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#23 - Geologist: The dominant view that petroleum formed

Brandonhsi
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Hello,

I selected (A) as my answer choice. I can understand why (D) weakens the argument. However, I believe (A) also weakens the argument a bit.

Since it is possible fossils doesn't have biomarkers (from (A)), it is possible the petroleum is not from living material (therefore, could be from others, like deep carbon deposits). Therefore, (A) weakens the argument a bit.

Am I interpret this question wrong in this way? Thanks!

Brandon
Emily Haney-Caron
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Hi Brandon,

A does not weaken the argument because it only tells us about fossils, not about petroleum - even if fossils exist without biomarkers, that doesn't help explain why petroleum DOES have biomarkers.

Does that help?
emilysnoddon
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I had a lot of difficulty with this problem. I am having a hard time seeing why D weakens the argument. I don't understand what certain trains of bacteria has to do with petroleum. Can someone please clarify this for me? Thank you!!
Clay Cooper
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Hi emily,

Thanks for your question.

There are some who argue that petroleum could have formed, not from plants and animals, but from carbon deposits left over from the earth's formation; our geologist claims that these people are wrong, because there are biomarkers in petroleum, and biomarkers indicate the presence of life; our geologist clearly thinks that these biomarkers are left over from the plants and animals that decayed to form the petroleum.

However, if D were true, the bacteria within the earth's crust could have provided the biomarkers, and it might still be possible that petroleum does not come from plants and animals, but instead from carbon deposits left over from the earth's formation. (Note that bacteria are neither plants nor animals.)

The bacteria, in other words, would provide a plausible alternate cause for biomarkers' having come to be in the petroleum, and would thus weaken its evidentiary value. Since the presence of these biomarkers is the only evidence the geologist offers us, doing so would significantly weaken his conclusion.
emilysnoddon
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Thank you, that explanation helps a lot. I just want to make sure my train of thought follows similarly... my prephrase for the question was to find an answer that showed that petroleum came from deep carbon and not living organisms, instead my prephrase should have been to show that petroleum didnt come from plants and animals. I eliminated D because I felt as though since bacteria is a living organism, it would strengthen the geologists argument. So basically I misunderstood the argument to be broader (encompassing all living things) than it really was. Is this correct?

Thanks!
Clay Cooper
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Hi emily,

Yes, that is basically correct. Bacteria is living but is not a plant or animal, so you were thinking of it too broadly if you included bacteria in that category. But don't feel bad, I did the same thing at first (hence my note in the previous post).

Also, don't stress too much about your prephrase. If anything, I would try to be less specific with it - it's possible that evidence will be introduced that bolsters the carbon deposit theory without affecting the living thing theory, or its possible that what will happen here happens, and the living thing theory will be weakened. I think it is unreasonable to expect yourself to be able to prephrase as specifically as it sounds like you do.
bk1111
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Hi, I had a very hard time with this question as well - all of the answer choices seemed out irrelevant to me. At the end, I went with B, as I thought it boosted the argument of the scientists who challenged fossilized plants/animals theory.

For this question, am I simply weakening the geologists' argument in favor of the deep carbon deposits theory? I think that is what led me to choose B.
AthenaDalton
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Hi bk111,

Yes, the prompt asks us to weaken the geologist's argument (who believes that petroleum formed from living organisms), so focus on the choices that undercut the geologist's theory. :)
dbpk
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When the geologist says "their theory is refuted", he refers to the scientists who argue that petroleum was formed "NOT from LIVING material" but from carbon deposits.
Although the dominant view refers specifically to plants and animals, the scientists to whom the geologist's argument is directed claim that petroleum does not form from living material generally. This is why I ruled out D because bacteria would count as living material, which would fail to weaken the geologist's argument.

Am I misreading the stimulus? Any help appreciated!
AthenaDalton
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Hi dpbk,

I think you're actually reading the stimulus correctly -- your explanation was on-point! :)

I suspect that your confusion stems from understanding what answer choice (D) is saying. Answer choice (D) tells us that certain types of bacteria can live very deep underground, presumably within the carbon deposits that have existed since the formation of the earth. This answer choice isn't saying that the carbon deposits are actually made up of bacteria -- just that bacteria happen to be living deep inside the earth where this carbon is found. Does that distinction make sense?

Since the geologist is arguing that the existence of biomarkers = carbon formed from fossilized plants and animals, any fact that could explain the existence of biomarkers apart from the fossilized plant/animal theory would weaken his argument.

Thanks for your question, and best of luck studying!

Athena Dalton