#21 - Global Reference, Must Be True, AP, Principle

[me2987a]

Whys is A incorrect in this question when it follows the passage in lines 17-25?

[James Finch]

Hi ME,

The problem with answer choice (A) is that it doesn't exactly track with what is said in lines 17-25; instead it gives a very concrete sequence of predator and prey population increases that seems to run counter to the information given in lines 6-14. These lines tell us that the it is first the cyclamen mites (prey) that infest the strawberry fields, then their Typhlodromus predators in the second year; the arrival of the predators means that the prey population never grows enough to devastate the strawberry crops. So the prey population grows first, with the predator population growing rapidly to counter the prey growth. This is the opposite of the sequence that (A) presents.

Contrast that to the correct answer choice, (D), which is supported by lines 23-37. In (D), the predator population must be responsive to the variations of the prey population, just as we are told that Typhlodromus is to the cyclamen mites.

Hope this helps!

[bella243]

Could someone please explain why E is wrong? Is it because the author never speaks about cases when pesticides should be used - just that they do more harm than good?

[evelineliu]

Hi Bella,

(E) is wrong because it's out of scope. The author's suggestion is simply to control pests with predators, but they do not provide information on what type of pesticides, if any, the predators can tolerate.

Hope that helps!
Eveline

[ROMI92]

Hi,

Can you please explain why D is correct?

[Luke Haqq]

Hi ROMI92!

As James notes above, look to the second paragraph for support for answer choice (D). This question asks us what the author would think is fundamental to long-term predatory control of agricultural pests. Answer choice (D) states that the "predator population’s level of consumption of the prey species should be responsive to variations in the size of the prey population."

For an example of support from the second paragraph, lines 25-27 note that an "ability to survive at low prey densities also contribute to the predatory efficiency of Typhlodromus." The paragraph goes on to state that, in the winter, Typhlodromus mites can survive by eating other things even when the levels of cyclamen mites are low. This is an example of what the author sees as a long-term form of control of cyclamen mites--namely, Typhlodromus mites--is responsive to variations in the size of the prey species.