Guillemots are birds of Arctic regions. They feed on fish that gather

Thinking about (D):


If these birds prey on special kind of fish, it's logical to assume, that without this fish guillemots won't be able to maintain current habitat.

So, if thin ice in southern arctics disappears guillemots will be forced to move north. It won't be the enlargement of guillemots' range, rather simply movement to better place.

Lets analyze the answer choices and see which one stands scrutiny. To find the choice which weakens the argument, we need to select the choice that provides evidence that the birds' range will not be extended.

(A): The keyword here is 'still'. If there are years now when the chicks are being killed by early snow, has it wiped out the birds? No. Therefore if conditions are favorable it cannot act as an impediment to their range expansion. Incorrect.
(B): Guillemots have been co-existing with their predators where they currently live. If the predators migrate northwards, why will this stop the birds from doing so too? Incorrect.
(C): If temperatures are rising then they will be higher than they are now in inland areas too, possibly allowing the birds to live there. Incorrect.
(D): CORRECT. If the ice in the southern arctic disappears, the birds will be forced to move northwards. However, their RANGE will not be extended as they will just shift from a more southern to a more northern point. There is no evidence that says that they will live over longer stretches of land.
(E): This means there will be more fish for the birds to eat in the North. This supports the conclusion that they will move north and extend their range.

B

gullimots predators will move north which weakens the conclusion I think.

between B & D, latter looks more correct as B says about extension of range of guillemots' predator but that doesn't weaken the conclusion as the argument in D. Spreading of predators will be a deterrent but if there is no food available in the southern coast they are bound to move northwards, daring the predator.

Whereas D is a better answer since it clearly refutes the concept of enlargement and imposes the idea that their dewelling has to move northwards due to lack of availability of food in south. ­

I understand (D) perfectly. But can someone please explain why fish under the ice will disappear because of melting ice?



We have to assume that fish needs ice in order to survive. But that's just another assumption.

an explanation could be since the premise says "Guillemots are birds for arctic regions. They feed on fish that gather beneath thin sheets of floating ice, and they nest on nearby lands." --> D suggests that if this ice has melted, it becomes easier to feed on fishes hence no reason to move northward

I choose D.
First, I will break down the stimulus.
Premise 1: Guillemots feed on fish beneath thin sheets of floating ice, and nest on nearby lands.
Premise 2: Guillemots need 80 consecutive snow free days to raise their chicks, presently, the guillemots' range was limited to the southernmost arctic coast.
Conclusion: if the warming continues, the guillemots' range will probably be enlarged by being extended northward along the coast.
We can see that this is a Cause n Effect reasoning. The warming => the guillemots' range will probably be enlarged by being extended northward

This is a weaken question type and we must identify an answer which shows that when the cause occurs, the effect doesnt occur or reversely or find an alternative cause for the effect...just as the method of CR Bible.
A) Even if the warming trend continues, there will still be years in which guillemots chicks are killed by an unusually early snow.
=> This doesnt effect the conclusion much because the conclusion tells us the guillemots come to grow in the northward.
B) If Arctic warming continues, guillemots' current predators are likely to succeed in extending their own range farther north
=> It is too far if we infer that guillemots' current predators succeeded in moving farther north and control the population of the guillemots there. And in this answer, the word is "likely" not "surely".
C) Guillemots nest in coastal areas, where tempratures are generally higher than inland areas.
=> OOS. The argument makes no statement about inland areas or any comparision between inland n costal areas.
D) If the Arctic warming continues much of the thin ice in southern arctic will disappear.
=> Thin ice disappear => birth moves from south to north, So, the guillemots' range wont be enlarged. This shows that when the cause occurs the effect doesnot occur. So it is a Contender.
E) The fish that guillemots eat are currently preyed on by wider variety of predators in southernmost arctic regions than they are farther north.
=> This actually strengthens the argument. Because the fish is more abundant in the north. if the birds move to the north, they will surely enlarge their range.

D is the correct answer.

Hope it helps.

I've eliminated D too, because the argument deliveres no further information whether it's good or bad if ice dissapears.... which influence it has on the fishes.. would be there more fishes or less etc.

