree doesn't tell us how its occupants first became able to fly. They could sleep near a tree without climbing it to glide, and the nest's location doesn't show whether they could launch themselves from the ground. A gives us proximity to trees without evidence about the flight mechanism. It doesn't strengthen the proposed account.
- B
This helps in a way I hadn't initially focused on: to glide out of a tree, the dinosaur first has to get up there. Claws and toes suited to climbing make that possible. They don't prove the dinosaurs glided, but they support a physical requirement of the scientist's explanation.
- C
These feathers are useful for gliding but provide little control during takeoff. That fits the gliding account better than the competing account in which the earliest fliers launched themselves from the ground. C gives evidence about the actual animals' equipment, not just a general claim that simpler wings could work.
- D
A running start is less plausible if the animals' feathers interfere with running. D doesn't directly establish that they glided, and we needn't pretend these are the only conceivable ways flight could develop. But weakening the specific competing explanation gives the scientist's explanation some support.
- E
Trees would offer refuge from the most dangerous predators. That gives these dinosaurs a reason to climb into trees, putting them where the proposed gliding could begin. This is less direct than evidence about their wings, but it still connects their circumstances to the gliding account. Nesting at a tree's base, by contrast, doesn't supply a reason to be up in its branches.
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