Logical Reasoning

PT135 · S2 · Q19 One theory to explain

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One theory to explain the sudden extinction of all dinosaurs points to "drug overdoses" as the cause.

Evidence

Angiosperms, a certain class of plants, first appeared at the time that dinosaurs became extinct.

These plants produce amino-acid-based alkaloids that are psychoactive agents.

Most plant-eating mammals avoid these potentially lethal poisons because they taste bitter.

Mammals have livers that help detoxify such drugs.

Dinosaurs could neither taste the bitterness nor detoxify the substance once it was ingested.

This theory helps explain why so many dinosaur fossils are found in unusual and contorted positions.

Conclusion

The sudden extinction of all dinosaurs points to "drug overdoses" as the cause.

Evaluate

To weaken this argument the correct answer could provide an alternative cause, an example of animals eating certain angiosperms but not finding their fossils in unusual or contorted positions, or an example of animal fossils found in unusual or contorted positions but from animals known not to eat angiosperms.

19.

Which one of the following, if true, would most undermine the theory presented above?

  1. Correct

    Many fossils of large mammals

    Why this is right

    This weakens the argument by providing the same observation (fossils found in contorted positions) in a context unlikely to have the same cause—mammals avoided eating angiosperms that produced amino-acid-based alkaloids because they were bitter.

    Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

    76% picked this

  2. Angiosperms provide a great deal

    Out of Scope

    Regardless of whether angiosperms provide a great deal of nutrition, the question is whether they are responsible for the extinction of all dinosaurs.

    5% picked this

  3. Carnivorous dinosaurs mostly ate other,

    Strengthens

    This strengthens the argument by resolving a gap in the reasoning—how the carnivorous dinosaurs could have died as a result of toxic plants.

    11% picked this

  4. Some poisonous plants do not

    Strengthens

    The asserted cause of the extinction of all dinosaurs is poisonous plants. This answer increases the amount and variety of poisonous plants and thereby increases the chances that the explanation is correct.

    5% picked this

  5. Mammals sometimes die of drug

    Strengthens

    This supports the causal explanation by showing a similar cause and effect relationship within another context.

    3% picked this

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