2.2.21 (HL)—Autotrophs vs. heterotrophs

Autotrophs build organic matter from inorganic carbon; heterotrophs obtain organic matter by consuming or absorbing it.

Light or chemical reactions supply energy for autotrophic carbon fixation. Heterotrophs transfer that stored chemical energy through feeding, detritus or parasitism.

A green plant is an autotroph; a fungus digesting leaf litter is a heterotroph, even though neither needs to hunt an animal.

Autotroph: its carbon comes from inorganic CO₂; the energy source can be chemical rather than light.

Autotroph does not mean ‘uses sunlight’; it refers to carbon source, not energy source.