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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands [#permalink]
My thoughts:
It's important to note the careful interpretation of the phrase "surviving sea otters" in option (C). If the statement had been "Sea otters usually live in a bay that is inaccessible to orcas," it would have weakened the argument instead, suggesting that orcas couldn't have been the cause of the decline. The precise wording in option (C) is crucial to its role as a strengthener of the argument. So, the primary cause of the sea otter population decline was likely predation by orcas. Option (C) states that the majority of the surviving sea otters are found in a location that orcas cannot access. This implies that the otters that were within the reach of orcas (those not living in the inaccessible bay) were the ones that experienced a decline. This observation aligns with and reinforces the argument's claim that orcas were preying on the otters, leading to their population decrease.

Please correct me if you find any discrepancies.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands [#permalink]
Hi GMATNinja egmat

Option B says - seals don’t eat sea otters

IMO this eliminates an alternate cause for the decline in population of Sea Otters.

Isn’t elimination of an alternate cause a strengthener in Causal Statements?
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands [#permalink]
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This video has the detailed explanation of this question: https://youtu.be/uPdDYbYpXuI?feature=shared



WillGetIt wrote:
Between 1980 and 2000 the sea otter population of the Aleutian Islands declined precipitously. There were no signs of disease or malnutrition, so there was probably an increase in the number of otters being eaten by predators. Orcas will eat otters when seals, their normal prey, are unavailable, and the Aleutian Islands seal population declined dramatically in the 1980s. Therefore, orcas were most likely the immediate cause of the otter population decline.

Which of the following, if true, most strengthens the argument‘?

(A) The population of sea urchins, the main food of sea otters, has increased since the sea otter population declined.

(B) Seals do not eat sea otters, nor do they compete with sea otters for food.

(C) Most of the surviving sea otters live in a bay that is inaccessible to orcas.

(D) The population of orcas in the Aleutian Islands has declined since the 1980s.

(E) An increase in commercial fishing near the Aleutian Islands in the 1980s caused a slight decline in the population of the fish that seals use for food.



Sea Otter Population

Step 1: Identify the Question

The words if true and most strengthen indicate that this is a Strengthen the Argument question.

Step 2: Deconstruct the Argument

80 to 00: Otter pop ¯

No disease, maln, so prob predators

Orcas eat seals, but seals ¯

© Orcas ate otters à pop ¯

Step 3: Pause and State the Goal

On Strengthen questions, the correct answer is a piece of information that makes the conclusion more likely to be true. What additional evidence could support the idea that the orcas were the cause of the declining otter population?

Step 4: Work from Wrong to Right

(A) An increase in the sea urchin population would be a logical result of a decline in sea otters because there were fewer otters eating the sea urchins. This information does not clarify whether orcas were the cause of the decline in otters.

(B) The argument states that the seal population declined at the same time as the sea otter population. Thus, competition for food with or predation by seals were unlikely to have been possible explanations for the decline in sea otters. Removing these as possible causes, then, does not actually strengthen the argument.

(C) CORRECT. The orcas couldn’t get to these otters and these otters survived. This makes it more likely that predation by orcas was the reason for the decline in the rest of the population.

(D) This information weakens the argument. If the orca population declined at the same time as the sea otter population, it is less likely that increased predation by the orcas caused the decline in sea otters.

(E) It is not clear how commercial fishing affects sea otters because the argument does not state that sea otters eat these fish. Moreover, the argument states that the sea otters did not suffer malnutrition so a lack of food is unlikely to be the cause of the decline in sea otters. Even if it were the case, this choice would weaken, not strengthen, the argument.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands [#permalink]
­Remember the conclusion, orcas were most likely the immediate cause of the otter population decline.


(A) The population of sea urchins, the main food of sea otters, has increased since the sea otter population declined-This only confirms whatever is stated as evidence of the fall in otter population. Does this strengthen our conclusion? No. Eliminate.

(B) Seals do not eat sea otters, nor do they compete with sea otters for food-This removes any alternative causation for the fall in sea otter population, we can hold on to it for now.

(C) Most of the surviving sea otters live in a bay that is inaccessible to orcas. A strong strengthener indeed. The only place where otters live today is where Orcas could not reach. Indeed in line with our conclusion. Eliminate B, Keep C.

(D) The population of orcas in the Aleutian Islands has declined since the 1980s.-Okay. This is a potential weakener at best. Eliminate D.

(E) An increase in commercial fishing near the Aleutian Islands in the 1980s caused a slight decline in the population of the fish that seals use for food. Okay, but how does this affect our conclusion? This may show that seals thrive more now, which may bring more food for orcas, but thats a long way to go. Eliminate E.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands [#permalink]
WillGetIt wrote:
Between 1980 and 2000 the sea otter population of the Aleutian Islands declined precipitously. There were no signs of disease or malnutrition, so there was probably an increase in the number of otters being eaten by predators. Orcas will eat otters when seals, their normal prey, are unavailable, and the Aleutian Islands seal population declined dramatically in the 1980s. Therefore, orcas were most likely the immediate cause of the otter population decline.

Which of the following, if true, most strengthens the argument‘?

(A) The population of sea urchins, the main food of sea otters, has increased since the sea otter population declined.

(B) Seals do not eat sea otters, nor do they compete with sea otters for food.

(C) Most of the surviving sea otters live in a bay that is inaccessible to orcas.

(D) The population of orcas in the Aleutian Islands has declined since the 1980s.

(E) An increase in commercial fishing near the Aleutian Islands in the 1980s caused a slight decline in the population of the fish that seals use for food.



Sea Otter Population

Step 1: Identify the Question

The words if true and most strengthen indicate that this is a Strengthen the Argument question.

