在以往的托福阅读考试中有关于雨林动物信息传递的考试文章。针对这道托福考题，前程百利小编为大家普及一下相关背景知识，这样有助于考生在面对这类题目时方便作答。托福阅读真题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.
以上就是今天的托福阅读材料，大家可以在练习托福阅读材料的同时，积累一些相关词汇及句型，以便考试的时候更好地把握文意，夺得托福阅读的高分。前程百利小编预祝大家托福考试取得优异成绩!
