Q21 - In modern deep-diving marine mammals

[skapur777]

Are they assuming that porous outer shell>deep divers, so porous is a sufficient condition? That's why I picked C, showing that being porous doesn't exactly tell us much of anything.

Here are my answer breakdowns:

A: don't know if this is true of prehistoric or modern species, but regardless it doesnt really tell us anything because they are saying porous is a necessary condition here in this statement and, according to the argument, it is a sufficient condition. does it attack the reasoning? not really
B- you can still be a deep sea diver, and this is about modern reptiles
D-these characteristics might help them be more efficient or something but that doesnt exactly attack the argument reasoning or conclusion
E- doesn't this kind of strengthen the idea that icthys are deep sea divers? Kinda confused by the specific role this answer choice stated but i knew by this point that C was a much better answer and thus i picked it

[noah]

Are they assuming that porous outer shell>deep divers, so porous is a sufficient condition? That's why I picked C, showing that being porous doesn't exactly tell us much of anything.

Yes!

Here are my answer breakdowns:

A: don't know if this is true of prehistoric or modern species, but regardless it doesnt really tell us anything because they are saying porous is a necessary condition here in this statement and, according to the argument, it is a sufficient condition. does it attack the reasoning? not really

I think your last part gets it - the issue with prehistoric isn't as relevant. I guess there is a potential gap there, that C addresses, but it's not the main one at play.

B- you can still be a deep sea diver, and this is about modern reptiles
D-these characteristics might help them be more efficient or something but that doesnt exactly attack the argument reasoning or conclusion
E- doesn't this kind of strengthen the idea that icthys are deep sea divers? Kinda confused by the specific role this answer choice stated but i knew by this point that C was a much better answer and thus i picked it

Nice work on those.

I just explained this to someone else, and here's what I wrote:

Here's an analogy to help you see what the issue is with this one:

law professors have elbow patches on their jackets -- this allows them to gesture a lot without ripping holes in their jackets.

Noah has elbow patches on his jackets, so he's probably a law professor.

In the argument at hand, the conclusion is that ich were deep divers. Why? Because they have the same sort of bone structure that modern deep divers have, which allows deep diving.

What's the gap? Well, maybe they have that structure, but they have it for some other reason. Maybe the porous bone structure also helps you run quickly.

(C) plays on this gap. If animals that didn't deep dive have that bone structure, then is it really an indication of deep-diving? No.

The shift from modern to prehistoric is also problematic. And, (C) bridges that nicely. However, at the same time, there's no reason to think we can't apply the biological facts from modern times to prehistoric ones.

As for the wrong answers...

(A) is about species that do not have porous outer shells. Out of scope. Similarly, who cares if you have to surface or not?

(B) is about animals without the porous bone structure. Who cares about them?

(D) is tempting, however the first indication that this answer is fishy is that "there is no clear evidence" -- that leaves a lot of wiggle room. Just because there isn't evidence, doesn't mean the phenomenon doesn't exist. In other words, who cares if whales also have, for example, special lens on their eyes, and we can't tell if ichthyosaurs had them. And even if they didn't have those lenses (or whatever those other features are), we don't have to have the two species have all the same traits for this argument to stand. (And, remember, whales were just one example of deep-diving mammals that have those porous outer shells.)

(E) is tempting as well. However, it's simply saying that the ich probably didn't even need porous bones. But so what? Does that mean that them having them indicates they were deep divers?

[Drake-ob]

Hi Noah,
My issue with C here was that it referenced "modern and prehistoric marine REPTILES" and we were dealing with marine mammals in the statement above. I thought this was a trick designed to throw us off. Otherwise C made complete sense, but I thought the reptile bit made it irrelevant. How do we know a reptilian species has anything to do with a mammalian one?
Thanks,
J

[noah]

Hi Noah,
My issue with C here was that it referenced "modern and prehistoric marine REPTILES" and we were dealing with marine mammals in the statement above. I thought this was a trick designed to throw us off. Otherwise C made complete sense, but I thought the reptile bit made it irrelevant. How do we know a reptilian species has anything to do with a mammalian one?
Thanks,
J

You're right, that's a bit of a jump. However, I think you can agree that it does weaken to some extent. We can always pick at counter-examples that are not exact replicas of the topic discussed in the argument, but if they share relevant characteristics--in this case, deep diving--then the counter-example can serve as a weakener.

