Biology (from Greek βιολογία - βίος, bios, "life"; -λογία, -logia) is the study of life and a branch of the natural sciences which studies living organisms and how they interact with each other and their environment. It examines the structure, function, growth, origin, evolution, and distribution of living things. Also, it classifies and describes organisms, their functions, and how species come into existence. Four unifying principles form the foundation of modern biology: cell theory, evolution, genetics and homeostasis
