QUESTION TEXT: Geologist: The dominant view that petroleum…
QUESTION TYPE: Weaken
CONCLUSION: It is wrong to say that petroleum formed from lifeless deep carbon deposits.
REASONING: Petroleum has biomarkers, and biomarkers come from living things or from things that were once alive.
ANALYSIS: This argument has a missing premise. The geologist is trying to prove that the petroleum formed from living things in the past.
The presence of biomarkers isn’t definitive proof, because the biomarkers could come from things that are alive now, or were recently. The geologist assumes, without evidence, that the biomarkers must have come from long dead life forms.
___________
- The author didn’t say that all fossils have biomarkers. It’s possible that some fossils lost their biomarkers due to the effects of time.
The geologist’s claim is that if you find a biomarker, then there must have been life. But something could have been alive even if we can’t currently find bi0markers. - The author didn’t say when petroleum formed. Both petroleum and living organisms might have formed long after the earth’s formation.
The only reference to the earth’s formation is that the carbon deposits formed not long after the earth did. But that doesn’t mean that petroleum formed soon after the earth did. Petroleum could have started forming later, when life existed. - The argument didn’t say how long petroleum takes to form. Several million years could be fine.
- CORRECT. If bacteria live deep in the crust, then they could live near petroleum. Perhaps the bacteria leave biomarkers in the petroleum. Therefore the biomarkers are not a sign the petroleum originally formed from life. They are merely a sign that bacteria are currently present.
- The geologist is defending the dominant view that petroleum formed from fossilized plants and animals. So knowing that at least some petroleum deposits formed from plants strengthens the geologist’s argument.
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Lyndsie says
I think my base-line knowledge of some of these science questions makes them impossible for me. For example, with this question I thought bacteria would count as a living organism, therefore making D a strengthener to the argument.
FounderGraeme Blake says
Bacteria *are* a living organism. The problem is that the geologist argues that plants and animals *on the surface of the earth* died, and then eventually became oil deposits below ground.
D raises the possibility that oil has biomarkers because of underground bacteria instead. Bacteria are life, but they aren’t plants and animals. So the bacteria are an alternate explanation for the presence of former life in the petroleum.
Note: This is an old comment but I wanted to clarify the point.
Amarachi Ubawike says
Hello, I am struggling with weaken questions. I approach weaken questions as a way of providing a different explanation of the premises Is D the correct because it gives an alternate explanation of petroleum having biomarkers?
FounderGraeme Blake says
Precisely correct! D shows the biomarkers could be bacteria rather than plants and animals.
Note: This is an old comment but I wanted to clarify the point.
John says
It makes no sense that we were supposed to assume “bacteria” to be synonymous with “biomarkers.” In order to get to this answer, this assumption must be made, or the fact that there is bacteria will not provide anything of use. Pretty disappointed in how they made this question, considering we are not supposed to assume anything outside what they provide in the passage. The answer should have been something like “Certain strains of bacteria, which can account for the presence of biomarkers, thrive deep inside the earth’s crust.”
FounderGraeme Blake says
The LSAT requires you to use reasonable outside knowledge. Any university graduate knows or ought to know that bacteria are alive and hence fit the definition of something which could provide a biomarker.
This is a hard question, but you can’t just shut your mind to outside information. If everyone would agree that something is true then it is a relevant fact you can work with.
Note: This is an old comment but I wanted to clarify the point.
Chloe says
(D) made me wary because I didn’t think the argument established that the “deep carbon deposits” in the new theory were necessarily from the earth’s crust. Do we have to assume that? Because it seems like if the deposits were from the earth’s mantle, (D) wouldn’t impact the argument.
Also, thank you for all of your explanations – they’re really helpful!
TutorLucas (LSAT Hacks) says
It’s great to hear that you were able to benefit so much from Graeme’s explanations!
As for this question: Even if we were to assume that the deposits were from the mantle, (D) would still weaken the argument because the bacteria and petroleum are in the crust. Since they’re located in the same region, perhaps the bacteria left biomarkers, and the petroleum was still formed from the carbon deposits.
Seungsoo says
facts:
1- petro contains biomarkers.
2- formation of earth came before crust.
3- biomarkers only indicate existence of life in present or past.
4- challenging theory says petroleum came from formation of earth. Not fossilized living material deep in crust.
the author says because biomarkers were found in petroleum (fact #1), it is sufficient to justify that theory (fact #4) is incorrect.
how would i weaken?
the author assumes that the presence of biomarkers in petroleum means that petroleum derived from fossilized living material in the crust and not carbon deposits from earth’s formation. This, in turn, would mean the biomarkers found in the petroleum could not have been from a living organism that was present.
So one potential weakener would be that the biomarkers found were from present living organisms.
The issue with both B and D was somewhat similar for me—the chicken or the egg?
B-if it was the case that petroleum did in fact come first before any life form it would 100% weaken the argument. But does the fact that biomarkers came after formation of earth indicate petroleum existed before it? B can be consistent with the fact that petroleum came long after living organisms emerged and hence the theory can either be true or false.
D-two distinct ways I saw D to be correct is either
1-the strains of bacteria found cannot be a source of petroleum
2-the strains of bacteria formed fairly recently.
Just like B, we are not given the relevant facts for absolute certainty with respect to time or outside info that would render the support useless.
chicken or egg problem in both cases. so how do i break this tie?
i looked at the argument again and tried to apply some principle approach:
1- the conclusion is an absolute claim: the theory that petroleum derived from formation of crust (non-living material) is Wrong!
Because: existence of life was found in petroleum.
2- to weaken an absolute claim, it is sufficient to simply show that the support is not definitive to justify the claim. We do not need to show that petroleum did in fact derive from formation of earth, we just need to show that the presence of biomarkers in petroleum does not definitively show that it did not derive from non-living material.
the main issue is we do not know which came first, petroleum or biomarker, and i think the correct AC is one that makes the order irrelevant. In other words, which one between B and D would allow for both petro and biomarkers to emerge independently?
B- the correctness of B requires knowing when petroleum was formed and for this reason I eliminated B.
D- even if the bacteria was from the past, or from when the formation of earth began, petroleum could still derive from non-living carbon deposits while occupying the same space with the bacteria.
This PT I am using as a drill, working through each question and explicitly writing out my rationale in the hopes of developing an approach that will minimize error in LR.
I just wanted to share this here because I spent a lot of time on it and was wondering what you thought.