Compare bacteria, archaea, and diverse eukaryotes, including how organisms acquire energy and carbon.
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Bacteria and archaea are distinct prokaryotic lineages. They lack a membrane-enclosed nucleus but have DNA, ribosomes, cytoplasm, and a plasma membrane.
Prokaryotes have remarkable metabolic diversity. Some decompose material, some fix nitrogen, some photosynthesize, and many have beneficial relationships with other organisms.
A microbe gets energy from light and carbon from CO₂. Is it a photoautotroph or a chemoheterotroph?
A photoautotroph.
“Photo” names its energy source, light. “Autotroph” means it builds organic compounds using inorganic carbon. Energy and carbon sources should be identified separately.
Protists include diverse eukaryotes, many of them single-celled. Some are photosynthetic, some consume food, and some combine strategies.
The traditional “protist” grouping does not represent one neat branch containing all descendants of a single exclusive ancestor. Endosymbiosis helped shape the origin of mitochondria and chloroplasts.