Vertebrates

• Mammals have fur or hair on the skin, external ears (pinna), and give birth to young.
• Reptiles have thick, dry, scaly skin, usually four legs, and conceive from an egg.
• Fish have wet scales, a streamlined body shape, external fertilization and soft eggs, and use gills to breathe.
• Amphibians have smooth, moist skin, external fertilization and soft eggs, can live on land and water, and most have four legs.
• Birds have feathers on the body and scales on the legs, maintain a constant internal body temperature, have hard eggs, and reproduce through internal fertilization.