First, I'd like to summarize the main processes of evolution as they are understood today.
Evolution can result from any of four main processes operating independently or together. Also there are the two ancillary processes that contribute to evolution.
Main Processes
"Mutation is the ultimate source of new genetic varieties. However, gene flow can be responsible for the introduction of new alleles into a population. The most rapid and dramatic evolution is due to natural selection. Recombination and non-random mating can change the frequencies of genotypes which in turn can be selected for or against by nature (or mates!). Genetic drift can also result in rapid evolution of the gene pools of small, reproductively isolated populations." (O'Neil, 2011)
ORIGIN OF SPECIES
Evolution can occur in two ways, adaptive radiation and successive speciation.
Adaptive radiation is the successive evolution of two species from one over time, mostly because of geographic isolation. One species can turn into two over long periods of time, because groups will adapt to different environments. Mutations, genetic drift and natural selection due to environmental pressures will occur and change each group to such an extent that they are eventually not able to reproduce with each other. At this point, they become separate species and will continue to evolve independently. We saw this with the salamanders in California. This split is called cladogenesis.
Successive Speciation occurs within a single evolutionary line without the branching of adaptive radiation. Single breeding population for many generations... the gene pool will transform. If descendents could go back in time to mate with ancestors, their offspring would not be viable. This non-branching evolutionary pattern is called anagenesis.
Both of these processes can happen simultaneously... or apart.
As we end our discussion of evolution, there are two links I will give you. One describes how scientists have been able to take the molecular components of DNA and create conditions that allow these components to assemble naturally. Revealing the origins of life.
I would also encourage you to read up on The Scope's Monkey Trial.
All Things Considered: Remembering the Scopes Monkey Trial
Darrow's examination of William Jennings Bryan
If you wish to have extra credit to bring up your grade, please write a paper discussing the Scope's Monkey Trial, why it was important during the 1920's and how the situation mirrors the current prevalence of belief in creationism.
Source: O'Neil, D. (2011). Anthropology Tutorials [website]. Modern Theories of Evolution: Non random Mating. Retrieved from http://anthro.palomar.edu/tutorials/biological.htm
Evolution can result from any of four main processes operating independently or together. Also there are the two ancillary processes that contribute to evolution.
Main Processes
- Mutation (creates variety)
- Genetic drift (small populations and reproductive isolation)
- Natural selection (rapid and dramatic)
- Gene flow (introduction of new alleles)
- Recombination
- Non-random mating
"Mutation is the ultimate source of new genetic varieties. However, gene flow can be responsible for the introduction of new alleles into a population. The most rapid and dramatic evolution is due to natural selection. Recombination and non-random mating can change the frequencies of genotypes which in turn can be selected for or against by nature (or mates!). Genetic drift can also result in rapid evolution of the gene pools of small, reproductively isolated populations." (O'Neil, 2011)
ORIGIN OF SPECIES
Evolution can occur in two ways, adaptive radiation and successive speciation.
Adaptive radiation is the successive evolution of two species from one over time, mostly because of geographic isolation. One species can turn into two over long periods of time, because groups will adapt to different environments. Mutations, genetic drift and natural selection due to environmental pressures will occur and change each group to such an extent that they are eventually not able to reproduce with each other. At this point, they become separate species and will continue to evolve independently. We saw this with the salamanders in California. This split is called cladogenesis.
Successive Speciation occurs within a single evolutionary line without the branching of adaptive radiation. Single breeding population for many generations... the gene pool will transform. If descendents could go back in time to mate with ancestors, their offspring would not be viable. This non-branching evolutionary pattern is called anagenesis.
Both of these processes can happen simultaneously... or apart.
As we end our discussion of evolution, there are two links I will give you. One describes how scientists have been able to take the molecular components of DNA and create conditions that allow these components to assemble naturally. Revealing the origins of life.
I would also encourage you to read up on The Scope's Monkey Trial.
All Things Considered: Remembering the Scopes Monkey Trial
Darrow's examination of William Jennings Bryan
If you wish to have extra credit to bring up your grade, please write a paper discussing the Scope's Monkey Trial, why it was important during the 1920's and how the situation mirrors the current prevalence of belief in creationism.
Source: O'Neil, D. (2011). Anthropology Tutorials [website]. Modern Theories of Evolution: Non random Mating. Retrieved from http://anthro.palomar.edu/tutorials/biological.htm
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