- Examples: sharks, bony fish, rays
- Characteristics: aquatic, possess gills, ectothermic
2. Amphibians:
- Examples: frogs, salamanders, toads
- Characteristics: semi-aquatic, transition from gills to lungs during life cycle, ectothermic, smooth and moist skin
3. Reptiles:
- Examples: snakes, lizards, turtles, crocodilians
- Characteristics: terrestrial, possess lungs, covered in scales, ectothermic
4. Birds:
- Examples: eagles, penguins, hummingbirds
- Characteristics: endothermic, feathered, possess beaks, forelimbs modified into wings
5. Mammals:
- Examples: humans, lions, whales, bats
- Characteristics: endothermic, have fur or hair, possess mammary glands , give birth to live young (except monotremes).