无忧雅思网_雅思预测_雅思机经_雅思考试_雅思资料下载_雅思名师_2018年雅思考试时间

SAT阅读考试模拟练习题electroreceptors

  Australian researchers have discovered electroreceptors

  (sensory organs designed to respond to electrical fields)

  clustered at the tip of the spiny anteater’s snout. The

  researchers made this discovery by exposing small areas of

  (5) the snout to extremely weak electrical fields and recording

  the transmission of resulting nervous activity to the brain.

  While it is true that tactile receptors, another kind of

  sensory organ on the anteater’s snout, can also respond to

  electrical stimuli, such receptors do so only in response to

  (10) electrical field strengths about 1,000 times greater than

  those known to excite electroreceptors.

  Having discovered the electroreceptors, researchers are

  now investigating how anteaters utilize such a sophisticated

  sensory system. In one behavioral experiment, researchers

  (15) successfully trained an anteater to distinguish between

  two troughs of water, one with a weak electrical field

  and the other with none. Such evidence is consistent with

  researchers’ hypothesis that anteaters use electroreceptors

  to detect electrical signals given off by prey; however,

  (20) researchers as yet have been unable to detect electrical

  signals emanating from termite mounds, where the favorite

  food of anteaters live. Still, researchers have observed

  anteaters breaking into a nest of ants at an oblique angle

  and quickly locating nesting chambers. This ability quickly

  (25) to locate unseen prey suggests, according to the researchers,

  that the anteaters were using their electroreceptors to

  locate the nesting chambers.

  1. According to the passage, which of the following is a characteristic that distinguishes electroreceptors from tactile receptors?

  (A) The manner in which electroreceptors respond to electrical stimuli

  (B) The tendency of electroreceptors to be found in clusters

  (C) The unusual locations in which electroreceptors are found in most species.

  (D) The amount of electrical stimulation required to excite electroreceptors

  (E) The amount of nervous activity transmitted to the brain by electroreceptors when they are excited

  2. Which of the following can be inferred about the experiment described in the first paragraph?

  (A) Researchers had difficulty verifying the existence of electroreceptors in the anteater because electroreceptors respond to such a narrow range of electrical field strengths.

  (B) Researchers found that the level of nervous activity in the anteater’s brain increased dramatically as the strength of the electrical stimulus was increased.