Q23 - Certain bacteria that produce hydrogen

[ohthatpatrick]

I had similar issues trying to get a mental picture of the first couple sentences. For me, it's confusing because oxygen is presumably in gaseous form, so it's everywhere. How could the bacteria possibly avoid being directly exposed to it?

I wasn't sure if the way you were describing your understanding of those sentence was an attempt to convert them into conditional ideas. Even though a lot of Inference questions involve conditional logic, I didn't see this one trying to create a chain of logic, so I was less inclined to try converting the ideas to conditional logic.

That said, we could probably say from the first sentence that

Exp directly to Oxygen --> Certain bacteria would die

And from the second sentence, we could probably say

Cert bact didn't have HS ---> They'd be harmed by oxygen

But let's get back to just forming an effective mental picture. I'm thinking of this HS as a cloud of vapor or a slime that totally covers the bacteria colony. That way, it can effectively neutralize any oxygen trying to get through. Also, if the HS is an external shield of vaporslime (new word, just coined it), then it's easier to picture how other organisms would come into contact with the HS and be killed by it.

I think the other picture you (and I) had at one point is that this HS is still in the bacteria's body ... whatever their equivalent of a colon would be ... and so it was confusing to think that oxygen was interacting with HS inside the bacteria (yet still not harming the bacteria?) and that HS inside the bacteria was somehow killing other organisms.

Since that picture just makes no sense, we have to assume that the HS waste is external to the bacteria.

A) is pretty much a paraphrase of the final sentence, synthesizing in what we've learned earlier about what's good (food) and bad (oxygen) for the survival of these bacteria.
B) the method by which the HS kills the other bacteria is out of scope. it doesn't have to be stealing oxygen. HS might just be toxic in and of itself.
C) MOST is too extreme. we have no idea if over 50% of all organisms could be a food source for these bacteria.
D) This is a reversal of A's logic. (A) said "if they can neutralize oxygen and find a food source, they can thrive indefinitely". (D) says "if they can thrive indefinitely, they can neutralize oxygen and find a food source". In more technical language, the stimulus established that [food + no oxygen] is sufficient for thriving, not that it's necessary for thriving.
E) ANY is too extreme. We only know about "certain bacteria that produce HS".

Hope this helps. Let me know if you want clarification on anything.


#officialexplanation

[LSAT-Chang]

I got this question right (was lucky) but want to go through the stimulus in detail. I wasn't exactly sure what each lines were meant to say.

"Certain bacteria that produce hydrogen sulfide as a waste product would die if directly exposed to oxygen"

Does this first sentence mean that if a bacteria released HS as a waste product, it would die if it was exposed to oxygen (without the HS being in the body)??? I understood it as to mean that these HS being in the bacteria is bad because if it meets an oxygen, then the oxygen kills the bacteria -- so bad.. right?

"The hydrogen sulfide reacts with oxygen, removing it and so preventing it from harming the bacteria"

Does this next sentence mean that if HS within a bacteria reacts with oxygen, it removes the oxygen and so the bacteria isn't harmed??

"The hydrogen sulfide tends to kill other organisms in the area, thereby providing the bacteria with a source of food"

Does this mean that the HS is still in the bacteria? Or released as a waste product and just floating around? I was so confused where this HS is when it kills other organisms, since I wasn't sure if I had understood the first sentence properly as well. Please please help

[LSAT-Chang]

Thanks Patrick, I really like your explanation of the "slime" -- and it does make it easier to "mentally" see what is going on. However, I am still confused about the very first sentence. I can see that the "slime" idea works for the rest of the sentences, but I don't understand how certain bacteria would DIE if exposed to oxygen when it produces hydrogen sulfide. It feels like the first and second sentences contradict each other, which I bet it doesn't -- but I don't know why I see it that way. If like you said, this "slime" is covering the bacteria, how is it possible for the bacteria to DIE when it is exposed to oxygen -- when in fact, the next sentence tells us that this slime removes the oxygen! Do you see my point? I'm probably just misunderstanding something in the first sentence but I don't know what it is..

