Q6 - As air-breathing mammals, whales must

[weiyichen1986]

Dear people,

Can you help me to figure out why D is wrong.

The stimulus is saying that fossilized whale skeleton did not have fully functioning hind limbs and partial pelvis.....but it is still the remanants of limbs whales once had.

so D helps to explain other mammals can also lives on land without a perfect hind limbs, thereby justifying the whale's imperfection.

do you think there is something wrong in my analysis?

Thank you in advance.

[ManhattanPrepLSAT2]

I think you may be interpreting the argument from a slightly different perspective than was intended --

The argument is essentially about "evolutionary leftovers" -- whales, and the recently found fossil in particular -- have remnants of a pelvis -- this is not meant to serve as evidence that these whales could live on land (we know whales can't live on land) but rather than previous ancestors of these whales used to live on land (otherwise, there would be no remnants of a pelvis).

(D) would, as you suggest, serve as analogous scenarios that support the idea that non-fully formed limbs could help the whale survive on land. That's not the author's point, per the reasons stated above. Furthermore, we're told specifically in the text that the whale w/the pelvis in question could not have survived on land.

I hope that is helpful. Please follow up if it's not clear, or if you have further questions.

[shaynfernandez]

I am having a hard time finding the core to this... Any idea?

[giladedelman]

The reason you're having trouble finding the core is because ... there is no core!

Well, there is one, but it's given to us in an unusual way. The stimulus itself only gives us some facts, i.e., premises. It's not until we read the question stem that we learn about the conclusion we're trying to strengthen: that "the fragile hind limbs are remnants of limbs that land-dwelling whales once had."

So the core is as follows:

P: for whales to have lived on land, they needed strong hind limbs
P: fossilized whale has partial pelvis and fragile hind limbs

------------> C: the fragile limbs are remnants of full limbs of the old land-dwelling whales

Does that answer your question?

[WaltGrace1983]

As noted above, there really isn't a core to this argument yet we can still analyze it just the same. It is a strengthen question.

Facts:

(1) Land-dwelling mammals needed hind limbs
(2) If animals had a pelvis, they had hind limbs
(3) Fossilized whale had fragile hind limbs and a partial pelvis

Conclusion: Fragile hind limbs are remnants of limbs that land-dwelling whales once had

So from what is given above, we need to support the conclusion. As Mike said, this a problem primarily about "evolutionary leftovers." We know that these whales had very fragile limbs and a partial pelvis - how can we conclude that this is all pointing to them having limbs sufficient to be land-dwelling? What I was initially thinking was that I would get something about evolution. Perhaps an answer choice would say something like, "There is evidence from fossils that date before the newly discovered fossil that whales had a stronger pelvis" - something like that. Perhaps it would give me an example of how whales have evolved in other aspects. Either way, without having a core it is really hard to pre-phrase the right answer.

(A) Well if they had full pelvises then, according to the stimulus, "we expect them to have hind limbs." This seems like a really good answer choice so I'll skip it and move on.

(B) This actually is the opposite of what I was initially looking for. I was looking for something saying that fossils have been found that gives some evolutionary evidence that there was some hind limbs.

(C) This is definitely wrong because, like (B), this makes us uncertain if we can really conclude a connection between the remnants of a limb and actually having a limb. This is saying that even scientists are uncertain as to if nonfunctioning limbs, i.e. the limbs shown in this fossilized whale, "derived from once-functioning limbs," aka the land-dwelling limbs that we are trying to assert that whales use to have. Now I will say that this answer choice is still about "other" mammals. So it could also be treated as a bit out of scope too.

(D) This is about the ability to land-dwell. Yet this isn't what we are concerned about! We are concerned about having the limbs necessary for land dwelling. We don't care if they actually land-dwelled or not - that is just a secondary tidbit of information.

(E) This is just out of scope, perhaps even weakening. It seems that we are talking about sea-mammals (dolphins) now when we are really concerned about sea-mammals then. However, it may also weaken because this continues to destabilize the link between used to having functioning limbs and not having functioning limbs. We want to link up those two things as much as possible - aka that not having limbs now still doesn't necessarily mean they didn't have limbs then.