Zoology, the study of animals. Zoology is a part of the science of biology, the study of all life. In its broadest sense zoology includes all the branches of medicine; the sciences of anthropology, psychology, and sociology; and such applied sciences as animal husbandry, conservation, and sanitation.

The Work of the Zoologist

Zoology is a broad and complex science, and for this reason zoologists specialize in its various subdivisions. Some of these specialties are basic to all biological study, and are described in "Biology:The Work of the Biologist." These fields of study are further broken down into other specialties.

Zoologists may concern themselves only with ornithology (the study of birds) or with entomology (the study of insects). The animal ecologist, who studies animals in relation to their environment, may concentrate on one type of animal, or may study effects of an environmental change—such as air pollution—on all animals.

Zoologists must have an understanding of other sciences including chemistry and physics. For example, a knowledge of chemistry helps a zoologist determine how pesticide wastes in the water supply affect animals; physics aids in explaining how birds fly. Geology and geography are related to studies of animal evolution and distribution.

Most zoologists work in educational institutions as teachers and researchers. Others engage in research for scientific institutions or commercial enterprises, such as drug companies. Zoologists are employed in public health and wildlife conservation, and on the staffs of zoos and museums.

History
Early Development

Prehistoric peoples must have studied the habits of the animals they hunted and must have been familiar with the animals' anatomy. The first systematic zoological studies, however, were probably limited largely to the human body and its functions. Ancient Babylon and Egypt made valuable contributions to medical knowledge, especially in the field of anatomy. However, superstition often hindered progress in the observation and understanding of nature.

It was not until the classic period of Greek culture that any real headway was made in separating zoological studies from superstition. Hippocrates (460?-357? B.C.) and Aristotle (384-322 B.C.) studied animal life by actual observation. In Rome, the Greek physician Galen (130-201? A.D.) also applied the scientific approach to the study of anatomy. After his death zoology as a science went into a decline that lasted throughout the Middle Ages.

15th-18th Centuries

With the Renaissance came a revival of scientific methods. Leonardo da Vinci of Italy and Andreas Vesalius, a Belgian physician, made accurate, detailed studies of anatomy. William Harvey, an English physician, discovered the mechanics of blood circulation. The invention of the microscope in the early 17th century opened up new fields of investigation. In the 18th century the Swedish naturalist Carl Linnaeus devised a classification system that became the basis of modern taxonomy.

Modern Zoology

In the 19th century the science of zoology expanded rapidly. Groundwork was laid in the fields of comparative anatomy, cytology (the study of cells), genetics, embryology, and physiology. Several theories of organic evolution were advanced by naturalists, including the Englishman Charles Darwin. Darwin's Origin of Species (1859) revolutionized biology.

In the 20th century, precision instruments and improved techniques brought about a more intensive application of experimental methods in zoology. Great advances were made in the study of genetics and ecology. The study of psychology was advanced by medical researchers and other zoological specialists. Genetic engineering and improved vaccines have improved the health and productivity of farm animals.