Natural Selection and Evolution in Bacteria

Darwin devoted much of his life to understanding and furthering the world knowledge of natural selection (Mayr 24). By studying the variants in many different species of animals, Darwin eventually concluded that these given animals experienced natural and evolutionary changes in size, body structure, and habits. Thinking deeper into natural selection and evolutionary change, I realize that cells must make evolutionary changes as well as the host being in which they reside. Let’s look a bit smaller into the world of cellular organisms, for they, too, experience and undergo natural selective changes in the evolutionary process (Darwin 128).

Examples of natural selection processes are well documented in life forms that have very rapid life cycles, such as bacteria. Bacteria are tiny, single-celled prokaryotic organisms. They reproduce quickly and therefore evolve quickly, even within a few weeks of their life cycle. Although many types of bacteria are helpful to human and animal health, some cause infectious diseases such as strep throat, ear infections, influenza, and tooth decay. These differences in the structure and purpose of bacteria are examples of evolutionary differences (Neese 462).
Natural selection processes in disease-causing bacteria are widely documented. For example, a person who is ill because of disease-causing bacteria can become well when given antibiotic drugs which destroy the bacteria in the person’s body. Bacteria that were once fought off by a particular type of antibiotic drug become resistant, or become used to, the given drug (over time). The first time the drug is used, most of the bacteria are killed, but some of them can survive, if they have a gene or genes that allow them to withstand the drug's effects even somewhat.

The bacteria that survive are better adapted to deal with that particular type of antibiotic drug, thus portraying significant signs of an evolutionary adaptation. If the surviving bacteria are able to reproduce inside the person’s body (for instance, if the patient stops taking antibiotics early), then the next generation of bacteria is better suited to deal with the antibiotic drug as well. If the drug is used again, the bacteria will be more resistant to the drug; more will survive and be able to reproduce and the person remains ill. That’s when a doctor will try a different type of antibiotic. Hopefully the bacteria will not be well adapted to the other drug, will be destroyed, and the person will get well. However, over the last 50 years doctors have had to make antibiotics stronger and stronger to deal with these quickly evolving microbes. Today, strains of bacteria have developed that are resistant to antibiotic drugs, so scientists are always trying to develop more effective medicines.







This video helps to further explain the process in which bacteria can undergo the process of evolution in a human host. Specifically, the video talks about tuberculosis and its variants due to vaccination in a Russian prison. I found this video to be informative and visually helpful. This is only one video of 6 relating to the topic.

WORKS CITED

"Antibiotic Resistance of Bacteria: An Example of Evolution in Action? - Answers in Genesis." Answers in Genesis - Creation, Evolution, Christian Apologetics. Web. 01 Dec. 2009. .

Darwin, Charles. "Selections from Darwin's Work." pp 67-254 in Darwin. 3rd ed. Philip Appleman, ed. New York: W.W. Norton,2001.

Mayr, Ernst. "Who is Darwin?" in Darwin 3rd ed. Philip Appleman, ed. New York: W.W.Norton, 2001.

"Natural Selection: How Evolution Works (ActionBioscience)." ActionBioscience - promoting bioscience literacy. Web. 01 Dec. 2009. .

Neese, Randolph M and George C. Williams. "Evolution and the Origins of Disease." in Darwin 3rd ed. Philip Appleman, ed. New York: W.W.Norton, 2001.