托福阅读背景材料(343)：雨林动物传递信息方式

　　托福阅读背景知识/材料之雨林动物传递信息方式，更多托福阅读背景材料/知识尽在新东方在线托福考试频道！

　　2014年5月25日托福阅读真题再现：

　　讲的是动物、昆虫的发声的问题

　　最开始怎么说的记不清楚了，第一层应该就是rain forest里面的小东东怎么让声音传播。热带雨林里面这么吵，要让同类听到自己还是很不容易的，尤其对于那些小昆虫什么的，而且很多小东西通过发声来求偶交配嘛，你们都懂的!!!Rain forest这里举了一个树蛙的例子，就是这小青蛙用的一种招数，它一般会进到有水的树洞， 身体一部分没入水中，然后开始发声，找到与大树能共鸣的频率，这不就能传的更高更远嘛。(有排除题)

　　下面一层应该是讲birds，同时提到了它们叫的时间一般是在早上和黄昏，那个时候声音能传得更远， 但是有些时候也会让天敌们发现之类的(没记错的话，最少有俩道题)

　　最后一层应该是提到了不同物种的发声频率不同，这能让它们被分辨出来。还有一个教授，把声音录下来回去分析，发现每个雨林的声音还不太一样，也是unique的，甚至可以像人类的指纹一样去分辨树林的独特声音什么的(有题)

　　解析：

　　本篇文章讲解了雨林中不同动物不同的传递信息的方式。属于生物学中典型的话题，请大家理解文章时重点关注生物传递信息的方式与雨林环境的适应性的体现。相应背景请参考下文：

　　The daytime quality of light in forests varies with the density of the vegetation, the angle of the Sun, and the amount of cloud in the sky. Both animals and plants have different appearances in these various lighting conditions. A color or pattern that is relatively indistinct in one kind of light may be quite conspicuous in another.

　　In the varied and constantly changing light environment of the forest, an animal must be able to send visual signals to members of its own species and at the same time avoid being detected by predators. An animal can hide from predators by choosing the light environment in which its pattern is least visible. This may require moving to different parts of the forest at different times of the day or under different weather conditions, or it may be achieved by changing color according to the changing light conditions. Many species of amphibians (frogs and toads) and reptiles (lizards and snakes) are able to change their color patterns to camouflage themselves. Some also signal by changing color. The chameleon lizard has the most striking ability to do this. Some chameleon species can change from a rather dull appearance to a full riot of carnival colors in seconds. By this means, they signal their level of aggression or readiness to mate.

　　Other species take into account the changing conditions of light by performing their visual displays only when the light is favorable. A male bird of paradise may put himself in the limelight by displaying his spectacular plumage in the best stage setting to attract a female. Certain butterflies move into spots of sunlight that have penetrated to the forest floor and display by opening and closing their beautifully patterned wings in the bright spotlights. They also compete with each other for the best spot of sunlight.

　　Very little light filters through the canopy of leaves and branches in a rain forest to reach ground level—or close to the ground—and at those levels the yellow-to-green wavelength predominate. A signal might be most easily seen if it is maximally bright. In the green-to-yellow lighting conditions of the lowest levels of the forest, yellow and green would be the brightest colors, but when an animal is signaling, these colors would not be very visible if the animal was sitting in an area with a yellowish or greenish background. The best signal depends not only on its brightness but also on how well it contrasts with the background against which it must be seen. In this part of the rain forest, therefore, red and orange are the best colors for signaling, and they are the colors used in signals by the ground-walking Australian brush turkey. This species, which lives in the rain forests and scrublands of the east coast of Australia, has a brown-to-black plumage with bare, bright-red skin on the head and a neck collar of orange-yellow loosely hanging skin. During courtship and aggressive displays, the turkey enlarges its colored neck collar by inflating sacs in the neck region and then flings about a pendulous part of the colored signaling apparatus as it utters calls designed to attract or repel. This impressive display is clearly visible in the light spectrum illuminating the forest floor.

　　Less colorful birds and animals that inhabit the rain forest tend to rely on forms of signaling other than the visual, particularly over long distances. The piercing cries of the rhinoceros hornbill characterize the Southeast Asian rain forest, as do the unmistakable calls of the gibbons. In densely wooded environments, sound is the best means of communication over distance because in comparison with light, it travels with little impediment from trees and other vegetation. In forests, visual signals can be seen only at short distances, where they are not obstructed by trees. The male riflebird exploits both of these modes of signaling simultaneously in his courtship display. The sounds made as each wing is opened carry extremely well over distance and advertise his presence widely. The ritualized visual display communicates in close quarters when a female has approached.