microevolution

Microevolution is the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as "change below the species level."^[1]

These changes may be due to several processes: mutation, natural selection, artificial selection, gene flow and genetic drift.

Population genetics is the branch of biology that provides the mathematical structure for the study of the process of microevolution. Ecological genetics concerns itself with observing microevolution in the wild. Typically, observable instances of evolution are examples of microevolution; for example, bacterial strains that have antibiotic resistance.

Microevolution can be contrasted with macroevolution, which is the occurrence of large-scale changes in gene frequencies in a population over a geological time period (i.e. consisting of extended microevolution). The difference is largely one of approach. Microevolution is reductionist, but macroevolution is holistic. Each approach offers different insights into the evolution process.

Origin of the term

The term was first used by Harvard-educated botanist Robert Greenleaf Leavitt in the journal Botanical Gazette in 1909, addressing what he called the "mystery" of how formlessness gives rise to form.^[2]

..The production of form from formlessness in the egg-derived individual, the multiplication of parts and the orderly creation of diversity among them, in an actual evolution, of which anyone may ascertain the facts, but of which no one has dissipated the mystery in any significant measure. This microevolution forms an integral part of the grand evolution problem and lies at the base of it, so that we shall have to understand the minor process before we can thoroughly comprehend the more general one...

However, Leavitt was using the term to describe what we would now call developmental biology, it was not until Russian Entomologist Yuri Filipchenko used the terms "macroevolution" and "microevolution" in 1927 in his German language work, "Variabilität und Variation", that it attained its modern usage. The term was later brought into the English-speaking world by Theodosius Dobzhansky in his book Genetics and the Origin of Species (1937)^[1].

"Misuse"

The term 'microevolution' has recently become popular among those who hold to the Intelligent Design theory, and in particular among young Earth creationists. Some scientists state that the claim that microevolution is qualitatively different from macroevolution is fallacious, as the main difference between the two processes is that one occurs within a few generations, whilst the other takes place over thousands of years (i.e. a quantitative difference).^{[3] [4]} Whether they describe the same process is debated. ^[5]

The attempt to differentiate between microevolution and macroevolution is considered to have no scientific basis by many scientific organizations, including the American Association for the Advancement of Science.^[6]There is still debate about whether evolution of life forms beyond the species level ("macroevolution", i.e. speciation) has indeed been observed and documented by scientists.^[7] Evolutionist David L. Stern states, "One of the oldest problems in evolutionary biology remains largely unsolved…Historically, the neo-Darwinian synthesizers stressed the predominance of micromutations in evolution, whereas others noted the similarities between some dramatic mutations and evolutionary transitions to argue for macromutationism." ^[8] Evolutionist Andrew M. Simons,states, "A persistent debate in evolutionary biology is one over the continuity of microevolution and macroevolution -- whether macroevolutionary trends are governed by the principles of microevolution."^[9]

See also

• Macroevolution

References

1. ^ ^{a b} Macroevolution: Its definition, Philosophy and History
2. ^ Leavitt, Robert Botanical Gazette 1909 vol.47 no.1 Jan. A Vegetative Mutant, and the Principle of Homoeosis in Plants http://www.jstor.org/pss/2466778
3. ^ Claim CB902: "Microevolution is distinct from macroevolution", TalkOrigins Archive
4. ^ Darwinist Myth: Have ID Proponents Invented Terms like “Microevolution” and “Macroevolution”?
5. ^ [1] The Scientific Controversy Over Whether Microevolution Can Account For Macroevolution
6. ^ Evolution Press Release American Association for the Advancement of Science
7. ^ Complete sourced list of observed instances of speciation, TalkOrigins Archive
8. ^ "Perspective: Evolutionary Developmental Biology and the Problem of Variation(2000): 1079-1091"
9. ^ "The continuity of microevolution and macroevolution," Journal of Evolutionary Biology 15 (2002): 688-701

External links

• Microevolution (UC Berkeley)
• Microevolution vs Macroevolution