In Colorado subalpine meadows, nonnative dandelions co-occur with a na

In Colorado subalpine meadows, nonnative dandelions co-occur with a native flower, the larkspur. Bumblebees visit both species, creating the potential for interactions between the two species with respect to pollination. In a recent study, researchers selected 16 plots containing both species; all dandelions were removed from eight plots; the remaining eight control plots were left undisturbed. The control plots yielded significantly more larkspur seeds than the dandelion-free plots, leading the researchers to conclude that the presence of dandelions facilitates pollination (and hence seed production) in the native species by attracting more pollinators to the mixed plots.

Which of the following, if true, most seriously undermines the researchers’ reasoning?

Question type: Weaken the Argument

Conclusion: This argument concludes that X has caused Y – The presence of dandelions has caused a greater number of seeds to be produced in the control plot. To weaken this, we need to find an option that shows that Z causes Y.

Task at hand: Find an option that shows that Z causes Y – Something else must have caused a greater number of seeds to be produced in the control plot. Or that something else must have caused a fewer number of seeds to be produced in the experimental plot

A. Bumblebees preferentially visit dandelions over larkspurs in mixed plots. Having a preference does not mean that bumble bees wouldn’t visit both plants. If the bees preferentially visit dandelions and these bees then visit the larkspur, this shows that the presence of dandelions does indeed bring about a greater chance of cross pollination, leading to greater number of seed production. Strengthens to a certain extent.

B. In mixed plots, pollinators can transfer pollen from one species to another to augment seed production. This option suggests that pollination is enhanced in mixed plots; therefore, this option strengthens the conclusion that presence of dandelions does indeed bring about a greater chance of cross pollination, leading to greater number of seed production.

C. If left unchecked, non-native species like dandelions quickly crowd out native species. Maybe, but it does not weaken.

D. Seed germination is a more reliable measure of a species' fitness than seed production. Species fitness is not the focus here.

E. Soil disturbances can result in fewer blooms, and hence lower seed production. This option points out that it is not necessarily the presence of dandelions that brought about a greater amount of seed production. When the dandelions were uprooted, it brought about soil disturbance in the experimental plot. So it is possible that the difference in pollination was not the presence or absence of dandelions but the fact that there was soil disturbance. The disturbance caused during the removal of the dandelions could have been responsible for the fewer seeds.

- Nitha Jay

In Colorado subalpine meadows, nonnative dandelions co-occur with a native flower, the larkspur.
P1: Bumblebees visit both species, creating the potential for interactions between the two species with respect to pollination.
In a recent study, researchers selected 16 plots containing both species; all dandelions were removed fiom eight plots; the remaining eight control plots were left undisturbed.

P2:The control plots yielded significantly more larkspur seeds than the dandelion-free plots,
leading the researchers to conclude that
the presence of dandelions facilitates pollination (and hence seed production) in the native species by attracting more pollinators to the mixed plots.

Assumption: dandelions absence is the only reason for cause.
Any other factor that can lead to same behavior can be used as a weakener.

Which of the following, if true, most seriously undermines the researchers’ reasoning?

A. Bumblebees preferentially visit dandelions over larkspurs in mixed plots.
B. In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.
>> Looking at premise, I feel this is in line with argument. Ignore.

C. If left unchecked, nonnative species like dandelions quickly crowd out native species.
D. Seed germination is a more reliable measure of a species’ fitness than seed production.
>>Irrelevant.

E. Soil disturbances can result in fewer blooms, and hence lower seed production.
>> By POE; As per premise, the plots that were left undisturbed gave good yield. So plot disturbed == soil disturbed.

I like all the questions from GMAC. Usually I do not doubt them at all.
But, For some reason - I did not like this question. Reason: The argument expects us to think that soil disturbances might have occurred when dandelions were removed. This is okay, but there could be plenty of other possibilities that could have occurred and be linked to the question as well.

Dear rachitshah,
I'm happy to respond.

I would say that many official CR questions are of the form that if, say, (B) is the OA, then (B) absolutely must play the role asked by the prompt question (strengthener, weakener, etc.), but in other official question, of all five answers, the OA (B) would be the only one that could play this role. Those latter questions are typically much harder questions, and those OAs are exceptionally easy to pass over. I would say this official question is of this latter sort.

Does this make sense?
Mike

I thought that the reasoning was that seed production was facilitated by the presence of dandelions attracting more pollinators. Answer choice B implies that attracting pollinators is not the mechanism through which see production is facilitated. So answer B weakens the argument, doesn't it?

But answer B implies that the result is not achieved by attracting pollinators, so it weakens the argument, doesn't it?

