You will now listen to part of a lecture. You will then be asked a question abou

Here we talk about biology. That is, animals in tropical rain-forests. Animals are like human beings: they also have minds and know to protect their own body and persue their own self-interest. Therefore, in order to survive and for some other reasons, they must evolve two kinds of behavior after long time of living: searching for food individually and making sounds to protect their territories.
The first behavior is about the way to search for food. Some big animals need a lot of food to fill their stomachs, such as apes. If they go out with others, there will certainly be conflict when they find a small amount of food since it is not enough for all of them. So they have a better chance if they go alone. Observations of experts show that apes search for food alone.
The other behavior is about the way they protect their territory. Some animals move from one tree to another tree every day and at every moment. They must develop some skills or methods to inform others about their territory or existence if they don’t want to be attacked and therefore survive in the forests. For example, a type of monkey usually protects its territory by making sounds. If other monkeys or animals enter their territory, they will make a sound to tell them that this is their territory. And other animals will leave or run away after hearing the sound.