Logical Reasoning

PT155 · S2 · Q3 Biologist: DNA analysis show

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Biologist: DNA analysis shows that Acacia heterophylla, a tree native to the Indian Ocean’s Réunion Island, is descended from the Hawaiian tree Acacia koa.

Curious Fact

How did A. heterophylla, a descendant of a tree (A. koa) from the Hawaiian islands end up on an island in the Indian Ocean?

Hypothesis

Seabirds carried A. koa seeds from Hawaii to the Reunion Island in the Indian Ocean.

Evaluate

With this Explain Curious Fact framework, we're always asking the same two questions: 1. could there be some Alternate Explanation for the curious fact? 2. how plausible is the Author's Explanation?

While the correct answer on Flaw, Weaken, Evaluate, and Necessary Assumption is much more likely to deal with #1, the correct answer on Strengthen is more likely to deal with #2.

Goal

Primarily look for something that increases the plausibility that seabirds managed to take seeds from this Hawaiian tree all the way across the Pacific ocean to an island in the Indian Ocean.

(Secondarily keep an eye out for an answer that rules out an Alternate Explanation for how the seeds got there.)

3.

Which one of the following, if true, most strengthens the support for the biologist's hypothesis?

  1. A. koa branches carrying seeds

    Weakens, if anything

    We would either say this does nothing to add plausibility to the seabird hypothesis, or we might even say that this strengthens the Alternate Hypothesis that the seeds could have potentially floated from Hawaii to Reunion. The author rejected it on the basis that, "If the seeds got wet, they wouldn't be able to grow on Reunion", but this answer is making it sound like maybe the seeds could make it there without getting wet? Maybe the tree branch could stay afloat long enough that some of the seeds would stay dry?

    1% picked this

  2. Correct

    There are mountain-nesting seabird species

    Why this is right

    This adds plausibility to the seabird hypothesis by telling us that there are bird species who live in both Reunion and Hawaii (thus, there might be a migratory pathway that seabirds take from one place to the other). When this biologist first says her hypothesis, "Maybe seabirds took the seeds from Hawaii to Reunion?", we can imagine a skeptic saying, "Bah! Are there even birds that can make that trip? Do seabirds ever fly from Hawaii to Reunion?" This answer is providing a clue that makes it sound like maybe there are seabird species making the trek back and forth.

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

    97% picked this

  3. A. koa is thought to

    No Impact

    This does nothing to increase the plausibility of the hypothesis that seabirds took seeds of A. koa from Hawaii to Reunion. This is just telling us an origin story for A. koa, which doesn't have any bearing on our conversation.

    1% picked this

  4. Ocean currents have sometimes carried

    Weakens, if anything

    This answer seems to support the Alternate Hypothesis that seeds floated from Hawaii to Reunion, because it's establishing the possibility of something floating from Hawaii to Reunion. This doesn't do anything to make us think that seabirds carried the seeds from Hawaii to Reunion.

    0% picked this

  5. Many seabird species return to

    Weakens, if anything

    This seems to somewhat hurt the hypothesis that seabirds took seeds from Hawaii to Reunion, because that would be a land-to-land trip, and this answer is saying that many seabird species very rarely return to land.

    1% picked this

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