TPO65阅读真题+题目+答案下载：The Pit Organs of Snakes

TPO65阅读真题+题目+答案下载：The Pit Organs of Snakes

It is thought that the facial pits or pit organs on the head of some snakes are specialized infrared (heat) receptors. When a rattlesnake strikes, the direction of the strike seems to be guided by the infrared radiation from its prey. A rattlesnake strikes only at warm-blooded prey, and when the prey is dead and at room temperature, the snake will not strike. However, a blindfolded snake strikes correctly at a dead rat that is pulled across the cage, provided the rat is warmer than the surroundings. Blindfolded, the snake cannot be guided by vision; nor is it guided by the sense of smell, for it will strike correctly even at a moving, cloth-wrapped electric bulb. The pit organs are evidently involved in sensing the location of warm objects. All snakes that have pit organs feed preferentially on warm-blooded prey, and this further supports the view that these organs are infrared sensors. In the rattlesnake the pit organs are located, one on each side, between the nostril and the eye: they are connected to many nerves, and this in itself suggests a sensory role for the organ.

1. According to paragraph 1, a rattlesnake will only strike at prey when

A. the snake is able to see the prey

B. the prey emits chemical odors

C. the prey is moving

D. the prey is warmer than its surroundings

2. Why does the author mention a "cloth-wrapped electric bulb " in the passage?

A. To illustrate t he size of prey usually attacked by snakes

B. To prove that blindfolded snakes will strike more often at a dead rat than an electric bulb

C. To eliminate the possibility that snakes locate prey by using a sense of smell

D. To explain how scientists were able to trick blindfolded snakes

The sensitivity of the facial pit has been examined by recording the activity in the nerve leading from the organ. A variety of stimuli, such as sound, vibration, or light of moderate intensity (with the infrared part of the spectrum filtered out), has no detectable effect on the activity in the nerve. However, if objects of a temperature different from the surroundings are brought into the receptive field around the head, there is a striking change in nerve activity, regardless of the temperature of the intervening air.

3. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?

Incorrect choices change the meaning in important ways or leave out essential information

A. However, if objects in t he surrounding area experience a temperature change, nerve activity causes a change in temperature in the receptive field around the snake's head

B. When objects that differ in temperature from the surroundings enter the receptive field around the head, the result is a dramatic change in nerve activity

C. Nerve activity changes when new objects are introduced into t he area around a snake' s head, regardless of how their temperature compares to that of the surrounding air

D. The temperature of the air in the receptive field around the snake' s head has an effect on the nerve activity of the snake if the objects in the fie ld are at a different temperature

How is the infrared radiation sensed? The pit is covered by a thin transparent membrane, and it has been suggested that a rise in temperature in the pit behind the membrane could cause an expansion of the gas with a consequent deformation of the membrane. This in turn could be sensed by a suitable receptor. This hypothesis is highly improbable, for a cut in the membrane that opens the pit to the outside air causes no loss in responsiveness, a result that is incompatible with the hypothesis that a pressure change is sensed.

4. The word "consequent " in the passage is closest in meaning to

A. resultant

B. eventual

C. premature

D. visible

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