The application of mathematics to biological systems. Just as physics underlies many engineering technologies, biology serves as a foundation for such disciplines as medicine, agriculture, animal husbandry, and environmental sciences, in which mathematical analyses have proved indispensable. Mathematical biology spans all levels of biological organization and biological function, from the configuration of biological macromolecules, as exemplified by the folding of proteins and the recognition properties of active sites in enzymes and receptors, to the entire ecosphere over the course of evolutionary time.