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Tufe Peninsula sunflowers

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Tufe Peninsula sunflowers

by BlueDragon2010 » Wed Jan 29, 2014 2:14 pm
Two centuries ago, Tufe Peninsula became separated from the mainland, isolating on the newly formed Tufe Island a population of Turfil sunflowers. This population's descendants grow to be, on average, 40 centimeters shorter than Turfil sunflowers found on the mainland. Tufe Island is significantly drier than Tufe Peninsula was. So the current average height of Tufe's Turfil sunflowers is undoubtedly at least partially attributable to changes in Tufe's environmental conditions.

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

(A) There are no types of vegetation on Tufe Island that are known to benefit from dry conditions.

(B) There were about as many Turfil sunflowers on Tufe Peninsula two centuries ago as there are on Tufe Island today.

(C) The mainland's environment has not changed in ways that have resulted in Turfil sunflowers on the mainland growing to be 40 centimeters taller than they did two centuries ago.

(D) The soil on Tufe Island, unlike that on the mainland, lacks important nutrients that help Turfil sunflowers survive and grow tall in a dry environment.

(E) The 40-centimeter height difference between the Turfil sunflowers on Tufe Island and those on the mainland is the only difference between the two populations.
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by Patrick_GMATFix » Wed Jan 29, 2014 2:47 pm
An assumption is something that is unstated, but that has to be true for the conclusion to be valid. In this case, the author concludes that the height of the flower is partly explained by environmental changes, based on the premise that the island is drier than the Peninsula was (note that the island and the Peninsula are the same land mass). Some potential assumptions are:

1) soil composition (or other factors) do not explain the heights' difference
2) the land mass (that was the Peninsula before becoming the island) has not always been dry
3) the height difference did not exist even before the Peninsula separated to become the island.

The solution below is taken from the GMATFix App.

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by [email protected] » Fri Jan 31, 2014 2:27 pm
Hi BrueDragon2010,

This CR prompt is built on the concept of "causality", meaning that one thing causes another. It's a type of logic that you'll see a few times on Test Day, so it's worth knowing. The big assumption with causality prompts is that first thing (and NOTHING ELSE) caused the second thing.

Here, we're told that the change in environment conditions (the Island is drier than the Peninsula) caused the Turfil sunflowers to be 40 cm shorter than mainland sunflowers. We're looking for an answer that confirms that the dryness is the only possible cause (and nothing else).

The only answer that confirms the causality is C, which tells us that the difference in the height of the sunflowers was NOT due to something that happened on the mainland.

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by ceilidh.erickson » Mon Feb 03, 2014 9:24 am
Rich rightly points out that a major logical flaw here is CORRELATION/CAUSATION.

Another major flaw that you'll see a lot of is FLAWED COMPARISONS. Any argument that compares two groups of people, two types of objects, etc - especially over time - assumes that those two groups are perfectly comparable in every way. If a change is observed in one group, and a conclusion is drawn from that, we're assuming that the other group is the control, that it hasn't changed. Always ask yourself:

- Have changes happened in the other group? What do I know about the other group?
- Have changes happened over time? Is this group comparable to what it was in the past?

Answer C is the only one that addresses these questions.

Here are some other posts that address changes over time:
https://www.beatthegmat.com/og-13-ques-1 ... tml#695921
https://www.beatthegmat.com/surveys-in-d ... tml#696451
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
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