PrepTest 101

[lcid:3503] Prep Test 101 LSAT — Reading Comp — S4 Reading comp

Passage

Questions 15-20  .        When the same habitat types (forests, oceans,  . grasslands, etc.) in regions of different latitudes are Remaining source text redacted.
Passage walkthrough
Passage Summary

Topic: Science


Paragraph 1

  • Paragraph note
    • "Latitudinal gradient" phenomenon (more species near the equator than poles)
  • Views, minor Meta-Structures, and the author's attitude
    • Comparison:
      • When you compare a habitat type that stretches out from the north to the south, there are more species near the equator than far from the equator (first sentence)
    • Author's attitude: "probably even more pronounced" (last sentence)

Paragraph 2

  • Paragraph note
    • "Time theory" hypothesis and author's rebuttal
  • Views, minor Meta-Structures, and the author's attitude
    • Cause-and-effect relationship, according to the "time theory" hypothesis:
      • Latitudinal gradient exists because tropics haven't been interrupted by ice ages and therefore have more time to develop species (first sentence)
    • Comparison, according to the "time theory" hypothesis:
      • Tropic zones have not been affected by ice ages, while temperate and arctic zones have (first sentence)
    • Author's view:
      • The "time theory" hypothesis isn't consistent with the evidence, as arctic conditions haven't actually been interrupted by ice ages, and there is a varying range of interruption in temperate areas (last sentence)
    • Author's attitude: "However" (last sentence)

Paragraph 3

  • Paragraph note
    • Species-energy hypothesis and author's rebuttal
  • Views, minor Meta-Structures, and the author's attitude
    • Cause-and-effect relationship, according to the species-energy hypothesis:
      • Latitudinal gradient exists because tropics have more energy from the sun, which causes high biomass and lower rates of extinction (first and last sentences)
    • Author's view:
      • The causal mechanism between biomass and increased local populations remains untested, and biomass and the number of species are not necessarily correlated (second through last sentences)
    • Author's attitude: "However" (second sentence); "remains untested" (last sentence)

Paragraph 4

  • Paragraph note
    • Climatic-stability hypothesis and author's rebuttal
  • Views, minor Meta-Structures, and the author's attitude
    • Cause-and-effect relationship, according to the climatic-stability hypothesis:
      • The tropics' stable climate causes a reliable resource supply, which allows more species to coexist (first through third sentences)
    • Author's view
      • The climatic stability hypothesis describes a local process that cannot explain the regional differences along the latitudinal gradient (fourth and last sentences)
    • Example of a local process, according to the author:
      • Competition (last sentence)
    • Example of regional differences along the species gradient, according to the author:
      • Forests along the equator and forces at higher altitudes (last sentence)
    • Author's attitude: "However" (fourth sentence); "cannot account for" (fourth sentence)

Paragraph 5

  • Paragraph note
    • Rate-of-speciation hypothesis and author's endorsement
  • Views, minor Meta-Structures, and the author's attitude
    • Cause-and-effect relationship, according to the rate-of-speciation hypothesis:
      • Latitudinal gradient exists because, in the tropics, the rate of speciation (the development of new species) is higher, and the extinction rate of species is lower (last sentence)
    • Author's attitude: "most plausible hypothesis" (first sentence)

Paragraph 6

  • Paragraph note
    • How rate of speciation works
  • Views, minor Meta-Structures, and the author's attitude
    • Cause-and-effect relationship/comparisons, according to the rerate-of-speciation hypothesis:
      • Speciation occurs when subgroups become isolated and differentiate from the main population (first and second sentences)
      • Subgroups are more likely to survive in the tropics than in the arctic, causing a higher rate of speciation and a lower rate of extinction in the tropics (third and last sentences)

Main Point: The rate-of-speciation hypothesis is the best explanation for why there exists a latitudinal gradient in species distribution.

Key Lines?

Paragraph 1, Sentence 1 (P1, S1) - Description of phenomenon

P5, S1 - The author's preferred explanation

P6, S4 - How the preferred explanation actually works 

Meta-Structure?

Phenomenon/Explanation: This passage follows a Phenomenon/Explanation Meta-Structure. Passages that utilize this Meta-Structure follow a consistent pattern. First, the passage will describe an observable fact, behavior, or situation. Then, the author will present one or more explanations of that observable fact, behavior, or situation. That's exactly the model this passage follows. The author describes our phenomenon — the latitudinal gradient of species distribution — and then presents four hypotheses that could explain this phenomenon.

In this type of Meta-Structure, if the author says that one explanation is the best, then that's the main point of the passage. Here, the author prefers the last hypothesis, "rate of speciation." So the main point is that the rate-of-speciation hypothesis is the best explanation for why there exists a latitudinal gradient in species distribution. 

