Another group of vertebrates is the reptiles. Reptiles have dry scaly skin and spend all of their lives on land. Like fish and amphibians, reptiles are cold-blooded animals. Unlike fish and amphibians, reptiles lay their eggs on land. Reptiles are different in many ways.
Birds are more advanced than fish, amphibians or reptiles.
The body covering on birds is called feathers. In almost every other way, birds are different from any of the vertebrates we have seen so far. They are also the first warm-blooded vertebrates so far. In other words, a bird's body temperature stays the same, no matter how cold or hot the air may be. A bird's feathers help to keep the bird warm.