Fish with teeth specialized for scraping

Answer choices

1. A

   Not Correlation vs. Causality7% picked this

   infers a cause merely from a

   This refers to one of the other 10 famous flaws, Causal, in which the author's conclusion assumes or states a causal explanation for some curious fact in the evidence that could potentially be explained a number of ways. Any Flaw answer structured like infers X merely from Y means that X is the conclusion and Y is the only premise. Does the conclusion state or assume a causal relationship between two things? No. It actually is claiming that the algae-scraping of the fish in Flower Lake evolved separately from the algae-scraping of the fish in Blue Lake.

   7%
2. B

   Not Unproven vs. Proven False11% picked this

   infers that just because the evidence for a particular claim has not yet been confirmed,

   This refers to one of the other 10 famous flaws, Unproven vs. Proven False, in which an author assumes that since someone has failed to prove X or doesn't have any evidence in favor of X, that X is therefore false. This answer says that the conclusion is "inferring that a claim is false", but our conclusion isn't disputing a claim anyone else made. And the evidence doesn't sound anything like, "the evidence that algae-scraping evolved only once hasn't been confirmed yet". The evidence was "these two species are not closely related".

   11%
3. C

   Correct68% picked this

   takes a sufficient condition as a

   Why this is right

   This is what we were looking for, because the argument presented a conditional premise and then argued via an illegal negation of that conditional. (illegal reversals and illegal negations are technically the same thing, so they are both Necessary vs. Sufficient errors). "Being closely related" is a sufficient condition, an If idea. If the two fish are closely related, then the algae-scraping evolved only once. "Being closely related" guarantees that the scraping evolved only once. However, our author acts like "being closely related" is necessary in order to believe that the scraping evolved only once. She acts like "being closely related" is the only way that scraping evolved only once, because she argues that if the two fish aren't closely related, then scraping didn't evolve only once.

   Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

   68%
4. D

   Not Possible vs. Certain11% picked this

   infers merely because something was likely to occur that it

   This refers to a semi-famous flaw (top 15, but not top 10) called Possible vs. Certain. We can also just look at the structure, infers merely because X that Y and then ask ourselves whether X matches the evidence and Y matches the conclusion. Is the conclusion saying that "something did occur"? Yes, it's saying that algae-scraping specialization evolved more than once. So then did the evidence say "it was likely that algae-scraping evolved more than once"? Nope. Since this doesn't match the argument, it can't be right.

   11%
5. E

   Not Inappropriate Appeal3% picked this

   appeals to the authority of biologists who may not be representative of all biologists with expertise

   This refers to one of the other 10 famous flaws, Inappropriate Appeals, in which the author's argument relies on the opinion of someone whose expertise hasn't been established (or, rarely, when the author's argument relies on an appeal to the listener's fear or emotion). Appealing to the authority of the biologists would mean arguing, "X must be true. After all, these biologists believe that X is true." This argument doesn't try to convince us that algae-scraping evolved more than once by saying that "biologists believe that it evolved more than once"

   3%