Knowledge Explorer lesson
Animal Groups
What are mammals, birds, reptiles, amphibians, and fish?
Scientists sort animals into groups by their body parts and how they live.
Mammals have hair or fur and feed their babies milk. Dogs, whales, bats, and people are mammals. Most mammal babies are born alive, but a few mammals, like the platypus, lay eggs.
Birds have feathers, and all birds lay eggs. Fish live in water, breathe with gills, and have fins. Most fish lay eggs.
Reptiles, like snakes, lizards, turtles, and alligators, have dry, scaly skin. Amphibians, like frogs, toads, and salamanders, have smooth, moist skin. Most amphibians start life in water and later live on land.
What you will learn
- Sort animals into five major groups by their body features
- Tell the difference between a reptile and an amphibian
- Name animals that lay eggs and animals that give birth to live young
Key facts
- Mammals have hair or fur and feed their babies milk.
- Birds have feathers, and all birds lay eggs.
- Fish breathe with gills and have fins.
- Reptiles have dry, scaly skin.
- Amphibians have smooth, moist skin, and most start life in water.
- A whale is a mammal, not a fish. It breathes air and feeds its babies milk.