This best-selling dictionary is the most comprehensive and up to date of its kind, containing over 6,000 entries on all aspects of zoology. Wide-ranging, authoritative, and with jargon-free definitions, this dictionary is an indispensable reference tool. Complemented by numerous illustrations, it includes terms from the areas of ecology, animal behavior, evolution, earth history, zoogeography, genetics, and physiology and provides full taxonomic coverage of arthropods, other invertebrates, fish, reptiles, amphibians, birds, and mammals. The fourth edition has been fully revised and updated and includes many new entries, for example, activational effects of hormones, aqueous humor, deprivation studies, immunization, and Psocoptera. It also features new terms from anatomy and physiology, biomechanics, neurophysiology, immunology, and evolutionary development. Recommended web links can be accessed via the Dictionary of Zoology companion website and provide valuable extra information by directing you to useful online resources and the homepages of relevant organizations. Detailed appendices include a list of endangered animals, the universal genetic code, the geologic time scale, SI units, and a taxonomic classification scheme based on the three-domain taxonomic system.