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Difficulty: MediumMethod of Reasoning

Consider the following argument:

Plant biologist: Many botanists maintain that when tomato plants are attacked by herbivores, they warn neighboring plants primarily through underground mycorrhizal fungal networks. They point out that neighboring plants connected by fungal hyphae activate defensive genes faster than isolated plants. However, this interpretation overlooks that airborne volatile chemicals released during herbivory travel rapidly and trigger identical defensive responses in nearby plants. In experiments where airflow between plants was completely blocked while fungal connections were preserved, neighboring plants exhibited no increase in defensive gene expression. Thus, the accelerated defense activation observed in previous studies is driven by airborne signaling rather than underground fungal networks.

Match each excerpt from the biologist's argument to its precise argumentative role.

  • When tomato plants are attacked by herbivores, they warn neighboring plants primarily through underground mycorrhizal fungal networks.A competing hypothesis whose causal adequacy the author challenges.
  • Neighboring plants connected by fungal hyphae activate defensive genes faster than isolated plants.An empirical finding cited by proponents of a rival theory that the author reinterprets.
  • In experiments where airflow between plants was completely blocked while fungal connections were preserved, neighboring plants exhibited no increase in defensive gene expression.Experimental evidence introduced to demonstrate that the rival mechanism alone is insufficient to produce the effect.
  • The accelerated defense activation observed in previous studies is driven by airborne signaling rather than underground fungal networks.The overall conclusion that the argument establishes.

Answer

The statement about warning via fungal networks matches the competing hypothesis being challenged; the observation that hyphae-connected plants activate genes faster matches the empirical finding cited by proponents that is reinterpreted; the experiment blocking airflow matches the evidence demonstrating the rival mechanism is insufficient; and the claim attributing defense activation to airborne signaling matches the main conclusion.
The author proceeds by introducing an existing scientific hypothesis, acknowledging the empirical data upon which it was based, presenting a confounding factor (airborne signaling), providing decisive experimental evidence that isolates the pathways, and drawing the conclusion that the confounding factor is the true causal driver.

Step-by-Step Solution

1
Identify the conclusion and target of the argument
The final sentence beginning with 'Thus' represents the primary conclusion, while the opening sentence states the opposing hypothesis being contested.
Determining the overarching claim and the target position sets the structural foundation of the argument.
2
Differentiate between the two empirical premises
The second sentence provides the rival camp's supporting evidence, whereas the fourth sentence provides new experimental counter-evidence isolating the fungal pathway.
Method of reasoning questions require distinguishing evidence cited by opponents from evidence introduced by the author to defeat a rival hypothesis.
3
Map each excerpt to its exact structural role
Excerpt 1 pairs with the challenged competing hypothesis, Excerpt 2 pairs with the reinterpreted finding, Excerpt 3 pairs with the experimental counter-evidence, and Excerpt 4 pairs with the overall conclusion.
Aligns the textual claims with standard abstract structural descriptions without misattributing intermediate roles.

Key Concept

Argument Structure and Method of Reasoning
Estimated Time:1m 15s
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Topics

Method of Reasoning

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