Fish: Animals That Live Underwater

Fish are animals that spend their lives underwater. Fish have backbones. In fact, they are the biggest group of animals with backbones on Earth. Earth is covered mostly by water, so it makes sense that fish are the biggest group.

Fish do everything underwater. They lay eggs underwater. They also eat and sleep underwater. Fish do not sleep in the same way mammals sleep. Fish can’t close their eyes because they don’t have eyelids. When they sleep, they float around or find a place to hide while they rest.

Fish have scales that cover their skin. Scales are smooth and round. The scales help fish move easily through the water. Fish also use the fins on their body and their tails to swim and glide. Some fish travel in groups called schools.

Like other animals, fish need to breathe in oxygen. But fish do not have lungs. They have gills. They use these gills to breathe in the oxygen they need from water.

Sometimes people throw garbage, like plastic, into the water. This is pollution, which can hurt fish. Pollution has a bad impact on fish’s habitats. To protect fish, humans can work together to clean up the water.