Lists: This most prominent minor Meta-Structure in this passage is a list. In fact, nearly the entire passage is dedicated to listing four separate hypotheses for the latitudinal gradient of species distribution. When the whole passage is organized around a list, we'll surely get at least a few questions about items on this list. This is why our notes must allow us to quickly determine which paragraph describes which hypothesis.

Causality: Like many science passages, cause and effect also figure heavily into this passage. Each hypothesis of the latitudinal gradient of species distribution proposes a causal mechanism to explain the phenomenon. For those of us who are less fluent in science than we'd like to be, it can help if we simplify the cause-and-effect relationships as much as possible. We've done so below for each hypothesis:

  • "Time theory": The lack of ice-age disturbance in the tropics is the cause, and more time for species to emerge in the tropics is the effect (P2, S1)
  • Species-energy: Greater energy from the sun is the cause, and more biomass, lower rates of extinction, and more species are the effects (P3, S2)
  • Climatic stability: The tropics' stable climate is the cause, and more resources and species are the effects (P4, S1-3)
  • Rate of speciation: The better chance of surviving in the tropics is the cause, and the lower rates of extinction and higher rates of survival in the tropics are the effects (P6, S4)

Last Thoughts?

The nice thing about this passage is that the middle paragraphs are formulaic. The second, third, and fourth paragraphs follow the same formula: the author describes a hypothesis and then dismisses the hypothesis with counterevidence. Even when the topics (like ecology and species distribution) are unfamiliar, noticing these patterns can help us follow the passage and decoct the structure.

Question prompt

As presented in the Remaining source text redacted.
Why the credited answer is right

Credited answer: A

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

Question Type

Science

Strategy Overview

Refer to notes or what you highlighted/underline to locate where the passage discusses the time theory, and refer to the relevant part of the passage as needed to find that answer choice that must be true.

Answer Anticipation

For questions that ask us to find a specific detail mentioned in the passage, quickly finding and reviewing that piece of information is paramount. That is why we make brief notes describing the role of each paragraph and highlight or underline definitions and the minor Meta-Structures — doing so helps us find the salient information efficiently and reliably.Here, the question asks about the time theory. Where did that show up in the passage? According to our notes, in the second paragraph. The central idea of the time theory is that species in places uninterrupted by ice ages (like the tropics) have had more time to develop (P2, S1). In other words, a lack of disturbances from ice ages allows species to develop, which causes increased species diversity. We'll look for a choice that reflects this idea.

Answer choices

  1. A
    In the absence of Remaining source text redacted.
    Why choice A matches the stem

    (A) Does this reflect the causal mechanism proposed by the time-theory hypothesis?

    Yes! Without ice ages, species in the arctic would also have more time to develop species diversity, so the number of species at high latitudes would ultimately increase. As a bonus, this answer choice modulates its claim with softer, easier-to-justify language ("could eventually"). We can select (A) and move on to the next question if we feel comfortable doing so.

  2. B
    No future ice ages Remaining source text redacted.
    Why choice B is not credited

    (B) Does this reflect the causal mechanism proposed by the time-theory hypothesis?

    No. We anticipated that the correct answer should describe a causal link between ice ages and species diversity. This answer choice mentions ice ages, but says that future ice ages won't change climatic conditions in temperate regions. That's the opposite of what the time theory hypothesis posits. They think ice ages would affect the climate in temperate areas, decreasing the number of species in those areas. So, this is inconsistent with that hypothesis's beliefs.

  3. C
    If no further ice Remaining source text redacted.
    Why choice C is not credited

    (C) Does this reflect the causal mechanism proposed by the time-theory hypothesis?

    Nope. The time-theory hypothesis holds that a lack of disturbances from ice ages would allow more species to emerge and eventually increase species diversity. The hypothesis doesn't claim that a lack of ice ages would make global climatic conditions uniform, as (C) suggests.

  4. D
    Researchers will continue to Remaining source text redacted.
    Why choice D is not credited

    (D) Does this reflect the causal mechanism proposed by the time-theory hypothesis?

    No, this option doesn't match our anticipation at all. We're not expecting anything about researchers finding new species. This is consistent with the author's prediction (P1, S2), not a claim advanced by proponents of the time-theory hypothesis.

  5. E
    Future ice ages are Remaining source text redacted.
    Why choice E is not credited

    (E) Does this reflect the causal mechanism proposed by the time-theory hypothesis?

    No. Although proponents of the time-theory hypothesis hold that a future ice age would interrupt the climatic conditions at high latitudes (P2, S1), they never claim that a future ice age will interrupt the climatic conditions at high latitudes. We have no idea if they believe future ice ages will occur.

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