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

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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 01 Aug 2015, 03:17
In option B:
I think option B makes more sense because if the seals did eat the otters then the argument that orcas were the reason for the decline of the otters does not hold true.
The seals could also have been responsible for the decline of the otter population.
(They have mentioned that the seal population declined dramatically, so there were still a few seals left)
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 03 Feb 2016, 03:08
Conclusion: orcas were most likely the immediate cause of the otter population decline. (orcas --- no otter)
Answer C shows that surviving otters are inaccessible to orcas (otter---no orcas)

B it seems a good one, but the conclusion is talking about the relation between orcas and otter not seal and otter
E maybe otter has source of food except fish

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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 09 Feb 2016, 13:10
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wizardofcoconuts wrote:
In option B:
I think option B makes more sense because if the seals did eat the otters then the argument that orcas were the reason for the decline of the otters does not hold true.
The seals could also have been responsible for the decline of the otter population.
(They have mentioned that the seal population declined dramatically, so there were still a few seals left)





I thought in the same lines initially.Either it should be B or C. i opted for B. We both missed a logic. Say If Seals eat otters. From the argument we know that seal population decreased. So we have to see an increase in otter population, Assuming that Orcas don't eat extra. But we haven't seen any increase in otter population. So this option B is wrong. That leaves us with option C.
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New post 09 Feb 2016, 19:05
Can someone please explain Answer choice C?

Thanks in advance :)
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 10 Feb 2016, 04:01
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Trainwithnolov3 wrote:
Can someone please explain Answer choice C?

Thanks in advance :)


Hi,
I'll help you with that..

lets rephrase the para..

1. in some period of 20 years, the number of 'sea otters' declined drastically.
2. No disease or food shortage was not there and hence has not been attributed to the decline.
3. Orcas will eat otters when seals, their normal prey, are unavailable,
4. starting of this period was the time when seals population declined.
5. from 4 above ,we can say that Orcas ate otters

now from choices, we have to look for a strengthener..
lets see the answer C..
Most of the surviving sea otters live in a bay that is inaccessible to orcas..
this tells us that the only ones which are surviving are in a bay , where the Orcas are unable to reach..
so it strengthens the conlclusion that indeed Orcas fed on the otters which were in accessible areas..
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 10 Feb 2016, 12:49
Hi chetan2u,

Now I got it. Indeed the Orcas did eat the Otters; otherwise, there won't be any surviving otters :) Thank you again for the fast reply and help!

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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 05 Apr 2016, 02:44
Premise: Sea otter population has declined precipitously. Orcas usually feed on seals, but when seals are not available orcas eat sea otters. Seal population declined in 1980's

Conclusion: Orcas are the cause for the decline in sea otter population.

Possible Strengtheners: 1) No other factor was responsible for the decline in sea otter population.
2) Orcas have fed on sea otters resulting in the elimination of sea otter population in that area.

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

B Seals do not eat sea otters, nor do they compete with sea otters for food. - Incorrect - According to the argument the seal population has already declined. Even if they feed on sea otter they are not the immediate cause of sea otter's decline.

C Most of the surviving sea otters live in a bay that is inaccessible to orcas. - Correct - This option states that the sea otter population has dwindled in the area accessible to orcas, strengthening our argument that orcas feed on sea otters if they are accessible.

D The population of orcas in the Aleutian Islands has declined since the 1980s. - Incorrect - Opposite

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. - Incorrect - Irrelevant

Answer: C
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 15 Jul 2016, 06:42
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1
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.
WRONG:- Irrelevant:- Of course the population of sea urchin will increase, if there is no otter to eat them. But this is not strengthening. This is just an implication.

B) Seals do not eat sea otters, nor do they compete with sea otters for food.
HOLD IT -So, Seals did not killed otters. OK !! But this is not directly strengthening that Orca's (which are whales by the way !) killed otter. LET IT GO !! WRONG

C) Most of the surviving sea otters live in a bay that is inaccessible to orcas.
RIGHT:- Only those otters survived that lived in area accessible to orcas. Therefore Orcas must be definitely responsible for killing otters.

D) The population of orcas in the Aleutian Islands has declined since the 1980s.
WRONG:- Irrelevant :- Useless information

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.
WRONG:- The food decreased slightly. BUT otter died in large numbers. (FROM ARGUMENT:-the sea otter population of the Aleutian Islands declined precipitously) so lack of food cannot be the reason. (FROM ARGUMENT:-There was no signs of malnutrition). Meaning lack of food was not the cause.

C IS THE ANSWER

NickHalden 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.

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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 20 Aug 2016, 23:05
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.

1980 ............................. 2000
Sea otter pop. 100 80

Reason of decline
1> Disease
2> malnutrition
3> predators

Predators : Orcas (when seal not available)
Aleutian Islands seal population declined dramatically in the 1980s so it should be orcas only.

question is why orcas? Why not other predators?

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.
" sea otter population declined." - This is not for question.

B Seals do not eat sea otters, nor do they compete with sea otters for food.
so We have established that "seal" is not the predator but still the question remains the same, "Why only orcas". THis statement only help us to remove one predator off the list. that's it.