Hi BrainLab,

Glad you raised the idea of certainty about the need for ice. The idea that Guillemots rely on ice, to at least a significant extent, isn't assumed. Yes, Guillemots could possibly get SOME fish from other means as you point out, but the facts in the prompt let us know that Guillemots specifically feed on fish that gather beneath thin sheets of floating ice. So would it SIGNIFICANTLY weaken (though not necessarily 100% destroy) the claim that the Guillemot range is likely to expand if the ice sheets that they typically feed on melt? For sure. They wouldn't be likely to feed in those areas, so it would be VERY challenging for the range to expand.

Guillemots are birds of Arctic regions. They feed on fish that gather beneath thin sheets of floating ice, and they nest on
nearby land. Guillemots need 80 consecutive snow-free days in a year to raise their chicks, so until average temperatures
in the Arctic began to rise recently, the guillemots’ range was limited to the southernmost Arctic coast. Therefore, if the
warming continues, the guillemots’ range will probably be enlarged by being extended northward along the coast.
Which of the following, if true, most seriously weakens the argument?

(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

If option D were true, then it would STRONGLY put the Guillemots' source of food in doubt. Would that weaken the notion that the Guillemot range would expand? Yes.

(B) If the Arctic warming continues, Guillemots’ current predators are likely to succeed in extending their own range farther north.

Now, option B) is the statistical runner up. B definitely represents a possible increased threat to Guillemots if predators further expand their territory, but to what extent do these predators pose a risk to the Guillemot population? It's altogether unclear. Perhaps the predators pose very little risk, and perhaps it's even a significant risk. Is there any way from the prompt to determine the degree of that risk that the predators pose? No. Predators could exist or always exist in Guillemot territory, but the species can coexist just fine.

In comparing B) and D), B) presents an ambiguous risk to the enlargement of the Guillemot range, whereas D) delivers a massive blow to that notion if the specific types of places where the species traditionally searches for food will likely be wiped out.

My issue with (D): what if, in spite of the thin ice in the southern Arctic disappearing, the guilletmots' range expands so far up north that the loss of thin ice in the south Arctic is insignificant?

the way i see it, there are a few possible ways to decrease the # of guillemots: 1) increase # of predators; 2) decrease food supply. i don't see how 1 can be preferred over the other. they're equally dangerous.

please help

The point of the argument is that "the guillemots’ range will probably be enlarged." We're not concerned with decreasing the number of guillemots, only the size of their range. The author's reasoning is that their range will expand as the bird moves northward.

The author assumes that the bird will only add to its range as it moves northward. Choice (D) suggests that the northward expansion will come with a decrease in the range along the southern coast. Although this doesn't necessarily disprove the author's point, it's seriously weakens the argument and is thus the best answer.

My take on this question, which was the toughest one for me in the entire Verbal portion of the Diagnostic Test:

GMAT™ Official Guide 2020, Diagnostic Test, Critical Reasoning, Page 32, Question 74.

Key points: The question asks about what would undermine an argument. Again, the focus is on the argument.
Breakdown:

1) The question could not be more straightforward: weakens the argument.

2) The passage describes the feeding and nesting habits of guillemots, a type of Arctic bird. Notice the transition “therefore” ahead of the last sentence. Whatever follows must be a conclusion based on the evidence that was presented before. In this case, temperature rises are expected to increase the range of the guillemots to more northerly areas. The positive correlation of increase in temperature, increase in range lies at the heart of the argument.

Answers:

(A) killed by an unusually early snow

Analysis: This sort of device could be thought of as an anti-deus ex machina, with the weather intervening to kill something rather than save it. Part of the correlation outlined above is addressed here, the increase in temperature, but the other part, about the range, is not. Moreover, “there will still be years” suggests that there will also not be years… and in the end, such a speculative construct does nothing to advance or devalue an argument. Red light.

(B) predators are likely to extend their own range

Analysis: This is as transparent a response as you could hope to find in a Critical Reasoning question. Both parts of the correlation are present: Arctic warming and a northward-extending range. “Their own” means that the guillemot range will also likely extend north. With both increases escaping attack, the argument would remain unscathed, which is the opposite of what the question asks. Red light.

