Examkin

Question

Difficulty: HardWeaken

Botanist: The traditional view among ecologists is that the rapid decline of the indigenous Luminis plant population in the valley was caused by an influx of herbivorous beetles. However, recent field data reveals that during the five years immediately preceding the plant's near-extinction, the plants significantly decreased their production of toxic alkaloids—their primary natural defense against the beetles. If the beetles were truly the primary threat, the plants would have evolved to increase, rather than decrease, their alkaloid production. Therefore, the decline of the Luminis plant must have been caused by a different environmental factor, such as nutrient depletion in the soil.

Which one of the following, if true, most weakens the botanist's argument?

  1. A
    Extensive soil testing in the valley confirms that the levels of essential nitrogen and phosphorus plummeted dramatically during the same five-year period.
  2. B
    The recent field data was collected using flawed chemical analysis methods that consistently underreported the true levels of alkaloids present in the plants.
  3. The herbivorous beetles recently developed a unique physiological reliance on the Luminis plant's toxic alkaloids, leading them to selectively target and devour only those plants with high alkaloid levels.Answer
  4. D
    The herbivorous beetles are known to occasionally migrate to neighboring agricultural farms when their preferred wild food sources are entirely depleted.
  5. E
    The toxic alkaloids produced by the Luminis plant are structurally different from the toxic compounds produced by other plant species in the same ecological family.

Answer

The correct answer states that the herbivorous beetles evolved a reliance on the alkaloids, selectively devouring plants with high alkaloid levels.
The correct answer undermines the botanist's argument by providing an alternative, counter-intuitive explanation for the premise. The botanist assumes that a decrease in defensive alkaloids means the beetles were not a threat. However, if the beetles evolved to specifically target and consume plants with high alkaloid levels, then possessing those alkaloids became a deadly disadvantage. In this scenario, the plant population would naturally evolve to produce fewer alkaloids precisely because the beetles were the primary threat. This completely destroys the botanist's assumption and supports the traditional view that the beetles caused the decline.

Step-by-Step Solution

1
Identify the core conclusion of the argument.
The botanist concludes that the decline of the Luminis plant was caused by an environmental factor (like nutrient depletion), not by the herbivorous beetles.
Evaluating any argument requires strictly defining the specific point the author is attempting to prove.
2
Identify the primary premise and the underlying assumption.
The premise is that the plants decreased their production of defensive toxic alkaloids. The assumption is that if beetles were the main threat, evolutionary pressure would force the plants to increase, not decrease, this defense.
Weakening an argument usually requires identifying and attacking the unstated assumption linking the premise to the conclusion.
3
Determine the criteria for a correct weakener.
A correct answer must provide a reason why the beetle threat would actually CAUSE the plants to decrease their alkaloid defense.
By explaining the premise in a way that points back to the beetles as the threat, you dismantle the author's logic completely.
4
Evaluate the options against this criterion.
The option showing that beetles selectively eat plants with high alkaloids perfectly explains why alkaloid production dropped—it was an evolutionary response to avoid the beetles.
This directly attacks the botanist's assumption and re-establishes the traditional view.

Key Concept

Argument Evaluation: Weaken (Alternate Explanation for Evidence)
Rate this question

Topics

Weaken

More questions from this topic