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Between 1980 and 2000 the sea otter population of the Aleutian Islands

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Fido10

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01 Nov 2022, 11:27

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KarishmaB

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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.

Please hit kudos if you like this post.

Responding to a pm:

Again, Official Answers are not debatable and really, I haven't seen an exception, at least in the verbal section.

Try to understand the logic of (C).

They have very smartly used the word: "surviving".

Let's take the argument first.

Premises:
Sea otter population declined - but no sign of disease and malnutrition so predators might have been responsible.
Seal population declined dramatically.
Orcas eat otters when seals are not available.

Conclusion:
Orcas must have led to otter population decline.

We need to strengthen that orcas are responsible for the huge decline in otter population.

C. Most of the surviving sea otters live in a bay that is inaccessible to orcas.
Had the option said, "Most sea otters live in a bay that is inaccessible to orcas," then the option would have weakened our argument.
But the option says, "Most of the surviving sea otters live in a bay that is inaccessible to orcas." This means that the otters that are left are the ones where orcas cannot reach. Wherever orcas can reach, otters have disappeared from there. It means that it is highly probable that orcas have been binging on otters wherever possible.

Imagine a meadow which was full of grass 2 months back. A small part of the meadow is fenced. Some cattle was introduced in the meadow two months back. What happens if after to months you see that most of the grass is gone except the small part which was fenced? The likely reason is that the cattle ate the grass and hence reduced it.

This is the same concept.

None of the other options are relevant.

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

B. Seals do not eat sea otters, nor do they compete with sea otters for food.
What seals eat is none of concern. What we need to strengthen is that orcas ate up the otters.

D. The population of orcas in the Aleutian Islands has declined since the 1980s.
This doesn't strengthen that orcas ate the otters. Perhaps some orcas couldn't adapt to decrease in seal population. We don't know.

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.
This might affect seal population. It doesn't strengthen that orcas ate otters.

Answer (C)

Dear KarishmaB

As per answer choice 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.

If we have a decline in the population of the ﬁsh that seals use for food
=>That leads to a decline to the population of seals
=> That leads to Orcas eat otters since seals are not available !
can you help explaining why this cannot be logical and thus E is incorrect

Tank you so much

KarishmaB

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02 Nov 2022, 00:07

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Fido10

KarishmaB

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Option (E) could lead to a decrease in seal population because their food decreased. But the fact that seal population decreased is something we already know.

We are given:
and the Aleutian Islands seal population declined dramatically in the 1980s.

Does it matter what the reason for the decline of the seal pop is? We already know that seal pop declined dramatically. We are basing our argument on that - that seal pop declined so orcas ate otters. Any premise that tells us why the seal pop could have declined has no impact on the given argument.
We need to give FURTHER proof that orcas could be eating otters.

If the argument had not mentioned that seal pop has declined then option (E) could have helped.

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28 Apr 2023, 05:11

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In my opinion, Options(C). Most of the surviving sea otters live in the bay that is inaccessible to orcas.
What about another sea otter other than surviving sea otter, it must have been eaten by orcas. that is the reason orcas were most likely the immediate cause of the otter population decline.

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19 Jun 2023, 00:07

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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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26 Oct 2023, 14:20

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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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14 Jan 2024, 03:26

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This video has the detailed explanation of this question: https://youtu.be/uPdDYbYpXuI?feature=shared

WillGetIt

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.

Show Spoiler

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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07 May 2024, 06:19

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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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13 May 2024, 22:37

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WillGetIt

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.

Show Spoiler

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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14 May 2024, 04:03

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agrasan

WillGetIt

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.

Show Spoiler

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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30 Dec 2024, 08:44

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AjiteshArun I think there is some fault in my approach to strengthen Q/s

Here is how I go about it
Strengthen answer choice should strengthen either support for conclusion, conclusion or any specific ask in Q stem
So, if I had to see option B which I selected this is how I read

Oh seals could have been the reason why otters declined (even declining popln of seals could cause harm) so by taking out a factor from the equation I strengthen what is given to me that is the conclusion - aka orcas must be doing it

In strengthen Q/s I take the conclusion for granted and the job of the strenghtener should just add more weight to it right?

But some choices are saying oh its ok seals didnt eat them but how do we know orcas did - hence B is out.
VS C does a more better job of putting the blame on Orcas

Can you help - it is kind of seeping in my ways to solve CR Strengthen

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04 Mar 2025, 04:46

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Hi experts GMATNinja KarishmaB ChiranjeevSingh

Let's say:
X = Orcas
Y = decline in population of Otters
Z = Seals
I went through all explanations but wanted to check to reject option B, can we say in simple words that if Z is not the reason for Y then our belief in the relationship X leads to Y remains unchanged? This is why option B doesn't add any value for us.
Please let me know if anything is wrong with this reasoning.

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04 Mar 2025, 22:47

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Yes, Z has no impact on Y so it doesn't impact our conclusion in any way. It stays what it is.
If Seals did eat otters and seal population was growing, then it could impact our conclusion.

agrasan

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05 Dec 2025, 06:06

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I have to be very carefully when reading answers, I don't pay attention on "surviving" so I wrongly do it

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14 Dec 2025, 08:08

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The goal is to find the option that most strengthens the conclusion: Orcas were most likely the immediate cause of the otter population decline.

The argument is structured as follows:
Observation: Otter population declined sharply (1980-2000).
Elimination of Causes: No disease or malnutrition. Conclusion: Predation increased.
Evidence for Orca Predation:
Orcas eat otters when their normal prey (seals) are scarce.
The seal population in the area declined dramatically in the 1980s.
Conclusion: Therefore, orcas were the most likely immediate cause.

To strengthen the argument, we need a piece of evidence that directly links the decline in the otter population to the presence or activity of orcas, or that eliminates an alternative cause related to predation.

Let's analysis each answer choice
(A) The population of sea urchins, the main food of sea otters, has increased since the sea otter population declined.

This supports the premise that the otter population declined due to predation, not lack of food (malnutrition). If the otters' food source increased, it confirms that the otters were not starving. However, it doesn't strengthen the specific link to orcas being the predator over any other potential predator.

Irrelevant to Conclusion. It only confirms the initial premise.

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

This statement simply clarifies the ecological relationship between seals and otters. It doesn't affect the argument that orcas shifted their diet from seals to otters. The argument already uses the decline of the seal population as a reason for the orcas' dietary shift, not as a competing cause for the otter decline.

Irrelevant.

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

This option establishes a direct correlation between protection from orcas and survival. If the otters that survived were primarily those in a location where orcas could not reach them, it provides strong empirical evidence that the predator killing the otters was, in fact, the orca. This links the cause (orca absence) to the effect (otter survival), thus strengthening the conclusion that the orca presence was the cause of the decline.

Strong Strengthener.

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

If the orca population declined, it would suggest a decrease in predation, which would normally lead to an increase in the otter population, or at least stabilize the decline. This evidence goes against the conclusion that orcas were the cause of the decline.

Weakener.

(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.

This explains why the seal population declined (it provides a cause for the cause). It strengthens the first part of the argument. While it makes the premise more robust, it doesn't directly strengthen the final, crucial link that orcas actually ate the otters, better than (C) does. Option (C) offers proof of survival linked to orca absence, which is a more powerful confirmation of the conclusion.

Moderate Strengthener (for the premise chain), but less effective than (C).

Conclusion
Option (C) provides the most compelling evidence by creating an experimental-like control group: otters protected from orcas survived, while otters exposed to orcas did not. This directly confirms the causal link asserted in the conclusion.