#23 - Global Reference, Main Point

[gabyd33]

Hi PowerScore,

After reading the passage analysis in the RC Bible and the question explanation, I still don't understand how a reader is meant to conclude that the main point of this passage is about the use of natural predators to control agricultural pests, instead of the predator-prey relationship between cyclamen mites and Typhlodromus mites. Aside from references in lines 1-3 and 34-37, there is no allusion to a greater point. If the example is the whole passage, how is a reader supposed to realize that the main point is not about the example. In other words, what did I miss that I should have been looking out for?

Thanks in advance!

[Rachael Wilkenfeld]

Hi Gaby,

Did you mean to post this is a different question thread? Number 23 is not about the main point, but is about the potential alternate experiment.

Overall, this passage is using the mites as an example of a larger point. It starts off by telling us the main point---the use of natural predators can be a highly effective means of pest control. The passage continues by stating that the mites are an example of the process that the passage introduced. You can think of the main point of the passage here as a frame---it's not explicitly and repeatedly called to in every part of the passage, but it's framing the information presented. The author is clear that this isn't JUST a story of mites, but instead a broader point about pests and predators.

Hope that helps

[mollylynch]

Hi,

Where is the support for A in the passage?

[Rachael Wilkenfeld]

Hi Molly,

The support is in the last two paragraphs of the passage. When the Typhlodromus mite is eliminated/harmed by the parathion, the cyclamen mites flourish because they have no predator to keep their numbers in check. But if there were a pesticide that attacked the cyclamen instead of the Typhlodromus mites, they would both have a predator AND a pesticide lowering their numbers. We wouldn't know what would happen with the Typhlodromus mites, but we can be confident that the cyclamen would decrease in population.

Hope that helps!

[baughy878]

Hello!

I believe A is correct because, despite its lack of connection to insecticide X, it would still most likely occur because of what we know from the passage. Is that correct?

Additionally, could you briefly go over why the other answers are incorrect? Thank you!

[Rachael Wilkenfeld]

Hi baughy,

Let's talk through these. We know cyclamen mites reproduce like wild. Three eggs per day over four or five days lead to 12 to 15 eggs per mite. Typhlodromus mites reproduce two to three eggs per day over eight to ten days which results in up to 30 eggs per mite. The suggested pesticide would lower the number of cyclamen in treated plots by reducing the number of cyclamen egg per mite, but untreated plots would also have decreased cyclamen because the typhlodromus mites would ramp up their reproduction to compensate for the extra cyclamen. We need the cyclamen to decrease in both plots.

Answer choice (A) is correct, and describes this.

Answer choice (B) wouldn't describe cyclamen decrease correctly. We don't know how they would be decreased in pesticide plots compared to the plots with the typhlodromus mites. They both should result in a decrease in cyclamen, but we don't know enough to compare the two control methods.

Answer choice (C): This is incorrect because it misunderstands reproductive synchronicity. The key isn't the exact ratio, but that the typhlodromous mites can adapt its reproduction based on the number of prey they have.

Answer choice (D): We don't know that the typhlodromus mites would increase in the treated plot. Once the cyclamen mite population decreases, the typhlodromus mites should also decrease.

Answer choice (E): There's no reason to think that the cyclamen mites would ever get to dangerous levels in the treated plots.

Hope that helps!