Adaptive radiation is the process by which one species evolves into two or more species.
This occurs as a result of different populations becoming reproductively isolated from each other, usually by adapting to different environments. Reptiles and birds lay amniote eggs. Amphibia the vertebrate class Amphibia spend part of their lives under water and part on land. Frogs, toads, and salamanders are amphibians. All of these animals must return to damp areas to reproduce since their eggs would dry out otherwise.