What is an autotroph?

• A. An organism that consumes other organisms for energy.
• B. An organism that uses chemical energy from inorganic molecules.
• C. An organism that converts energy from sunlight into chemical energy.
• D. An organism that stores energy as fat.

Answer: (C)

Autotrophs are organisms that build their own organic matter from inorganic inputs. The most familiar mode is photosynthesis, where light energy is converted into chemical energy stored in sugars, enabling these organisms to synthesize organic molecules from carbon dioxide and water. This direct capture of light energy to drive the creation of organic compounds is the classic description of autotrophy, so describing energy from sunlight into chemical energy is the clearest and strongest representation. By contrast, consuming other organisms describes heterotrophs, and storing energy as fat is simply a storage outcome rather than a defining energy acquisition mechanism. Chemoautotrophs do rely on inorganic chemical energy, but the sunlight-based description best captures the everyday concept of autotrophy.