Q9 - Paleontologists have discovered fossils

[b91302310]

Could anyone explain why (B) strengths the argument ?

Thanks.

[bbirdwell]

(B) says that all centipedes ever discovered were land dwellers. This supports the idea that a newly discovered centipede is also a land dweller. It doesn't prove it, but it helps.

[ccalice21]

I am still confused why (D) is better than (C). Could someone explain it?

I interpret (C) as a choice that undermines(hence "least support") the paleontologist's view, since the "rock...occasionally covered by river water", thus more likely containing water-dwelling animals?

Thanks!

[bbirdwell]

Yeah, but the rocks were only occasionally covered by water. This supports the view that the rocks could contain fossils of land-dwelling animals AND water-dwelling animals.

(D) is the LEAST supportive of the conclusion because the type of rock that the previously discovered animals were found on is irrelevant. Who cares about the other group? We're talking about this one.

It's like saying, "The oldest car I've seen is red." By saying, "The previous oldest car I'd seen was yellow," I do nothing to support or weaken my claim.

(A) strengthens by putting centipedes on land
(B) ditto
(C) strengthens by giving a reason for the occurrence of water-dwelling fossils on the same rocks.
(E) strengthens by showing that land-dwelling animals clearly inhabited the same area

[WaltGrace1983]

I thought this one was super tough because this is one of those questions that, while I had a really hard time eliminating (C), I thought that (D) simply sounded much better. This inability to fully eliminate all the incorrect answers always makes me uneasy! Either way, I'll do a full breakdown to help myself (maybe others too?!)

Centipedes are 20 million+ older than the earliest land-dwelling animals previously identified
+
Centipedes discovered in rock alongside animals known to be water-dwelling
→
But centipedes are still land-dwelling

There are two premises in this question and it looks an awful lot like an explain the discrepancy question. However, instead of explaining the discrepancy, we almost want to undermine the discrepancy by stating that, "there isn't a discrepancy at all! We can still totally have these water-dwelling fossils inhabiting the same rock while these centipedes are land-dwelling." There are a few ways that we can do this:

(1) Show why what is found alongside the centipede doesn't matter: show that it is a common instance that water-dwelling and land-dwelling animals can share the same rock.
(2) Strengthen the evidence: show that these evidence about centipedes that are at least 20 million years YOUNGER actually says something about these centipedes that are fossilized 20 million years prior. Who's to say that centipedes didn't change? We want something to show that they probably didn't

There really isn't too much else we can do because there are only two premises but we are going to expect four answers to play into these two ways we can strengthen the claim. Let's start with the easier eliminations.

(A) This supports. If the legs of the fossilized centipedes were suited to land, this definitely strengthens the idea that they were land dwelling. If something is suited to land, it probably was for a reason.

(B) This sets up precedent. While this isn't the very strongest strengthener that this question could have given us, it does make the idea a little more plausible that these centipedes TOO were land-dwelling.

(E) Again, not the strongest strengthener, but if we have fossils that ALSO share the same rock that can only breath air (hence, land-dwelling) we can find it more plausible that these centipedes were also land-dwelling. The key word here is "only."

Now for the harder ones.

(C) The key word here is "occasionally." If the fossil was occasionally covered with river water, then this could give us an explanation as to how the water-dwelling animal also got there. However, it may also give us a bit of a reason as to how the centipede got there. This is why I went on to (D) to see if it was any better.

(D) This simply doesn't help. In fact, it may hurt the argument. This argument gives us one situation: purportedly land-dwelling centipedes are found in the same rock as a water-dwelling animal. (D) gives us another situation: land-dwelling animals are NOT found in the same rock as water-dwelling animals. So what does (D) do for us? Nothing really.

(D) could have absolutely strengthened if it would have said, "Fossils of the earliest land-dwelling animals that had previously been identified were found in a rock that DID contain fossilized remains of water-dwelling animals." This would absolutely strengthen because we KNOW that these animals were land-dwelling (unlike the centipedes which are purported to be land-dwelling). If we KNOW that these animals are land-dwelling AND they too are found in the same rock as water-dwelling animals, we can clearly see that it is POSSIBLE for a land-dwelling and water-dwelling animal to have the same rock.

[WaltGrace1983]

Could anyone tell me if my thinking above is right?

(C) the fossil was occasionally covered with river water, then this could give us an explanation as to how the water-dwelling animal also got there. However, it may also give us a bit of a reason as to how the centipede got there. This is why I went on to (D) to see if it was any better.

[AlexisE386]

Could anyone tell me if my thinking above is right?

(C) the fossil was occasionally covered with river water, then this could give us an explanation as to how the water-dwelling animal also got there. However, it may also give us a bit of a reason as to how the centipede got there. This is why I went on to (D) to see if it was any better.

I think you are right. thanks a lot for posting this. it helps me a lot!