Zoology is a branch of biology that concentrates on the study of animals. The term comes from two Greek words: "zoon," which means "animal," and "logos," which means "the word about." Although the Greek philosopher Aristotle is sometimes called "the father of zoology," humans have always been interested in learning about animals, so it is difficult to say when zoology originated.
Because the animal kingdom is by far the largest and most varied of all the kingdoms, zoology is an extremely broad discipline. It includes such topics as the anatomy, physiology, embryology , genetics, and ecology of animals. It was natural, therefore, that this topic became subdivided as human knowledge increased. An early partition distinguished vertebrate zoology from invertebrate zoology, but because about 97 percent of all animals are invertebrates (spineless), that was not an appropriate distinction. While classical zoologists of the 1800s and 1900s were concerned largely with discovering new kinds of animals and describing their structure and their evolutionary relationships, twenty-first-century zoology focuses on understanding how different animals solve the common problems of survival (such as obtaining energy, coping with temperature changes, and coordinating behavior), a field known as comparative animal physiology.
Hall, Thomas S. A Source Book in Animal Biology. New York: Hafner Publishing Company, 1964.
Hays, Hoffman Reynolds. Birds, Beasts, and Men: A Humanist History of Zoology. Baltimore, MD: Penguin Books, 1973.