Self-study
Support The top 50 centimeters of soil on Tiliga Island contain bones from the native birds eaten by the islanders since the first human immigration to the island 3,000 years ago. █ ██████████ ██ ████ ███ █████ ████ ███ ██████████ ████████████████ ██ ██████████████████ ████ ███████████████████████ ████ ██████ ██████ ███████ ██ ███████ █ ████ ██████ ███ ████ ███████ ██████████ ██ █████ █████ ██████ █████ ███ ███████ ██ ██████ ████████████ █████████ ███ ██████████ ███ █████████ ██ █████ ██ ███████
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the arrival of humans on Tiliga caused a decrease in the population and diversity of the island’s bird population. As support for this hypothesis, the author compares the top 50 cm of soil (which was accumulated over the 3,000 years since humans arrived) with the lower 150 cm of soil (which was accumulated over the previous 80,000 years). This comparison showed that before humans arrived, there was a larger and more diverse bird population.
Notable Assumptions
The author assumes that it was the arrival of the humans, not something else, that caused the decline in the population and diversity of birds. It could be that some thing else led to both the arrival of the humans and the decline in the bird population. We have a correlation between the arrival of humans and decline of birds, and the author is assuming a causal connection.
4.
Which one of the following ███████████ ██ █████ ████ █████████ ███████ ███ █████████
a
The bird species █████ ██ ████ ████ █████ ██ ███ █████████ ███ ███ ███████ █████████ ██ ███████
This reduces the strength of an alternate hypothesis (the alternate hypothesis being that predators may have been responsible for the declining bird population). Reducing the strength of alternate hypotheses is a way to strengthen arguments, so this does not weaken the argument.
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
Many of the ████ ███████ ████ ███████████ ████ ██████ ███ ███ █████████ ████ ██████ ████████ ███████████ ███████ █████ ████ ██████
(B) says that birds disappeared much more slowly without humans. “Many” is too vague to make any strong inferences here, but this does give some reason to believe that the presence of humans is related to faster disappearance of birds, which is consistent with the argument.
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).
c
The arrival of █ ███████ ██ ████████ ███████ ██ ████ █████ ███ ██████ ██ ████ ███████ ███████████ ████████ ███ █████ █████ ███████████ ██ ███████
This weakens the argument because it introduces an alternate hypothesis. (C) suggests that a microbe that arrived at the same time as humans could be responsible for the disappearance of the birds.
Alternate explanation
Alternate explanation
Weaken: Introduce or support an alternate explanation for a phenomenon.
Strengthen: Helps to eliminate an alternate explanation for a phenomenon.
d
Bones from bird ███████ █████ ██ ████ ████ █████ ██ ███ █████████ ████ █████ ██ ███ ██████████ ████████████████ ██ █████
The birds that humans ate would have already existed (and died) on the island so it makes sense that their bones were found in the lower 150 cm of soil. This is consistent with the argument and doesn’t weaken the claim that humans caused a decrease in the bird population.
Illusory inconsistency
Illusory inconsistency
Answer is attractive because it seems to (but doesn't actually) contradict the premises or conclusion.
e
The birds that █████ ██ ██████ █████ ██ ███ █████ █████ ███████████ █████████ ███ ███ ███ █████
Information about birds’ abilities to fly is completely irrelevant to the argument.