Flexi Says: There are two basic types of autotrophs: photoautotrophs and chemoautotrophs. They differ in the type of energy they use to synthesize food. Photoautotrophs are organisms that use energy from sunlight to make food by photosynthesis. Photoautotrophs such as plants, algae, and photosynthetic bacteria are at the base of most of Earth's food webs. In places without enough light to provide energy for photosynthesis, chemoautotrophs use the energy stored in chemical compounds to make organic molecules by chemosynthesis.