Hi HiLine,

The reasoning behind your question is not entirely clear. Please elaborate.

This is how I read the whole thing:

The conclusion says that the presence of dandelions facilitates seed production by attracting pollinators. Answer B implies that dandelions facilitate seed production by allowing pollinators to transfer pollen from one species to another, thus weakening the argument.

Let me know if you need further elaboration.

Dear HiLine,
I'm happy to respond. As a huge Beethoven fan, I very much enjoy the icon you have chosen for your representation.

Here's the text of (B).
(B) In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.
This choice is not suggesting a mechanism for pollen transfer different from the pollinators. The pollinators are still involved. If pollinators are attracted to the mixed plot, as the prompt suggests, then choice clarifies that the pollinators, who have already been attracted, can cross-fertilize the two plants. It is 100% consistent with the original argument and hence strengthens it.

Does this make sense?
Mike

In Colorado subalpine meadows, nonnative dandelions co-occur with a native flower, the larkspur. Bumblebees visit both species, creating the potential for interactions between the two species with respect to pollination. In a recent study, researchers selected 16 plots containing both species; all dandelions were removed from eight plots; the remaining eight control plots were left undisturbed. The control plots yielded significantly more larkspur seeds than the dandelion-free plots, leading the researchers to conclude that the presence of dandelions facilitates pollination (and hence seed production) in the native species by attracting more pollinators to the mixed plots.

Which of the following, if true, most seriously undermines the researchers' reasoning?

(B) In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.

(E) Soil disturbances can result in fewer blooms, and hence lower seed production.



Type: Weaken
Boil It Down: Dandelions removed, larkspur down -> Dandelions boost pollination of native
Missing Information: Were there other factors?
Goal: Find the option that shows that the difference in pollination between the two groups in the study is not about the presence of dandelions.

B) This option would also appear to strengthen the argument that the presence of dandelions boosts pollination of native plants since this option would suggest that pollination is enhanced in mixed plots (those that include dandelions).

E) Yes! Here we have an option that directly offers an alternative explanation. The difference in pollination in the study wasn't the presence of dandelions (or the lack of them) but rather the fact that the removal of the dandelions in the study disrupted blooms, and thus pollination. This option exposes the dark truth that this study is miserably flawed.

Hi HiLine,

To confirm your reasoning: you're saying that B provides a counter-theory in that B refers to instances of the SAME pollinators transferring pollen to different plant species to boost pollination, therefore it appears to run counter to the claim that mixed plots increases the NUMBER of pollinators.

Two Critical And Larger GMAT Perspective Issues
I'm glad you asked because your question will enable us to look at some bigger perspective items that will help boost your accuracy.

1) Correct GMAT Weakener Options NEVER, EVER directly contradict the facts. That's actually one of the reasons why we urge such caution when GMAT students feel inclined to use non-official material to try to save money---we've seen inferior question sources outright contradict the prompt. That will never happen on the real thing. So, that said, your read on B requires the interpretation that it contradicts the stated fact that the number of pollinators increased. That interpretation must be ruled out immediately.

2) "CAN" - The GMAT test-writers love to measure the unfounded assumptions test-takers make. How often is "can"? It could be 1 in 1,000,000, and thus statistically irrelevant. For B to be of perceived value, you'd have to make the assumption that "can" implies a relevant frequency. We can't make that kind of assumption here or in any CR question.

Mike, that makes sense. But the increased seed production could be caused merely by the cross-species pollen transfer, which provides no ground for the conclusion that seed production is argumented by dandelions attracting more pollinators (sorry I forgot to include the key word "more" in the previous post! )

Ha great to run into someone that appreciates my avatar! You must be smart for liking Beethoven's music.

My read on B does not require the interpretation that it contradicts a stated fact. Where is it established in the text that the number of pollinators actually increased? From what I see, that the number of pollinators increased is a hypothesis.

Answer choice E, like answer choice B, uses the word "can".

Hi HiLine,

Glad you're all set with point 2, but for point 1, we need to take a deeper look since this raises an important distinction that tends to be widely misunderstood, or not understood at all. For that, I'm thankful your follow up prompted us to explore this distinction a little further. There are two things that no correct option in an Official GMAT Weaken question has ever done:

1) Directly contradict the conclusion stated - For example, simplifying the conclusion of this very prompt: pollination is increased by attracting more pollinators to the mixed plots. GMAT options would never effectively say: More pollinators were not attracted to the mixed plots. Your interpretation of option B is essentially tantamount to a direct rebuttal of the conclusion (hypothesis). No correct option to an Official GMAT Weakener has ever directly attacked the conclusion (hypothesis). The right option will always attack the underlying, presumed information.

