2018年11月25日托福听力机经精准预测

2018年11月25日托福听力机经精准预测

　　题目

　　1.What is the purpose of the lecture?

　　A.To suggest that cryptic patterns in the animal kingdom can be reduced to only a few basic forms

　　B.To explain how cephalopods change cryptic patterns based on their visual perception

　　C.To contrast underwater and dryland crypsis strategies

　　D.To trace the evolution of crypsis in animals as a defense against

　　2. hat can be inferred about an animal that only uses stipple crypsis?

　　A. It will have a difficult time hiding from predators. B.It is likely to be of a medium body size.

　　C.It will tend to avoid areas with multiple colors and patterns. D.It will most likely be found close to a seashore.

　　3. hat happens to some cephalopods when they swim over a gravel patch on the seafloor?

　　A.They change their skin color to match the color of the darkest pieces of gravel.

　　B.They display irregularly shaped dark and light patches.

　　C.They display a disruptive coloration to match the local environment.

　　D.They quickly swim away from the gravel patch.

　　4. hat features of disruptive crypsis does the professor mention? A.It disguises the outline of the animal that uses it.

　　B. It works by contrasting with the colors in the surrounding habitat.

　　C. It is most effective when used against a single-colored background.

　　D. It can incorporate a combination of other crypsis patterns. 5.Why does the professor mention the tiger?

　　A.To illustrate that the results of the cephalopod research can be extended to many other animals

　　B.To give an example of an animal whose crypsis strategy has been extensively studied

　　C.To point out how different its crypsis strategy is from the strategy used by smaller animals

　　D.To argue that predators rely on crypsis less than prey species do 6.What does the professor imply when she says this:

　　A.Crypsis in cephalopods can rarely fool human visual perception. B.Few animals use crypsis to hide from predators.

　　C.New information has led to the reevaluation of some previous assumptions.

　　D.More cephalopod research needs to be done to obtain accurate

　　data.

　　听力文本

　　Narrator:

　　Listen to part of a lecture in a biology class. Teacher:

　　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 leaves or flowers, frogs that look like rock, 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 there are a thousand of patterns that animals use to hide from predators. However, recent research involving cephalopods is teaching us that there is 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 color 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. A mottled body pattern consist of

　　alternating irregularly shaped dark and regularly 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 color patterns are irregular patches of different shapes and colors that serve to distract the observer’s intention and obscure the outline, or the 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 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, 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.

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