PrepTest 156

[lcid:3720] Prep Test 156 LSAT — Reading Comp — S1 Reading comp

Passage

 Discovered in 1993, the site known as Ukhaa Tolgod, in the Gobi desert of Mongolia, is one of the world's Remaining source text redacted.
Passage walkthrough
Passage Summary

Topic:
Science

Paragraph 1

  • Paragraph note
    • Phenomenon, explanation, evidence it's wrong
  • Views, minor Meta-Structures, and the author's attitude
    • Phenomenon - Ukhaa Tolgod has very well preserved fossils
    • Old Explanation - Big, sudden sandstorms buried animals
    • New Evidence - Geological formations - Sandstorm hypothesis wrong


Paragraph 2

  • Paragraph note
    • New evidence/geological formations
  • Views, minor Meta-Structures, and the author's attitude
    • 3 types of sandstone
      • Tilted layers, sorted by particle size = wind - Footprints, no fossils
      • Tilted layers, not sorted = wind - No fossils
      • No layers, pebbles = not wind - All the fossils


Paragraph 3

  • Paragraph note
    • Explanation for third layer
  • Views, minor Meta-Structures, and the author's attitude
    • Not wind, but water from heavy rains → sudden debris flow
    • New explanation - Sudden debris flow from rain, not wind


Paragraph 4

  • Paragraph note
    • Cause of sandslides
  • Views, minor Meta-Structures, and the author's attitude
    • Cause - Not well understood
    • Evidence - Clay plays a role, with dunes and vegetation also relevant
    • Implication - If sandslide explanation correct, then desert not sterile but had dunes/plants/rain


Main Point:

New evidence suggests sandslides caused by sudden, heavy rains — rather than sandstorms caused by wind — may have preserved Ukhaa Tolgod fossils.



Key Lines?

P1, S2 - Phenomenon
P1, S3 - Old Explanation
P1, S4 - Evidence suggests Old Explanation is wrong
P3, S3 - New Explanation
P4, S1 - Cause of New Explanation not fully understood
P4, S7 - Implication of New Explanation



Meta-Structure?

Old Explanation/New Explanation (or Phenomenon/Explanation): The passage opens with a description of an area with unexpectedly well-preserved fossils. While that doesn't necessarily establish a Meta-Structure, we know that Science passages often fall into the Phenomenon/Explanation Meta-Structure, and the "extraordinar[y]" nature of these fossils suggests that the passager might head in that direction. Paragraph 1, Sentence 3 (P1, S3) reinforces this prediction, as the author raises an explanation: the preservation was "due to" immense, sudden sandstorms. At this point, we might think that this is a Phenomenon/Explanation passage. But then the author goes in a different direction, claiming that evidence suggests the sandstorm explanation is wrong and a new explanation is warranted. The author eventually elaborates on this new explanation in paragraph 3: sandslides, rather than sandstorms, preserved the fossils.



The third paragraph's alternative explanation suggests that the author uses an Old Explanation/New Explanation Meta-Structure (though we could still consider it a Phenomenon/Explanation passage, only with this added wrinkle). In the former Meta-Structure, the author's preferred explanation is the main point; in the latter, it's the author's opinion on the new explanation. Here, the author is the one presenting the new explanation, though the author may not be 100% committed to it (note the noncommittal language in P3, S3 — "could have trapped"; and P4, S7 - "If the animals…"). So the main point is the new explanation, though we have to be careful not to oversell how committed the author is to that explanation.



Causality: Outside of the typically causal nature of a Phenomenon/Explanation passage (in which the explanation is generally causal, as it is here), the author spends a lot of time walking through the causal chain of events that may lead to a sandslide in P4. We probably don't want to get too bogged down with understanding and memorizing it as we read. Still, a prudent test taker would note that P4 is a cause-and-effect-focused paragraph to help answer any questions about P4 or the possible causes of a sandslide.



Comparison: the author spends P2 comparing the different types of sandstones and the evidence found at each site of Ukhaa Tolgod to build to her intermediate conclusion (the sandstorm hypothesis is probably mistaken). These comparisons could feature in a question, and they play into the role of P2, which very well could itself be a question (see "Last Thoughts?", below).



