What is the theory of evolution?

(http://wolfevolution.webs.com/images/evolutionhumans.jpg)

Definition: The theory of evolution, in a modern sense, can be described as a two-stage process. The production and redistribution of variation, throughout many generations and natural selection, acts on variation determining how successfully one will reproduce (Jurmain pp.85).

Explain how it works:Evolution works in way that it is a change in allele frequency from one generation to the next.Genetic variation must be produced first by mutation, which is then acted upon by natural selection. The driving force in natural selection, in determining whether a specie is going to reproduce successfully or not, is the environment(Jurmain pp.85).

These process help increase variation:

• Mutation: A change in DNA is a type of mutation, and many genes have two or more forms called alleles. If one allele changes to another , that is if the gene itself is altered, a mutation has occurred (Jurmain pp.86).

• Examples among domesticated and wild animals in regards to mutation: Some examples of animals that have been domesticated are foxes, chickens, cats, horses, and ferrets. Examples of wild animals would be jaguars, lions, and bears. An experiment was performed on domesticating foxes, this article explains more of the finer details when changing its behavior and picking out traits that we want from a species ( http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763232/ ). In this article, experiments were performed on foxes that were cage bred to see if they would increasingly become friendlier with humans socially throughout many generations. Researchers picked only the most tamed foxes out of the group that were friendly with human contact. The ones that showcased aggressive behavior were put in a another group. Throughout many generations the foxes began to exhibit dog like behaviors like whimpering, tail wagging, and licking in a dog like manner. They also formed physical characteristics of dogs as well too. Although, only a very small amount of foxes were able to become fully domesticated. Once this point was reached, the amount of domesticated foxes began to increase generation after generation. By the end of the experiment almost all of the foxes of the domesticated population were categorized as the behavioral elite. This took a little more than 30 generations to do so. In a sense we forced evolution on these foxes and changed their behavior overtime to benefit us as humans. The foxes adapted more dog-like behavior. Dogs generally have the association of a "man's best friend". The real question is if a fox could ever be one too.

(http://www.animalgalleries.org/Small-Land-Mammals/Fox-Galleries/Red-Fox-Gallery/Red+Fox+Vulpes+vulpes+face.jpg.php)

• Crossing Over: The definition of crossing over is described by (http://anthro.palomar.edu/synthetic/glossary.htm) as the exchange of genetic material (DNA) between homologous chromosomes at the beginning of meiosis.  This results in sperm and ova with greater genetic diversity due to a recombination of genes.  Specifically, a portion of the end of a chromosome is broken and reattached on another chromosome.

• Gene flow:Gene flow is the exchange of genes between populations. This only occurs when immigrants interbreed. An example of how gene flow influences micro evolutionary changes are present in human populations such as African Americans. While most of them are descendant from west African decent, there is also European American genes mixed in with them also. We can determine this by measuring the allele frequencies for specific genetic loci, then estimating the amount of migration of European alleles in the gene pool of the African Americans(Jermain pp.86). 

Processes that decrease Variation:

• Genetic Drift and Founder Effect:Another component of the theory of evolution  is Genetic Drift. This can be defined as evolutionary changes, or changes in allele frequencies, that are produced by random factors in small populations. Genetic drift mainly happens in small populations in which if an allele is rare, it could completely disappear and not be passed on at all. A certain kind of genetic drift, also called the founder affect, is present in modern and non human populations. The founder effect happens over time in which "founders", which are the offspring of the parent group, leave and create a new population and form another colony elsewhere. As long as member of that colony reproduce within their own group, they will all be descended from the initial group of founders (Jurmain pp.87-88).

 

• Non-random mating: This occurs when no classification criteria of possible mates are considered, its is mainly a matter of chance. One example of this is rape of randoms victims because no known group of humans legally mate randomly. An effect of non-random mating is a significant alteration in gene frequency that can occur through long term patterns of mate selection.(Chipley, Unit 1)