(C) coastal areas, where temperatures are generally higher

Analysis: This statement says that guillemots nest in an established manner, seeking out warmer coastal areas. It is given in the passage that their range “was limited to the southernmost Arctic coast” (my italics). Perhaps they would be content with the coast they already occupy if temperatures increased, which would have no effect on their range. But perhaps not. Some guillemots could indeed move farther north if those coasts warmed up. Due to the nuances of these questions, I want to see if I can disprove the remaining two answers to feel better about picking this one. Yellow light.

(D) thin ice in the southern Arctic will disappear

Analysis: It is unclear what the fish would do if the thin sheets of ice disappeared, and it is therefore unpredictable what the birds that prey on them would do in turn. If we are inclined to believe that the fish and their guillemot predators need the thin ice, then if anything, an exodus from the southern Arctic would be expected, and that would not necessarily increase the range of the guillemots. Yellow light.

(E) The fish… are currently preyed on by other predators

Analysis: Rising temperatures are missing altogether from this statement, and if the guillemots currently face more competition for the fish they desire, then they clearly must have risen to the occasion, since their range lies in the predator-dense southern coastal areas of the Arctic. This answer is more off-topic than some of the others; it is difficult to make a prediction one way or the other about the range of the guillemots without more information. Red light.

This is another tough one for me, as no answer leaps out as being the one and only that can be justified. At its base, the argument deals with movement, an expansion. Consulting the passage again, I see that the second line says that guillemots “feed on fish… and they nest on nearby land.” That illustrates a simple relationship--where they eat → where they nest. There is nothing about eating in choice (C), leaving the statement more open to interpretation. The guillemots might prefer the warmer northerly coasts, but they might not. That is, their range could stay the same, but it could also increase as some of the birds migrated to warmer coastal regions in the north while others stayed behind and enjoyed the relatively more comfortable southerly temperatures. But with (D), you can bet that if the fish moved, the birds and their eventual nests would move as well, and that sort of movement would not represent an expansion, but more of a relocation. Since that would weaken the argument, I am going to go with (D).

Guessing: Phew, I dodged a bullet there. You will probably have noticed by now that I find open-ended questions, which require a degree of speculation to work, much more difficult than their closed-loop counterparts. Add to that the fact that three of the five answer choices here--(A), (B), and (D)--rely on a conditional if-then construct, and I have to focus extra hard on looking for flaws. Still, I want you to appreciate that (A), (B), and (E) are all easier to remove from the equation (for reasons discussed above), and that that leaves a 50/50 for further consideration. Keep putting yourself in a 50/50 position, and you are going to walk away with more correct answers.

Good luck with your studies.

- Andrew

GMATNinja, gmat1393, GMATNinjaTwo, nightblade354
dear experts,
I am still confused with B,D,E although I read the whole thread, would you please clarify further and point out what I missed.

I picked up B because


if B is true, then why guillemots go to farther north, where maybe danger(if more predators) or similar danger (if as many as predators).
B weakens the conclusion by showing that it is less likely for guillemots to extend northward.

as for D,

before the temperature rise, the guillemots are limited southmost,
if the warming continues, the thin ice disappears, then it is likely for guillemots to extend northward to find a proper area.
I still think D strengthens the conclusion by showing warming causes ice disappear and then cause guillemots extend northward.

as for E

if farther north area is less dangerous, why not go there,
E shows another reason -- fewer predator--for guillemots to go northward, instead of warming,
Doesn't E weakens the conclusion that warming cause the extend of range.

Take another look at the exact wording of the conclusion: "if the warming continues, the guillemots’ range will probably be enlarged by being extended northward along the coast."

The author is primarily arguing that the guillemot's range will be enlarged. He/she then further clarifies exactly how this will occur: "by extending northward along the coast."

With that in mind, take another look at (D):

From the passage, we know that the guillemots depend on thin ice near the coast, because they feed on the fish that gather there. If this ice disappears, then the guillemots potentially will not be able to feed!

So, if (D) is true, then the guillemots will probably extend northward to find a suitable climate. But will their range be enlarged, as the author argues?

Not necessarily. Because the southern arctic region will no longer be suitable for guillemots, then moving northward could just shift the range of the birds to a different location, rather than actually enlarging their range.

