Kate: The recent decline in numbers of the Tennessee warbler, a North American songbird that migrates each fall to coffee...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Weaken

MEDIUM

...

Notes

Post a Query

Kate: The recent decline in numbers of the Tennessee warbler, a North American songbird that migrates each fall to coffee plantations in South America, is due to the elimination of dense tree cover that formerly was a feature of most South American coffee plantations.

Scott: The population of the spruce budworm, the warbler's favourite prey in North America, has been dropping. This is a more likely explanation of the warbler's decline.

Which of the following, if true, most seriously calls Scott's hypothesis into question?

The numbers of the Baltimore oriole, a songbird that does not eat budworms but is as dependent on South America coffee plantations as is the Tennessee warbler, are declining

The spruce budworm population has dropped because of a disease that can infect budworms but not Tennessee warblers

The drop in the population of the spruce budworm is expected to only be temporary

Many Tennessee warblers have begun migrating in the fall to places other than traditional coffee plantations

Although many North American songbirds have declined in numbers, no other species has experienced as great a decline as has the Tennessee warbler

Solution

Passage Analysis:

Text from Passage	Analysis
Kate: The recent decline in numbers of the Tennessee warbler, a North American songbird that migrates each fall to coffee plantations in South America, is due to the elimination of dense tree cover that formerly was a feature of most South American coffee plantations.	What it says: Kate thinks Tennessee warblers are declining because South American coffee plantations removed their dense tree cover What it does: Sets up Kate's explanation for the warbler population drop What it is: Kate's hypothesis about the cause Visualization: Before: Coffee plantations with thick tree cover + \(100\) warblers \(\rightarrow\) After: Coffee plantations without tree cover + \(60\) warblers
Scott: The population of the spruce budworm, the warbler's favourite prey in North America, has been dropping.	What it says: Scott points out that spruce budworms (the warbler's main food source in North America) are also declining What it does: Introduces a competing factor that contradicts Kate's South America focus What it is: Scott's counterevidence Visualization: North America: \(200\) spruce budworms \(\rightarrow\) \(80\) spruce budworms = less food for warblers
This is a more likely explanation of the warbler's decline.	What it says: Scott believes the budworm decline better explains why warblers are disappearing What it does: Directly challenges Kate's hypothesis and offers Scott's alternative explanation What it is: Scott's competing hypothesis

Argument Flow:

We have two people offering competing explanations for the same problem. Kate blames habitat loss in South America, while Scott blames food shortage in North America. The question asks us to find evidence that would weaken Scott's explanation.

Main Conclusion:

There isn't a single main conclusion here - we have two competing hypotheses. Kate concludes that habitat loss in South America caused the warbler decline, while Scott concludes that food shortage in North America is the more likely cause.

Logical Structure:

This is a classic competing explanations setup. Kate's logic: Habitat destroyed in South America \(\rightarrow\) Warblers decline. Scott's logic: Food source drops in North America \(\rightarrow\) Warblers decline. Since the question targets Scott's hypothesis, we need to find evidence that either supports Kate's view or shows that food shortage isn't the real problem.

Prethinking:

Question type:

Weaken - We need to find information that reduces belief in Scott's hypothesis that the decline in spruce budworm population (the warbler's favorite prey in North America) is the more likely explanation for the Tennessee warbler's decline.

Precision of Claims

Scott's claim is about causation - he's saying the budworm decline is MORE LIKELY than Kate's coffee plantation explanation to be the cause of warbler decline. We need to be precise about what would make his explanation less credible as the primary cause.

Strategy

To weaken Scott's hypothesis, we need information that either:

shows that despite budworm decline, warblers should still be doing fine if that were the real cause
demonstrates that the South American factor (Kate's explanation) is actually more impactful than the North American food issue
reveals that the budworm decline wouldn't actually affect warbler populations the way Scott assumes

Answer Choices Explained

The numbers of the Baltimore oriole, a songbird that does not eat budworms but is as dependent on South America coffee plantations as is the Tennessee warbler, are declining

This directly weakens Scott's hypothesis by showing that Baltimore orioles, which don't eat budworms but depend equally on South American coffee plantations, are also declining. If Scott's budworm explanation were correct, Baltimore orioles should be unaffected since they don't rely on this food source. The fact that both species are declining despite only one eating budworms suggests the common factor - dependence on South American coffee plantations - is the real cause, not the budworm decline.

The spruce budworm population has dropped because of a disease that can infect budworms but not Tennessee warblers

This actually supports rather than weakens Scott's hypothesis by providing a specific cause for the budworm decline (disease). While it clarifies why budworms are declining, it doesn't challenge Scott's core claim that this decline is causing the warbler population drop. If anything, it strengthens the causal chain Scott proposes.

The drop in the population of the spruce budworm is expected to only be temporary

This doesn't meaningfully weaken Scott's position. Even if the budworm decline is temporary, it could still be causing the current warbler decline that we're trying to explain. The temporary nature doesn't negate Scott's explanation for what's happening right now.

Many Tennessee warblers have begun migrating in the fall to places other than traditional coffee plantations

This information is ambiguous and doesn't clearly weaken Scott's hypothesis. Warblers migrating to other places could be either a cause or an effect of population decline, and it doesn't help us determine whether budworm decline or habitat loss is the primary driver of the overall population drop.

Although many North American songbirds have declined in numbers, no other species has experienced as great a decline as has the Tennessee warbler

This provides context about the severity of the Tennessee warbler's decline compared to other songbirds, but it doesn't help us evaluate whether Scott's budworm explanation or Kate's habitat explanation is more accurate. The uniqueness of the decline doesn't point toward either cause being more likely.

Rate this Solution

Tell us what you think about this solution

...

Forum Discussions

Start a new discussion

Post

Previous Attempts

Loading attempts...