Mammals reproduce through live birth, while other animals such as reptiles and birds lay eggs where the embryo develops inside the egg. Both mammals and reptiles produce sexually. Most mammals have fur or hair, however, other animals such as reptiles/birds have feathers/scales.
Mammals and reptiles, two of the five classes of vertebrates, are among the most complex animals on Earth. There are approximately 8,240 species of reptiles, including snakes, turtles and lizards, which make it a more diverse group than mammals, of which there are about 5,400 species. Mammals, which include whales, bears and primates, are believed to have evolved from reptiles 240 million years ago.
