Q12 - Paleontologist: Pleosiosauromorphs were gigantic

[noah]

Good explanations above!

Let me add mine:

The conclusion of this argument is that plesios--a marine reptile--probably hunted by chasing their prey a long way. Why? Because they have fins that are similar in design to birds that fly a long way.

What's the gap here? Well, I see two:

1. Can we apply design/movement ideas about birds to marine reptiles?

2. Does the fact that something has a body built for long distances mean it's hunting by chasing prey for long distances? Maybe it's just going the distance to deal with climatic issues (e.g. like old folks from Toronto going to Florida every winter).

(E) deals with the first gap. We need there to be a parallel between the design/movement idea for birds and marine animals. Perhaps this is a bit broad in that we need it only to apply to marine reptiles, but so be it.

(A) is tempting; it seems to address that first gap by pointing out a shared evolutionary history. But, even if two animals share an evolutionary ancestor, there still could be differences in how physical features affect movement.

(B) is irrelevant. Who cares if plesios were the only one built that way, or, negated, if many animals had that design?

(C) is tempting because it's confusing and uses terms that make it seem like it's addressing a gap. In short, it's saying that big marine animals need to chase prey over long distances to be able to survive. Do we need this assumption? Could the argument still stand if some big animals were able to survive on some other hunting strategy? Yes, the argument could still stand, and so no, this assumption is not necessary. It's fine if other marine monsters get by through just opening their mouths very very widely. We still may be able to conclude that our plesios still might be using the old hunt-'em-till-they-drop trick since they have those long thin fins like long-distance birds.

(D) is another tempting one. It seems to address the second gap I identified (design for long distance --?--> hunting using long distance trick). However, this actually tells us this: hunting using long distance trick --> designed for long distance. It's reversed. Also, how does "most" help us here? Even if this assumption were correct direction-wise, we don't need most marine animals to be fitting this pattern, we need this one to fit.


#officialexplanation

[yoohoo081]

I'm putting up this explanations to getting the right answer. Please correct me if my process of elimination is wrong!
Thank you!

We know that since we have to find an arguement DEPENDS on an assumption, this assumption is NECESSARY and if negated, it will ruin the argument in the paragraph.
Correct answer: E
If negated, it ruins the argument because we know that the fin's shape affected the swimming abilities. also, this assumption connects the premise of "like the wings of birds" by stating "same way as the shape of a bird's wing"

Wrong Answers:
(A) nothing about common evolutionary ancestors in the paragraph. we're just saying Plesiosauromorph fins are LIKE birds.
Also, if you negate this assumption, doesn't ruin the paragraph.

(B) don't know and don't care about Plesiosauromorphs being ONLY marine reptiles with long, thin fins. doesn't connect the long and thin characteristics which were like wings of birds to chasing prey over long distance.

(C) By negating this argument- If it did hunt by chasing prey over long distance, gigantic marine animal would be able to find enough food to meet the caloric requirement dictated by its body size - shows that it actually supports the statement, not ruin it. The assumption is a reversal of premise and conclusion.

(D) crossed this out because MOST marine animals may not include Plesiosauromorphs and also, we don't know if it's associated with long-distance swimming. the paragraph only states, "lurked and quickly ambushed their prey", not lurked and chased them for a long distance.

[LSAT-Chang]

Quick question: (C) has two "nots" -- are you supposed to take out both of them? I thought it was just one, which in that case, won't support the argument. Thoughts?

[timmydoeslsat]

For (C), I would do this in my head:

~Hunt ---> ~Find enough food

Found enough food ---> Hunt

Even if they found enough food, they would not necessarily hunt.

That is the proper way to negate a conditional, show that the necessary condition is not necessary to the sufficient condition. Commonly, people simply place no in the necessary instead of "not necessarily."

This answer choice really does not have an impact on our argument and conclusion. We are concerned about how plesio's hunted.

If you notice in this argument, the ONLY evidence given to back up the conclusion of "plesio's probably hunted by chasing their prey over long distances" is the last statement about wings and fins.

[chiach2]

If "D" didnt have the word "most" in it, would it be valid. Is that "word" most the only way to disqualify "D" or are there others ways pertaining to its "distances are specialized for long-distance swimming".?

[joseph.m.kirby]

The main problem with (D) is that it says "Most" (which is not necessary). If (D) said "at least some marine animals (PSM) that chase prey over long distances are specialized for long-distance swimming" then it would be a necessary assumption.

