Organisms that fix carbon/are autotrophs/form the .
In terms of the trophic structure of ecosystems and equivalently in terms of food chains, primary producers are consumed by primary consumers. Though most primary producers photosynthesize (i.e., are photoautotrophs), this is not always the case as chemoautotrophs (, a.k.a., ) also are primary producers.
Contrast with and secondary productivity. See also simply producer and .
See furthermore primary production, gross primary production, net primary production, and net ecosystem production.