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Register now and save up to $200 Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code ## Between 1980 and 2000 the sea otter population tagged by: Brent@GMATPrepNow This topic has 6 expert replies and 4 member replies gmatdriller Master | Next Rank: 500 Posts Joined 04 Jul 2010 Posted: 418 messages Followed by: 2 members Thanked: 6 times #### Between 1980 and 2000 the sea otter population Mon Aug 03, 2015 2:44 am Elapsed Time: 00:00 • Lap #[LAPCOUNT] ([LAPTIME]) Between 1980 and 2000 the sea otter population of the Aleutian Island 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 Island 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 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 fish use for food. Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums! ### GMAT/MBA Expert GMATGuruNY GMAT Instructor Joined 25 May 2010 Posted: 13352 messages Followed by: 1779 members Thanked: 12877 times GMAT Score: 790 Mon Aug 03, 2015 3:17 am gmatdriller wrote: Between 1980 and 2000 the sea otter population of the Aleutian Island 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 Island 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 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 fish use for food. Conclusion: Orcas were most likely the immediate cause of the otter population decline. In a causal argument, the conclusion is that A CAUSES B. One way to strengthen a causal argument is to show the following: If A does not happen, then B does not happen, STRENGTHENING the conclusion that A CAUSES B. Answer choice C: Most of the surviving sea otters live in a bay that is inaccessible to orcas. Implication: If A does not happen (if orcas are unable to access sea otters), then B does not happen (the otters are not eaten), STRENGTHENING the conclusion that orcas CAUSED the decline in the otter population. The correct answer is C. _________________ Mitch Hunt GMAT Private Tutor GMATGuruNY@gmail.com If you find one of my posts helpful, please take a moment to click on the "Thank" icon. Available for tutoring in NYC and long-distance. For more information, please email me at GMATGuruNY@gmail.com. Last edited by GMATGuruNY on Mon Aug 03, 2015 7:23 am; edited 1 time in total Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now. ### GMAT/MBA Expert Jim@StratusPrep MBA Admissions Consultant Joined 11 Nov 2011 Posted: 2278 messages Followed by: 265 members Thanked: 659 times GMAT Score: 770 Mon Aug 03, 2015 7:21 am The argument says that orcas will eat sea otters is seals are unavailable, so we want to find a statement that says the seals are not a strong enough food source. C says exactly this. _________________ GMAT Answers provides a world class adaptive learning platform. -- Push button course navigation to simplify planning -- Daily assignments to fit your exam timeline -- Organized review that is tailored based on your abiility -- 1,000s of unique GMAT questions -- 100s of handwritten 'digital flip books' for OG questions -- 100% Free Trial and less than$20 per month after.
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Brent@GMATPrepNow GMAT Instructor
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Mon Aug 03, 2015 8:06 am
Mitch points out one way to strengthen a cause-and-effect argument.

Two more ways to strengthen a cause-and-effect argument:
- provide additional information that supports the causal effect
- eliminate the possibility that something else causes the event.

Cause-and-effect arguments are common on the GMAT, as are statistical arguments and analogy arguments, so be sure you know how to strengthen and weaken these argument types.
We have a free video on common argument types: http://www.gmatprepnow.com/module/gmat-critical-reasoning?id=1134

We also have a free video on strengthening the argument: http://www.gmatprepnow.com/module/gmat-critical-reasoning?id=1138

Cheers,
Brent

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gmatdriller Master | Next Rank: 500 Posts
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Mon Aug 03, 2015 12:21 pm
Trying to paraphrase:

In the presence of otters, there will be predation by orcas.
(provided no seals are available).

The stem went on to say seals declined dramatically, so the
absence of otters is most likely attributable to orcas.

C suggests that the surviving ones only escaped predation from otters 'cos they are
inaccessible. Thus strengthening the claim that orcas are responsible for otters decline.

Given that seals are NOT available:
If otters are available, Predation will take place by orcas (If A, then B)
If otters are NOT available, Predation will NOT take place by orcas(If NOT A, then NOT B)

Pleased to point out issues with my reasoning.

Thanks

ahmedbari.ace@gmail.com Junior | Next Rank: 30 Posts
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Mon Aug 10, 2015 4:52 pm
Please explain why B is incorrect.
If I negate B i.e. to say that seals ate otters or competed with them for food,I can very well prove an alternate reason for the decline of otter population.
Although this argument is faulty when compared with the premise that seal population is also declining.Yet is it sufficient to eliminate B based on that.
If not then please specify the POE for B.
Cheers!

