The Three Domains of Life Essay

To begin with, the concept of ‘The Three Domains of Life” refers to the group of prokaryotic organisms, which is currently studied by a significant number of biologists. Dr. Carl Woese, who is known as a professor in the Department of Microbiology at the University of Illinois, the notion of ‘prokaryotic organisms’ introduced his explanation of the notion of ‘prokaryotic organisms’. In accordance with the scientist, “these organisms lived in extreme environments – deep-sea hydrothermal vents, “black smokers”, hot springs, the Dead Sea, acid lakes, slat evaporation ponds – environments that scientists had never suspected would contain a profusion of life” (“Biodiversity: The Three Domains of Life”, 2012). The majority of modern biologists distinguish between the three main domains of life, which involve bacteria, archaea, and eucaryota.

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Heterotrophic Bacteria is one of the common examples that represent the biological domain of bacteria. The two common examples of this particular domain involve mycoplasma and cyanobacteria. According to the researchers, who study the three domains of life, “Even though bacteria are prokaryotic cells just like Archaea, their membranes are made of unbranched fatty acid chains attached to glycerol by ester linkages” (Naik, u.d). Since these cells are able to withstand certain environmental conditions, it is needed to mention the basic elements of their structure. These bacteria are usually unicellular, filamentous, or colonial algae. Being surrounded by the gelatinous sheath, these cells play a significant role in recycling iron, sulfur, and nitrogen. Usually, cyanobacteria involve multiple storage bodies, which may include “glycogen (polyglucose) granules, which store carbon; cyanophycin granules, which are nitrogen stores composed of arginine and aspartic acid” (Vincent, 2009). These particular storage bodies give cyanobacteria an opportunity to accumulate the required nutrients and energy, and as a result, these cells are able to survive in the extreme environment conditions. Apart from the interesting cell structure, cyanobacteria have a great number of damage repair mechanisms, which are important for repairing the UV-damaged proteins. Since the majority of cyanobacteria are exposed to the sunlight, the high tolerance to the ultraviolet illumination is a great defense mechanism, which is important for the ecological success of these particular cells. Many biologists claim that cyanobacteria may survive in a wide range of temperatures. In accordance with the scientists, “however, most tend to have warm temperature optima for growth., they tolerate the cold and grow very slowly relative to their optimal growth rates at much higher temperatures” (Vincent, 2009). Cyanobacteria is considered to be a representative of the three domains of life due to the fact that it is able to survive in the extreme habitats.


In accordance with the biologists, “Archaea are prokaryotic cells which are typically characterized by membranes that are branched hydrocarbon chains attached to glycerol by ether linkages” (Naik, n.d). This particular domain is represented by the two main cell types, which include thermophiles and halophiles. These cells are able to resist the ultimate temperatures as well as strongly acidic environmental conditions. The interesting thing is that both halophiles and thermophiles need a different environment in which these cells survives. Whereas the thermophiles are able to withstand the high-limit temperatures, another kind of archaea cells – halophiles- can resist highly acidic environment. The use of thermophiles is considerably important for a variety of chemical industrial processes. In accordance with Juergen Wiegel and Francesco Canganella, “many chemical industrial processes employ high temperatures, which would have to be lowered in order to use bioprocesses from mesophiles, and this could be avoided using enzymes from thermophiles” (Wiegel & Canganella, 2011). This particular type of cell can be regarded as the representative of the three domains of life because of their ability to withstand extreme temperatures and strongly acidic environments.


The domain of eucaryota involves “protista, fungi, animalia, and plantae” (“Biodiversity: The Three Domains of Life”, 2012). These particular cells involve different major groups, which are usually regarded as ‘Kindoms’. In accordance with the article published by Regina Bailey, the most common examples of eucaryota include: “algae, amoeba, fungi, molds, yeast, ferns, mosses, flowering plants, sponges, insects, and mammals” (Bailey, 2018). One of the most interesting groups is considered to be the protista kingdom, which involves not only unicellular organisms but also the multicellural ones. The representatives of this kingdom require to live in the water environment so as they have an opportunity to survive. The most common examples of the appropriate environmental area include marine water, fresh water, or damp soil. Sometimes, these particular cells may live in the wet hair of wild animals (Girard, 2018). The Protista kingdom can be divided into three main categories – protozoa-like protists, algae-like protists, and fungus-like protists, Each of these groups differs from one another in the way they absorb the required nutrients. In general, “protozoa obtain their food with phagocytosis, algae contain chlorophyll and obtain their food through photosynthesis just like organisms in the planta kingdoms, and fungus-like protists absorb their nutrients from their environment directly into their cytoplasm” (Girard, 2018). These cells can be regarded as the representatives of the three domains of life because they inhabit the main part of the world’s water reservoirs.

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Works Cited

Bailey, R. (2019). Three Domain System. Retrieved from
Biodiversity: The Three Domains of Life. (2002). Retrieved from
Girard, L. (2018). What Are the Four Eukaryotic Kingdoms?. Retrieved from
Naik, A. Three Domains of Life. Retrieved from
Vincent, W. (2009). Cyanobacteria. Retrieved from
Wiegel, J., & Canganella, F. (2011). Extreme Thermophiles. Naturwissenschaften, 98, 253–279. doi: 10.1038/npg.els.0000392