Reading ComprehensionDifficulty: Hard

PT124 S4 P4 Q25 Explanation

Cyclamen Mites

A free, expert breakdown of this official LSAT Reading Comprehension question.

TopicsLocal PurposeScience

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Passage

Sometimes there is no more effective means of controlling an agricultural pest than giving free rein to its natural predators. A case in point is the cyclamen mite, a pest whose population can be effectively controlled by a predatory mite of the genus Typhlodromus. Cyclamen mites infest strawberry plants; they typically establish year, rapidly subdue the cyclamen mite populations, and keep them from reaching significantly damaging levels.

Typhlodromus owes its effectiveness as a predator to several factors in addition to its voracious appetite. Its population can increase as rapidly as that of its prey. Both species reproduce by parthenogenesis—a mode of reproduction in which unfertilized eggs develop into fertile females. Cyclamen mites lay three eggs per day over the the seasonal rises and falls of its prey, are common among predators that control prey populations.

Greenhouse experiments have verified the importance of Typhlodromus predation for keeping cyclamen mites in check. One group of strawberry plants was stocked with both predator and prey mites; a second group was kept predator-free by regular application of parathion, an insecticide that kills the predatory species but does not affect the cyclamen with Typhlodromus, but their infestation attained significantly damaging proportions on predator-free plants.

Applying parathion in this instance is a clear case in which using a pesticide would do far more harm than good to an agricultural enterprise. The results were similar in field plantings of strawberries, where cyclamen mites also reached damaging levels when predators were eliminated by parathion, but they did not attain were about 25 times more abundant in the absence of predators than in their presence.

What this question is testing

Local Purpose

Your task

Identify why the author included the referenced detail at that point in the passage — its function, not its content.

Common trap

Answers that merely repeat or summarize the topic of the detail instead of describing the role it plays.

Winning move

Ask what job the detail does for the paragraph, then for the passage's broader point.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
25.

The author mentions the egg-laying ability of each kind of mite (Second Paragraph) primarily in order to support which one

Answer choices

  1. Word Blender3% picked this

    Mites that reproduce by parthenogenesis do so at approximately

    The fact that they reproduce by parthenogenesis is presented consecutively with the idea that the reproductive rates are approximately equal, but these two things aren't connected the way this answer suggests.

  2. Strong: "typically" Opposite7% picked this

    Predatory mites typically have a longer reproductive life span than do

    This seems to go against the local gist that the reproductive cycles are essentially a match. Yes, the Typhlo's cycle is 8-10 days at lower density while the cyclamens cycle is 4-5 days at a higher density, but the point is that the total number of offspring over those cycles is about the same. If we swapped those two cycles, the passage would be making the exact same point, which is that part of what makes Typhlodromus an effective predator is that it can reproduce as quickly as its prey.

  3. Word Blender21% picked this

    Typhlodromus can lay their eggs in synchrony with

    This is close. We know that overall the population of each mite is increasing at a similar rate, but it's not quite synchrony, since the cyclamens cycle is 4-5 days and the Typhlodromuss cycle is 8-10 days. Synchrony is a term stolen from the NEXT factor introduced, which is that overall population levels of Typhlodromus have seasonal synchrony with populations of cyclamen.

  4. Correct68% picked this

    Typhlodromus can reproduce at least as quickly as

    Why this is right

    This is a closer match than (cyclamen) was to the meaning of "its population can increase as rapidly as that of its prey".

    Skill tested: Local Purpose · how this choice captures the passage's function is the move to repeat next time.

  5. Opposite1% picked this

    The egg-laying rate of Typhlodromus is slower in the presence of cyclamen mites than it

    We learn that Typhlodromus ramps up reproduction in response to lots of cyclamens and stops reproducing when cyclamens go away.

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