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yashika001
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Guillemots are birds of Arctic regions. They feed on fish that gather 18 Oct 2024, 09:55
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Hii GMATNinja

can you please prove how D is weaking the conclusion, if the fishes might move to northward then the birds have strong motive to move northward , hence that is enlarging the birds range .

Please explain?

Regards,
Yashika

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So poor GMATNinjaTwo lives in New Jersey, where he's suffered through something called a "bomb cyclone" that caused sub-zero (Fahrenheit!) temperatures. He says that he saw a guillemot in his own backyard last week, but that sighting hasn't been verified. And he recommends this two-minute video about guillemot chicks: https://video.nationalgeographic.com/video/guillemots.

Anyway, back to the GMAT... the conclusion of the argument is that the guillemots’ range will probably be enlarged by being extended northward along the coast IF the warming in the Arctic continues. How does the author arrive at this conclusion?

  • We are told that guillemots reside in Arctic regions and feed on fish that gather beneath thin sheets of floating ice.
  • The birds nest on land near the floating ice.
  • The birds need 80 consecutive snow-free days in a year to raise their chicks. Until recently, this fact limited the birds' range to the southernmost Arctic coast.
  • However, average temperatures in the Arctic have begun to rise.
  • The author thinks that the rise in temperatures will cause the birds' range to be extended northward along the coast. This might make sense... we can infer that it gets colder as you head north, so at some point along the coast there's a limit beyond which it is too cold/snowy for the birds' to raise chicks. If it starts to get warmer in general, that limit might be pushed northward.

Now we need an answer choice that would WEAKEN this logic:

Quote:
(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.
An unusually early snow could happen even along the southernmost coast of the Arctic. As long as this is an unusual occurrence and not a regular occurrence, it would not prevent the guillemot's from moving northward. Sure, it would cause some bad years for the guillemots, but that would be true regardless of where they are living (i.e. regardless of how far north they live). Eliminate (A).

Quote:
(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.
Choice (B) is tempting, but make sure you notice the word "current". The guillemots already have predators in the south. That doesn't PREVENT the guillemots from living in the south; it simply provides a challenge that the guillemots have to deal with.

If there were FEWER predators farther north, that would certainly make it easier for the guillemots. But if the guillemots' current predators simply move north as well, then the guillemots will face the same danger that they did in the south. Again, this wouldn't PREVENT the guillemots from living in the north; instead, it would mean they have to deal with the same predators that they deal with in the south.

Choice (B) can be eliminated.

Quote:
(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.
This fact has no bearing on the author's argument. Will the rising temperatures allow the guillemots to expand their range? Choice (C) provides no evidence either way and can be eliminated.

Quote:
(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
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 (if the thin ice disappears, the fish that gather under the thin ice might have to move northward). Although this doesn't necessarily disprove the author's point, it's seriously weakens the argument. Hang on to this one.

Quote:
(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.
Choice (E) suggests that the guillemots would have LESS competition for food as they move northward. This is evidence that the guillemots WILL be able to survive as they move in that direction. If instead choice (E) said the opposite (that the fish are preyed on by a wider variety of predators farther north), then it would weaken the argument. As is, choice (E) strengthens the argument and can be eliminated.

(D) is the best answer.
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Guillemots are birds of Arctic regions. They feed on fish that gather 15 Dec 2024, 09:24
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yashika001
Hii GMATNinja

can you please prove how D is weaking the conclusion, if the fishes might move to northward then the birds have strong motive to move northward , hence that is enlarging the birds range .

Please explain?

Regards,

Yashika
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Sure, but if the northward INCREASE in range is counteracted by a DECREASE in range to the south, then there might not be any significant NET change in range.

For more on that, check out our full explanation here: https://gmatclub.com/forum/guillemots-a ... l#p1994517.
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Guillemots are birds of Arctic regions. They feed on fish that gather Updated on: 25 Mar 2025, 08:49
Originally posted by agrasan on 24 Mar 2025, 23:01.
Last edited by agrasan on 25 Mar 2025, 08:49, edited 1 time in total.
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Hi experts GMATNinja KarishmaB IanStewart MartyMurray

I am a bit confused with the option D.

