Professor: A marine biologist argues that transmission of sea lice fro

Let's start by considering the structure of the marine biologist's argument.

The marine biologist concludes that "the archipelago's 25–30 parts per thousand salinity range between March and June...tends to suppress sea-lice proliferation." This conclusion is based on the premise that the salinity in this area is 25-30 parts per thousand in the spring, and that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival."

So the marine biologist's conclusion relies on the premise that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival." The professor then undermines the argument by attacking this premise. More specifically, the professor claims that "salinities of 25–30 parts per thousand in combination with British Columbia's cool spring temperatures favor the flourishing of sea lice."

As a result, the premise that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival" is false, which makes (C) correct.

You raise an interesting question about cool spring temperatures being an "edge case" of an otherwise reliable premise. Should we assume the premise that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival" is generally sound? If so, would that make it true?

Unfortunately, the passage doesn't give us any evidence to help resolve this question. We know that the marine biologist has cited numerous studies, but we have no idea how complete or representative those studies are. All we know is that the professor claims the premise is not ALWAYS true. In other words, the professor claims the premise is false.

Yet even if we could somehow prove that the professor's point about cool spring temperatures was just an "edge case," how would that affect the premise?

Notice the premise doesn't say that salinities less than 30 parts per thousand are GENERALLY unfavorable to sea-lice survival, but simply that they ARE unfavorable to sea-lice survival. So if any situations arise where salinities less than 30 parts per thousand are favorable to sea lice, that would show the premise as written is false. So either way, (C) is the best answer.

I hope that helps!

Hi hadimadi,

Let's use X ~salinities less than 30 parts per thousand, Y ~cool spring temperatures, and Z ~transmission of sea lice from farm salmon to wild salmon (BA ~Broughton Archipelago). Here's the biologist's argument:

B1. X is unfavorable to Z
B2. Between March and June is the critical period for Z
B3. BA has X between March and June
therefore
B4. Z will not happen in BA

The professor's argument is:
P1: X in combination with Y favors Z
therefore (not explicitly mentioned):
P2: {The biologist is wrong}

If we think about B1, we'll see that it's an absolute. X is unfavorable to Z. If that statement is true, we won't expect anything to be able to change the fact that X should always be unfavorable to Z. However, as soon as the professor says that X is actually good for Z when combined with Y, we can say that the absolute statement (without any conditions) that X is unfavorable to Z is false.

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.

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?

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 ?

Let's start by considering the structure of the marine biologist's argument.

The marine biologist concludes that "the archipelago's 25–30 parts per thousand salinity range between March and June...tends to suppress sea-lice proliferation." This conclusion is based on the premise that the salinity in this area is 25-30 parts per thousand in the spring, and that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival."

So the marine biologist's conclusion relies on the premise that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival." The professor then undermines the argument by attacking this premise. More specifically, the professor claims that "salinities of 25–30 parts per thousand in combination with British Columbia's cool spring temperatures favor the flourishing of sea lice."

As a result, the premise that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival" is false, which makes (C) correct.

You raise an interesting question about cool spring temperatures being an "edge case" of an otherwise reliable premise. Should we assume the premise that "salinities less than 30 parts per thousand are unfavorable to sea-lice survival" is generally sound? If so, would that make it true?

Unfortunately, the passage doesn't give us any evidence to help resolve this question. We know that the marine biologist has cited numerous studies, but we have no idea how complete or representative those studies are. All we know is that the professor claims the premise is not ALWAYS true. In other words, the professor claims the premise is false.

Yet even if we could somehow prove that the professor's point about cool spring temperatures was just an "edge case," how would that affect the premise?

Notice the premise doesn't say that salinities less than 30 parts per thousand are GENERALLY unfavorable to sea-lice survival, but simply that they ARE unfavorable to sea-lice survival. So if any situations arise where salinities less than 30 parts per thousand are favorable to sea lice, that would show the premise as written is false. So either way, (C) is the best answer.

I hope that helps!

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.

the professor attempts to undermine the biologist's argument by claiming that there is evidence showing that one of its premises is false

C. claiming that there is evidence showing that one of its premises is false
The biologist thinks that sea lice transmission is unlikely because the conditions in the archipelago "tend to suppress" sea-lice proliferation. The professor provides additional information, and then says that, actually, the conditions "favor the flourishing of sea lice."

Because the information provided by the professor completely contradicts the biologist's premise, we can determine that this additional evidence shows that the biologist's premise is false.

(C) is looking good.

D. questioning the reliability of the biologist's scientific sources
The professor never questions WHERE the biologist got his/her information, or the validity of those sources. (D) is out.

Hi tt147,

If we say that a "conclusion is inconsistent with its premises", what we mean is that we can't get to that conclusion from its premises. But we can get to the biologist's conclusion as long as we assume that every premise is correct. So, if it is actually the case that

1. salinities less than 30 parts per thousand are unfavorable to sea-lice survival
and
2. the archipelago's salinity is 25–30 parts per thousand between March and June, the critical period for wild salmon migration

then we should be able to conclude that

3. transmission of sea lice from farm salmon to wild salmon is unlikely in the archipelago.

What the professor does is bring in new information that helps us see that (1) doesn't hold under certain conditions (a review of the literature shows that...). This is very different from saying "the premises are fine but we can't get to the conclusion using that support".

Here is the video solution to this problem: https://youtu.be/wHlmmLzIx3Q

This is what the Professor says:

- A biologist argues that transmission of sea lice from farm salmon to wild salmon is unlikely because 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 will 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.

So the Professor tells us that as per the Biologist, salinities less than 30 ppt are unfavourable to sea lice. But a review of lit shows that 25-30 ppt salinities with cool temp favours sea lice.

So the Professor claims that one of the Biologist's premises (salinities less than 30 ppt are unfavourable to sea lice) is false.

Hence answer is (C)

tt147 -

E. showing that its conclusion is inconsistent with its premises

The professor does not undermine the biologist's argument by showing that the biologist's conclusion is inconsistent with his premises.
The biologist's premises (salinities less than 30 ppt are unfavourable to sea lice, Archipelago has 25–30 ppt salinity range between March and June, March and June the critical period for wild salmon migration) are in line with his conclusion (transmission of sea lice from farm salmon to wild salmon is unlikely in the Broughton Archipelago)

The Professor states that one of his premises (salinities less than 30 ppt are unfavourable to sea lice) itself is false.

­ 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?