Self-study
Fish with teeth specialized for scraping algae occur in both Flower Lake and Blue Lake. ████ ██████████ █████ ████ ███████ ████ ███████████ ███████████████ ███ █████ ████ ███████ ████ ████ ████ ██████ ██ ████████ ██ ██ ███████ ████████ ██ ████ ███ ███████ ████████ ████ ███ ██████████████ ██████████████ ███████ ████ █████ ███ ███████ █████ ████ ████ ███ ███ ██████████████ ████████ ████████ ████████ ████████ ███ ███ ███████ ████████ █████ ███ ██████████████ ██████████████ ███████ ████ ████ █████
Summarize Argument: Counter-Position
The author concludes that the algae-scraping specialization of certain fish species in Flower Lake and Blue lake evolved more than once. This is based on the fact that if the fish in these lakes are closely related, then the algae-scraping specialization evolved only once. But the fish in these lakes are not closely related.
Identify and Describe Flaw
The author confuses a sufficient condition for a necessary condition. The fish being closely related is sufficient for the algae-scraping specialization to have evolved only once. But this doesn’t mean the fish being closely related is necessary. So even if the fish aren’t closely related, it’s still possible the specialization evolved only once.
22.
The reasoning in the argument ██ ██████ ██ ████ ██
a
infers a cause ██████ ████ █ ███████████
The argument’s reasoning is based on an attempted application of a conditional rule. There is not conclusion or assumption of a causal relationship from a correlation.
b
infers that just ███████ ███ ████████ ███ █ ██████████ █████ ███ ███ ███ ████ ██████████ ████ █████ ██ █████
The author doesn’t argue, “We haven’t confirmed the specialization evolved only once, so it must have evolved more than once.”
c
takes a sufficient █████████ ██ █ █████████ ███
The author takes a sufficient condition (fish being closely related) for the specialization being evolved only once as a necessary condition. This is flawed because even if the fish are not closely related, the specialization still could have evolved only once.
d
infers merely because █████████ ███ ██████ ██ █████ ████ ██ ███ █████
The author doesn’t argue, “The specialization is likely to have evolved more than once. So it must have evolved more than once.”
e
appeals to the █████████ ██ ██████████ ███ ███ ███ ██ ██████████████ ██ ███ ██████████ ████ █████████ ██ ███ ████████ ████
The author’s reasoning doesn’t rely on the authority of biologists. It relies on the attempted application of a conditional statement.