Comparative anatomy is the study of differences and similarities in the body structures of different animals. A comparative anatomist might compare the circulatory systems of sharks, frogs, and cats. Paleontology is the study of prehistoric organisms. Paleontologists and comparative anatomists have made important contributions to knowledge about the evolution of many animals. Zoologists who study embryology deal with the formation and development of organisms from fertilized eggs to birth.
Physiology is the study of the functions of animals.
Physiologists may observe how the heart pumps blood, how nerves transmit impulses, and how muscles contract. Other areas of zoology include genetics and ecology. Genetics is the study of heredity, the passing on of characteristics from parents to their young. This field of zoology is important in breeding livestock and in understanding certain human diseases. Ecology is the study of the relationship of organisms to their environment.