Microevolution, broadly defined, is the inevitable small-scale changes in allele frequencies in a population within the same species. Under this broad definition, this change in overall allele frequencies occurs with every birth or death of a member of the species. In other words, some generations of people might be taller than the last or shorter than the last based on the number of individuals who happen to have the "tall" gene.
Microevolution in Bacteria
Microevolution is the process by which bacteria may develop resistance to antibiotics. We regularly use antibiotics to stop bacterial infections. When a colony of bacteria is exposed to an antibiotic, the bacteria are likely to die if they do not have genes that produce molecules to inhibit the action of the antibiotic. If the survivors reproduce, the colony will contain mostly bacteria that have inherited resistance genes. A second application of the same antibiotic will not affect them.
Genes to resist various antibiotics are natural for bacteria to produce because the many species of bacteria war with each other for more space using these chemicals on each other. In order to protect itself a given species of bacteria would at least have genes for resistance to the particular antibiotic it produces. Resistance genes can also be produced by random mutation, usually through mistakes in copying the DNA during cell division. Furthermore, bacteria can pass genes for antibiotic resistance between strains and even between species.
Because antibiotics have been used so widely in medicine, there is increasing concern about developing strains of bacteria that can acquire multiple resistances to most of the antibiotics we use. High compliance with infection control measures and a prudent and more restrictive use of antibiotics are the key measures to prevent epidemics based on bacteria with multiresistance.
Microevolution in Creation Science
While there are different forms of creation science, generally Creationists agree with the concept of microevolution, but call it adaptation. From the creationist point of view there is a large difference between microevolution and macroevolution. The one occurs; the other does not.
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