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Listen to part of a lecture from a Biology class.
請聽生物課上的部分內容。
When we humans walk from place to place, we move on the Earth's surface, across the Earth's surface.
當我們人類從一個地方走到另一個地方時，我們是在地球的表面移動，或者橫穿地球表面。
Many animals of course do the same thing.
當然很多動物也是這樣。
Horses and dogs and cows and so on, all move on the surface, across the surface of the Earth.
馬、狗、牛和其他動物都是在地球表面移動，橫穿地球表面。
There are also, there are quite a few animals that have the ability to move from place to place underground, beneath the Earth's surface.
但也有一些動物可以通過地下從一個地方到達另一個地方，它們在地表以下移動。
This moving around underground is known as subsurface locomotion.
這種在地下四處移動的行為被稱作地下運動。
Subsurface locomotion has a number of benefits.
地下運動有諸多好處。
One benefit of subsurface locomotion is that it enables animals to minimize their exposure to extreme temperatures.
其中一個好處就是：可以減少動物暴露在極端氣溫下的幾率。
This is very helpful for animals that live in areas with harsh climates,
這對生活在嚴峻環境中的動物來說很有益處，
where it could be very dangerous to spend large amounts of time on the surface.
在這種嚴峻環境里，長時間待在地球表面是很危險的。
For example, in the Sahara Desert, in Africa,
比如，在非洲的撒哈拉沙漠里，
there's a type of lizard that's able to move beneath the surface, through the sand, very quickly.
有一種蜥蜴能夠穿過沙子在地表以下移動，動作十分迅速。
Because this lizard can move so easily and so quickly underground,
由于這種蜥蜴在地下移動十分簡單迅速，
it doesn't have to travel on the surface, where it would be exposed to dangerously high temperatures.
它并不需要在地面活動，否則將暴露在致命高溫下。
Another benefit of subsurface locomotion is that it can help animals capture prey.
地下運動的另一個好處就是能夠幫助動物捕食。
That's because animals on the surface can't see predators that are approaching underground.
這是因為地面上的動物看不見從地下接近它們的捕食者。
Our lizard in the Sahara Desert is again, a good example.
撒哈拉沙漠的蜥蜴同樣又是很好的例子。
The way it works is, when an insect is walking nearby on the surface, it produces very subtle vibrations in the sand.
具體原理是這樣的：昆蟲在附近的地面移動時會在沙子中產生非常輕微的震動。
When the lizard senses these vibrations, it moves very quickly.
一旦蜥蜴感知到了這些震動，便會迅速行動起來。
Underground, where it can't be seen, toward the source of the vibrations.
它在地下朝著震源移動，而它的獵物卻渾然不覺。
It then suddenly pops up directly under the insect and catches it completely by surprise.
接著它會猛得從昆蟲下方直接沖出，完全出其不意地將獵物捕獲。
