PrepTest 135, Section 2, Question 19
One theory to explain the sudden extinction of(94 more words not shown)
Which one of the following,(9 more words not shown)
- AMany fossils of(7 more words not shown)
- BAngiosperms provide a(4 more words not shown)
- CCarnivorous dinosaurs mostly(8 more words not shown)
- DSome poisonous plants(5 more words not shown)
- EMammals sometimes die(6 more words not shown)
Reading the argument
Could these plants really explain the extinction of all the dinosaurs?
The timing is suggestive: the plants appeared when the dinosaurs became extinct. And the proposed mechanism is understandable. The plants contain potentially lethal substances, while dinosaurs supposedly lacked mammals' ability to taste the bitterness and help detoxify the drugs. But I'd still want to know whether enough dinosaurs ate enough of the plants to cause the claimed result. A possible mechanism isn't yet an explanation of an entire extinction.
Then we reach the theory's strongest stated support: contorted fossils. Does dying in an unusual position identify an overdose? Perhaps another kind of death, or what happened to a body afterward, could produce a contorted fossil. A catastrophic event is one possibility to investigate, not something we're entitled to insert as the established cause.
What we’re looking for
To weaken the theory, I'd look for evidence that the fossil positions aren't the distinctive sign the argument treats them as. We can question that evidence without having to establish exactly what killed the dinosaurs.
Working the answers
- ACorrect
Large mammals also leave contorted fossils, even though the passage describes mammals as better able to avoid or detoxify these substances. That makes the contorted position less persuasive as evidence of the dinosaurs' particular vulnerability to plant overdoses. Some other process might produce the same result.
Be careful: mammals aren't said to be completely immune to these poisons. A doesn't prove that every mammal fossil had another cause, or that no dinosaur overdosed. It weakens the theory's strongest stated evidence by showing the same fossil pattern in a group with protections against the proposed mechanism.
- B
A plant can provide nutrients and still contain poison. Nutritional value doesn't establish that the dinosaurs could eat it safely, so this doesn't undermine the proposed cause of death.
- C
This offers a possible way for plant-derived substances to reach meat-eating dinosaurs through their prey. We'd still need to know whether enough toxin passed along to harm them, but C doesn't supply a reason to reject the overdose theory. It potentially extends the theory's reach.
- D
Other kinds of poisonous plants don't show that these plants couldn't have caused the deaths. The theory concerns the substances produced by angiosperms. The existence of a different poison doesn't by itself provide evidence against this one.
- E
Mammals sometimes dying from the plants supports the claim that the plants can be lethal. Their protections aren't described as perfect. This doesn't give us a reason to doubt that dinosaurs without those protections could be harmed; it is not the challenge to the theory we're seeking.
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