The argument says - "They feed on fish that gather beneath thin sheets of floating ice, and they nest on nearby land."
Option D = If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

If we believe that option D is true then we don't have any information from the argument to support or make any conclusion on what will happen to fish if floating ice is not present, so it is still possible that Guillemots are able to get fish in the form of food even in the absence of floating ice.

Please let me know where I am making a mistake here.
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Guillemots are birds of Arctic regions. They feed on fish that gather 25 Mar 2025, 07:34
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What underlies this question is a key test-taking skill in CR, one that requires breaking a habit that we all have from normal discussions about unfamiliar topics.

1. One key is not over-interpreting the question - "most seriously weakens the argument" does NOT necessarily mean it actually seriously weakens the argument. Your job here is just to simply rank the answer choices for weakening the argument. Often there are 4 choices that either strengthen the argument or have no effect on the argument. The remaining one might only slightly weaken the argument but it's the only only that falls on the weaken side, so it's the only choice after eliminating the others.

2. Understanding the power of elimination -- if you can quickly eliminate 4 answers, then remaining one has to be the answer if it's not eliminated. You don't have to waste time assessing if the thin ice is needed for the fish to be there.

The greatest success in GMAT prep is when you pay attention to test taking skills that work -- mastering them helps you with 10 questions rather than just 1 or 2.
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Guillemots are birds of Arctic regions. They feed on fish that gather 25 Mar 2025, 11:29
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agrasan
I am a bit confused with the option D.

The argument says - "They feed on fish that gather beneath thin sheets of floating ice, and they nest on nearby land."
Option D = If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

If we believe that option D is true then we don't have any information from the argument to support or make any conclusion on what will happen to fish if floating ice is not present
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If "they feed on fish that gather beneath thin sheets of floating ice", then if there is no ice, there can be no "fish that gather beneath thin sheets of floating ice" for the birds to feed on.

I think this is a useful question to study, because there are some traps people will fall into when they aren't thinking about CR in an ideal way. When the author prefaces the conclusion with "probably", we should take that to mean "based on what we know about guillemots" -- i.e. based on what we are told in the passage. We should not take that to mean "based on guesses we might make that have no factual support in the passage". So we should not be guessing "the fish will become more accessible to the guillemots if the ice vanishes", for example. Then we're just making things up that we have no reason to think are "probably" true. We have just as much reason to guess that the fish need the ice to survive, or that the birds need the ice to find the fish. Instead, we must rely on the premises the author relies on to construct the argument, namely that the birds

- need somewhat warm weather (no snow)
- need fish under floating ice for food

In many questions, including this one, you need to understand the conclusion precisely, and this is the second important takeaway from the question. GMAT Ninja (and probably others, I didn't read every post) emphasizes the crucial wording in the argument: the author concludes that the birds' habitat will be enlarged (and not simply that the birds will be able to live further north). So the author thinks the birds will be able to live both in the south and in the north as the temperatures go up. We can weaken that argument if we learn about some as-yet unmentioned problem with the north, or if we learn that the south will become inhospitable for the birds -- then the birds will just move north; they won't expand their range to include both south and north. And since D tells us the south won't be home to the floating ice we should assume the birds need for food, answer D suggests the birds will move north, not that their range will expand.
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Guillemots are birds of Arctic regions. They feed on fish that gather 29 Apr 2025, 06:45
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This indeed seems the most logical reason as to why option D weakens the conclusion, where others are talking about and assuming the river ice will melt in the north too, and birds will not migrate but stay in the south. Your reasoning has clearly justified what I was thinking, that if the northern region is usually cooler than the southern part, how can a rise in the temperature equally or worsen the river ice in the north as it does in the south. Specifically, you mentioned the range would not extend as birds will move north, and this weakens the range not getting extended as the south will be useless for the birds.
KarishmaB
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B. If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their 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!

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)
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