سوالات گفتاری ۶

Speaking Question 6

Listen to part of a lecture from a Biology class.

When we humans walk from place to place, we move on the Earth’s surface, across the Earth’s surface. Many animals of course do the same thing.

Horses and dogs and cows and so on, all move on the surface, across the surface of the Earth. But there are also quite a few animals that have the ability to move from place to place underground, beneath the Earth’s surface. This moving around underground is called subsurface locomotion.

Sub surface location has a number of benefits. One benefit of subsurface locomotion is that it enables animals to minimize their exposure to extreme temperatures. This is very helpful to animals that live in areas with harsh climates, where it could be very dangerous to spend large amounts of time on the surface.

For example, in the Sahara Desert, in Africa, there’s a type of lizard that’s able to move beneath the surface, through the sand, very quickly. Because this lizard can move so easily and so quickly underground, it doesn’t have to travel on the surface, where it would be exposed to dangerously high temperatures. Another benefit of subsurface locomotion is that it can help animals capture prey.

That’s because animals on the surface can’t see predators approaching underground. Our lizard in the Sahara Desert is again, a good example. The way it works is, when an insect is walking nearby on the surface, it produces very subtle vibrations in the sand. When the lizard senses these vibrations, it moves very quickly.

Underground, where it can’t be seen, toward the source of the vibrations. It then pops up directly under the insect and catches it by surprise.