2) Directly contradict the evidence stated - For example, one of the points of evidence is that: all dandelions were removed from eight plots. You wouldn't see a correct Official GMAT Weakener say something to the effect of: It's not true that all dandelions were removed from the eight plots.

Both of these routes involve surface level attack. If you'd like to solidify your sense of the standard that these two avenues are not used by GMAC, you can take a look at the publicly available Official GMAT questions in the main OG, as well as the supplements, and you'll notice that not a single correct option ever directly attacks the evidence or conclusion (hypothesis).

GMAC engineers the questions to measure the test-taker's ability to dismantle the engine of the argument (the missing information taken for granted by the author) since that is a high-level skill important to business school and beyond.

Here, option E undercuts the presumption that there were no other factors that could have accounted for the increased seed production, and that's why E is our winner.

Thanks for eliciting this further discussion. I think this distinction is really important for other readers of this thread to see. I've Kudo'd your initial question.

Max,

Thanks for your response and kudos. I get what you're saying, but what really is the distinction between answer choices B and E? Both options provide alternative explanations for seed production being higher in the mixed plots. Answer choice B does not say that not more pollinators were attracted; rather, it says that not necessarily more pollinators were attracted, just as answer choice E does. And both answer choices use the word "can".

Dear HiLine,
I'm happy to respond.

The prompt argument ends as follows:
... leading the researchers to conclude that the presence of dandelions facilitates pollination (and hence seed production) in the native species by attracting more pollinators to the mixed plots.
Fundamentally, they are getting more seed because of the pollinators. This discusses attracting the pollinators to the plot.

Here's (B).
(B) In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.
Again, they are getting more seed because of the pollinators. This discusses the role of the pollinators in cross-pollination.

We could draw a hypertechnical distinction between these two, but both of them concern the pollinators are the principle agent of the increase seed production. The fundamental story, pollinators are responsible for greater seed production, is the same in both, although they emphasize different and complementary angles of it. If some researchers published the prompt argument, and then another researcher came along and published (B), then this second paper would be seen as generally supporting the original point, even though the emphasis is slightly different. It is eminently possible to imagine both of these being true at the same time and supporting each other, both part of a larger coherent narrative.

You see, to be a weakener, we can't say something that we have a hard time distinguishing from the original argument, or that requires really fine grade distinctions. A weakener has to provide a strong contrast: it's not due to X, but due to Y, which is totally different.

This is why (E) is such a successful and strong weakener. It draws a sharp distinction. The enhanced seed growth had absolutely nothing to do with the pollinators at all: it had to do with soil disturbance, which is entirely different from the action of pollinators. The original researchers, in looking at the pollinators, were looking in the wrong place!

This is an extremely subtle issue with GMAT CR. CR is not math. In mathematics, the tiniest little difference, e.g. 1.01345 vs. 1.01346, is just as meaningful as the biggest difference. That's not true in CR. In GMAT CR, we need to be discerning and thoughtful, but not picayune and legalistic. On the one hand, we can't afford to be so sloppy that we overlook meaningful differences. On the other hand, we can't allow ourselves to become paralyzed in over-analyzing the minutiae. It's a very subtle balance that involves both cognitive skills and emotional intelligence. This same sort of balance is essential in all the deals & decisions that a manager has to make in the real business world. A familiarity with the nature of the distinctions in real-world business deals would help immensely with skill on GMAT SC. See:
GMAT Critical Reasoning and Outside Knowledge

As I have typed this response, I have been listening to Claudio Arrau play the Piano Sonata in E-flat, Op. 31, #3. I think Beethoven was one the greatest geniuses who has ever lived.

Mike

I always thought there was only one correct answer choice for each GMAT question, until I ran into this one. Thanks for your detailed answer which makes perfect sense to me and demonstrates a different level of understanding of the way GMAC designs their questions and answers. While I believe this type of questions is rare, I set out a goal for myself to be able to comfortably answer any official GMAT question encountered, and therefore your answer to my questions is tremendously helpful.

I am impressed. You're really good at GMAT CR. You must listen to a lot more Beethoven music than I do.

Case in point: A big fan of Beethoven as I am, I had not listened to this one sonata in full until you pointed it out to me! I had listened to only the second movement.

Hi HiLine,

What happens if you negate choice B?

(B) In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.
Pollinators can't transfer pollen from one species to another to augment seed production. Add this to the argument and the conclusion doesn't make much sense. That means that choice B is a strengthen. Hope that helps in crossing this choice out.

Happy Studies,

A.