Logical Reasoning

PT149 · S4 · Q2 When the ancient fossils

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When the ancient fossils of a primitive land mammal were unearthed in New Zealand, they provided the first concrete evidence that the island country had once had indigenous land mammals.

Conclusion (thus)

The lack of competition from mammals is not why New Zealand has a rich and varied native bird population.

Evidence

Previously, it was believed that New Zealand had no land mammals, but recent findings indicate that at least one land mammal existed there.

Evaluate

This is a "Weaken" question, and our task is to find a way to accept the evidence while resisting the author’s conclusion. We need to support the original theory that the richness of New Zealand's bird population is due to a lack of competition with mammals, despite the newfound evidence of a land mammal.

Goal

Identify an answer choice that allows for the reconciliation of the evidence (presence of a mammal) with the idea that the birds thrived because they faced little to no mammalian competition.

2.

Which one of the following, if true, most seriously weakens the argument?

  1. The unearthed land mammal is

    Strengthens

    This choice implies that there were several mammals, which would suggest more competition, which helps the author argue "See? There was lots of competition from mammals. So that theory is wrong."

    4% picked this

  2. Correct

    The recently discovered land mammal

    Why this is right

    This choice states that the newly discovered mammal went extinct long before the birds established themselves in New Zealand. It weakens the conclusion by allowing the original theory to hold—that the birds thrived due to a lack of competition with any existing mammals when their population was growing.

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

    90% picked this

  3. The site at which the

    No Impact

    Finding reptiles and insects alongside mammal fossils does not affect the causality concerning bird populations and mammalian competition, leaving the conclusion unchallenged.

    2% picked this

  4. Countries with rich and varied

    No Impact

    This sort of reinforces the background idea that "when there are tons of mammals, birds won't do as well". Both the author and her opponents accept this. The opponents think that NZ didn't have mammals, so that's why birds did well. The author thinks that NZ did have mammals, so there must be some other reason why NZ birds did well. We don't know if NZ ever had a rich and varied land mammal population. So this doesn't help us analyze whether NZ's bird population was ever competing with mammals.

    3% picked this

  5. Some other island countries that

    No Impact

    This refers to other island countries having unexpected land mammals and aligns with the author's evidence, slightly reinforcing it rather than undermining it. It has no substantial effect on the argument about the lack of competition leading to New Zealand's rich bird population.

    1% picked this

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