Last Thoughts?

Two things, both about the second paragraph ...



First, it's important to understand the role of that paragraph in the passage's overall organization. P2 and P1 are closely tied. P1 cites "geological formations" as new evidence that the sandstorm hypothesis (the Old Explanation) is probably wrong. The sandstone at the site, discussed in P2, are those "geological formations."



Second, it's important to understand how the author uses this evidence to undermine the old hypothesis. The author brings up three layers of sandstone and highlights similarities and differences between them. Crucially, it's only the third layer that contains fossils. The first layer explicitly doesn't contain fossils, and the second layer implicitly doesn't since "all the vertebrate skeletal fossils" are found in the third layer. Wind caused the first two layers, but wind couldn't have caused the third. Since the fossils are all in the third layer, wind/sandstorms cannot explain why the fossils are "extraordinarily well preserved." Ergo, something else must have preserved those fossils. Understanding this argument will likely play a role in answering at least a few questions!

Question prompt

The author's main purpose Remaining source text redacted.
Why the credited answer is right

Credited answer: B

The notes below walk through why it fits the stem and how to eliminate the rest.

Question Type

Science

Answer choices

  1. A
    question the wisdom of Remaining source text redacted.
    Why choice A is not credited
    (P1, S4) Questioning the wisdom of someone is to call their reasoning into question. Doing so, in this case, would likely involve the author questioning whether the old evidence was sufficient to support the traditional explanation. However, in this passage, the author argues that newevidence suggests the traditional explanation is wrong. The author never questions the sufficiency of old evidence or any inferences drawn, so the author doesn't question the wisdom of its proponents.
  2. B
    provide the basis for Remaining source text redacted.
    Why choice B matches the stem

    Question Type:
    Argument Structure

    Strategy Overview:
    Review the purpose of Paragraph 1, then use that and the immediate context around the last two sentences to define the purpose of those lines

    Answer Anticipation/Relevant Lines:
    We know that the overall point of the passage is to argue against an old hypothesis about the well-preserved fossils at Ukhaa Tolgod and for a new hypothesis. Looking at our notes for P1, we can see that it's where the author brings up the phenomenon and the old hypothesis.

    Digging into the specifics, we can see that the sandstorm hypothesis is that old hypothesis. The last two sentences in the first paragraph introduce that old hypothesis while also bringing up the "new evidence" that suggests this hypothesis is "probably mistaken." So the purpose of the discussion of this hypothesis in Paragraph 1 is to argue that the traditional explanation for the fossils at Ukhaa Tolgod is probably wrong.

    Answer Choice Explanation:
    This answer reflects the Meta-Structure of the passage, and it captures the role of Paragraph 1. In this paragraph, the author introduces the old explanation before arguing that it's likely mistaken, setting the stage for her discussion of the new explanation throughout the rest of the passage. This answer is, therefore, correct.

    Key Takeaway:
    Don't forget your Meta-Structures when dealing with an Argument Structure question! These questions will generally ask about details that play a crucial role in the passage's overall structure. So defining the passage's structure through your Meta-Structures will usually help lead you to the correct answer.

  3. C
    explain the geological basis Remaining source text redacted.
    Why choice C is not credited
    (P1, S4) While the author does mention "geological formations" in the first paragraph, this evidence is used to support the sandslide theory, not the sandstorm theory. Therefore, the point of these lines is not to describe the geological nature of the evidence supporting the sandstorm theory. Moreover, this answer choice fails to address that the whole point of the sandstorm discussion is to present an old explanation that will be contrasted by a new explanation. 
  4. D
    show how adherence to Remaining source text redacted.
    Why choice D is not credited
    Paragraph 1 doesn't discuss any areas of research hindered by the old explanation, so this answer misdescribes the role played by those lines.
  5. E
    establish that scientists formulating Remaining source text redacted.
    Why choice E is not credited
    (P1, S4) The evidence is noted as being "new evidence," so there's no indication that this evidence was available when the sandstorm hypothesis was being formulated. Thus it couldn't have been ignored by the scientists formulating it.

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