What Is a Fish?
A fish is a vertebrate animal that lives in water and breathes through gills. Fish are cold-blooded, meaning their body temperature changes with the environment around them. They have fins for swimming and scales to protect their bodies from predators. Most fish also have an organ called a swim bladder which helps them stay buoyant in the water. There are over 32,000 species of fish living on Earth today, ranging from tiny minnows to giant whale sharks.
Fish can be found all over the world in both fresh and saltwater habitats such as rivers, lakes, oceans, coral reefs and even underground caves! Many species of fish migrate long distances each year between different areas where they feed or spawn eggs. Some types of fish live alone while others form large schools for protection against predators or just because it’s more fun! Fish play an important role in many ecosystems by providing food for other animals like birds and mammals as well as helping keep aquatic plants healthy by eating algae off rocks and other surfaces.