TOEFL Listening: ETS-TOEFL听力机经 - 45N93MCB2TCQ833QQ$

Lecture: CrypsisAuthor: QQ-464094252: Narrator: Listen to part of a lecture in a biology class. Professor: In the animal kingdom, camouflage is a common strategy to avoid predation. There are many examples. The most famous might be the chameleon, a lizard that can change its skin color to match its surroundings. But there are also insects that look like leaves or flowers, frogs that look like rocks, you could probably think of a dozen more examples. First of all, let me introduce a technical term that's often used for camouflage, and that's crypsis. When we examine crypsis in the animal kingdom, it may appear that there are a thousand different patterns animals use to hide from predators. However, recent research involving cephalopods is teaching us that there is actually less there than meets the eye. Squid, octopuses and cuttlefish are cephalopods and they're uniquely suited for crypsis research because individual animals don't have a fixed coloration but actually can very quickly change the appearance of their skin to match almost any habitat. Cephalopods can produce up to fifty different colors, patterns, and textures, but what the research is telling us is that all these patterns employed by the cephalopods are variations under three basic types of crypsis. The first is uniform, or stipple. The word stipple is taken from visual art. It means making small dots to create the impression of a solid color. Anyway, uniform or stipple body patterns are used by cephalopods to match their skin color to fairly uniform backgrounds like a sandy sea bottom. A sandy sea bottom has one basic color with little variation. So, an octopus would only need to change its skin color to one basic color to match the environment. When a cephalopod needs to blend into a non-uniform, a more varied background like gravel, which is made up of small rocks of various sizes and colors, the cephalopod shows a mottled body pattern. Mottled body patterns consist of alternating irregularly shaped dark and light patches in the skin that roughly match the size of the dark and light objects in the immediate area. And finally, cephalopods also use what's called disruptive coloration. Disruptive body patterns are irregular patches of different shapes and colors that serve to distract the observer's attention and obscure the outline, or true shape of the animal. In other words, a disruptive pattern makes it difficult to perceive the shape and size of the animal. Disruptive patterns can also achieve some level of general resemblance to the background. That is, they often contain small regions with mottled pattern, or even in the front of it. Cephalopod will adopt this crypsis strategy when the background is irregular and contains relatively large and varied patches of colors and texture. Now, you may be asking yourself why studying cephalopod crypsis is important. Well, while evolution has produced a wide variety of body colorations and patterns in the animal kingdom, the basic pattern type we've observed in cephalopod are used throughout the animal kingdom and ecological habitats. And that goes not just for animals that can change their cryptic patterns, but also for animals that have just one cryptic pattern they cannot change. In other words, the same basic strategies are used by the chameleons and frogs, and insects we talked about, and by larger animals as well. For example, the tiger's pattern of the black stripes on a lighter background is a form of disruptive coloration.