Practice question

Protists exhibit remarkable nutritional diversity including photoautotrophy via chloroplasts, heterotrophy through phagocytosis, osmotrophy absorbing dissolved organics, and mixotrophy combining photosynthesis and ingestion in genera like Euglena and Dinobryon. Chemoautotrophy, however, involving oxidation of inorganic substrates such as ammonia, hydrogen sulfide, ferrous iron to generate energy for carbon fixation, is restricted to prokaryotic Bacteria and Archaea including nitrifiers and sulfur oxidizers. No free-living protist employs inorganic chemical lithotrophy for autotrophic growth, marking absence of chemoautotrophic protists and metabolic boundary between eukaryotic protists and chemolithotrophic bacteria.