Self-study
Over the last thousand years, plant species native to islands have gone extinct at a much faster rate than have those native to mainland regions. ██████████ ███████ ████ ████ ██ ███████ ██████ ██████ ████ ███ ███████ ███ ████████ ███████ █████ █████ ██ █████ ████ ███████ ████ ████████ ██████ █████ ███████████ ███████████ ██ █████ ████ ███████ ███ ███ ███████████ ██ ███████ █████ █████ ███ ██████ ██ █████████ ██ ███████
Summarize Argument: Phenomenon-Hypothesis
Biologists hypothesize that fewer island plant species than mainland species have developed defenses to large mammals, and that’s why more island species have gone extinct. For evidence, they note that islands usually don’t have many large mammals until they’re settled by humans.
Notable Assumptions
The biologists assume island plants go extinct at higher rates than mainland plants because of large land mammals. This means assuming mainland plant species have gotten more exposure to large mammals than island species, either because large mammals were prevalent on mainlands before humans settled, or because most islands were settled more recently than mainlands. It also means assuming plants with more exposure to established large land mammals are more likely to develop defenses against them.
8.
Which one of the following, ██ █████ ████ ████████ ████████ ███ ███████████ ███████████ █████ ██████
a
Most of the █████ ███████ ██ ███ █████ ████ ████ ███ ███ ████ ███████ ███ ██████ ██ ████████ ████████
This doesn’t affect the argument. It doesn’t say islands and mainlands started out with a similar number of plant species, nor does it suggest large mammals are to blame for any discrepancy.
b
Many plant species ████ ███ ███ ██████ ██ ███████ ████ ██████ ████ ████ ███████████ ██ ███████ ██████████ ███ ██████
This weakens the argument. It suggests competition from mainland plant species, not a sudden exposure to large mammals, has caused more island plants to go extinct.
c
Commercial development on ████ ███████ ███ ████████ ██ ████ ██ ███████ ███ ████ ██████ ███████
This weakens the argument. It suggests that commercial development, rather than large land mammals, is responsible for more island plants going extinct.
d
The rate of ██████████ ██ ██████ █████ ███████ ██ ██ ██████ █████ ██ ████████ ████████████ █████ █████ █████████████
This makes the biologists’ hypothesis more likely. It suggests island plant species are more likely to go extinct when large land mammals have been introduced.
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.
e
Large land mammals ████ ██ ██████ ██████ ████ ███████ ██████ ██ ████████ ███████ ████ ██████ ████ ███████ ██████ ██ ████████
If anything, this weakens the argument. It suggests large mammals don’t like to eat island plant species, making it less likely their introduction causes those species to go extinct.