[Drake-ob]

Yeah, got it thanks.

re: Answer choice E...Is it accurate to say that even though this choice weakens the relevance of a premise (that porous outer shell of bones is what enables deep diving), it does not weaken the conclusion, that ichs were deep divers? When I saw E I thought, 'Boom this weakens the idea that porous outer shells were necessary for deep diving, so this is the right answer.' This gets into what weakening the "argument" must constitute...in a situation like this, where we can seemingly choose between weakening a conclusion (C) and weakening a premise (E), should we prefer the one that weakens the conclusion?

Thanks Noah.

[noah]

Yeah, got it thanks.

re: Answer choice E...Is it accurate to say that even though this choice weakens the relevance of a premise (that porous outer shell of bones is what enables deep diving), it does not weaken the conclusion, that ichs were deep divers? When I saw E I thought, 'Boom this weakens the idea that porous outer shells were necessary for deep diving, so this is the right answer.' This gets into what weakening the "argument" must constitute...in a situation like this, where we can seemingly choose between weakening a conclusion (C) and weakening a premise (E), should we prefer the one that weakens the conclusion?

Thanks Noah.

Here comes Noah the LSAT explanation downer :

I don't see (E) as weakening the relevance of any premise. There's no premise that says that ichys needed those bones. Also, just because one feature can help with deep diving doesn't mean that another animal couldn't have some other feature that does the trick. So, there's no "need" around here, other than the general argument which is that if an animal has this feature, we need to be able to conclude that it also has the deep-diving characteristic.

I also don't see (C) as only addressing the the conclusion, I see it as dealing with the assumption that the bones are really for that purpose--maybe there was another reason and they indicate something else about an animal.

[ericha3535]

A quick question!

isn't D also wrong because of the "whale part?" We could say: yeah ichthyosaurs doesn't share the same physical aspects but that does not mean they were not divers; in fact they could be sharing some physical aspects that are attributable to other deep divers such as shark (I don't know if shark is a mammal but you know what I mean)

[noah]

A quick question!

isn't D also wrong because of the "whale part?" We could say: yeah ichthyosaurs doesn't share the same physical aspects but that does not mean they were not divers; in fact they could be sharing some physical aspects that are attributable to other deep divers such as shark (I don't know if shark is a mammal but you know what I mean)

Good thinking! I agree.

[timsportschuetz]

I would like to add some comments regarding (C) and (E), and a very big scope shift that has been overlooked by the above posters.

(C): A previous poster mentioned that this is a bad answer choice since it is talking about reptiles instead of mammals. However, notice that the premise leading to the conclusion of the argument SPECIFICALLY states that the animal in question was an extinct marine reptile!

(E): Should be immediately eliminated on the bases of shifting the scope to "surfacing" from "to the surface"! Let me explain: The argument talks about the porous bones aiding in the swim from the depth of the ocean TO THE SURFACE! The argument NEVER talks about actually SURFACING! Those are two VERY different meanings and a often-used trap by test-writers... They prey upon test-takers inherent nature to make unwarranted assumptions without realising of doing this! During my first time reading this question, I initially interpreted the premise to mean "surfacing" as well. However, after closer inspection of the details, I noticed that this was a severe scope shift! You should confidently eliminate answers (A) and (E) based on the above. "Surfacing" means poking something out of the surface (as in whales sticking their blow-holes out of the water). "Swim back to the surface" means the process of swimming from deep depths TO THE SURFACE. The argument is specifically referring to this SWIM FROM DEPTH TO SURFACE... NOT the ACTUAL SURFACING (which is inherently wrong as well due to the scope shift)!

Always look for scope shifts! For example, a lot of questions will talk about the "development of a certain disease during a study" due to taking some certain "widget". Attractive wrong answer choices utilize this type of language and will often offer something such as: "Some of the test subjects were not screened for the existence of such a disease prior to the research". Notice how DEVELOPMENT of a disease is much different than ALREADY HAVING THE DISEASE! These subtle scope shifts are extremely common and very useful for the process of eliminating answer choices (although, it does take considerable practice in order to be able to quickly spot these shifts).