(D) weakens the author's argument, so it is the correct answer.


The guillemots currently coexist with their predators in the southern arctic region. If both the guillemots and their predators extend northward, there is nothing to suggest that the predators will completely stamp out the guillemots in the north. The guillemots' range will still be enlarged, so the information in (B) does not weaken the author's argument.


The author argues that guillemots will extend northward because rising temperatures will allow them to raise chicks in more northerly areas of the coast.

(E) just tells us that the guillemot's food source may also have a good shot of thriving farther north. This actually provides additional support for the argument that "if the warming continues, the guillemots’ range will probably be enlarged by being extended northward along the coast." It doesn't matter that this evidence is different than the evidence supplied in the passage -- it doesn't weaken the author's conclusion, so eliminate (E).

I hope that helps!

VeritasKarishma AndrewN

B. If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.

C. Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.

D. If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

I'd picked option B through my pre-thinking and after reading the above posts I see how B cannot weaken the argument (the birds need not thrive in the new regions, they may be equally under threat in the new northern regions), however, I'd made some assumptions about option C which made me think that it was a contender as well. Please confirm if this thought is logical -

Since Guillemots nest in coastal areas, and their primary food source is the fish under thin ice then they would continue to be restricted to that part of the arctic and not move inward into farther northern regions. Meaning that coastal birds would always continue to inhabit coastal regions, irrespective of whether the temperatures are higher there. Is my assumption that "northward" in Arctic terms means more "landlocked" and thereby unsuitable for coastal birds, incorrect?

Thanks for your help !

Hello, aritrar4. Even though I know you said you understand how (B) is out of the running, to me, it is a rare instance in which the language of the response itself provides grounds for automatic dismissal. Specifically, are likely to succeed in extending their own range already tells us that guillemots must be likely to extend their range, and that would not weaken the conclusion at all, not to mention that these predators would currently be preying upon guillemots as well, so this new information adds nothing to the mix. As for (C), I understand your line of reasoning, but it could also be true that the coastline itself could be enlarged with additional melting. That is, perhaps previously solid-frozen ground might get mushy and form the thin layers of ice that attract the fish, and if that ring around the core of Antarctica were larger, then the guillemots might, in fact, extend their range more inland. Could-be-true thinking almost always leads in the wrong direction on CR and RC questions. The less you have to labor for an answer—the more you follow the linear logic of the passage—the more likely you are to walk away with a correct answer. The linear logic at work here is that if the birds feed on fish that gather beneath thin sheets of ice, and that ice starts to melt, then the fish might seek cover under other thin sheets of ice, and the birds that prey on such fish will likely follow, nesting on nearby land. Displacement seems more likely than expansion in this scenario, and that is all we are after.

I hope that helps. Thank you for thinking to tag me.

- Andrew

You re assuming that northwards there are no coastal areas. The argument clearly implies that there are.

"Therefore, if the warming continues, the guillemots’ range will probably be enlarged by being extended northward along the coast."
The argument says that the range will be extended northward along the coast.

Guillemots feed on fish beneath thin sheets of floating ice, and they nest on nearby land.
Guillemots need 80 consecutive snow-free days in a year to raise their chicks
So till now guillemots’ range was limited to the southernmost Arctic coast.
It's getting warmer now.

Conclusion: If the warming continues, the guillemots’ range will probably be enlarged by being extended northward along the coast.

The point that the conclusion is making is that the range will be enlarged. That northward along the coast will become accessible to them too. We need to weaken this.

(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.

Irrelevant. Our conclusion is about extended range.

(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.

Correct predators will follow up north too. Irrelevant. Again, we are talking about extended range. Those predators exist here in south and will follow up north too.

(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.

The argument already tells us that they nest in coastal areas. We are talking about extending range northward along the coastline itself.

(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

The conclusion talks about enlarged range. If much of the thin ice disappears from the south, it is possible that south is no more viable for the bird. So they may move north and still have a similar range only. Northwards may become hospitable but south may not remain suitable any more. Hence this weakens our conclusion.

(E) The fish that guillemots eat are currently preyed on by a wider variety of predators in the southernmost Arctic regions than they are farther north.

They will have more food available in north. This doesn't weaken our conclusion.

Answer (D)