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.


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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.

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?

(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.
OUT OF SCOPE- IF WARMING CONTINUES=> UNUSUAL EARLY SNOW??
(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.
PREDATORS ARE SAME AS THEY WERE IN SOUTHERN MOST PART SO HUNTING RATE WILL NOT BE EFFECTED.
(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.
YES IT IS STRENGTHEN ANS=> THEY WILL NOT GO TO INLAND AND WILL REMAIN ALONG THE COAST => STRENGTHENS
(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
BINGO=> IF THE WARMING CONTINUES AND ICE MELTS => THEN THE WILL THAT USED TO GATHER BENEATH THIN LAYER WILL NOT BE THERE ANYMORE => FOOD SOURCE WILL BE OVER => IMPLYING END OF HABITAT AND => WEAKENING THE ANSWER.
(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.
IT MEANS FISH WILL BE IN MORE QUANTITY IN NORTHERN PART SO STRENGTHENS.



ALSO IF YOU NEGATE THE OPTION D=> IF MORE WARMING AND THEN ICE WILL NOT DISAPPEAR => IT MEANS THEY WILL STILL GET MORE FISH => MEANS THEY CAN GO TO NORTH WITHOUT FOOD PROBLEM
SINCE FISH IS THE ONLY SOURCE. THEREBY NEGATION IS STRENGTHENING THE QUES => ITS A WEAKEN ANSWER.

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.

Now this one's a tricky question. Answer D.

Let me attempt this:

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

Now since we have to weaken this conclusion, we have to try proving either of the following things:
1. The overall Guillemont's population will not enlarge (i.e. will remain same or decrease) when they extend northwards along the coast, OR
2. The Guillemonts will not be able to extend northwards along the coast altogether

Now, let's the consider the supporting premises which are necessary for the Guillemont's survival:
1. fish that gather beneath thin sheets of floating ice
2. 80 consecutive snowfree days

Having considered the premises and the conclusion lets weigh the options B and D:

Option B : If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.
The way this option has been worded (emphasis on current predators) makes us believe that Guillemots even before extending to North have predators in the current habitat i.e. along the south coast. And the Guillemots have been been surviving in the south in spite of the presence of predators and hence they will extend and survive in the north even if their predators extend in the north.

Option D : If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
This option tells us that the Guillemot's survival is directly affected by the thinning of the ice and in turn the food that they feed on. And hence the extension of the birds to the North will not enlarge their numbers but will infact will remain same(or probably decrease?) as there is no food for them in the south.

Hence Option D.

+1 for option D. My take:

This is a weaken type question.

The conclusion is - "As the temperature increases because of global warming, the guillemots’ range will probably increase ".

The premise on which this conclusion is based upon :

1) Guillemots feed on fish just below thin ice.
2) Guillemots need 80 consecutive snow free days to lay their eggs

Pre-think/Logical Gap:

What if rising temperatures manifested into loss of food or habitat ?

POE

Option a : So what, does it talk about range ? No - Out
Option b : Predators might increase their range, so do guillemot. Is the argument weakened ? No - Out
Option c : Irrelevant
Option d : This is in line with our pre thinking. The rise in temperature causes loss of food , resulting in a decrease in range
Option e : This does the opposite in fact.

The answer is option D.

Hi All,

I thought this was a rather difficult answer and this one required a good amount of thinking. When I initially reviewed my work, I thought D would weaken the argument because if the thin ice melts, it would be even EASIER to get food in the southern region and therefore, there would be no reason for them to extend their range farther north. Definitely a hard CR question but please let me know if this logic makes sense and could ultimately get to the right answer. I initially chose B because I could imagine it in my head but choice D was kinda hard to picture when answering this question timed.

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

This is a very helpful and detailed explanation, thank you!