Self-study
Biologist: DNA analysis shows that . ██████ █████████████ █ ████ ██████ ██ ███ ██████ ███████ ████████ ███████ ██ █████████ ████ ███ ████████ ████ ██████ ████ ████ █████ ████ ████████ ███████ ██ ███ █████ ███████ ████ ██████ ██ █████████ ███ ████ ███████████ ██ ████████████ █████ ███ █████ ████ ███ █████████ █████ █████ ██████ ██ █████████ █████████ ████ █████ ████ ██ ███ ██████████ ███ ████ ███ ██████ ████████ █████████ █████ █████ █████ ██████████ ██ ████ ████████ ██████ ███ ██████████
Summarize Argument: Phenomenon-Hypothesis
The biologist hypothesizes that seabirds brought Acacia koa seeds from Hawaii to Réunion Island. He supports this by noting that seabirds can carry seeds over long distances, and by pointing to DNA evidence that shows that Acacia heterophylla trees on Réunion Island are descended from the Hawaiian Acacia koa. He argues that it’s unlikely that the seeds floated to Réunion Island because they won’t germinate after being soaked in seawater and because both trees grow in the mountains, not near the shore.
Notable Assumptions
The biologist assumes that the seeds couldn’t have floated across the ocean without being soaked in seawater. He also assumes that his hypothesis is the most likely, without considering whether there actually are seed-carrying seabirds on these islands, or whether another explanation, like humans transporting the seeds, is more likely.
3.
Which one of the following, ██ █████ ████ ███████████ ███ ███████ ███ ███ ███████████ ███████████
a
A. koa branches ████████ █████ ███ ██████ ██████ ███ █████████ ███████ ██ █████
This supports the alternative hypothesis that the seeds floated across the ocean. It doesn’t support the biologist’s hypothesis that seabirds carried the seeds to Réunion Island.
Directionally wrong
Directionally wrong
Answers that, if they have any effect, do the opposite of what we want (weaken when we're trying to strengthen, or strengthen when we're trying to weaken).
b
There are mountain-nesting ███████ ███████ ██████ ██ ████████ ███ ███████
This strengthens the biologist's argument by addressing the assumption that seabirds actually live on both Réunion and Hawaii and are likely to carry seeds between the mountains. If mountain-nesting seabirds are common to both islands, his hypothesis becomes much more likely.
Plausibility
Plausibility
Presenting evidence that corroborates (in Strengthen) or conflicts (in Weaken) with the author's hypothesized explanation or the predictions that follow from that explanation.
c
A. koa is ███████ ██ ██ █████████ ████ ██████ ████████████ █ ████ ██████ ██ ███████ ██████████
The argument is only concerned with the fact that A. heterophylla is descended from A. koa. It doesn’t matter what tree A. koa is descended from.
d
Ocean currents have █████████ ███████ ███████ ███████ ████ ██████ ██ █████████
Like (A), this supports the alternative hypothesis by implying that the seeds could’ve floated from Hawaii to Réunion. Instead, we need an answer choice that strengthens the biologist’s hypothesis that seabirds carried the seeds between the islands.
e
Many seabird species ██████ ██ ████ ████ █████████████ ███ █████ ██ ██ ████ ██ ██████
Irrelevant— we don’t know whether the “many seabirds species” in (E) are living on Réunion or Hawaii. Even if they are, this weakens the argument by suggesting that the seabirds rarely return to land to disperse the seeds.