Professor: A marine biologist argues that transmission of sea lice

Question

Professor: A marine biologist argues that transmission of sea lice from farm salmon to wild salmon is unlikely in the Broughton Archipelago, British Columbia, citing numerous studies suggesting that salinities less than 30 parts per thousand are unfavorable to sea-lice survival. The biologist concludes that the archipelago's 25–30 parts per thousand salinity range between March and June, the critical period for wild salmon migration, tends to suppress sea-lice proliferation. But a review of the literature shows that salinities of 25–30 parts per thousand in combination with British Columbia's cool spring temperatures favor the flourishing of sea lice.

In this passage, the professor attempts to undermine the biologist's argument by

A. pointing out that a condition claimed to be necessary for sea-lice survival is not sufficient for it

B. citing studies that suggest that salinity levels were not measured reliably

C. claiming that there is evidence showing that one of its premises is false

D. questioning the reliability of the biologist's scientific sources

E. showing that its conclusion is inconsistent with its premises

CR81021.02

hadimadi · Answer

Hi AjiteshArun the red part of yours of equivalent to: If X and Y -> X is good for Z Can you please show where the professor says that? I can't find that statement in the passage. All I can find is the professor saying: If X and Y -> Z But: (X and Y -> Z) != (X and Y -> X is good for Z) Why? Because it could be that X is still counterproductive for Z, and Y is super productive for Z, producing a net positive effect for Z. Thanks a load and sorry for being so annoying, but I can't just leave it at that if I have doubts

AjiteshArun · Answer

Hi  hadimadi ,

I didn't really say that X is good. I said "X is actually good for Z when combined with Y", which is what the professor also says in the stimulus:
 
In other words, "X in combination with Y favors Z" or, moving the modifier to the front, "in combination with Y, X favors Z". I think it's reasonable to say that X has a positive role to play here.

himanshu0123 · Answer

in the question stem: '' salinities less than 30 parts per thousand are unfavorable to sea-lice survival''

is this a necessary condition or sufficient condition against the survival of sea lice ?

KarishmaB · Answer

This is not a black/white situation.

'unfavourable' implies 'unlikely to survive' but we cannot say 'they will not survive.'

Hence, we are not looking for necessary or sufficient conditions. 
If we had been given: "Sea lice cannot survive in salinities less than 30 ppt" then we would have said "salinities less than 30 ppt" are sufficient to kill sea lice.

If we had been given: "To survive, sea lice need salinities more than 30 ppt" then we would have said that "salinities more than 30 ppt" are necessary for sea lice survival.

Notice another thing: 'A is necessary for B' is the same as 'B is sufficient for A.' Think how.

himanshu0123 · Answer

KarishmaB

Could you please elaborate more on below:

''A is necessary for B' is the same as 'B is sufficient for A''

Lets say, 'more than 30 ppt salt is necessary for the survival of sea lice''. What are A and B in the given context?

KarishmaB · Answer

Say, 30% salinity (A) is necessary for sea lice survival (B).

Can we say that if we know that sea lice survived (B), it is sufficient to say that there was 30% salinity (A)? Sure.

Since A is necessary for B, knowing that B happened is sufficient to say that A happened.

Now flip the case: A is sufficient for B.

Consistent effort is sufficient for good grades. So if you put consistent effort, you will get good grades. 
Then we can say that good grades are necessary (have to happen) in case of consistent effort.

We write sufficient condition as "If A then B" and necessary condition as "Only if A, then B"

Given 'if A then B,' it is the same as 'only if B, then A'
Given 'only if A then B,' it is the same as 'if B, then A'

RonTargetTestPrep · Answer

It's neither.

Definitely not necessary, since the sea lice (like all other living organisms) can be killed in plenty of other ways too.

Not sufficient, since the person presenting this idea says only that these salinities are "unfavorable" to the sea lice. 
"Sufficient against their survival" would mean LETHAL / DEADLY to them!

Elite097 · Answer

avigutman   GMATNinja 
I am not really sure about the justification given for both the cases presented to justify against the conclusion that the premise is false. I do think that the premise can easily be true if cool temp is an additional evidence, considering which professor is make his argument but this surely does not convey that the premise as false because cool temp is basically giving an additional reason for professor's conclusion. We cannot say the biologist is wrong because we do not have an evidence to show his premise is false. If his premise is true, then also professor can make use of his premise + cool temp to argue that this would be favourable to transmission of sea lice.

avigutman · Answer

I think you misunderstood the question,  Elite097 . Answer choice (C) claims the following:
 
The question didn't ask us whether WE believe the premise is true or false. The question asks us about the professor's position - not our position, not reality. Just the professor's position.

ridamagarwal · Answer

GMATNinja

I have two questions.

1) What does 'the' mean in the phrase 'a review of THE literature'? Does it imply that the professor reviewed the same studies that the biologist had referred to? Or does it imply that he reviewed all of the relevant literature out there on this topic?

2) How is the biologist's premise and the professor's corrective premise related to the biologist's conclusion? Both the premise (bio's and prof's) are about conditions necessary for proliferation of sea lice in wild salmons. But the conclusion is about transmission of sea lice FROM FARM SALMONS (FS) TO WILD SALMONS (WS)? How is whether sea lice can survive where wild salmons live related to sea lice being transmitted from farm salmons to wild salmons?

I am thinking the sea lice could have been transmitted from FS to WS irrespective of whether it survived after transmission. After all, the transmission is happening from FS to WS and not the other way around. The salinities related conditions have been mentioned with respect to WS and not FS.

