#10 - Many species of plants produce nectars known as

[Administrator]

Complete Question Explanation

Strengthen, CE. The correct answer choice is (B).

This is a Strengthen question. As always, our first step for Strengthen questions is to identify the conclusion. Here, that's the last sentence of the stimulus. The rest of the stimulus is premises. So our argument looks like this.

Premise 1: Some plants produce EFN
Premise 2: EFN attracts certain ants that defend the plants against leaf-eating insects
Premise 3: Studies show jumping spiders are attracted to EFN plants, and eat the nectar.
Conclusion: Jumping spiders defend against leaf-eating insects.

For Strengthen questions, we're on the lookout for any "gap" between the premises and our conclusion. Does our conclusion follow 100% logically from our premises? Or is there some sort of leap.

Here, there is a large gap between the premises and our conclusion. The premises tells us that ants are attracted to EFN plants and defend them; the premises then tells us that jumping spiders are also attracted to EFN plants. Based on that and nothing else, the argument concludes that jumping spiders defend these plants against leaf-eating insects.

Here's a parallel argument for the NBA fans out there: "The Milwaukee Bucks play basketball at a very fast pace. They are one of the best teams in the league. The Minnesota Timberwolves also play basketball at a very fast pace. Therefore they must also be one of the best teams in the league." This argument of course has a serious gap: it assumes that just because one fast team is good, every fast team must be good.

Similarly, our argument seems to assume that just because one group (ants) is attracted to EFN plants and defends the plants, that means another group (jumping spiders) that is attracted to EFN plants will also defend the plants.

So the argument provides little support for its conclusion. As such, we are looking for any answer choice that provides any evidence whatsoever for the conclusion that jumping spiders defend the plants. There are many possible answer choices that could provide support, so it's difficult to create an exact Pre-Phrase. Still, before coming down to my answer choices I might think of a possible answer or two, such as "Things that eat EFN nectar also tend to eat leaf-eating insects". With that, I come down to my answer choices, looking for the one that provides some evidence of jumping spiders defending the plants from leaf-eating insects.

Answer Choice (A). Does nothing to provide evidence for the stimulus's conclusion that jumping spiders defend the plants. In fact, it doesn't discuss anything about the spiders.

Answer Choice (B). This is the correct answer. Adding jumping spiders into an environment caused the number of EFN producing plants to increase. This is at least possible evidence that the spiders played a role in defending the EFN producing plants. It doesn't prove the conclusion in the stimulus, but it at least provides some modicum of support for it.

Answer Choice (C). Again, this choice doesn't discuss anything about the spiders.

Answer Choice (D). At least this answer choice discusses the spiders. But it doesn't strengthen our stimulus's conclusion that jumping spiders defend the plants. So what if other types of spiders also defend the plants? That doesn't affect our conclusion one way or the other. We're looking for some piece of evidence that jumping spiders defend the plants. Pointing out that other types of spiders don't defend the plans does not function as that necessary piece of evidence.

Answer Choice (E). Again, this choice does nothing to strengthen the connection between jumping spiders and defending the plants. Answer Choices (A), (C), and (E) can all be quickly ruled out for this reason.

[vbkehs]

So the stimulus/question/answers read:

Many species of plants produce nectars known as extrafloral nectories (EFNs), which are known to attract certain ants that defend the plants against leaf-eating insects. Recently, greenhouse experiments have found that jumping spiders jump onto plants with active EFNs six times more often than they jump onto plants without EFNs, and regularly eat the nectar. So, like the ants, jumping spiders apparently defend EFN-producing plants against leaf-eating insects.

Which one of the following, if true, would most strengthen the argument above?
A For many species of nectar-producing plants, productivity is increased when a plant is protected from leaf-eating insects.
B In field experiments, the introduction of jumping spiders into an environment was followed by a significant increase in the population of EFN-producing plants.
C Some species of EFN-producing plants cannot survive without some outside agent protecting them from leaf-eating insects.
D Experiments with types of spiders other than jumping spiders suggest that these other types of spiders do not defend EFN-producing plants.
E Regions with large populations of ants also tend to have large populations of EFN-producing plants.

Between B and D (because these were the only answer choices mentioning the jumping spider), I chose D because I thought that "other types of spiders [not defending] EFN-producing plants" eliminated an alternate explanation (that spiders in general, or of other varieties could protect the plants). Can you explain why B was a stronger option and what's wrong with D?

[Paul Marsh]

Hi vbkehs! Let's walk through this one. Please refer to the full explanation I posted above. Hope that helps! Please let us know if you have any additional questions!

[vbkehs]

I understand now, thanks for your help!

Hi vbkehs! Let's walk through this one. Please refer to the full explanation I posted above. Hope that helps! Please let us know if you have any additional questions!

[leejihyesarah]

Wasn't it a little bit of a stretch to say that increasing the population of EFN producing plants = because they were defended from the leaf- eating insects by the jumping spiders?? That's what drew me away from this correct answer choice...

[Robert Carroll]

leejihyesarah,

It is a bit of a stretch! But two things:

1. This is a Strengthen question. Any answer that makes the conclusion more likely to any degree is correct. So, does answer choice (B) make the conclusion more likely? Yep!

2. There is no answer here that strengthens the argument besides answer choice (B), so it's a stretch vs absolutely no help (and maybe some wrong answers weaken!). So answer choice (B) helps a little, nothing else is positive at all, so again, it's correct.

Robert Carroll