Autotroph

An autotroph produces organic compounds from inorganic substances using light energy or chemical energy. Autotrophs form the primary producer base of many ecosystems.

Carbon fixation: The incorporation of inorganic carbon, usually carbon dioxide, into organic molecules. It is the central process by which autotrophs build organic matter from inorganic carbon.
Organic compound: A carbon-containing chemical compound, commonly associated with molecules produced by living organisms. Autotrophs synthesize these compounds from inorganic starting materials.
Food chain: A sequence of organisms through which energy and nutrients pass as one organism consumes another. Autotrophs commonly occupy its first trophic level by producing biomass.
Heterotroph: An organism that obtains organic compounds by consuming or absorbing them from other organisms or their products. Heterotrophs acquire organic carbon rather than producing it from inorganic carbon.
Cyanobacteria: A phylum of bacteria that performs oxygen-producing photosynthesis. They are widespread photoautotrophs that helped oxygenate Earth's atmosphere.
Photosynthesis: The conversion of light energy into chemical energy, often used to fix carbon dioxide into organic compounds. Photoautotrophs use this pathway to power carbon fixation.
Inorganic compound: A chemical compound not classified as organic, such as water, carbon dioxide, or a mineral salt. These substances supply the raw materials autotrophs transform into organic matter.
Primary production: The rate at which organisms create biomass from inorganic substances in an ecosystem. It measures the ecosystem-level output of autotrophic activity.
Mixotroph: An organism that combines autotrophic and heterotrophic modes of nutrition. Mixotrophs blur the distinction between self-produced and externally acquired organic matter.
Nitrifying bacteria: Bacteria that obtain energy by oxidizing ammonia or nitrite during nitrification. Some fix carbon dioxide using energy from these chemical reactions.

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