Circa 384-322 b.c. Founded by Aristotle. There are not many major subdivisions within zoology to which Aristotle did not make a contribution.
Development of anatomy and physiology
Circa 130-200 b.c. Roman Investigator, Galen, has been praised for centuries for his concept of scientific methods. He has had a great influence on the science departments in schools and professional settings.
First accurate description of blood circulation
Between the years of 1616 and 1628, William Harvey depicted the first accurate demonstration of blood circulation. This was a key experiment that created the base for modern physiology. He explained bodily processes in physical terms and cleared away a lot of the mystical interpretation.
All life from the egg
William Harvey worked as an embryologist and published his De Generatione Animalium which discussed observations on the embryological process.
Discovery of cells
Robert Hooke made investigations on cells using a cork
Concept of species
J. Ray was the first to apply the species concept to a particular kind of organism
discovery of oxygen
helped understand oxidization and the exact role of respiration in organisms
nature of animal respiration demonstrated
Antoine L. Lavoisier explained the life process and overthrew the mystical hypothesis that previously existed
Concept of reflex action
Marshall Hall described the method by which a stimulus triggers a response and coined the phrase "reflex action"
discovery of x-rays
W. Roentgen. This discovery was followed by its application in the interpretation of bodily structures.