The problem with (C) is that this answer adds information that is not particularly necessary to the argument.

(C) says ~hunted by chasing long-distances --> ~be able to find enough food to support caloric req.
(be able to find enough food to support caloric req. --> hunted by chasing long-distances)

So, if we put (C) into the original argument, we get:

P: Fins were like wings of birds who flew long-distances

P: be able to find enough food to support caloric req. --> hunted by chasing long-distance

C: PSM hunted by chasing long-distances


(C) may allow the conclusion to follow but (C) is not necessary. Perhaps for a PSM, being slightly malnourished is OK. Additionally, it could be the case that even if PSMs were able to find food, the food itself is in low supply. All of these ideas are kind of missing the point (and gap) of the argument.

P: Fins were like wings of birds who flew long-distances
-Gap-
C: PSM hunted by chasing long-distances (new information)

To make this argument follow, we need to connect the premise to the new information which (E) does. If we negate (E), it completely obliterates the argument.

[theanswer21324]

how do we know to pick (E) as a necessary assumption? the argument is really poorly crafted, so it's hard to tell what sentences are being used as premises to support the conclusion.

(E) make sense if you word the argument like this: "Plesio fins were quite long and thin, like the wings of birds specialized for a long distance flight. The shape of a marine animal's fin affects the way animal swims in the same way as the shape of a bird's wing. Therefore, p's probably hunted by chasing their prey over long distances."

however, (E) does not make sense if you word the argument like this: "p's were gigantic, long-necked marine reptiles. therefore, p's probably hunted by chasing their prey over long distances." (E) would not help in this case - you'd need a necessary assumption saying something like: "long-necks are not helpful for ambushes" or "long-necks are conducive to long distance hunting"

i guess my question is how do you know what sentences to pick to form the core

thank you

[noah]

how do we know to pick (E) as a necessary assumption? the argument is really poorly crafted, so it's hard to tell what sentences are being used as premises to support the conclusion.

(E) make sense if you word the argument like this: "Plesio fins were quite long and thin, like the wings of birds specialized for a long distance flight. The shape of a marine animal's fin affects the way animal swims in the same way as the shape of a bird's wing. Therefore, p's probably hunted by chasing their prey over long distances."

however, (E) does not make sense if you word the argument like this: "p's were gigantic, long-necked marine reptiles. therefore, p's probably hunted by chasing their prey over long distances." (E) would not help in this case - you'd need a necessary assumption saying something like: "long-necks are not helpful for ambushes" or "long-necks are conducive to long distance hunting"

i guess my question is how do you know what sentences to pick to form the core

thank you

The key here is to recognize that this is a form of a classic LSAT argument structure:

Some people say X
They're wrong
Here's why

Conclusion is in red, support in blue.

In this case, the first sentence is just background.

Noticing the "however" is important to seeing this argument's structure (and the "probably" helps you know that it's a claim, not a fact). Also, the content of the last sentence lets you reason that it's in support of the preceding sentence.

I hope that helps.

[timsportschuetz]

Nobody has touched on the most obvious and simple reason allowing to solve this question! Notice how the conclusion is drawn by relying on an ANALOGY! Therefore, in order to IMPACT such a conclusion, we MUST explicitly IMPACT the stated analogy! Thus, stating that the analogy is NOT SIMILAR would WEAKEN an argument. Stating that the analogy IS SIMILAR would STRENGTHEN the argument. If you negate E, it would say that the analogy is faulty since the comparison is not valid. Therefore, it would DESTROY the argument; hence, this MUST be the correct answer.

[jrnlsn.nelson]

Nobody has touched on the most obvious and simple reason allowing to solve this question! Notice how the conclusion is drawn by relying on an ANALOGY!

I completely concur timsportschuetz -- nice post.

The Paleontologist's conclusion -- i.e. "However, plesiosauromorphs probably hunted by chasing their prey over long distances." -- entirely depends on the veracity of the premise -- i.e. "Plesiosauromorph fins were quite long and thin, like the wings of birds specialized for long-distance flight."

Negate answer choice (E) (which is an effective strategy for dealing with Assumption Questions) and you get:

"The shape of a marine animal's fin DOES NOT affect the way the animal swims in the same way as the shape of a bird's wing affects the way the bird flies."

This clearly undermines the Paleontologist's conclusion, and thus indicates that answer choose (E) is correct.