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  3. HOW ANIMALS IN RAIN FORESTS MAKE THEMSELVES HEARD (1) Scientists have discovered that animals are experts at exploiting weat

HOW ANIMALS IN RAIN FORESTS MAKE THEMSELVES HEARD (1) Scientists have discovered that animals are experts at exploiting weat

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问题                                             HOW ANIMALS IN RAIN FORESTS MAKE THEMSELVES HEARD
    (1) Scientists have discovered that animals are experts at exploiting weather conditions and the physical conditions of their environments so that they are heard or not heard, and seen or not seen. The species living in rain forests must engineer their calls to accommodate all of the obstacles, such as leaf cover, that can deflect and degrade the sounds intended for a potential receiver. Over, short, loud bursts of sound tend to be more effective than longer calls at cutting through the dense foliage.
    (2) There is no natural environment on Earth noisier than a virgin rain forest. In the Peruvian rain forest, every species has developed clever or remarkably sophisticated strategies to ensure that its voice is heard. The noise creates a real challenge for the smaller residents, such as male tree crickets, which need to get the attention of females, often from a relatively long distance. Some species of crickets maximize the volume of their calls by chewing a hole in the middle of a leaf to create a sound baffle, similar to a stereo speaker. The leaf functions as a speaker cabinet, with the cricket in the center acting as the speaker.
    (3) A species of tree frog in Borneo has an inventive approach to getting its mating call heard over the noise. Mataphrenella sudana, which is only an inch long, has learned to exploit the sound properties of a water-filled hole in a tree in the same way that a person uses resonance, the intensification and enrichment of a sound by added vibration, in the shower to sing like a professional performer. The frog searches for a suitable hole and then partially submerges itself in the water. Its forte is the ability to adjust the frequency of its call to the size of the hole and play the tree like a musical instrument. As it sits in the hole, it begins vocalizing at different frequencies until it hits the one note that makes the hole and tree resonate.
    (4) The time of day affects how sound travels in any environment, and this fact is not lost on animals and insects. Early morning and late evening produce conditions that allow sound to travel greater distances than during the middle parts of the day. Sound travels best at night, which is why the rain forest is so wonderfully noisy between dusk and dawn. For species that sleep at night, dusk and dawn are their windows of opportunity to get the best resonance and distance out of a signal. This is why animals, especially birds, tend to be more active and noisy in the early morning and late evening. The British call the phenomenon of birds singing in the early morning the dawn chorus. Because of the superior sound conditions, dusk and dawn are the times to conduct the serious business of attracting mates and defending territories. For predators, it is the best time to track down their noisy prey.
    (5) Another way animals and insects ensure that their calls connect with the intended receivers is by developing their own specialized frequencies, which are determined primarily by the size of their bodies. [A] Recently, a scientist visiting the Peruvian rain forest made an audio tape of a little of the night’s music. [B] When he took the tape back to his lab and analyzed it, he discovered that this seemingly chaotic banquet of sound was actually highly ordered. [C] Each animal and insect is tuned to and calling on its own species-specific frequency, in the same way that radio stations use different signals so that many stations can broadcast at the same time. [D]
    (6) Bernard Krause, a professor at the University of Oregon in Eugene, has found that in older tropical rain forests some species, such as the Asian paradise flycatcher, have become so specialized that their voices occupy several niches of the sound spectrum at the same time, thus laying territorial claim to several audio channels. His recordings from undisturbed rain forests around the world demonstrate a remarkable stability in the combined voices of the residents from year to year. The stability of the ambient sound gives each region a unique sound signature, or fingerprint.
Why does the author describe how some cricket species "maximize the volume of their calls"?
选项 A、To argue that crickets are a major source of noise in virgin rain forests
B、To help explain why it is difficult for many smaller animals to be heard in rain forests
C、To help explain why rain forests are noisier than other natural environments
D、To illustrate a sophisticated way of making a call heard in a rain forest
答案D
解析 本题是修辞目的题，问作者为什么要描述一些蟋蟀提高自己叫声音量的方式。要解题，首先要了解本段的中心论点：在秘鲁的雨林中，每一种生物都练就了或机巧的，或十分娴熟的本领，来传播自己的声音。作者举蟋蟀的例子是为了证明这一论点，故D项“来说明原始雨林中一种传播声音的娴熟手段”的说法正确。A项“说明蟋蟀是原始雨林里噪音的主要来源”，蟋蟀的例子只是众多声音中的一种，原文并无信息可表明或暗示蟋蟀发出的声音是主要来源。B项“用来解释为什么较小的动物在雨林中传声更困难”，如果选B项，文章应该说噪音如何给较小的动物带来阻碍，而不是解释体型较小的动物如何巧妙地发声，故B项与段落逻辑和主旨不符。C项“用来解释为什么雨林比其他自然环境更吵”，这些蟋蟀提高自己的音量不足以成为使热带雨林比其他自然环境更吵的原因，因果关系不成立。
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