Energy from the sun enters an ecosystem when a plant uses sunlight to make sugar molecules in a process called photosynthesis. During photosynthesis, plants, algae, and some bacteria capture solar energy. Solar energy drives a series of chemical reactions that require carbon dioxide and water, as shown in Figure 1. The result of photosynthesis is the production of sugar molecules known as carbohydrates. Carbohydrates are energy-rich molecules that organisms use to carry out daily activities. As organisms consume food and use energy from carbohydrates, the energy travels from one organism to another. Plants, such as the sunflowers in Figure 2, produce carbohydrates in their leaves. When an animal eats a plant, some energy is transferred from the plant to the animal. Organisms use this energy to move, grow, and reproduce.