关于海豚的简单英文介绍

Dolphins are mammals of the order Cetacea. They are animals that live in the water, in the sea or in rivers.
The name dolphin is used for oceanic dolphins and river dolphins. But oceanic dolphins and river dolphins are not directly related.
Their name, dolphin, comes from the Ancient Greek δελφίς (delphis) meaning with a womb, because it was first thought to be a fish with a womb. It is now known to be very different from fish, because it breathes air and has warm blood, like all other mammals. They are believed to be very smart.
The brain of a dolphin is like a human brain in size and development. Dolphins have good eyesight. They can watch a thing in the water, and they can see colors, too. They can also see in dark places. Dolphins breathe air. Their nose on top of the head to be easy to breathe on the surface of the water. A dolphin's hearing is better than their sight. There are some small holes behind the eyes, and they are the ears of a dolphin. Dolphins can hear a sound underwater. They can know the direction of the sound very well. The skin of a dolphin has no scales. It is soft and smooth.
Dolphins do not sleep in a norman way. Each of the two sides of their brain can be made to stop thinking. They let the right brain and the left brain be unused in turn to sleep.