This is a major new textbook that is intended to lead students away from purely descriptive zoology courses into an experimental approach that emphasizes asking and answering questions about nature. The book gives a panoramic view of vertebrate life, classification, ecology and behaviour. Section I of the book describes the major groups of vertebrates and their origins. The second section covers classification and its methodology. Section III describes the ecology of vertebrates from two standpoints: how individuals cope with environmental extremes, and principles of population and community ecology as illustrated by experiments carried out in the field. Section IV describes the geographic distribution of vertebrates. The fifth section discusses migration. Vertebrate behaviour is the subject of the final section and covers observations and the theories and experiments they have inspired.