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Difficulty: Very hardResolve the Paradox

To control the silver-winged locust, agricultural researchers introduced a parasitic wasp that preys exclusively on locust larvae. Comprehensive field data confirm that the wasps are highly effective, consistently reducing the total number of locust larvae in the region by 60 percent each spring. Yet, over the five years since the wasps were introduced, the total adult population of silver-winged locusts recorded during the summer mating season has consistently doubled compared to the years immediately preceding the intervention, even though the locusts' habitat size, available food supply, and other predator populations have remained strictly constant.

Which of the following, if true, most helps to resolve the apparent discrepancy described above?

  1. Before the wasps were introduced, the extreme density of the larval population caused severe competition for a scarce nutrient, resulting in the starvation of nearly all larvae just before they reached adulthood.Answer
  2. B
    The methodologies used by the researchers to estimate the larval population heavily oversampled the specific agricultural zones where the wasps had been most densely released.
  3. C
    The parasitic wasps exclusively hunt during the early spring, meaning that the smaller subset of locust larvae that hatch in late spring face absolutely no threat from wasp predation.
  4. D
    The parasitic wasps carry a highly contagious viral pathogen that is lethal to adult silver-winged locusts, frequently transmitting this virus to the larvae that manage to survive the initial predation.
  5. E
    Local agricultural boards have fiercely debated whether the initial financial cost of introducing the parasitic wasps was justified by the resulting changes in the regional ecosystem.

Answer

The correct answer states that before the wasps were introduced, extreme larval density caused severe competition for a scarce nutrient, starving nearly all larvae before adulthood.
The correct answer resolves the paradox by identifying a compensatory mechanism. If the initial larval population was so massive that nearly all of them died from competition before reaching adulthood, reducing that initial population by 60 percent would drastically reduce competition. Since the total food supply remained constant, this allows a much higher absolute number of the remaining larvae to survive to adulthood, perfectly explaining how a 60 percent reduction in larvae leads to a 200 percent increase in adults.

Step-by-Step Solution

1
Identify the two seemingly contradictory facts presented in the stimulus.
Fact 1: Parasitic wasps consistently reduce the total locust larvae population by 60 percent. Fact 2: The adult locust population has nevertheless doubled without any increase in food supply or habitat.
A 'Resolve the Paradox' question requires pinpointing exactly what makes the situation confusing before evaluating the answer choices.
2
Determine what a correct answer must accomplish.
The correct answer must explain how a massive reduction in the initial stage of a population (larvae) can directly lead to a massive increase in the final stage of that same population (adults), without contradicting the 60 percent reduction rate.
The correct answer must bridge the two premises, allowing both to be simultaneously true in the real world.
3
Evaluate the answer choices against the required function.
The option describing severe competition for a scarce nutrient explains the discrepancy. If the wasps eliminate 60 percent of the larvae, the remaining 40 percent face drastically reduced competition, allowing a much higher absolute number of individuals to secure the nutrients needed to survive to adulthood.
This provides the missing causal link (alleviation of density-dependent mortality) that logically reconciles the reduction in larvae with the increase in adults.

Key Concept

Resolve the Paradox
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Resolve the Paradox

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