Animal Classification

Vertebrates are animals with backbones. The following groups of animals are all vertebrates.

• Mammals are the only animals whose young feed on the mother's milk. They are also the only animals that have hair or fur. Examples include people, whales, lions, dogs, and raccoons.
• Fish have gills and live in water environments. They can be found in salt water and in fresh water. Examples include sharks, eels, trout, sea horses, and bass.
• Amphibians have scaleless skin and usually live part of their lives in water and part on land. Examples include toads, frogs, and salamanders.
• Reptiles have dry scaly skin and lungs. They can live on land or in water. Examples include snakes, lizards, and alligators.
• Birds have feathers, wings, and beaks. Examples include hummingbirds, penguins, ostriches, bluejays, and eagles.

Invertebrates are animals without backbones. The following groups of animals are all invertebrates.

• Worms are tube-shaped animals that may be found in land or water environments. Examples include earthworms, leeches, tapeworms, and hookworms.
• Mollusks have hard shells, rough tongues, and single muscular feet. Examples include snails, squids, octopuses, and clams.
• Arthropods have jointed legs and hard exoskeletons. Examples include lobsters, spiders, centipedes, and insects.