Prescott's Microbiology 8th Edition by Joanne Willey, Linda Sherwood, Christopher J. Woolverton, Lansing Prescott, John Harley, Donald Klein

Exercise 3

Compare and contrast Bacteria, Archaea, protists, fungi, viruses, viroids, virusoids, and prions. Why do you think viruses, viroids, virusoids, and prions are not included in the three domain system?

Step 1 of 3

The bacteria, Archaea, protists and fungi are cellular organisms. Bacteria are single celled organisms that contain a cell wall made up of peptidoglycan and one or two lipid bilayers. Members of the domain Bacteria play important roles in the environment by recycling nutrients like oxygen and nitrogen and in the human body by aiding in digestion. However, they can also cause diseases. Archaea lack peptidoglycan in their cell walls and utilize different lipids in their membranes. Many members of Archaea are able to tolerate extreme conditions such as low temperature or high salt. The domain Eukarya includes microorganisms such as protists and fungi as well as large multicellular organisms like humans. Protists are usually unicellular and include algae, protozoa, slime molds, and water molds. Fungi can either be unicellular or multicellular.