: a branch of biology that deals with the classification and the properties and vital phenomena of animals
: the properties and vital phenomena exhibited by an animal, animal type, or group
Branch of biology concerned with members of the animal kingdom and with animal life in general. The science originated in the works of Hippocrates, Aristotle, and Pliny. The contributions of individuals such as William Harvey (the circulation of blood), Carolus Linnaeus (system of nomenclature), Georges-Louis de Buffon (natural history), Georges Cuvier (comparative anatomy), and Claude Bernard (homeostasis) greatly advanced the field. The 1859 publication of Charles Darwin's On the Origin of Species by Means of Natural Selection was a major turning point. Since that time, the study of genetics has become essential in zoological studies.