Biology is the study of life and living organisms, including their physical and chemical structure, function, development, and evolution. Modern biology is a vast field, composed of many branches, but there are unifying concepts that consolidate it into a single, coherent field. Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation of new species. It also concludes that all organisms survive by consuming and transforming energy and regulating their internal environment.