[rickytucker]

This one threw me through a loop. It's intentionally badly written with a combination of a misdirect, lack of indicator words, and vague references.

After the first sentence establishes if directly exposed to oxygen --> dead bacteria. It then goes on to presumably (misdirect) explain how this oxygen exposure kills the bacteria because the HS reacts with the oxygen, removing it (vague reference) and so preventing it (vague reference) from harming the bacteria. At this point I reread from the beginning because of the apparent contradiction.

At some point I realize that just because the HS reacts with the oxygen does not mean that the bacteria has been "directly exposed" to the oxygen. It's not explaining how the oxygen exposure kills the bacteria but, rather, how this certain bacteria's two-punch system allows it to thrive indefinitely by (1) removing a threat and (2) provide itself with food. They also conveniently left out an indicator word in-between the first and second sentence, something like "however" or "but since" would have been nice.

The test-makers at it again by exploiting my preconceived notions that its passages will be structurally solid and properly written.

[T.J.]

Some folks may have problems absorbing the meaning of this question or they feel like this question is poorly written and they expect something better than this from the LSAC. However, a distaste of the LSAT won't help us at all. The only goal is to get the question right. As future lawyers, we should not expect everything in law to be perfectly written. Sorry, I'm a philosophy major...

As I understand it, the stimulus first introduces two functions of hydrogen sulfide - removing oxygen and providing food. Then the last sentence says that "as a result", a colony of these bacteria continue to thrive indefinitely. "As a result" means "because of this" or "for the reasons mentioned above". So the stimulus is saying that because hydrogen sulfide can do these two things for the bacteria, they can continue to thrive indefinitely. Then what's the link? It is that the bacteria can continue to produce HS indefinitely to serve itself for elimination of oxygen and source of food.

The connection might not be as strong as expected, but this is a most strongly supported question after all. Hope this is helpful.

[kyuya]

Beginning to really hate hard most strongly supported Q's..

if directly exposed to oxygen ---> certain bacteria that produce hydrogen sulfide as a waste product would die

In this group of CERTAIN bacteria, the sulfide reacts with the oxygen which removes the oxygen and prevents it from harming bacteria.

Okay so what we know so far is:

In CERTAIN bacteria, sulfide removes oxygen and helps the bacteria stay alive. BUT WAIT! That's not all that the sulfide does. The sulfide also kills other organisms in the area, which this certain subgroup of bacteria then eat.

Because the sulfide removes oxygen + and kills bacteria in the area providing food, now this certain sub group of bacteria can live forever.

Wow! Sulfide is pretty amazing for this particular subgroup of bacteria. It gets rid of deadly oxygen and provides infinite food. But what if we didn't have the sulfate? Would it be reasonable to think the benefits given to the bacteria would disappear? Sure it is. Look, sulfide is the reason the oxygen is being removed, and it is the reason bacteria is being killed and served up as infinite food. Take away the bacteria's life line (sulfate) and it would no longer be able to survive.

(A) This answer choice picks up on the last bit of my explanation. If it did indefinitely continue to produce the sulfide, the benefits of the sulfide would probably be pretty hard to keep. The sulfide is reacting with the oxygen, suggesting that it is necessary for it to be there - opposed to it giving the bacteria a benefit that would now stay even if the sulfide were to be removed. The sulfide has an active role in keeping it alive found in both getting rid of the oxygen and providing food.

(B) We don't know HOW other organisms are being killed. We just know that it is a benefit of sulfide. The answer choice is conflating the benefits of sulfide and suggesting that one of them (getting rid of oxygen) is the reason another (killing of other things) is occurring. Really though, they are independent benefits that are not shown to have a causal relationship among each other - rather they are benefit of another.

