Trophic types কী?

An organism is classified by three answers. Its energy source: light (phototroph) or chemical reactions (chemotroph). Its electron source: inorganic substances — $\mathrm{H_2}$, $\mathrm{H_2S}$, $\mathrm{NH_4^+}$, $\mathrm{Fe^{2+}}$, water — (lithotroph) or organic molecules (organotroph). Its carbon source: $\mathrm{CO_2}$ (autotroph) or organic carbon (heterotroph). Plants and cyanobacteria are photolithoautotrophs; animals, fungi and E. coli are chemoorganoheterotrophs; the nitrifying and sulfur-oxidising bacteria are chemolithoautotrophs, which make their organic matter from $\mathrm{CO_2}$ with energy drawn from the oxidation of minerals, in the dark. Almost every combination exists somewhere among prokaryotes; eukaryotes occupy only two.