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GMATGuruNY GMAT Instructor
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Tue Aug 11, 2015 4:38 am
ahmedbari.ace@gmail.com wrote:
Please explain why B is incorrect.
If I negate B i.e. to say that seals ate otters or competed with them for food,I can very well prove an alternate reason for the decline of otter population.
Although this argument is faulty when compared with the premise that seal population is also declining.Yet is it sufficient to eliminate B based on that.
If not then please specify the POE for B.
Cheers!
Your reason for eliminating B is correct.
Premises:
The Aleutian Island seal population declined dramatically IN THE 1980s.
BETWEEN 1980 AND 2000 the sea otter population of the Aleutian Island declined precipitously.
Since few seals remained after 1980, the decline of the otter population cannot be attributed to the seals.
Thus, the information in B is irrelevant.
Eliminate B.

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RBBmba@2014 Legendary Member
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Sat May 14, 2016 10:26 am
GMATGuruNY wrote:
Premises:
The Aleutian Island seal population declined dramatically IN THE 1980s.
BETWEEN 1980 AND 2000 the sea otter population of the Aleutian Island declined precipitously.
Since few seals remained after 1980, the decline of the otter population cannot be attributed to the seals.
Thus, the information in B is irrelevant.
Eliminate B.
I got the above explanation, but just would like to know - is the following interpretation of B correct ?

We don't have any info whether the population of SEALS increased post-1980s and before 2000! Even if population of SEALS had increased post-1980s and before 2000, then also B would NOT have STRENGTHENED the CONCLUSION that orcas were most likely the immediate cause of the otter population decline. (It might be because of some other PREDATORS in the sea...not conclusive yet!)

So, Option B doesn't really affect the CONCLUSION!

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DavidG@VeritasPrep Legendary Member
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Sun Jul 31, 2016 6:53 am
Quote:
We don't have any info whether the population of SEALS increased post-1980s and before 2000! Even if population of SEALS had increased post-1980s and before 2000, then also B would NOT have STRENGTHENED the CONCLUSION that orcas were most likely the immediate cause of the otter population decline. (It might be because of some other PREDATORS in the sea...not conclusive yet!)

So, Option B doesn't really affect the CONCLUSION!

Well, it's true that we don't necessarily know what happened to the seal population in the 90's, but because we're told that the seal population decreased dramatically in the 80's, there's nothing in B that would cause us to consider the possibility that seals made a dramatic recovery before 2000. But you're right, even if the seal population had miraculously rebounded, it wouldn't matter. If anything, it would weaken the conclusion, as the argument is predicated on the notion that the Orcas shifted their attention to otters because there were fewer seals to eat.

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Save $100 off any live Veritas Prep GMAT Course Thanked by: RBBmba@2014 Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now! RBBmba@2014 Legendary Member Joined 30 May 2012 Posted: 888 messages Followed by: 4 members Thanked: 8 times Mon Aug 01, 2016 7:06 am DavidG@VeritasPrep wrote: Quote: We don't have any info whether the population of SEALS increased post-1980s and before 2000! Even if population of SEALS had increased post-1980s and before 2000, then also B would NOT have STRENGTHENED the CONCLUSION that orcas were most likely the immediate cause of the otter population decline. (It might be because of some other PREDATORS in the sea...not conclusive yet!) So, Option B doesn't really affect the CONCLUSION! Correct me please if wrong! Well, it's true that we don't necessarily know what happened to the seal population in the 90's, but because we're told that the seal population decreased dramatically in the 80's, there's nothing in B that would cause us to consider the possibility that seals made a dramatic recovery before 2000. But you're right, even if the seal population had miraculously rebounded, it wouldn't matter. If anything, it would weaken the conclusion, as the argument is predicated on the notion that the Orcas shifted their attention to otters because there were fewer seals to eat. ABSOLUTELY. Even if seals don't eat otters (as given in B), that doesn't NECESSARILY mean that Orcas ate otters. Right ? ### GMAT/MBA Expert DavidG@VeritasPrep Legendary Member Joined 14 Jan 2015 Posted: 2292 messages Followed by: 115 members Thanked: 1061 times GMAT Score: 770 Mon Aug 01, 2016 9:59 am RBBmba@2014 wrote: DavidG@VeritasPrep wrote: Quote: We don't have any info whether the population of SEALS increased post-1980s and before 2000! Even if population of SEALS had increased post-1980s and before 2000, then also B would NOT have STRENGTHENED the CONCLUSION that orcas were most likely the immediate cause of the otter population decline. (It might be because of some other PREDATORS in the sea...not conclusive yet!) So, Option B doesn't really affect the CONCLUSION! Correct me please if wrong! Well, it's true that we don't necessarily know what happened to the seal population in the 90's, but because we're told that the seal population decreased dramatically in the 80's, there's nothing in B that would cause us to consider the possibility that seals made a dramatic recovery before 2000. But you're right, even if the seal population had miraculously rebounded, it wouldn't matter. If anything, it would weaken the conclusion, as the argument is predicated on the notion that the Orcas shifted their attention to otters because there were fewer seals to eat. ABSOLUTELY. Even if seals don't eat otters (as given in B), that doesn't NECESSARILY mean that Orcas ate otters. Right ? Correct. _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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