Reading comp PrepTest 101 · Section 4 · Question 20

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

With which one of 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

Strategy Overview

Consult your notes or passage to recall the author's attitude about the topic in question, and find the answer that best reflects your understanding of the author's opinion on that topic.

Answer Anticipation

This question asks us about the author's view, but doesn't provide much insight into the topic of the correct answer or where the supporting information might show up in the passage. It asks about the author's thoughts on possible explanations for the latitudinal gradient. Unfortunately, possible explanations for the gradient are … the entire passage.This means the correct answer is likely to relate back to the author's main point. As such, we'll need to rely on our big-picture understanding of the passage to answer this question. We should start by reminding ourselves of the main point (either by reviewing what we said after reading the passage or by re-reading our answer to the main point question). We can also review any notes about the author's attitude or any text we highlighted because it expressed the author's opinion. After doing that, we can head to the answer choices, tabling those that don't line up with the main point. For those answer choices that conform to the author's main point, we'll use our notes and the passage to see if it's correct.

Answer choices

  1. A
    The time theory is Remaining source text redacted.
    Why choice A is not credited

    (A) Is this consistent with the author's main point or what you recall reading about the author's opinions?

    No. Although the author prefers the rate-of-speciation hypothesis to the time-theory hypothesis, you probably don't remember reading that the time-theory hypothesis is worse than the others. Decisive test-takers would recognize that they'd probably remember this hyperbolic claim if the author made it and would feel comfortable eliminating (A). Although we wouldn't recommend checking the passage, a quick review of the first paragraph would reveal that the author never claims the time-theory hypothesis was the least plausible.

  2. B
    The rate–of–speciation hypothesis addresses Remaining source text redacted.
    Why choice B matches the stem

    (B) Is this consistent with the author's main point or what you recall reading about the author's opinions?

    This answer choice reflects the author's preference for the rate-of-speciation hypothesis. Because this is consistent with the main point, we should review the passage to see if the rate-of-speciation hypothesis addresses the author's objection to the climatic-stability hypothesis.

    So, what was the author's objection to the climatic-stability hypothesis? The author objects that the climatic-stability hypothesis describes a local process that cannot explain the regional differences along the latitudinal gradient (P4, S4-5). Does the rate-of-speciation hypothesis address that issue? Yes, that hypothesis shows how there could be more species near the equator than far from the equator. According to that hypothesis, isolated subgroups are more likely to survive in the tropics near the equator than in the arctic far from it (P6, S3-4). This causes a higher speciation rate and a lower extinction rate near the equator (P6, S4).

    So, we can be confident that this answer choice is correct. However, since this isn't something the author explicitly states, all but the most brazen test-takers would prefer to check the remaining answer choices before selecting (B). Once we eliminate the field, we can select this with more confidence.

  3. C
    The major objection to Remaining source text redacted.
    Why choice C is not credited

    (C) Is this consistent with the author's main point or what you recall reading about the author's opinions?

    You probably don't remember reading the author object to the time-theory hypothesis because it doesn't reflect the latitudinal distribution of species. Well-prepared test-takers would feel comfortable eliminating (C) for this reason. Although we wouldn't recommend checking the passage, a quick review of the second paragraph would reveal that the author's main objection to the time-theory hypothesis was that it 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 (P2, S2).

  4. D
    Despite the claims of Remaining source text redacted.
    Why choice D is not credited

    (D) Is this consistent with the author's main point or what you recall reading about the author's opinions?

    Probably not. You may remember reading about the author's issues with the species-energy hypothesis's correlation between high biomass and high growth and reproduction rates. But does the author think that low biomass will be more likely to lead to high growth and reproduction rates? If you're not sure, we can review the third paragraph. There, the author says, "high production rates can exist with low biomass" (P3, S2). The author's weak claim ("can") is not enough to justify the bold claim ("more likely") this answer choice makes.

  5. E
    An important advantage of Remaining source text redacted.
    Why choice E is not credited

    (E) Is this consistent with the author's main point or what you recall reading about the author's opinions?

    This reflects the author's preference for the rate-of-speciation hypothesis. So, we should probably review the passage to see if this answer choice is supported. Does the author think that the rate-of-speciation hypothesis considers competition in a regional context?

    No. In fact, if we review what the author said about competition, we'd see the author describes species competition as a "[l]ocalized economical process[]" (P4, S5). Therefore, the author would consider "species competition in a regional ... context" a contradiction of terms.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 10%
  2. B Credited 42%
  3. C 12%
  4. D 10%
  5. E 27%

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