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

(A) Bumblebees preferentially visit dandelions over larkspurs in mixed plots.


Bumblebees --> dandelions --> it should lead to increased seed production --> it means presence of dandelions facilitates pollination (and hence seed production) in the native species by attracting more pollinators to the mixed plots.
It is strengthening the conclusion.


Conclusion : presence of dandelions facilitates pollination (and hence seed production)
Find some reason : not because of dandelions that seed production was more than dandelion-free plots.

We need to find out any reason that give us reasoning that it is not because of absence of dandelions that production was decreased but due to something else.

Option E gives that alternate reason of decrease of seed production.

Bees can contribute to pollination if there is successful or plenty of blooms. So, E weakens the argument of the researchers.

Quite confused with why A is wrong. Here is my reasoning:

Fact: In the mixed spot we have D and L
Fact: In the mixed spot L have more seeds
Conclusion: The reason L have more seeds in the mixed spot is D
Correct AC Qualification: "NO it is not D"

Answer Choice A:
States that bees prefer D over L. So, in the mixed spot bees prefer (and therefore visit) D => If bees prefer/visit D, bees does not create the interaction between D and L => As a result, D does not have an effect on L => Meaning => "There must be some other reason L have more seeds in the mixed spot" equals "NO it is not D"

So AC A is a weakener. Any opinion would be appreciated!

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.

P: Dandelions co-occur with the larkspur
P: Bumblebees visit both species, creating interactions
P: In an experiment, the treatment plot contained dandelions only, whereas the control contained a mix of both species
P: Control plots yielded more larkspur
C: Dandelions facilitate pollination by attracting more pollinators to the mixed plots

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

(A) Bumblebees preferentially visit dandelions over larkspurs in mixed plots.

Incorrect. This choice attacks a premise in the argument. We know that the control plots yielded significantly more larkspur seeds.

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

This seems to strengthen the argument…it explains how the pollination occurs among mixed plots.

(C) If left unchecked, nonnative species like dandelions quickly crowd out native species.

Possibly, but this doesn’t weaken the idea that they can facilitate pollination.

(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.

Correct. This gives us an alternative explanation for why the treatment plot had less seed production – soil disturbances. In other words, we cannot attribute the lack of pollination success in the treatment plot to the absence of dandelions.

Can someone please shed some light on this point?

Regards

COnclusion says: It is because of presence of dandelions that there was more seed production.

Strengthener: dandelions were reasons behind higher seed production
Weakner: dandelions were NOT reasons behind higher seed production

Question: most seriously undermines the researchers’ reasoning?


A says : it is because of dandelions.
So A is strengthener or weakner?

I hope you get it.
A is strenghener
E is weakner

mSKR

My friend, thank you for your response.

However, I think you miss a subtle point with the conclusion. Since this is a Weaken question, we cannot take the given conclusion as correct (as we try to show that is has a flaw). In your response you wrote:



This is part of the conclusion. So, I believe you should not use it to say this:



That's why, even tough I again thank you for your response, I don't see my exact question is answered...

When we evaluate any option independently , we can add option to the argument to see the effect on conclusion given.


That's why, even tough I again thank you for your response, I don't see my exact question is answered...

[/quote]


Here to understand A, you need to see the tendency of the option on conclusion. If bees prefer D , it doesn't means all bees only goes to D , it doesn't mean there would be no interaction between D and L. It doesn't mean there would be no effect on L. It doesn't mean there would be some other reason L has more seeds in mixed spot. There is no proof given in the statement to assert your statements.

We need to stick to statement what is given . bees prefer D , we can only derive that D may have seeds more than L can have. That's all. Beyond this thought, you are going in unknown territory.

If you get confused in such situation, you can related with your life examples. When you say I prefer coffee, Does it mean you never take Tea or other beverages? If it is so, you could have said , I only take coffee. similarly, statements could have been : Bees only choose one ; but not others.

I hope it is clear.

I had the same doubts here. It reminds me a lot of the following question: https://gmatclub.com/forum/researchers- ... 06114.html

If we can find some other explanation for what the scientists suggest in the prompt, it would weaken their hypothesis.

Scientists say: The cross-pollination occurs because bees are MORE ATTRACTED when dandelions are there.
B says: No, they do not get MORE ATTRACTED, they just happen to cross-pollinate more because they fly around more.

However, I realise now that B HAS TO INDICATE that they do get more attracted, because otherwise they could have just been flying around cross-pollinating to the same extent in the non-mixed plot.

With 'B' I got this wrong.
But the discussions and explanations here are helpful in understanding the reasoning behind correct answer choice 'E'. Thanks to all the experts.

I think (a wild guess), what most candidates (who got this question wrong) mistake on 'this' question is, they misread or misinterpret the question:

Question Given:
......
......
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.


Misinterpretation:
......
......
The control plots yield increased significantly more larkspur seeds than that from 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.

This question (and the explanations here) really taught me an already known fact: Reading closely is a critical skill on GMAT.

Though the correct answer is the option (E), I would like to share some of my thoughts of the option (A). I think (A) is an interesting contender--it has been interpreted differently in the official explanation and at this forum.

(A) Bumblebees preferentially visit dandelions over larkspurs in mixed plots

How the adverb "preferentially" plays a role here is interesting, and perhaps even decisive in determining whether the option (A) is a strengthener or just an irrelevant option. Does it mean that bumblebees only visit dandelions and ignore the larkspurs completely? Or, does it mean that bumblebees prefer the plots that contain dandelions to the plots without dandelion, and when they visit the former, they visit dandelions first and larkspur later?

The first interpretation should not be correct, as it is not what the word "preferentially" means. But, even if we agree that the second interpretation is right, the option (A) could still be understood in two ways.

First, the option (A) can be a strengthener.

If the 16 plots, eight in the control group and eight in the experimental groups, are adjacent to others, the bees will prefer to visit the eight plots that contain both dandelions and larkspur. If the number of flowers is relatively high to the number of bees, it might be even likely that the bees will not visit the other eight plots that contain only larkspur, as the pollen produced by dandelions and larkspur in the first eight plots will be enough to feed the bees.

If the option (A) is understood this way, it suggests that bees just love the mixed plots more than the plots containing only the larkspur. Thus, it is compatible with the conclusion that the presence of dandelions facilitates pollination and seed production in the larkspur by attracting more pollinators (bees) to the mixed plots. Clearly, the option (A) cannot weaken the argument.

By the way, this was how I understood the option (A) when I practiced this CR question for the first time. Later, I was a bit surprised to find out that the official explanation interprets the option (A) differently, but I am not alone at this forum--some members also think that the option (A) is a strengthener.

In another way (the way adopted by the official explanation), the option (A) can be an irrelevant option. The official explanation says that the option (A) "would suggest that the larkspur pollination should have been lower in the plots with dandelions, so it does not provide a plausible alternative explanation for the study's findings."

I have to say that initially I did not get the logic of this explanation. Later, I figured out that the person who wrote this explanation might have made some assumptions. First, the two groups of plots are located far from each other. Secondly, the numbers of bees visiting the two groups are similar. Thirdly, the number of bees visiting the mixed plot is not much higher than the amount of pollen produced by both dandelions and larkspur. (I am sure that there are other assumptions but I just name some.)

With these assumptions, we have a scenario in which the bees will still visit the plots containing only the larkspur even though they preferentially visit dandelions, since the plots containing dandelions are far away. When they visit the plots containing only the larkspur, all they can do is pollinating the species, so the seed production is good, or normal. On the other hand, another group of bees will visit the mixed plot too, but they will pollinate dandelions first as they prefer the species. Because the number of bees is not relatively high to the number of flowers, most of bees might be "fed enough" with the pollen of dandelions, and few of them will actually pollinate the larkspur. Therefore, there is a chance that the larkspur pollination in the mixed plot will be lower than that in the experimental group, as the official explanation says.

It is quite interesting that the above reasoning would be easily forced to change if the passage introduced new information or variables. For example, if the passage said "though the mixed plots contain both dandelions and larkspur, most of the plants are still larkspur," we would have another story here--since bees will still need to pollinate the larkspur as there is no enough pollen of dandelions, the larkspur pollination in the mixed spot might still be good. How these subtle but game-changing settings are presented in the CR questions is fascinating, (although I do not want to meet an over-complicated one in the real test....)

IanStewart

Hi Ian, could I know your take on the option (A)? I have to say the logic of the official explanation is not really accessible. I am curious how you address this option or the adverb "preferentially" in such questions involving experiments. Thank you!

The interpretation of "preferentially" in answer A is unambiguous when we account for the premise I've highlighted in red. We know the bees visit both larkspur and dandelion, so A only tells us they visit dandelions more often.

If A is true, we face a question: why, if bees prefer dandelion, would we still have more larkspur seeds when dandelion grows alongside larkspur? I'd expect larkspur to do better if there was no competition from dandelion. But the experiment tells us otherwise. Everything makes sense though if the dandelion is responsible for attracting a great number of bees to the plot. Even if the majority of those bees go to the dandelion flowers, there may still be a lot more bees on the mixed plot going to larkspur than on the larkspur-only plot. So really it's one of those GMAT CR situations which test if you confuse ratio and number. If, on the mixed plot, only 1/4 of the bees go to larkspur, but there are 10 times as many bees as on a non-mixed plot, it can make sense that the larkspur fares better in the mixed setting.

So answer A for me just reinforces the researchers' hypothesis. The researchers believe dandelions attract more bees. Answer A just says that bees are attracted to dandelions. It's what you'd expect to be true if the hypothesis is true. I suppose it strengthens the argument, in that it further establishes that dandelions attract bees. The official explanation (or at least what you quoted from it) is also right, and doesn't contradict that interpretation, because the official explanation is looking at things differently. It's not even asking if answer A strengthens the argument. It's just assuming the researchers' hypothesis is false from the outset (so it's assuming bees were equally attracted by both types of plot), and is then asking which answer choice explains the experimental results in a different way. That's not the only way to approach a CR question like this, but it's logically fine.

Answer E offers a new plausible explanation for the results of the experiment, so it's the right answer (I haven't read the thread, but I assume E has been discussed in detail already so I won't say more about it).

Actually I just did skim the three top replies in this thread (maybe I should have done that first, but I try to only read others' posts after writing my own), and I think I now have a better understanding of why you asked about "preferentially", because none of those posts seem to discuss A correctly. The top reply in the thread rules out A because it is "inconsistent with the evidence". But it's logically impossible in a GMAT CR question like this for an answer to be inconsistent with the evidence in the stem, because the question asks "which of the following, if true..." There must be a way for the stem and answer choice to be true at the same time, and if we can't imagine a way the stem and answer choice can both be true, we just haven't been imaginative enough. That explanation misconstrues the meaning of "preferentially", which is why it thinks there's an inconsistency that doesn't actually exist. The other two top replies are both essentially correct when discussing A, but they don't acknowledge the premise that I highlighted in red in my previous post, so they both treat something the passage tells us is true as if it were an open question. We know as a fact that dandelion and larkspur "co-occur" and that bees visit both plants, and it's not something we need to wonder about.

IanStewart

Ian, thank you so much for your reply! It is high-quality and informative. But I do have some follow-up questions and hope that you could answer them when you are available.



I have no problem for this part. I tend to consider the option (A) a strengthener because of similar reasoning.



I have some difficulty understanding this part:

How could the official explanation assume that the bees were equally attracted by both types of plot, when it deals with the option (A), which explicitly says that bees preferentially visit dandelions over larkspurs in mixed plots? Does not the assumption kind of directly contradict with the option (A) itself?

Or, Ian, do you mean that before addressing the answer choices, the official explanation assumes that the bees could be equally attracted by the mixed and non-mixed plots, since it aims to weaken the conclusion, which is basically the researchers' hypothesis that more bees will visit the mixed plots because of the dandelions? With this assumption, the official explanation then checks which option can offer an explanation for the study's findings (higher seeds of larkspur in the mixed plot) and thus rules out the option (A)?

I can understand why this technique is logically fine--it seems that this is a "negated conclusion" technique. The writer of the official explanation still accepts the premises such as the bees' behavior and the study's findings, but he or she just denies the conclusion( the researchers' hypothesis) and tries to find an option that can both coexist with the negated conclusion and explain for the findings.

But, isn't this technique a bit too extreme? I mean, we surely hope to disprove the conclusion in the weaken-type CR questions, but in harder weaken-type question, often we can only find an option that could "likely" cast some doubt on the conclusion. I think in this question, the correct answer choice (E) does not disprove the conclusion either--it just offers another reason for higher seed production and thereby weakens the importance of the presence of dandelion.

I am unsure whether I want to adopt this "negated conclusion" technique in my practice.

I hope that I did not misunderstand your response or the way the official explanation addresses the option (A). I am just curious why the official explanation interprets the option (A) differently. Thank you once agin for your response!

There are two separate issues in this question:

#1. when bees are flying around out in the world, and they can choose to go to any plot of land at all, where do they go?
#2. if bees decide to hang out in a mixed dandelion-larkspur plot of land, which flowers do they go to?

Notice there's no necessary relationship between the answers to these two questions. Maybe when bees are flying around, they're attracted by plots of land with colourful flowers, but when bees get close to the flowers, they're attracted not by colour but by smell. So there's no contradiction in the official explanation if it assumes these two things: bees are equally attracted by both plots of land (maybe bees just choose plots at random), but once in a dandelion-larkspur plot, bees prefer dandelions. The answer to question #1 and the answer to question #2 don't logically need to have any relationship with each other.

The researchers in the argument propose an answer to question #1. They think that when bees are flying around, if the bees see dandelions, they go to the plot of land with the dandelions. Answer choice A doesn't really address question #1. Instead A addresses itself to question #2: when a bee is already on a plot of land containing both flowers, answer A tells us the bee tends to prefer the dandelion. You could say that answer A reinforces the researchers' hypothesis, that bees are attracted by dandelion, or you could say it's not really relevant, because it addresses the wrong question (we care about question #1, not question #2). Either way, the stem tells us "bees visit both species" in nature, and the dandelion-larkspur control plots replicate what happens in nature, so we know when bees find themselves in a dandelion-larkspur plot, some bees will go to the larkspur even if bees prefer dandelion.



I didn't mean to suggest it was a CR technique one should use. It often seems to me that the preambles in the official explanations in the OG are written by someone who is psychic. The writer knows in advance what the correct answer is, and knows exactly how the correct answer will weaken the argument (or strengthen it, or whatever the question asks). So the OG explanation writer often adopts the perfect perspective on the question in advance, even though a test taker would have no way to guess, before reading the answer choices, that the question could be approached in that way. In this question, the writer seems to know that the right answer is going to offer an alternate explanation, and then considered A from that perspective.

IanStewart
Thank you so much for your time and responses!
I am impressed by the sentences in boldface--they demonstrate how subtly different multiple layers of thinking can be. I think this is one of the reasons why CR questions can be really challenging.

Back to the option (A), so we indeed could consider (A) a strengthener or an irrelevant option. Either way, (A) cannot weaken the argument.



I also think the the writers of official explanations are just so lucky that in most cases their pre-thinking reasoning matches perfectly with the reasoning behind the correct answers. I know the explanations are specially designed and few people can get really that lucky in the real test. It is just that I tend to compare my reasoning with that of official explanations and that of other members at this forum in order to see where I can improve.

Thank you so much!

Hi,

In choice B, it says that "In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.".
I chose option B because it states that the pollination can happen between any two species. From this I understood that it is not that the pollination happened in the mixed plot only because dandelions were present.
If it was some other plant, say plant X, still pollination would have occurred at the same pace and the amount of larkspur seeds produced would have been greater than that of mixed plot. Therefore, it undermines the conclusion that dandelions in specific played a central role in augmenting seed production.

Can someone please help me understand the flaw in my reasoning. Thanks.