GMATNinja · Answer

You raise an interesting question: what EXACT literature did the professor consult? Does it include ALL relevant literature on the topic? Does it include the same studies the biologist used? The problem is, because the passage doesn't give us much detail, that question is tough to answer with 100% certainty. So where does that leave us? Well, we know that the biologist cites "numerous studies suggesting that salinities less than 30 parts per thousand are unfavorable for sea-lice survival." The professor, by contrast, reviews some literature which says that "salinities of 25-30 parts per thousand in combination with British Columbia's cool spring temperatures favor the flourishing of sea lice." So basically, the professor is attacking one of the biologist's premises. According to the biologist, there is evidence that the conditions in British Columbia won't support sea-lice. According to the professor, there is evidence that the conditions ARE favorable for sea-lice. Keeping that in mind should be enough when tackling the answers. You raise another interesting question about the transmission of sea-lice: where exactly are these farm salmon living? Do they live in fish tanks somewhere? Are they kept in the Broughton Archipelago, maybe in underwater cages or something? Since the passage doesn't tell us, it's hard to say. (Personally, I'm picturing a cornfield in Iowa full of salmon, and I know that can't be right... but corn and salmon are a surprisingly tasty combo.

) Anyway, we don't really need to pin this down to answer the question. The biologist is claiming that wild salmon are unlikely to pick up sea-lice (from farm salmon) while in the Broughton Archipelago. To support this claim, the biologist suggests that sea-lice can't survive in the archipelago. The professor then attacks the premise that the sea-lice can't survive in the archipelago. As long as we keep this structure in mind, we should be in good shape. I hope that helps!

ashutosh_73 · Answer

Hi KarishmaB GMATNinja I was stuck between (C) and (D) and ended up choosing the wrong answer. Below is my understanding, please help! Biologist: Conclusion: ''transmission of sea lice from farm salmon to wild salmon is unlikely in the Broughton Archipelago, British Columbia Premise-1: numerous studies suggesting that salinities less than 30 parts per thousand are unfavorable to sea-lice survival. Premise-2: archipelago's 25–30 parts per thousand salinity range tends to suppress sea-lice proliferation. Prof. X: salinities of 25–30 parts per thousand in combination with cool spring temperatures favor the flourishing of sea lice. So, when Prof. provides the evidence, it automatically attacks ''Premise-1'' as well, right? Doesn't the Prof's evidence question the ''numerous studies findings'' as well? This is why i chose (D) over (C), even though both seemed equally probable. Thanks

KarishmaB · Answer

If we were to question the reliability of the studies, we would have said something like:
The studies were conducted by amateurs.
The studies were conducted by the owners of fish farms and they wanted to establish the safety of the interaction of their farm salmon with wild salmon.
The sample size was very small. 
The conditions in the study were not what exist naturally.
etc.

He says nothing of the kind. Perhaps the less than 30 ppt number is accurate under other conditions. 
He says that literature tells us that a range of 25-30 ppt along with cool temp is good for sea lice. So the premise that salinities less than 30 parts per thousand are unfavorable to sea-lice survival is wrong. In some cases, it can be favourable.

KarishmaB · Answer

Here is a video solution to this troublesome problem:

https://www.youtube.com/watch?v=wHlmmLzIx3Q

imRaj · Answer

Hi  AjiteshArun , What's wrong with option D? Reliability means not trustable,right? Isn't that's what happening here.the biologist gives evidence through the studies that salinities less than 30 parts per thousand are unfavorable to sea-lice survival. Professor argument attacks it.So,one can doubt the evidence given by studies,right? ie. we cannot trust the trueness of the studies. What's the flaw in my answer?

imRaj · Answer

Hi  KarishmaB , Can u pls explain me  What's wrong with option D? Reliability means not trustable,right? Isn't that's what happening here.the biologist gives evidence through the studies that salinities less than 30 parts per thousand are unfavorable to sea-lice survival. Professor argument attacks it. He says less than 30 ppt is favourable for sea lice. So,one can doubt the evidence given by studies,right? ie. we cannot trust the trueness of the studies. What's the flaw in my answer?

AjiteshArun · Answer

Hi imRaj,

I don't think that your answer is flawed, but there are a couple of things we should keep in mind:

1.  The professor doesn't say that {salinities < 30 ppt are unfavorable to sea-lice survival} is always wrong. He/she says that it's wrong  under certain conditions  (BC spring). At best, we can say that the professor questions the studies only indirectly/weakly.

2.  We should choose the best option. Option C basically tells us that the professor brings in evidence to show that one of the biologist's premises is false. This is great, because (a) the professor does bring in evidence ( a review of the literature shows that... ), and (b) we don't need to worry about whether the studies are wrong or the biologist's inference is wrong, as the option just says that one of them is wrong.

Option D, on the other hand, isn't as accurate. "Questioning" is not as precise as "claiming that there is evidence", and "the reliability of the biologist's scientific sources" forces us to target only one of the premises.

KarishmaB · Answer

No, the argument does not question the reliability of the study.

Take a simpler example: 
Numerous studies have found that lack of regular exercise in youth leads to lower muscle mass in later years. 
But if people who do not exercise drink protein shakes regularly, they do not experience lower muscle mass later. (hypothetical example only!)

Does it mean we are doubting the studies? No. As a general rule, it is possible that what the studies say occurs. But when researching the same thing under a set of specific conditions, it is possible that it doesn't apply. That doesn't mean that the general rule is not correct.

Also, questioning the reliability of the study is not the same as questioning the result of the study. 
The reliability of the study is questioned when I raise doubts on the methods used to measure something, the bias in the sample etc. The result is obtained from a sample in every study. It may or may not be true. A study only indicates the veracity of the result; it doesn't prove it. 
I have discussed this point in this video too: https://youtu.be/wHlmmLzIx3Q

VerbalBot · Answer

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

Professor: A marine biologist argues that transmission of sea lice

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Critical Reasoning (CR) Questions

Professor: A marine biologist argues that transmission of sea lice

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards