amatya wrote:
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?
(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.
(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.
(E) Soil disturbances can result in fewer blooms, and hence lower seed production.
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Dear
amatya,
I'm happy to help.
As always, this
OG question is a great question!
The scientists concluded that "
the presence of dandelions facilitates pollination (and hence seed production) in the native species by attracting more pollinators to the mixed plots." We want to weaken this conclusion.
(A) Bumblebees preferentially visit dandelions over larkspurs in mixed plots.If all the bees were visiting dandelions, then this would not explain why the larkspurs got so pollinated, producing a great quantity of seeds. This is simply inconsistent with the evidence. This is not correct.
(B) In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.This is a strengthener. If this is true, then it would explain why having dandelions in the plot would result in more pollination for the larkspurs. This is a typical GMAT CR trap, having a strengthener for a weakener, or vice versa. This is not correct.
(C) If left unchecked, nonnative species like dandelions quickly crowd out native species.This is a problems down the road, a reason why in the big picture dandelions might be a problem for larkspars, but it doesn't do anything to address the issue of which plants get pollinated and how many seeds are produced. This is not correct.
(D) Seed germination is a more reliable measure of a species’ fitness than seed production.Even if this is true, it is not relevant, because in terms of the experiment, only seed production was measured. There was no measurement of seed germination: at most, it was merely inferred from seed production. The experiment left no means to distinguish between these two, so the distinction in this context is experimentally meaningless. This is incorrect.
(E) Soil disturbances can result in fewer blooms, and hence lower seed production.This may appear irrelevant at first glance, but think about it. The control plot (with dandelions) produced more seeds than the experimental, dandelion-free plot. How was that latter plot prepared? The prompt says: "
all dandelions were removed from eight plots." In other words, all the dandelions were ripped out, disturbing the soil. According to this answer choice, this soil disturbance would have inhibited seed production in the control group. This provides an alternative explanation to the experimental results: according to this view, the fact that the control group had more seeds than the experimental group has nothing to do with the presence or absence of dandelions, but with the presence or absence of soil disturbance. Providing a cogent alternative explanation shatters the reliability of the argument. This is a weakener.
(E) has to be the OA. This is a brilliant question, because at first glance, it may appear that (E) is entirely out-of-scope and irrelevant. You have to think about the details of the prompt to recognize why it is so relevant.
Does all this make sense? Here's a blog with more thoughts about weakening arguments:
https://magoosh.com/gmat/2012/how-to-we ... reasoning/Mike
Thanks for the great explanation.I was able to answer this question correctly.However,the passage looked extremely difficult and I had to read a couple of times.
Can you please tell how to read such passage or any complex passage of this type when running against time?
As of now my approach is simply the passage in my own words..and then stick to the conclusion..
Say I would read as ..
:Native and Nontive Dandellions species pollinate.Bublebees help in pollination..
Presence of Dandellions do not help in pollination and hence seed production.There is some other reason for that.I will keep repeating this to myself and look for options .
Based on the experiment of controlled and controlled plot ,they have arrived at the reason.I will look for some other explanation for this scenario.