All living organisms on Earth are made of ceils. The organism can be made of one cell and be unicellular or made of many cells and be multicellular. In addition these cells can be prokaryotic or eukaryotic. All multicellular organisms have eukaryotic cells. These cells contain an organized nucleus and membrane bound organelles. Bacteria and archaea are exclusively unicellular organisms and are eukaryotic cells. Therefore they do not have an organized nucleus or membrane bound organelles.
More on cell theory and types of Cells
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