PrepTest 115

Incorrect. The relationship between frogs and humans is noted as something that biologists agree on, so it serves as a basis for both theories, not as evidence against the lungfish theory.

Incorrect. The relationship between frogs and humans is noted as something that biologists agree on, so it serves as a basis for both theories, not as evidence against the coelacanth theory.

Incorrect. While the two theories bring up lungfish and coelacanths as two potential fish that were the progenitors of humans and frogs, there's no one who contends that it must be one of these two fish. The author could have highlighted these two theories while believing that there are several other plausible fish out there that may be the ancestor in question!

Correct. Argument or Facts:
Argument

Valid or Flawed:
Valid

Question Type:
Argument Structure

Stimulus Summary:
Biologists agree - Humans evolved from fish, and frogs are related to that fish
Dr. SH - Match of mDNA between frogs and lungfish means that humans evolved from lungfish
Dr. G - mDNA isn't good evidence. Coelacanth hemoglobin is similar to frog hemoglobin, so humans evolved from coelacanths
Conclusion - Biologists disagree on which species of fish humans evolved from

Answer Anticipation:
This argument is meant to highlight the different theories that biologists have on which fish humans evolved from. Two biologists are used to highlight two different theories on which fish it is.

So how do frogs play into this? Well, the frogs are related to a similarity between the two theories—something that biologists "agree" on. That humans and frogs evolved from the same fish is a similarity between the theories—something that they all agree on. As such, the role of the statement in question (that humans and frogs evolved from the same fish) serves as a basis from which both theories build. Since they both rely on similarities between certain fish and frogs, the relationship between humans and frogs is key to making the evidence for both theories relevant to the conclusion.

Let's find an answer that highlights it as a relationship/similarity that biologists agree on and that allows the evidence for the different theories to be relevant.

Answer Explanation:
This answer highlights that it's a shared basis for both of the mentioned theories. Since both deal with similarities between frogs and the fish, the relationship between frogs and humans is an assumption that's required to make that evidence relevant.

Key Takeaway:
At its heart, this argument is about comparing some theories. The conclusion is about agreement/disagreement, which is inherently comparative. And bringing up multiple theories always implies that there are differences between them that should be noted. As such, seeing that the statement in question here was a shared element of both theories led us to an answer that reflected it as a similarity while allowing us to eliminate any answer that focused on differences.

Incorrect. This answer is trying to science you into picking it. It sounds smart and presents a potential further study to be done, but the argument doesn't establish that one of these two fish is the ancestor of frogs and humans, just that they're both presented as that ancestor by different biologists.