The book describes the diversity and features of various vertebrate groups, ranging from the oldest living fishes to the relatively more recent groups to evolve such as mammals. The authors cover the structures of body systems including organs and tissues, as well as their functions and how they differ in various vertebrate groups. They also discuss the evolution of vertebrate groups from the earliest extinct ancestors to the living vertebrates as well as related groups that are now extinct. The book contains illustrations to clarify various issues and discussions of the features that enable vertebrates to adapt to aquatic and terrestrial environments they inhabit.