Although Stillwater Pond has been polluted by farm runoff for years

Question

Although Stillwater Pond has been polluted by farm runoff for years, several species of fish still live there. The local fishing guide says that “the most populous fish species in the pond is also the one that has adapted best to living in polluted water.” So if, as recent studies suggest, the most populous fish species in the pond is the bullhead catfish, then it must be that the local fishing guide believes that the species of fish in the pond that has adapted best to living in polluted water is the bullhead catfish.

The argument above is most vulnerable to criticism on the grounds that it

(A) takes for granted that the local fishing guide believes that Stillwater Pond has been polluted by farm runoff for years

(B) fails to take into account the possibility that the catfish in Stillwater Pond had to adapt very little to survive in polluted water

(C) fails to take into account the possibility that the recent studies on fish populations in Stillwater Pond are inaccurate

(D) fails to take into account the possibility that the local fishing guide mistakenly believes that some fish species other than the bullhead catfish is the most populous fish species in Stillwater Pond

(E) takes for granted that Stillwater Pond has only one species of catfish living in it

ankushsambare · Answer

The conclusion is:
The fishing guide believes that the fish best adapted to polluted water is the bullhead catfish.
Why?
 
 The guide says: the most populous fish species is the one best adapted to polluted water. 
 Recent studies say the most populous species is bullhead catfish. 
 Therefore, the argument concludes the guide must believe bullhead catfish is best adapted.  
The flaw:
The argument mixes up what the studies say with what the fishing guide believes.
The studies may say bullhead catfish is most populous, but the guide himself may believe some other fish is most populous.
Check choices:
(A) Irrelevant. The argument does not depend on what the guide believes about pollution history.
(B) Irrelevant. Even if catfish needed little adaptation, the reasoning problem remains.
(C) The argument does not depend on whether the studies are actually accurate. The issue is about the guide’s belief.
(D)  Correct.  The argument ignores the possibility that the guide believes another species, not bullhead catfish, is the most populous species.
(E) Irrelevant. Number of catfish species does not matter.
 Answer: (D)

TheYagami · Answer

OA: E

option E states the flaw that there might be a possibility that the fishing guide considers some other type of fish most populous.

guddo · Answer

Although Stillwater Pond has been polluted by farm runoff for years, several species of fish still live there. The local fishing guide says that “the most populous fish species in the pond is also the one that has adapted best to living in polluted water.” So if, as recent studies suggest, the most populous fish species in the pond is the bullhead catfish, then it must be that the local fishing guide believes that the species of fish in the pond that has adapted best to living in polluted water is the bullhead catfish.
 
 The argument above is most vulnerable to criticism on the grounds that it

The argument moves from what recent studies suggest to what the fishing guide believes. But the guide’s belief depends on what the guide thinks is the most populous species, not on what the studies suggest.  The flaw  is that the guide may not believe the bullhead catfish is the most populous species.

(A) takes for granted that the local fishing guide believes that Stillwater Pond has been polluted by farm runoff for years

Wrong. The conclusion is about which species the guide believes is best adapted, not whether the guide believes the pond is polluted.

(B) fails to take into account the possibility that the catfish in Stillwater Pond had to adapt very little to survive in polluted water

Wrong. The issue is the guide’s belief, not whether the adaptation was large or small.

(C) fails to take into account the possibility that the recent studies on fish populations in Stillwater Pond are inaccurate

Tempting, but not the main flaw. Even if the studies are accurate, the guide may not know or accept them.

(D) fails to take into account the possibility that the local fishing guide mistakenly believes that some fish species other than the bullhead catfish is the most populous fish species in Stillwater Pond

Correct. The guide says the most populous species is the best adapted. But if the guide believes some other species is most populous, then the guide would believe that other species is best adapted. So the argument cannot infer the guide’s belief from  the studies’ claim alone .

(E) takes for granted that Stillwater Pond has only one species of catfish living in it

Wrong. The argument is about bullhead catfish specifically, not about how many catfish species live in the pond.

Answer: (D)

yc168 · Answer

OE for reference:

Overview:  
The central premise of the argument is the statement that a local fishing guide has claimed that the most populous fish species in Stillwater Pond is the one best adapted to polluted water. The argument concludes that if, as studies suggest, the most populous fish species in that pond is the bullhead catfish, then the guide must believe that the bullhead catfish is best adapted to polluted water. You are asked to identify the grounds on which this argument is most vulnerable to criticism.

The Correct Answer:

D  Nothing in the argument indicates that the fishing guide is aware of the studies, so the guide might well mistakenly believe that some species other than the bullhead catfish is the most populous fish in Stillwater Pond. In that case, the guide's claim would express the belief that this other species is the one best adapted to polluted water (even though, unbeknownst to the guide, it is not actually the most populous). This possibility exposes a significant flaw in the argument, so the argument is vulnerable to criticism for failing to take it into account.

The Incorrect Answer Choices:

A  Although we are told that Stillwater Pond has been polluted by farm runoff for years, nothing in the argument addresses whether the guide believes this is the case. Moreover, the guide might believe that a species is best adapted to polluted water even if the guide doesn't believe that the water it lives in is actually polluted. So the argument isn't vulnerable to (A)'s criticism.

B  The argument does not address how much any species of fish has had to adapt to survive in polluted water. It does address the guide's beliefs about which species is  best  adapted to doing so, but a species could be best adapted to living in polluted water even if it did not have to adapt very much. So the argument does not need to account for the possibility raised in (B).

C  If the recent studies on fish populations in Stillwater Pond are inaccurate, then it could well be that a species other than the bullhead catfish is the most populous. But the argument concludes merely that  if  the bullhead catfish is the most populous, then the fishing guide believes that it is best adapted to polluted water. That conclusion could be strongly supported even if the studies are inaccurate, so the argument need not account for the possibility described in (C).

E  The bullhead catfish might be the most populous species in Stillwater Pond, and the fishing guide might believe that it is best adapted to polluted water, even if that pond contains other species of catfish. Since the presence of other catfish species wouldn't affect the argument, there's no reason to think that it takes for granted that the pond contains only a single catfish species.

officiisnobis · Answer

Notes - 
Most populous ->Adapted 
Bullhead -> Most populous 
Adapted -> Bullhead

(A) takes for granted that the local fishing guide believes that Stillwater Pond has been polluted by farm runoff for years - Irrelevant

(B) fails to take into account the possibility that the catfish in Stillwater Pond had to adapt very little to survive in polluted water - Does not matter how much it had to adapt to survive. It just has to be most adapted than others

(C) fails to take into account the possibility that the recent studies on fish populations in Stillwater Pond are inaccurate - Attacking the premise

(D) fails to take into account the possibility that the local fishing guide mistakenly believes that some fish species other than the bullhead catfish is the most populous fish species in Stillwater Pond - CORRECT ANSWER

(E) takes for granted that Stillwater Pond has only one species of catfish living in it - Irrelevant

Although Stillwater Pond has been polluted by farm runoff for years

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Although Stillwater Pond has been polluted by farm runoff for years

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