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Difficulty: HardFlaw in the Reasoning

Ecologist: A plant species can successfully colonize high-salinity coastal marshes only if it produces specialized root membrane transport proteins that actively exclude sodium ions. Recent genetic analysis revealed that the coastal cordgrass population in the northern estuary possesses active genes encoding these specialized transport proteins. Therefore, this cordgrass population will establish a thriving, permanent colony in the northern estuary marshes.

Which one of the following most accurately describes a flaw in the ecologist's reasoning?

  1. A
    generalizes about the physiological traits of all marsh plants based on a sample consisting entirely of northern cordgrass
  2. infers that a characteristic essential for colonizing a habitat is by itself enough to guarantee that colonization will succeedAnswer
  3. C
    disregards the possibility that the genetic analysis of the northern cordgrass population was methodologically flawed
  4. D
    relies on the assumption that every environmental factor affecting coastal cordgrass remains permanently constant
  5. E
    confuses an intermediate evidentiary finding regarding gene expression with the overarching conclusion of the argument

Answer

The argument infers that a characteristic essential for colonizing a habitat is by itself enough to guarantee that colonization will succeed.
The stimulus establishes that producing specialized root membrane transport proteins is a necessary condition for a plant species to colonize high-salinity marshes, introduced by the indicator phrase 'only if'. The ecologist then establishes that the northern cordgrass satisfies this requirement and concludes that colonization will inevitably succeed. The flaw in this reasoning is that satisfying a requirement does not guarantee success; other essential factors (such as soil nutrients, competition, or water depth) may prevent colonization.

Step-by-Step Solution

1
Analyze the formal structure of the premises
Premise 1 establishes a conditional rule: Successful colonization requires specialized transport proteins (Colonization -> Transport Proteins). Premise 2 states that northern cordgrass possesses active genes for these proteins.
Deconstructing conditional relationships into necessary and sufficient components reveals the boundaries of valid deduction.
2
Examine the relationship between the premises and the conclusion
The ecologist concludes that the cordgrass will definitely colonize the marshes simply because it possesses the transport proteins.
Identifying the gap between having a prerequisite and achieving the guaranteed outcome exposes the logical fallacy.
3
Match the identified flaw with the correct description
The argument commits a conditional error by treating a necessary condition (a required characteristic) as a sufficient condition (one that guarantees the outcome).
Selecting the option that accurately describes this conditional confusion without relying on out-of-scope flaws or attacking premises.

Key Concept

Mistaking a Necessary Condition for a Sufficient Condition
Estimated Time:1m 45s
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Topics

Flaw in the Reasoning

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