Microevolution

Microevolution and its complement macroevolution are terms used by creationists in an attempt to divide examples of biological evolution into distinct categories. Microevolution covers the small, distinct changes in a species, typically attributable to a single genetic change, while macroevolution refers to a change much larger in scope, such as the proposed evolution of apes into men, or from simple single-celled organisms into complex multi-celled organisms.

Typically, observable instances of evolution are examples of microevolution. Examples include the famous peppered moths whose wings turned black in England's sooty industrial environment and the development of bacterial strains which have become resistant to antibiotics. Since microevolution can be observed directly, both pro-evolution and anti-evolution groups agree that it is a fact of life.

Opponents of evolution, such as creation scientists, have proposed that microevolution always takes the form of destructive genetic mutations, which happen to confer an advantage to individuals in a specific environment. Because macroevolution requires many constructive genetic changes, they argue that microevolution cannot lead to macroevolution. One example of a destructive mutation which conferred a competitive advantage under a specific situation is a form of bacteria (name?) which has become resistant to penicillin. The bacteria naturally produce a small quantity of a substance which protects them from penicillin. The mutation crippled the limits on the amount of this substance produced, allowing enough to be generated to protect the bacteria. However, production of this substance is expensive, and under normal conditions (an environment free of penicillin), this strain cannot compete with the normal bacteria and is crowded out.