Step 2: Deconstruct the Argument

80 to 00: Otter pop ¯

No disease, maln, so prob predators

Orcas eat seals, but seals ¯

© Orcas ate otters à pop ¯

Step 3: Pause and State the Goal

On Strengthen questions, the correct answer is a piece of information that makes the conclusion more likely to be true. What additional evidence could support the idea that the orcas were the cause of the declining otter population?

Step 4: Work from Wrong to Right

(A) An increase in the sea urchin population would be a logical result of a decline in sea otters because there were fewer otters eating the sea urchins. This information does not clarify whether orcas were the cause of the decline in otters.

(B) The argument states that the seal population declined at the same time as the sea otter population. Thus, competition for food with or predation by seals were unlikely to have been possible explanations for the decline in sea otters. Removing these as possible causes, then, does not actually strengthen the argument.

(C) CORRECT. The orcas couldn’t get to these otters and these otters survived. This makes it more likely that predation by orcas was the reason for the decline in the rest of the population.

(D) This information weakens the argument. If the orca population declined at the same time as the sea otter population, it is less likely that increased predation by the orcas caused the decline in sea otters.

(E) It is not clear how commercial fishing affects sea otters because the argument does not state that sea otters eat these fish. Moreover, the argument states that the sea otters did not suffer malnutrition so a lack of food is unlikely to be the cause of the decline in sea otters. Even if it were the case, this choice would weaken, not strengthen, the argument.


Hi GMATNinja KarishmaB MartyTargetTestPrep ScottTargetTestPrep

I saw Option B as a trap choice, so I came up with the below reasoning to eliminate it and wanted to make sure that is correct.Thinking on Option B - Let's assume Seals are not present in the Aleutian Islands, then how competition for food between Seals and Otters will come into the picture? Even if Seals are present then why Orcas will eat Otters as the argument mentioned that sealfish is normal prey for Orcas (conditional statement in argument). Hence, either way, this option doesn’t make sense to support the argument.

Please let me know if my reasoning is inaccurate somewhere.­
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands [#permalink]
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agrasan wrote:
WillGetIt wrote:
Between 1980 and 2000 the sea otter population of the Aleutian Islands declined precipitously. There were no signs of disease or malnutrition, so there was probably an increase in the number of otters being eaten by predators. Orcas will eat otters when seals, their normal prey, are unavailable, and the Aleutian Islands seal population declined dramatically in the 1980s. Therefore, orcas were most likely the immediate cause of the otter population decline.

Which of the following, if true, most strengthens the argument‘?

(A) The population of sea urchins, the main food of sea otters, has increased since the sea otter population declined.

(B) Seals do not eat sea otters, nor do they compete with sea otters for food.

(C) Most of the surviving sea otters live in a bay that is inaccessible to orcas.

(D) The population of orcas in the Aleutian Islands has declined since the 1980s.

(E) An increase in commercial fishing near the Aleutian Islands in the 1980s caused a slight decline in the population of the fish that seals use for food.



Sea Otter Population

Step 1: Identify the Question

The words if true and most strengthen indicate that this is a Strengthen the Argument question.

Step 2: Deconstruct the Argument

80 to 00: Otter pop ¯

No disease, maln, so prob predators

Orcas eat seals, but seals ¯

© Orcas ate otters à pop ¯

Step 3: Pause and State the Goal

On Strengthen questions, the correct answer is a piece of information that makes the conclusion more likely to be true. What additional evidence could support the idea that the orcas were the cause of the declining otter population?

Step 4: Work from Wrong to Right

(A) An increase in the sea urchin population would be a logical result of a decline in sea otters because there were fewer otters eating the sea urchins. This information does not clarify whether orcas were the cause of the decline in otters.

(B) The argument states that the seal population declined at the same time as the sea otter population. Thus, competition for food with or predation by seals were unlikely to have been possible explanations for the decline in sea otters. Removing these as possible causes, then, does not actually strengthen the argument.

(C) CORRECT. The orcas couldn’t get to these otters and these otters survived. This makes it more likely that predation by orcas was the reason for the decline in the rest of the population.

(D) This information weakens the argument. If the orca population declined at the same time as the sea otter population, it is less likely that increased predation by the orcas caused the decline in sea otters.

(E) It is not clear how commercial fishing affects sea otters because the argument does not state that sea otters eat these fish. Moreover, the argument states that the sea otters did not suffer malnutrition so a lack of food is unlikely to be the cause of the decline in sea otters. Even if it were the case, this choice would weaken, not strengthen, the argument.

Hi GMATNinja KarishmaB MartyTargetTestPrep ScottTargetTestPrep

I saw Option B as a trap choice, so I came up with the below reasoning to eliminate it and wanted to make sure that is correct.Thinking on Option B - Let's assume Seals are not present in the Aleutian Islands, then how competition for food between Seals and Otters will come into the picture? Even if Seals are present then why Orcas will eat Otters as the argument mentioned that sealfish is normal prey for Orcas (conditional statement in argument). Hence, either way, this option doesn’t make sense to support the argument.

Please let me know if my reasoning is inaccurate somewhere.­

­
We cannot assume that seals are not present there. We are given that they are. 
Given: the Aleutian Islands seal population declined dramatically in the 1980s.

Their population declined in 80s which means they were present there.
The point is what seals eat is irrelevant.
If they do not eat otters, there is no impact on the argument. (as given)
If seals did eat otters, then a decline in seal population would have led to an increase in otter population but that is not the case. The otter population has reduced a lot too. 
All in all, option (B) does not tell us whether the predator orcas have caused the reduction in otter population or not. It doesn't strengthen that orcas are responsible for lower otter population. 
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands [#permalink]
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