Galapagos Tortoises vs Mainland Tortoises : GMAT Critical Reasoning (CR)
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Galapagos Tortoises vs Mainland Tortoises

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Galapagos Tortoises vs Mainland Tortoises [#permalink]

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02 Jul 2013, 10:40
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The Galapagos Islands formed at least 8 million years ago and a tortoise population from the South American mainland was estimated to have found its way to the island at least 5,000 years ago. A small isolated population of Galapagos Tortoises emerged. Based on a sample, this population's descendants can grow to be on average, 25 kilograms heavier than similar tortoises found on the South American mainland. The Galapagos Islands are drier than the South American mainland. Thus, the current average weight of Galapagos Tortoises is undoubtedly at least partially attributable to changes associated with the Galapagos' environmental conditions.

Which of the following is an assumption on which the argument depends?

(A) There are no types of vegetation on the Galapagos Islands that are known to benefit from dry conditions.
(B) There were about as many tortoises on the mainland five thousand years ago as there are on the Galapagos Islands today.
(C) The mainland's environment has not changed in ways that have resulted in tortoises on the mainland growing to be 25 kilograms lighter than they were five thousand ago.
(D) The soil on the South American mainland, unlike that on the islands, lacks important nutrients that help tortoises survive and grow heavy in a dry environment.
(E) The 25-kilogram weight difference between the tortoises on the Galapagos Islands and those on the mainland is the only difference between the two populations.

[Reveal] Spoiler:
C

Sourced from GMAT Pill Platform CR Question
[Reveal] Spoiler: OA
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Re: Galapagos Tortoises vs Mainland Tortoises [#permalink]

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08 Jul 2013, 13:04
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Here is a visual approach to this question:

The first big step is to identify what the conclusion? What is it exactly that we're trying to strengthen?

Then visualize the passage using the table-top framework. Now you can see visually what exactly the argument is trying to do.

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Re: Galapagos Tortoises vs Mainland Tortoises [#permalink]

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08 Jul 2013, 13:11
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There are a few key words in the claim that is made in the last sentence. "Undoubtedly" suggests a definite association that is made -- but that association is qualified by using the words "at least partially attributable".

Still, the use of the word "undoubtedly" suggests a definite connection...we can disprove that connection as being "definite" if we can introduce some possible doubt. As a result, this signals for us to use "exclusive negation" -- which is GMAT Pill CR Framework #4 Exclusive Negation

As such, we use Framework #4 as our pre-thinking, going into our answer choices. #2 shown is the negated version that our framework advises, can we find an answer choice that resembles this negated form?

Sure enough, we do find the correct answer choice that is exactly the answer choice we are looking for. Framework #4 advised us to look for a negated form of the conclusion -- and the answer indeed was that. That helped us save a lot of time in answering the question.
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Re: Galapagos Tortoises vs Mainland Tortoises [#permalink]

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02 Jul 2013, 10:49
GMATPill wrote:
The Galapagos Islands formed at least 8 million years ago and a tortoise population from the South American mainland was estimated to have found its way to the island at least 5,000 years ago. A small isolated population of Galapagos Tortoises emerged. Based on a sample, this population's descendants can grow to be on average, 25 kilograms heavier than similar tortoises found on the South American mainland. The Galapagos Islands are drier than the South American mainland. Thus, the current average weight of Galapagos Tortoises is undoubtedly at least partially attributable to changes associated with the Galapagos' environmental conditions.

Which of the following is an assumption on which the argument depends?

(A) There are no types of vegetation on the Galapagos Islands that are known to benefit from dry conditions.
(B) There were about as many tortoises on the mainland five thousand years ago as there are on the Galapagos Islands today.
(C) The mainland's environment has not changed in ways that have resulted in tortoises on the mainland growing to be 25 kilograms lighter than they were five thousand ago.
(D) The soil on the South American mainland, unlike that on the islands, lacks important nutrients that help tortoises survive and grow heavy in a dry environment.
(E) The 25-kilogram weight difference between the tortoises on the Galapagos Islands and those on the mainland is the only difference between the two populations.

[Reveal] Spoiler:
C

Sourced from GMAT Pill Platform CR Question

This is a rephrased question form of GMAT PREP question.
Here is the link of discussion:
q40-two-centuries-ago-tufe-peninsula-became-separated-form-46879.html
http://www.manhattangmat.com/forums/gma ... 11138.html
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Re: Galapagos Tortoises vs Mainland Tortoises [#permalink]

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04 Feb 2017, 08:55
Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Galapagos Tortoises vs Mainland Tortoises   [#permalink] 04 Feb 2017, 08:55
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