LR Question 23 Explanation, by LSATHacks
QUESTION TEXT: Scientist: Some colonies of bacteria produce antibiotic…
QUESTION TYPE: Strengthen
CONCLUSION: Phenazines bring nutrients to bacteria in the interior of the colony.
REASONING: No evidence is given for the hypothesis.
ANALYSIS: To answer this, you must imagine a colony of bacteria. The question says “interior bacteria”. So presumably some parts of the colony are in touch with the outside environment, and some aren’t.
The right answer is creative. I couldn’t have prephrased it. But I saw it supported the idea that interior bacteria couldn’t get nutrients without phenazines.
___________
- CORRECT. Think about it. If interior bacteria need phenazines for nutrients, what will happen without phenazines? The interior bacteria will suffer. So this wrinkled shape is a response. It puts more interior bacteria in direct contact with the outside.
If phenazines are present, then it seems wrinkling is not required, because the phenazines send nutrients directly inside. - This answer has nothing to do with nutrients.
- This is a false comparison. We don’t know what happens to colonies in nutrient-poor soil. The answers implies that they will grow less quickly without phenazines, but that’s not something we can assume – we need a direct comparison.
- This answer is about how well bacteria can fend off other bacteria. The hypothesis was about phenazines and interior nutrition, not about how phenazines help fend off other bacteria.
- This doesn’t help the argument. The hypothesis is that phenazines help interior bacteria! It’s not useful to learn that interior bacteria die faster than outer bacteria.
(Technically, this is a false comparison. It’s useless information. We don’t know if interior bacteria are also more likely to die without phenazines.)
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Question: In identifying “false comparison” as the logical fallacy exercised in both, c & e, is the comparison at fault related to answer choice vs stimulus. Or is it related to the constituent elements involved in the answer choice, alone?
In C: they told us what happens in nutrient rich soil, but neglected to tell us what happens in other soil.
In E: They told us what happens in bacterial colonies that produce phenazines. They neglected to tell us what happens in colonies that don’t.
I’m not sure I’d hang my hang on false comparison being the decisive reason those are wrong, but it’s important to notice when the LSAT implies a comparison but didn’t actually provide one.
Note: This is an old comment but I wanted to clarify the point.
(C) was quite tempting for me, and it indeed strengthens the argument.
But, it does not do it as obviously as (A). Whenever I am stuck between to answer choices in a strengthen-question (and it happens the most to me in those type of questions), I check which answer choice makes the argument more “bullet-proof”.
In this case, I can hardly imagine another reason why the bacteria would form the wrinkled surfaces besides getting nutrients in (A). While, in (C), I can think of several reasons why it could be wrong:
– Who says that in a nutrient-poor soil, they would not grow as quickly or even faster (unlikely, though).
– It could be the case that they normally grow slower because, without P, it is harder for them to fend off other bacteria. Nutrient-rich soil might just compensate for that and make them grow faster.
C doesn’t strengthen though. The argument makes no claims about the relative growth rates of bacterial colonies with and without phenazines. The only claim is that phenazines act as pipelines.
There’s no grounds for calling this unlikely. We have no information. Interpreting C as a strengthen requires adding on several assumptions the argument didn’t make.
Don’t put in work making an answer right by adding assumptions to it. An answer has to stand on its own merits.
Note: This is an old comment but I wanted to clarify the point.
I had eliminated (A) because I thought it required me to make an extra assumption that lack of nutrients would cause a wrinkled surface. I hadn’t liked any of the other answer choices but I had felt that this extra assumption was too big a leap since the stimulus never stated a relationship between wrinkled surfaces/non wrinkled surfaces and nutrients absorbed. What are your thoughts?
“an extra assumption that lack of nutrients would cause a wrinkled surface.”
There’s no assumption required. The answer choice says explicitly that lack of phenazines (not nutrients) causes wrinkles. We don’t have to assume anything: the answer directly states that lack of phenazines causes wrinkles.
The fact that wrinkled surfaces increase the amount of bacteria in contact also directly supports the argument. The claim was that phenazines provide nutrients to interior bacteria. This implies that interior bacteria can’t get them otherwise. The right answer says that without phenazines, wrinkles form to give more bacteria direct access.
This is consistent with the idea that bacteria either need direct access or phenazines. Hope that helps!
Know this is long after your reply but I am having a hard time agreeing that no assumptions have to be made and that the answer choice explicitly tells you that lack of phenazines causes wrinkles. It just states “Bacteria colonies that do not produce phenazines form wrinkled surfaces”. It could be anything that causes the wrinkled surfaces that is not at all related to phenazines. It also doesn’t mention what happens to bacteria colonies that DO produce phenazines – maybe they also form wrinkles. In that case, it would seem whether or not the colony produces phenazines, wrinkled surfaces may form and has no impact on interior bacteria receiving essential nutrients. Is this line of thinking flawed?
We’re looking for the answer choice that provides the most support for the hypothesis. This answer choice provides one potential form of support for the hypothesis. It’s true that:
(1) The wrinkled surfaces might not be at all related to phenazines
(2) The answer choice doesn’t mention what happens to bacteria colonies that do produce phenazines
But, these two points are making assumptions outside what’s given to us in the answer choice. We need to take the answer choice as it is, and in it’s current form, it does provide some validity to the scientist’s hypothesis.
I 100% agree, I think there is a logical leap from the stimulus to “Bacteria colonies that do not produce phenazines form wrinkled surfaces.” The stimulus doesn’t talk about colonies that don’t produce Phenazines.