Plants, algae, and phytoplankton are some common examples of autotrophic organisms. These organisms can all create food energy from the environment.
The main source of nutrients for autotrophic organisms are light, water and carbon dioxide. Most autotrophs use photosynthesis to create food, where these elements are converted into a form of sugar called glucose. Glucose is then used as a form of energy to drive various life functions, such as cellulose, which is used to create cell walls.
There are also bacterial autotrophs that use a different process called chemosynthesis, which is a method where energy is sourced through chemical reactions. These autotrophs tend to live in extreme environments, such as volcanic springs or hydrothermal vents, where chemicals such as methane and hydrogen are prevalent.