Examples
All sorts of combinations may exist in nature. For example most cyanobacteria are photoautotrophic, since they use light as an energy source, water as electron donor, and CO2 as a carbon source. Fungi are chemoorganotrophic since they use organic carbon as both an electron donor and carbon source. Eukaryotes are generally easy to categorise. All animals are heterotrophic, as are fungi. Plants are generally photoautotrophic. Some eukaryotic microorganisms, however, are not limited to just one nutritional mode. For example, some algae live photoautotrophically in the light, but shift to chemoorganotrophy in the dark. Even higher plants retained their ability to respire heterotrophically on the starch at night which had been synthesised phototrophically during the day.
Prokaryotes show a great diversity of nutritional categories. For example, purple sulfur bacteria and cyanobacteria are generally photoautotrophic whereas purple non-sulfur bacteria are photoorganotrophic. Some bacteria are limited to only one nutritional group, whereas others are facultative and switch from one mode to the other, depending on the nutrient sources available.
Read more about this topic: Primary Nutritional Groups
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