This academic program explores the interactions of living systems with one another and with their environment. In Biology 20, the underlying theme is energy and matter exchange. The four topics covered are: Energy and Matter Exchange in the Biosphere, Ecosystems and Population Change, Photosynthesis and Cellular Respiration and Human Systems. Prerequisite: Science 10: 50%. Students without the prerequisite must withdraw from class with no refund if they are under 20 years of age as of September 1 of the current school year.