(C) Most organisms can be killed ? We do not know of the proportion of organisms that can be killed, we just know that at least some are killed and provide sufficient food. Perhaps there is one organism that is very abundant that also happens to be one of few sources of food for the sub group of bacteria in question.

(D) the key word here is ONLY. We don't know if this is the ONLY scenario in which this bacteria would thrive. We are just given one scenario and some details about it. Its conceivable that there are other scenarios where this bacteria may thrive.

(E) ANY is the key word here. Remember, this whole time we have been discussing a subset of bacteria. Furthermore, the language in the stimulus says that "the hydrogen sulfide TENDS to kill other organisms in the area.." which suggests that it is too strong of a statement to claim that the bacteria colony here would be ENSURED source of food.

[contropositive]

I wasn't sure if the way you were describing your understanding of those sentence was an attempt to convert them into conditional ideas. Even though a lot of Inference questions involve conditional logic, I didn't see this one trying to create a chain of logic, so I was less inclined to try converting the ideas to conditional logic.

Are you suggesting that on inference questions, if there are no conditional logic chains then we should be cautious about picking conditional logic chain as an answer choice? for example, besides the word "any" in answer choice E, could it also be eliminated because it's trying to create a chain of logic? answer choice D also...

[andrewgong01]

I understand for these family types the argument core is not important.
However, for this question, do you think there was any assumptions that could have showed up as a most strongly supported answer choice because I noticed the argument jumps from talking about bacterias by themselves as single units to concluding something is true of the group in general. In fact , I think "A" somewhat touches on this because "A" is saying a dense colony is possible even though all the premises were around a single bacteria unit . However, would an answer choice like "Multiple bacterias together do not harm each other's ability to survive through competition for food" also be strongly supported because it is an assumption the argument must make [ similar to a part vs whole flaw - somewhat] to allow the conclusion to be drawn and we are interested here in not attacking the reasoning/conclusion but on what has to be 'most true' based of what we know

[ohthatpatrick]

The question stem describes this paragraph as "information", so there is ZERO part of my brain looking for conclusions/assumptions.

I'm just reading facts and looking for whichever answer choice seems most derivable from those facts.

That said, I think your hypothetical answer IS relatively derivable since the fact that dense colonies can thrive allows us to infer that bacteria do not screw each other over by living in too-close proximity to each other.

[MK597]

I think the approaches stated here are problematic. Many of you seem to approach this question with MBT. I can't agree with this. We can't infer with 100% certainty that hydrogen sulfide (HS) is NECESSARY for the bacteria's survival. The passage simply states that HS does wonders for the bacteria.

Do we know that this is the ONLY substance (that is produced by the bacteria) that does these things? who knows. Maybe it produces many other things that does exactly the same thing, and HS is one of them. Just because we are told about HS only does not mean that others do not exist.
Therefore, we cannot make the logical inference that HS is necessary for there to be food and to remove oxygen.

Without looking at other choices, I don't think it is logically possible to choose A. I am not disputing that the answer is A though; it is most supported among the other answer choices (since all we know is that HS does these things and it would make sense if the bacteria COULD produce HS indefinitely). This is, after all, a most supported question so any choice with some support would suffice.

Others are just unsupportable.

Choice B. This cannot be supported at all since we have no information about mechanism at all.

Choice C. We have absolutely no support for 'most organisms'

Choice D. I think this is the most attractive choice. This says "if thrive --> HS has removed ALL oxygen and killed other organisms". This is unsupported
at all.
First, we don't NEED ALL the oxygen to disappear. Maybe some tiny bit of oxygen is acceptable. We don't need ALL of members of the colony to survive for us to be able to say 'thrive' by the dictionary sense.
Second, we don't need HS to do it. We could put the bacteria in an aquarium, feed it food and remove oxygen for it without ever having to produce HS.
In other words, it is possible to DISPROVE this statement entirely. As such, no support.

E. If produce HS (any bacteria) --> food and protection from oxygen secured; this just makes no sense.