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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.
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.
10 Sep 2015, 11:23
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amatya
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
21 Sep 2015, 22:25
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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.
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.
A) This option doesn't weaken for two reasons: 1) A preference doesn't necessarily mean that bumblebees still wouldn't visit both plants 2) The option flat out doesn't weaken the argument. In fact, if anything it appears to have the flavor of a strengthener since a preference toward dandelions would seem to support the findings of the study that dandelions are luring bumblebees to native plants.
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).
C) Overcrowding could very well occur, but that wouldn't weaken the claim that the presence of dandelions still boosts native plant production. Gone.
D) This option centers on the measurement of species fitness, but species fitness is a completely different topic. This option is completely Out of Focus.
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.
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.
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.
A) This option doesn't weaken for two reasons: 1) A preference doesn't necessarily mean that bumblebees still wouldn't visit both plants 2) The option flat out doesn't weaken the argument. In fact, if anything it appears to have the flavor of a strengthener since a preference toward dandelions would seem to support the findings of the study that dandelions are luring bumblebees to native plants.
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).
C) Overcrowding could very well occur, but that wouldn't weaken the claim that the presence of dandelions still boosts native plant production. Gone.
D) This option centers on the measurement of species fitness, but species fitness is a completely different topic. This option is completely Out of Focus.
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.
30 Sep 2021, 22:25
Kudos
Bookmarks
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
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
