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托福TPO62口语原文（第四部分）

Listen to part of a talk in a biology class.

Okay, so on the topic of animal survival strategies, one type of strategy that's fascinated people for centuries is protective resemblance. That's when animals resemble their environment in some way or another by taking on the color or shape, or both of the physical objects that are behind or beneath them.Today, we'll talk about two kinds. Which kind of protective resemblance an animal has, well It depends on whether the animal moves through different environments in the course of its life, or whether it's environment is more or less permanent. For example, animals like the homed frog, well they've got the permanent kind of protective resemblance, which is fine, because well during the course of their lives, they don't visit other places.So the horn frog is brown, just like the dead leaves on the forest floor where it lives. And it's got brown lines running down its body just like the veins of the leaves. The color and shape of its protective resemblance is fixed, like its environment.So when the horn frog is on the forest floor, it's almost impossible for predators to see it.

Now, other animals like uh like the lizards display a different sort of protective resemblance.They actually change color, which is important for them, because they travel through different environments as they live and grow.

So the protective resemblance they exhibit is adaptive, depending on the environment they're in. The lizard has special moving pigments in its cells, which change to match the color of whatever environment it's currently occupying. If the lizard is walking among the dead leaves of the forest floor, it'll tum the same brown color as the leaves. But if the lizard runs into some green shrubs, well it'll tum green.

Using the examples of the horned frog and the lizard, explain the differences between the two types of protective resemblance discussed by the professor.

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