C Most of the surviving sea otters live in a bay that is inaccessible to orcas.
Now this raises a question, the area where orcas is not there, Sea otters are thriving. Must be "Orcas" only.

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.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 04 Dec 2016, 19:54
I am quiet confused here. I selected last one. reasoning is they are giving a point for validating that seal population is declining cause of fish. so orcas have to eat otters. make sense to me.

C is saying that most of the surviving otters live in bay , inaccessible to orcas. but where is the proof that this situation is due to orcas. this cud be killer whales, sharks ???

How orcas are responsible for this crime ????
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New post 05 Dec 2016, 07:51
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aragonn wrote:
I am quiet confused here. I selected last one. reasoning is they are giving a point for validating that seal population is declining cause of fish. so orcas have to eat otters. make sense to me.

C is saying that most of the surviving otters live in bay , inaccessible to orcas. but where is the proof that this situation is due to orcas. this cud be killer whales, sharks ???

How orcas are responsible for this crime ????


Conclusion: Orcas were primarily responsible for the decrease in sea otter population.

We have to strengthen the conclusion.

According to 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. --> Here you are trying to establish that orcas consumed sea otters because the population of seals reduced. But this is already stated in the argument and we are strengthening the stated facts. Moreover, we know that the number of fishes reduced but did the number reduce so drastically that the seals could not feed on them anymore. We also have no information available to infer that the seals did not consume any other organism to survive. For the stated reasons, this option can easily be eliminated.

Option C: Most of the surviving sea otters live in a bay that is inaccessible to orcas. --> Presents evidence in support of the conclusion by stating that if there are no orcas the sea otters thrive.

Hope it helps.
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New post 17 Dec 2016, 23:39
The OA is correct and explanations provided in the thread appear sufficient. If there are any specific questions, please post them here and then click again on the "Request Expert Reply" button – closing this request.
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New post 23 May 2017, 19:39
I was confused between B and C.
I chose B. My reasoning was that B gets rid of another reason why it should have ONLY been orcas that were responsible.
I let go of C because there could be another reason why surviving otters are in an inaccessible place. Basically, I couldn't find a strong relation here for strengthening. it seemed mildly strengthening. Please help.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 23 May 2017, 22:18
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ss18 wrote:
I was confused between B and C.
I chose B. My reasoning was that B gets rid of another reason why it should have ONLY been orcas that were responsible.
I let go of C because there could be another reason why surviving otters are in an inaccessible place. Basically, I couldn't find a strong relation here for strengthening. it seemed mildly strengthening. Please help.


Hello,

IMHO (B) doesn't help get rid of alternative reason(s) for decline of sea otters population, because 2 situations "Seals DO eat sea otters" and "seals DO compete with sea otters for food" cannot be the reason why sea otters population is reduced. Why? Let's look back at stimulus. It is mentioned that "seal population declined dramatically", so if seals actually eat and compete with sea otters for food, then the decrease in seals number will result in increase in sea otter number. This totally contrasts with premise.
That's why (B) is not correct.

Hope this helps.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 23 May 2017, 22:21
thank you so much! This helps immensely!

Lucy Phuong wrote:
ss18 wrote:
I was confused between B and C.
I chose B. My reasoning was that B gets rid of another reason why it should have ONLY been orcas that were responsible.
I let go of C because there could be another reason why surviving otters are in an inaccessible place. Basically, I couldn't find a strong relation here for strengthening. it seemed mildly strengthening. Please help.


Hello,

IMHO (B) doesn't help get rid of alternative reason(s) for decline of sea otters population, because 2 situations "Seals DO eat sea otters" and "seals DO compete with sea otters for food" cannot be the reason why sea otters population is reduced. Why? Let's look back at stimulus. It is mentioned that "seal population declined dramatically", so if seals actually eat and compete with sea otters for food, then the decrease in seals number will result in increase in sea otter number. This totally contrasts with premise.
That's why (B) is not correct.

Hope this helps.



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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 25 May 2017, 19:14
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Awesome explanation yet again, @LucyPhuong! :thumbup:
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 25 May 2017, 21:23
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GMATNinja wrote:
Awesome explanation yet again, @LucyPhuong! :thumbup:


Thank you so much GMATNinja :D

A compliment from an expert encourages me alot! Hope to continue to learn from you. :)
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 11 Jun 2017, 01:38
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.

My 2 cents.

Very good question.
On a real test, I might get this question wrong if not careful.

As highlighted in several books, it is important to establish AND keep in mind the conclusion.
Conclusion : Orcas are the cause of otter population decline.

After 1st review of ACs, I got down to B and C.
B is tempting because it makes sense but the conclusion is about the relationship between Orcas and otters, not Seals and otters. Hence out.
C is saying those survived can be found in a bay, another way of saying is those that did not survive lived in an area accessible to orcas...and probably orcas ate them.
Hence C.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands  [#permalink]

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New post 11 Jun 2017, 04:46
IMO C
C gives us the consequence why population of sea otter decreased .
Those surviving sea otters remained inaccessible to orcs .
Ad they been accessible to orcas they would have been eaten by orcas thus strengthening our conclusion.
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Re: Between 1980 and 2000 the sea otter population of the Aleutian Islands &nbs [#permalink] 11 Jun 2017, 04:46

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