TOEFL Speaking Task 4 Practice 023Environment

Narrator:Listen to part of a lecture in a Biology class.

Professor:So we know animals in many climates have to develop strategies, um...ways to protect themselves when the weather becomes especially hot and dry in the summers. Let's start talking about how one small creature, a snail can do this. Now, as you know, a snail is a very small creature, with a soft, moist body, most of which is protected by a hard shell. A snail is a good example of an animal that has developed certain strategies for coping with high temperatures and drought or lack of water. First to avoid the heat, when the sun comes out, snails move into the shelter of vegetation, you know, plants or leaves, to get out of the sun and into the shade. Now, of course, the ground can become very hot in the sun, it absorbs and radiates heat. So snails will move up off of the ground to places where it is cooler. They may attach themselves to a wall or a tree where it is cooler than on the ground. Now it's not just heat that snails need to worry about, they also need to avoid drying out due to lack of water. So during a really warm, dry day or during the summer months, snails secrete a sticky, slimy substance, made up of calcium, and it covers the opening of their shell, covers and closes it up. This keeps the moisture inside the shell and prevents the snails from drying out. Snails can stay inside their shells, closed up like this for a long time, even several months if it's a really dry summer. Their bodies, well, everything slows down and so they don't need food. They can survive on what food they've stored up. But when it rains and water is available again, the snail opens up its shell to get some.