There are three domains of life: Bacteria (also known as Eubacteria), Archaea, and Eukarya. The Bacteria and Archaea are made up entirely of microorganisms; the Eukarya contains plants, animals, and microorganisms such as fungi and protists. The Bacteria and Archaea have been grouped together and called Prokaryotes because of their lack of a nucleus, but the Archaea are more closely related to the Eukaryotes than to the Bacteria. Here are other major differences between the three domains.
| Bacteria | Archaea | Eukaryotes | |
|---|---|---|---|
| Cell type | Prokaryotic | Prokaryotic | Eukaryotic |
| Cell wall | Made of peptidoglycan | Does not contain peptidoglycan | In plants and fungi, composed of polysaccharides |
| Sensitivity to antibiotics | Yes | No | No |
| First amino acid during protein synthesis | Formylmethionine | Methionine | Methionine |
| DNA | Mostly circular chromosome and plasmids | Circular chromosome and plasmids | Linear chromosome, rarely plasmids |
| Histones | No | Yes | Yes |
| Organelles | No | No | Yes |
| Ribosomes | 70S | 70S | 80S |