Self-study
Amphibian populations are declining in numbers worldwide. ███ ███████████████ ███ ███████ █████ █████ ███ ████ ████████████ ████████ ██████████ ███ ████ ██ ██████ ███████████ █████ ██████ █████ █ ████ ██ ███████████ █████████ ████ ██ ████████████ ████████ ██ ███ ████ ███ █████ ███ ██████ ██████ ███████ ██████████ ████ █████ █████ ██ ████████ ██ ██████ █████ ████ ███ ████████████ ██████████ ██ ████ ██████████ ██ █████████ █████ ██████████ ████ ████ ███ ██████████ ██ ████████ ██ ████ ███████ █████ ███ ███████ █████ ██ ███ █████████ █████████ ██████████ ██ ███ █████████ ██ ███ █████ ██████
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the main cause of the declining amphibian population is the depletion of the ozone layer. This is based on the following facts. First, the ozone layer has been continuously depleted over the last 50 years. Second, ozone blocks UV-B, to which amphibians are vulnerable due to their lack of hair/hide/feathres and because their eggs lack leathery/hard shells.
Notable Assumptions
The author assumes there’s no more significant causal factor for the declining amphibian population than the declining ozone layer.
20.
Each of the following, if █████ █████ ██████████ ███ ████████ ███████
a
Of the various █████ ██ █████████ ███████ ██ ███████████ ██████ ████ ██ ███ ████ ████ ████ ███ ██████ ██████
This tells us that there are other types of radiation blocked by atmospheric ozone. But if these other types don’t damage genes, there’s no reason to think they play a role in damaging amphibians. So, there’s no clear impact.
b
Amphibian populations are █████████ ███ ████ ███████ ████ ███ ███ ███████████ ██ ████████████ ███████ █████ ███████ ███ ████ ████ ████ ███████ ██████████ ████ █████
This provides evidence that the lack of protection to UV-B is helping to cause amphibian populations to decline.
c
Atmospheric ozone has ████ █████████████ ████████ █████ ███ ███ █████ ██ ███ █████ ██ █████ █████████ ███████████ ███ ██████████
This strengthens the connection betwen ozone depletion and declining amphibian populations.
d
The natural habitat ██ ██████████ ███ ███ ██████ ███████ ████ ███ ████ ████████
This strengthens by eliminating an alternate explanation for the declining amphibian population. If the natural habitat had been getting smaller, that could have been the main reason amphibians are dying off. (D) eliminates this possibility.
e
Amphibian populations have ████████ ████████████ ███ ███ ████ ██ ██████
Since we’re told the ozone depletion has been occurring “continuously” over the past 50 years, (E) helps strengthen the connection between the declining amphibian population and the depleting ozone.