Reading comp PrepTest 107 · Section 2 · Question 18

Passage

Questions 16-21  .        Scientists have long known that the soft surface of  . the bill of the platypus is Remaining source text redacted.
Passage walkthrough
Passage Summary

Topic: Science


Paragraph 1

  • Paragraph note
    • New evidence from scientists including Bohringer shows that the platypus uses its bill to sense and snap at prey by while underwater.
  • Views, minor Meta-Structures, and the author's attitude
    • Platypus’s bill has sensitive nerve endings (first sentence)
    • Explanation of phenomenon: Platypus uses bill to locate prey while underwater (second sentence)
      • Eyes, ears, and nostrils sealed while underwater (second sentence)
    • New evidence: neurophysiological studies showed bill has mechanoreceptors, which detect touch, and electroreceptors, which sense electric fields (third sentence)
      • Bohringer: strength of input from mechanoreceptors indicates that bill is platypus’s primary sensory organ (fourth sentence)
        • Supported by studies showing touch on the bill induces snapping movement of jaws (fifth sentence)
      • These findings don’t explain how platypuses locate prey at a distance (sixth sentence)
      • Author’s attitude: “long known” (first sentence); “new evidence” (second sentence); “suggested by the fact” (second sentence); “recently revealed” (third sentence); “extraordinarily sensitive” (fifth sentence)

Paragraph 2

  • Paragraph note
    • The work of Scheich shows that platypuses use electroreceptors to locate prey at a distance via the weak electrical fields that the prey emit underwater.
  • Views, minor Meta-Structures, and the author's attitude
    • Schech’s studies: platypuses, when feeding, exhibit patrolling behavior until an electrical field is detected, then switch to searching behavior along the bottom of a body of water until they locate and seize prey (second-third sentences)
      • Hypothesis: platypus differentiates prey from other objects using electrosensory system (fourth sentence)
      • Scheich’s study: induced platypuses to switch from patrolling to searching behavior using a battery that emitted a weak electrical current (fifth sentence)
        • Platypus could detect and locate the battery at a distance of up to 30 cm (sixth sentence)
        • Platypus attacked battery as if it were food (seventh sentence)
      • Tail flicks of freshwater shrimp create an electric field similar to that emitted by the battery (eighth sentence)
        • Hypothesis: platypus’s common prey, underwater invertebrates, all emit electrical fields (ninth sentence)
      • Author’s attitude: “contribute to solving this mystery” (first sentence); “Scheich hypothesized” (fourth sentence); “rapidly oriented” (sixth sentence); “identical response” (eighth sentence); “reasonable to assume” (ninth sentence)

Main Point: New scientific research by Bohringer, Scheich, and others strongly suggests that the platypus uses its bill to locate prey underwater.

Key Lines?

Paragraph 1, Sentence 2 (P1 S2) - Thesis: platypus uses bill to locate prey underwater

P1 S3 - Bill has mechanoreceptors and electroreceptors

P1 S4 - Bohringer: bill is primary sensory organ

P1 S6 - Stimulating mechanoreceptors leads to snapping of bill

P2 S4 - Scheich: platypus senses prey at a distance using electroreceptors

Meta-Structure?

Phenomenon/Explanation: This passage uses a Phenomenon/Explanation Meta-Structure. The phenomenon under investigation is the ability of the platypus to locate prey while underwater. The author presents the hypothesis that the animal’s bill, which contains mechanoreceptors and electroreceptors and seems to be the only sensory organ in operation while the platypus is underwater, is the means by which it locates prey. The research and hypotheses of scientists Bohringer and Scheich is presented as evidence to support the author’s contention. Bohringer determined that stimulation of the mechanoreceptors on the platypus’s bill induced the jaws to snap, and Scheich showed that stimulation of the electroreceptors on the bill attracted the animal to the source of an electric current, suggesting that the platypus senses the weak electric fields emitted by prey.

The author seems to endorse the views of both Bohringer and Scheich, whose research is complementary and seems to explain the behavior and sensory abilities of the platypus.

Last Thoughts?

There are no hidden agendas in this passage. The author presents and tacitly endorses the views of two scientists, Bohringer and Scheich, and describes their experiments as evidence to back up an explanation of how the platypus senses prey underwater.

Question prompt

During the studies supporting Remaining source text redacted.
Why the credited answer is right

Credited answer: E

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/underlined to locate where the passage discusses the studies that supported Bohringer’s finding about the motor cortex of the platypus, 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. Once we review that part of the passage, we can look through the answer choices to see which one is best supported by what we reviewed.Here, the question asks about the studies that supported Bohringer’s finding about the motor cortex of the platypus. These studies were mentioned in P1 S5-6, where the author states that stimulation of the mechanoreceptors in the bill sent a nerve impulse through the fifth cranial nerve into the neocortex and from there to the motor cortex. The question asks about what happened before the impulse reached the motor cortex. Let’s look for an answer choice that is in accordance with what we read.

Answer choices

  1. A
    The electroreceptors sent the Remaining source text redacted.
    Why choice A is not credited

    (A) Does this answer choice describe a step that took place before the nerve impulse reached the motor cortex in the P1 S5-6 study?

    No. The study mentioned in P1 S5-6 was of the mechanoreceptors, not the electroreceptors. The mechanoreceptors sense touch, while the electroreceptors sense electrical fields (P1 S3). This answer choice is inaccurate.

  2. B
    The neocortex induced a Remaining source text redacted.
    Why choice B is not credited

    (B) Does this answer choice describe a step that took place before the nerve impulse reached the motor cortex in the P1 S5-6 study?

    No. The neocortex sent the nerve impulse to the motor cortex, which then induced a snapping movement of the bill. The neocortex did not induce the snapping on its own. So this is not the right answer choice.

  3. C
    The mechanoreceptors sent the Remaining source text redacted.
    Why choice C is not credited

    (C) Does this answer choice describe a step that took place before the nerve impulse reached the motor cortex in the P1 S5-6 study?

    No. The mechanoreceptors did indeed send the nerve impulse via the fifth cranial nerve, but they sent it to the neocortex, not to the electroreceptors. The electroreceptors were not involved in the study at all. So this answer choice is inaccurate.

  4. D
    The platypus opened the Remaining source text redacted.
    Why choice D is not credited

    (D) Does this answer choice describe a step that took place before the nerve impulse reached the motor cortex in the P1 S5-6 study?

    No. The passage does not mention pores opening at all in response to any kind of stimulation or condition. This answer choice has no support in the passage.

  5. E
    The fifth cranial nerve Remaining source text redacted.
    Why choice E matches the stem

    (E) Does this answer choice describe a step that took place before the nerve impulse reached the motor cortex in the P1 S5-6 study?

    Yes. This answer choice describes a step that took place before the nerve impulse in the study reached the motor cortex and induced a snapping movement of the bill.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 14%
  2. B 2%
  3. C 7%
  4. D 2%
  5. E Credited 74%

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