The Living Environment The study of organisms and their interactions with the environment. Topics Unit 1: Ecology Unit 2: The Cell Unit 3: Genetics Unit 4: History of Biological Diversity Unit 5: The Human Body Unit 2: The Cell Chemistry in Biology Cellular Structure and Function Cellular Energy Cellular Reproduction The Building Blocks of Life All organisms are made up of carbon-based molecules. Specifically molecules called hydrocarbons. (...they contain C and H) Macromolecules are large molecules that are formed by joining smaller organic molecules together. There are four major categories of biological macromolecules: Carbohydrates: store energy and provide structural support. Lipids: store energy and provide barriers