Logical Reasoning

PT148 · S3 · Q23 Scientist: Some colonies of bacteria

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Scientist: Some colonies of bacteria produce antibiotic molecules called phenazines, which they use to fend off other bacteria.

Conclusion / Hypothesis

Phenazines serve as molecular pipelines that give interior bacteria access to essential nutrients in the environment surrounding the colony.

Evaluate

There isn't any support provided for this hypothesis, so we're not evaluating an argument. Normally when we see the word 'hypothesis' we use our Curious Fact / Explanation mindset.

Here, the Curious Fact would just be,

However, we already have one valid answer -- they're antibiotic molecules that fend off other bacteria. The scientist's hypothesis is speculating an additional possible explanation for phenazines.

Usually with Curious Fact / Explanation problems, we're thinking about affecting the argument in two different ways: - considering Alternate Explanations for the curious fact - considering the plausibility of the Author's Explanation

But since we already have an explanation for phenazines, we wouldn't waste any time worrying, "Could there be some other reason for phenazines?" We already know that fending off bacteria is one reason.

So all we're concerned with is the plausibility of the author's additional explanation -- that phenazines act like pipelines that give interior bacteria access to essential nutrients in the environment surrounding the colony?

Picture a bacterial growth on a piece of moldy bread. It ends up looking like a big oval type shape. That whole shape is full of molecules of bacterium. The colony grows outward as it consumes more nutrients that facilitate its growth. But how do the molecules of bacterium on the inside of the colony get food? They're just surrounded by more bacteria, not by more bread to consume.

According to this scientist, phenazines are taking the nutrients from the not-yet-moldy bread on the exterior of the colony and shuttling it into the interior of the moldy spot in order to feed the bacteria living at "city center" (it's almost like when metropolitan cities are surrounded by a Beltway, and there are some roads that lead from the Beltway to the city center).

Goal

We just need an answer that makes it seem somewhat more plausible that phenazines act like a pipeline that shuttles nutrients from outside the moldy circle to the inside of the circle.

The most common way that LSAT strengthens the argument is "No Cause, No Effect", so that would mean something like,

23.

Which one of the following, if true, provides the most support for the scientist's hypothesis?

Correct
Bacteria colonies that do not
Why this is right
This answer is using the classic "No Cause, No Effect" type structure, but it's pretty confusing to process. The "problem" that phenazines are supposedly solving is, "How do we get nutrients from the outside of the colony to the inside? The bacteria in the inside of the colony are trapped. They're surrounded by other bacteria in the colony. They can't eat their own colony. So we have to pass them food from the exterior". If the bacteria has a wrinkled surface, then more of the colony is in direct contact with the surrounding environment. We don't have bacteria that are trapped. Most / all of them have some direct contact with the surrounding environment, so they can get their own food. Thus, since they don't have the problem of "how do we get food to the bacteria that has no direct contact with the environment", they don't have the evolutionary "solution" of phenazine pipelines.
Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.
48% picked this
The rate at which a
No Impact
This doesn't give us any reason to think these things work as pipelines to get food from the exterior of the colony to the trapped bacteria on the inside. Instead, this answer reinforces the other function of phenazines, defending against foreign bacteria. This answer is showing how phenazine production is proportional to "need to defend against foreign bacteria". Since the growth of phenazine is directly tied to this other function, if anything this answer would weaken the notion that phenazine is also integral as a food pipeline (this answer suggests that if there were no foreign bacteria in the surrounding environment, there might not even be phenazines).
10% picked this
When bacteria colonies that do
Weakens, if anything
If phenazines were nutrient-pipelines that help feed the starving centers of bacteria colonies, then we would expect colonies with phenazines to be more successful than colonies without. But according to this answer, if you throw both types of bacteria into nutrient-filled soil, they do about equally well.
10% picked this
Bacteria colonies that produce phenazines
No Impact
This is similar to (B). It's related to the known function of phenazines -- fending off bacteria. This answer provides nothing that helps support the idea that phenazines also perform the function of being a nutrient pipeline to the city-center of the bacteria colony.
24% picked this
Within bacteria colonies that produce
Unclear Impact
On one hand, maybe we could say, "See? The hypothesis is right. These bacteria that have phenazines have a problem with interior bacteria starving because they're trapped from nutrients!" But on the other hand, we could say, "Hmmm, looks like the hypothesis is wrong. Supposedly the phenazine should be piping nutrients to these interior bacteria, but it looks like they're not, since those interior bacteria are dying." I think LSAC intended this more as a Weaken idea.
8% picked this

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