Final answer:
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One-celled microorganisms include bacteria, viruses, fungi, and protozoa. Bacteria and protozoa are cellular organisms, while viruses are acellular, and fungi can be either unicellular or multicellular organisms like molds and yeasts.
Step-by-step explanation:
One-celled microorganisms are referred to by several terms including germs, but the more specific scientific classifications for one-celled organisms include bacteria, viruses, fungi, and protozoa. Each of these categories of microorganisms has distinct characteristics that set them apart from each other. Bacteria are unicellular and prokaryotic, meaning they lack a true nucleus. Viruses are acellular and require a host to reproduce. Fungi can be unicellular or multicellular, and they include yeasts and molds. Finally, protozoa are unicellular, eukaryotic organisms that are mostly motile and can be free-living or parasitic. Among them, bacteria and protozoa are comprised of cells, while viruses are acellular, and fungi can be unicellular or form multi-celled structures like molds.