Animal Classification

There are millions of different animal species on Earth. To keep track of them all, scientists sort them into groups. This is called classification. Animals are grouped together when they share important features like body structure, how they breathe, and how they have babies.

The Main Animal Groups

The biggest groups of animals are vertebrates and invertebrates. Vertebrates have backbones and include mammals, birds, reptiles, amphibians, and fish. Invertebrates do not have backbones. Insects, spiders, worms, and jellyfish are all invertebrates. About 97 percent of all animals are invertebrates.

Why We Classify Animals

Classification helps scientists study and talk about animals. When an animal is classified, scientists know a lot about it right away. They can tell if it is warm-blooded or cold-blooded. They know if it lays eggs or gives live birth. Classification also helps scientists understand how different animals are related to each other.

Fun Facts

• Scientists have discovered and named about 1.5 million animal species so far.
• A Swedish scientist named Carl Linnaeus invented the modern system of classification in the 1700s.
• New animal species are still being discovered every year, especially in the deep ocean.

Did You Know?

The platypus confused scientists for a long time because it has fur like a mammal, a bill like a duck, and lays eggs like a reptile. It is classified as a mammal because it feeds its babies milk!