What do all animals - from fish to mammals - have in common?
Vertebrates. From the smallest of fish to us. One of the main features we all have in common is our backbone. The Vertebrates chapter describes the biological features of fish, amphibians, reptiles, birds, and mammals.
Vertebrates. From fish to mammals. Obviously a tremendous amount of differences among these groups of species. But also many similarities. Fish had to evolve first. Then they moved onto land as amphibians, but they still had to live close to the water. Then they moved farther away from the water as reptiles. Reptiles could live anywhere, and they did. Reptiles became very large and dominated life on the planet. Some reptiles evolved flight and turned into birds. Others stayed small and became mammals. When all the large reptiles were extinct, what remained? Smaller animals, including mammals, which then became the dominant form of life.