ZOOLOGY

branch of biology concerned with the members of the animal kingdom and with animal life in general. It embraces all conceivable forms of study, not only of the components of the animal body and the vital processes that sustain it but also of the relations of individual animals or animal groups with one another and the environment. Because of its vast scope, zoology is divided into a number of subdisciplines of which the chief ones include cytology, embryology, morphology, physiology, pathology, paleontology, genetics and evolution, taxonomy, ethology, ecology, and zoogeography. The science of zoology has its origins in ancient Greece and the Roman Empire, in the works of Hippocrates, Aristotle, and Pliny. Later naturalists continued in the Aristotelian tradition. In the 15th century the invention of the printing press greatly aided the dissemination of information. The contributions of individuals such as William Harvey (the circulation of blood), Carolus Linnaeus (system of nomenclature), Georges-Louis Leclerc de Buffon (natural history), and Georges Cuvier (comparative anatomy) further advanced the field of zoology. The identification of the cell as the common structural unit of living things and the advancement of the study of chemistry clarified for Claude Bernard the concept of homeostasisthe stability of the internal bodily environment. As technology progressed, a number of new biological disciplines, such as embryology, began to develop. A major turning point in zoological studies occurred in 1859, when Charles Darwin's On the Origin of Species by Means of Natural Selection was published. In it Darwin formulated his theory of evolution. Since that time the study of genetics has grown essential to a number of biological disciplines. While specialization has increased, the necessity for interdisciplinary studies also has become clear. branch of biology that studies the members of the animal kingdom and animal life in general. It includes both the inquiry into individual animals and their constituent parts, even to the molecular level, and the inquiry into animal populations, entire faunas, and the relationships of animals to each other, to plants, and to the nonliving environment. Though this wide range of studies results in some isolation of specialties within zoology, the conceptual integration in the contemporary study of living things that has occurred in recent years emphasizes the structural and functional unity of life rather than its diversity. Additional reading Willy Ley, The Dawn of Zoology (1968), contains a fascinating account of certain historical aspects of zoology. General texts include Robert L. Dorit, Warren F. Walker, Jr., and Robert D. Barnes, Zoology (1991), an introductory-level survey; Paul A. Meglitsch and Frederick R. Schram, Invertebrate Zoology, 3rd ed. (1991); F. Harvey Pough, John B. Heiser, and William N. McFarland, Vertebrate Life, 4th ed. (1996); and Richard C. Brusca and Gary J. Brusca, Invertebrates (1990), a systematic treatment. Robert Lynn Carroll, Vertebrate Paleontology (1988), shows how the data from fossils are used to understand evolutionary change. Two advanced texts are Hans-Peter Schultze and Linda Trueb (eds.), Origins of Higher Groups of Tetrapods: Controversy and Consensus (1991); and Jan L. Mason (ed.), Evolution of Domesticated Animals (1994), a comprehensive sourcebook for vertebrate species from mammals to fish. Earl Dorchester Hanson The Editors of the Encyclopdia Britannica