1) Anaximander developed the theory that humans evolved from fish. Hippocrates was known as the "Father of Modern Medicine" and authored the Hippocratic Oath.
2) Aristotle observed and classified animals and wrote extensively on biology, establishing him as the "Father of biology". Galen established the idea of pulmonary circulation and contributed to experimental physiology.
3) Key figures included Robert Hooke who discovered cells, Edward Jenner who pioneered vaccination, Charles Darwin for his theory of evolution, and Alfred Wallace for independently discovering evolutionary change.