ABSTRACT
Energy is defi ned as the capacity to do work. Although energy is found in many forms (Table 2.1), all forms have the capacity to do work. Light energy coming from the sun is the most important and universal type of energy, supporting all life on Earth. Plants have the capacity to capture, or “fi x,” light energy and convert it into chemical energy, which is used by the plants themselves and the animals that feed on them. Many human activities, most prominently agriculture and forestry, rely on solar energy. Solar energy is also fundamental to wind power, hydroelectric power, and other types of energy systems.
