Critical Reasoning

In Colorado subalpine meadows, non-native 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 6 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 attractive more pollinators to the mixed plots.

Which of the following, if true, mostly 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, non-native 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

@ GmatGuru, Jim@Stratusprep, & [email protected] thanks for your contributions to my previous cr questions.

Above question is similar to A causes B, and we are asked to weaken. The question appears confusing with plenty words but simple after careful analysis. [spoiler]Eliminating Alternative cause
[/spoiler]

gmatdriller wrote:In Colorado subalpine meadows, non-native 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 6 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 attractive more pollinators to the mixed plots.

Which of the following, if true, mostly 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, non-native 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

@ GmatGuru, Jim@Stratusprep, & [email protected] thanks for your contributions to my previous cr questions.

Above question is similar to A causes B, and we are asked to weaken. The question appears confusing with plenty words but simple after careful analysis. [spoiler]Eliminating Alternative cause
[/spoiler]

Core:

P1: Two species of flowers are grown simultaneously.
P2: BBees are pollinators for both these species.
P3: Recent study indicates plot with mixed species yielded significantly nor L seeds than D free plots.
C: Presence of Dandelion facilitates seed productions by attracting more pollinators.

Question type:

Weaken ... there are three ways to deal with it.

1. A reverse logic should exist i.e., Dandelion are grown because of more pollinators -> does not make sense.
2. It's just a coincidence
3. Provide an alternative cause.

Lets evaluate options.

A: Bumblebees preferentially visit dandelions over larkspurs in mixed plots
This is the conclusion - Eliminate.

B: In mixed plots, pollinators can transfer pollen from one species to another to augment seed production.
Not sure of what it is .. so will keep it for now.

C: If left unchecked, non-native species like dandelions quickly crowd out native species
If this was the case then more Dandelion seeds than larkspur seeds should have been created.

D: Seed germination is a more reliable measure of a species' fitness than seed production
Out of context since we are dealing with seed production here.

E: Soil disturbances can result in fewer blooms, and hence lower seed production
Noting mentioned about soil distribution.

Thus, by POE, IMO B.

gmatdriller wrote:In Colorado subalpine meadows, non-native 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 6 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 attractive more pollinators to the mixed plots.

Which of the following, if true, mostly 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, non-native 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[/b]

Premise:
After dandelions were removed from 8 plots, these 8 plots yielded fewer larkspur seeds than did the control plots.
Conclusion:
The presence of dandelions facilitates pollination.

The assumption is that there is NO OTHER EXPLANATION for the lower seed yield in the 8 plots from which dandelions were removed.
One way to weaken the conclusion is to suggest an ALTERNATE EXPLANATION for the lower seed yield in these 8 plots.

Answer choice E: Soil disturbances can result in fewer blooms, and hence lower seed production.
Implication:
The lower seed yield in the 8 plots was due NOT to the absence of dandelions but to the SOIL DISTURBANCE that occurred when the dandelions were removed, WEAKENING the conclusion that the presence of dandelions facilitates pollination.

The correct answer is E.

Hello Mitch,

One question here...

How do we know that soil disturbances occurred when the dandelions were removed? This can possibly be implied but cannot be confirmed I guess?

Many Thanks,
Amit

gmat_for_life wrote:Hello Mitch,

One question here...

How do we know that soil disturbances occurred when the dandelions were removed? This can possibly be implied but cannot be confirmed I guess?

Many Thanks,
Amit

From the passage:
All dandelions were removed from eight plots; the remaining eight control plots were left UNDISTURBED.
Implication:
Whereas the control plots were left UNDISTURBED, the other eight plots WERE disturbed.
How were they disturbed?
By the removal of the dandelions.

Hi - please let me know where i might be going wrong here

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E : Soil disturbances can result in fewer blooms, and hence lower seed production

My interpretation of E : because of disturbances in the soil specifically , fewer blooms (aka dandelion plants) are produced --hence even lower seeds are produced

Goal : weaken the argument which states dandelions facilitates pollination and seed production (not necessarily seed yield)

Question : just because soil disturbances result in fewer blooms (fewer grown Dandelion plants)...... why does this imply, Dandelions do not facilitate pollination ......

jabhatta wrote:Hi - please let me know where i might be going wrong here

---------------

E : Soil disturbances can result in fewer blooms, and hence lower seed production

My interpretation of E : because of disturbances in the soil specifically , fewer blooms (aka dandelion plants) are produced --hence even lower seeds are produced

Goal : weaken the argument which states dandelions facilitates pollination and seed production (not necessarily seed yield)

Question : just because soil disturbances result in fewer blooms (fewer grown Dandelion plants)...... why does this imply, Dandelions do not facilitate pollination ......

Imagine that scientists hypothesize that Drug X can extend the lifespan of gerbils. So they do an experiment. They give one set of gerbils Drug X and they give another set a placebo. The gerbils given Drug X live five months longer than the gerbils given the placebo. So the drug looks good, right? Well, what if it turns out that the placebo contains lethal amounts of poison. Suddenly, we'd have an alternative explanation: rather than Drug X being effective, the placebo was actually shortening life expectancy. Does this prove that Drug X doesn't work? No. But it surely hurts the argument that it does.

Same logic here. We're told that the plots with both types of flowers had greater yields of larkspur seeds. One explanation is that the presence of dandelions improved the larkspur seed yields in the plots containing both. An alternative explanation, offered by E, is that the disturbance caused by removing the dandelions hurt the seed yields in the plots with only larkspur. (In this case, disturbing the soil is analogous to the presence of poison in the placebo - it's a variable that contaminates the purity of the experiment.) Does it mean that dandelions can't help yields? No. But it certainly weakens that argument that they do.

A: Bumblebees preferentially visit dandelions over larkspurs in mixed plots - INCORRECT- this is the conclusion of the passage.
B: In mixed plots, pollinators can transfer pollen from one species to another to augment seed production - Yes. So? It is mere a fact.- INCORRECT-
C: If left unchecked, non-native species like dandelions quickly crowd out native species -INCORRECT- Again, it has nothing to do with the argument
D: Seed germination is a more reliable measure of a species' fitness than seed production - INCORRECT- same as D
E: Soil disturbances can result in fewer blooms, and hence lower seed production - YES! this is the right choice. Now, the author says that the bees are attracted to dandelions and more pollination happens in the mixed plots becoz of that. But if E were true, then we know that the plot where dandelions were removed had disturbed soil and due to this, there was lower pollination and hence lower seed production.