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Difficulty: MediumStrengthen

Entomologists studying leafcutter ants (*Atta cephalotes*) observed that worker ants harvest fresh leaves to nourish their symbiotic fungal gardens (*Leucoagaricus gongylophorus*). When foragers supply leaves containing chemical compounds that inhibit fungal development, the colony completely ceases collecting foliage from that specific plant species within two days, even though the worker ants themselves suffer no toxic effects from the plant. The entomologists hypothesize that the cultivated fungus emits chemical signaling molecules that condition the ants to discontinue harvesting harmful vegetation.

Statement: The finding that worker ants persist in collecting toxic leaves when supplied with fungal gardens whose chemical secretions are chemically inhibited, even as the fungal garden suffers visible tissue necrosis, provides logical support for the entomologists' hypothesis.

Answer: Answer

Answer

True, because establishing that blocking fungal chemical secretions prevents the foraging change despite visible fungal decay confirms chemical signaling as the governing causal mechanism and eliminates the competing explanation of physical observation.
The statement is correct because the described experimental finding demonstrates that blocking chemical secretion prevents the avoidance behavior despite the presence of visible fungal damage. This confirms that chemical cues are the active mechanism and eliminates the alternative explanation that ants react directly to physical deterioration.

Step-by-Step Solution

1
Identify the argument's premises and the central hypothesis.
Premise: Worker ants stop gathering toxic leaves within 48 hours despite being immune to the plant toxins. Hypothesis: The fungus produces chemical signals that condition the ants to avoid the plant.
Understanding the precise causal link asserted between fungal chemical emissions and ant behavioral change is necessary to evaluate supportive evidence.
2
Analyze the reasoning gap and potential alternative explanations.
The argument assumes that chemical cues, rather than visual or physical cues of fungal damage, trigger the ants' avoidance behavior.
Strengthening a causal claim requires providing evidence that validates the specific mechanism or rules out alternative triggers.
3
Evaluate the impact of the supplementary statement.
When chemical cues are blocked, avoidance fails to occur even though visible necrosis is present, proving chemical cues are necessary and that physical necrosis alone does not trigger avoidance.
This experimental control isolates the chemical variable and eliminates the rival hypothesis of visual or structural cues, thereby strengthening the hypothesis.

Key Concept

Causal strengthening via control of alternative mechanisms
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