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第1段
1 .<-NARRATOR:-> Listen to part of a lecture from a biology class.
请听生物课上的部分内容。
第2段
1 .<-FEMALE PROFESSOR:-> When we humans walk from place to place, we move on the Earth's surface,
当我们人类从一个地方走到另一个地方时，我们是在地球的表面移动，
2 .across the Earth's surface.
或者横穿地球表面。
3 .Many animals, of course, do the same thing -
当然很多动物也是这样。
4 .horses, and dogs, and cows, and so on all move on the surface,
马、狗、牛和其他动物都是在地球表面移动，
5 .across the surface of the earth....
横穿地球表面。
6 .But there are also quite a few animals that have the ability to move from place to place underground,
但也有一些动物可以通过地下从一个地方到达另一个地方，
7 .beneath the earth's surface.
它们在地表以下移动。
8 .This moving around underground is known as subsurface locomotion.
这种在地下四处移动的行为被称作地下运动。
9 .Subsurface locomotion has a number of benefits.
地下运动有诸多好处。
第3段
1 .One benefit of subsurface locomotion
其中一个好处就是：
2 .is that it enables animals to minimize their exposure to extreme temperatures.
可以减少动物暴露在极端气温下的几率。
3 .This is very helpful for animals that live in areas with harsh climates,
这对生活在严峻环境中的动物来说很有益处，
4 .where it could be very dangerous to spend large amounts of time on the surface.
在这种严峻环境里，长时间待在地球表面是很危险的。
5 .For example, in the Sahara Desert, in Africa,
比如，在非洲的撒哈拉沙漠里，
6 .there's a type of lizard that's able to move beneath the surface-
有一种蜥蜴能够穿过沙子在地表以下移动，
7 .through the sand-very quickly.
动作十分迅速。
8 .Because this lizard can move so easily and so quickly underground,
由于这种蜥蜴在地下移动十分简单迅速，
9 .it doesn't have to travel on the surface,
它并不需要在地面活动，
10 .where it would be exposed to dangerously high temperatures.
否则将暴露在致命高温下。
第4段
1 .Another benefit of subsurface locomotion
地下运动的另一个好处
2 .is that it can help animals capture prey.
就是能够帮助动物捕食。
3 .That's because animals on the surface
这是因为地面上的动物
4 .can't see predators that are approaching underground.
看不见从地下接近它们的捕食者。
5 .Our lizard in the Sahara Desert is again a good example.
撒哈拉沙漠的蜥蜴同样又是很好的例子。
6 .The way it works is,
具体原理是这样的：
7 .when an insect is walking nearby on the surface,
昆虫在附近的地面移动时会在沙子中
8 .it produces very subtle vibrations in the sand.
产生非常轻微的震动。
9 .When the lizard senses these vibrations,
一旦蜥蜴感知到了这些震动，
10 .it moves very quickly - underground,
便会迅速行动起来。
11 .where it can't be seen -
它的猎物却浑然不觉。
12 .toward the source of the vibrations.
它在地下朝着震源移动，
13 .It then suddenly pops up right under the insect,
接着它会猛得从昆虫下方直接冲出，
14 .and catches it completely by surprise.
完全出其不意地将猎物捕获。