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The following is from my written notes. I read books, make notes, and then post notes to my own website for later reference. Almost none of this is from other web sites. When there are quotes from other web sites, I will post the URL. Otherwise, the material is largely from several authors - some of which I paraphrased, but I believe the context is accurate. I post these references when I feel it's important.

Evolution consists of six components, all of which make up the body of evidence. They are evolution itself, gradualism, speciation, common ancestry, natural selection, and non-selective mechanisms of evolutionary change.

This particular scope of understanding is from "Why Evolution is True" by Jerry Coyne, 2009. Coyne is a professor of biology currently teaching at the University of Chicago in the Department of Ecology and Evolution. His concentration is speciation, ecological and evolutionary genetics.

1. Evolution simply means that a species undergoes genetic change over time. It presumes that plants and animals living today are descended from those that lived earlier.

2. Gradualism presumes that these evolutionary changes occur gradually over long periods of time - hundreds, thousands, or even millions of years. Some evolutionary changes can happen in a short time (for us) since a reproductive generation in a fruit fly may occur in just a few days (or as short as 20 minutes for some microbes). species will evolve faster or slower depending on evolutionary pressures, but it does not mean these changes occur at an even pace.

3. Speciation is the study of how traits are passed on the future generations and the consequence of genetic splitting. Sometimes we do not see anatomical differences right away. In other instances - as when a a plant uses a different pollinator to reproduce - there may be no physical change at all. "Missing links" are sometimes found that show where things split, but if one looked at these animals and plants over a long period of time, the results might be only barely noticeable. Also, species don't have to split. Many species may simply evolve to the point where they no longer can interbreed. Most (99%) go extinct without leaving any physical descendants.

4. Common ancestry is the flip side of speciation. That is, we can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors. These are sometimes outlined in graphical hierarchies and fall into sortable traits and classifications.

5. Natural Selection is the most commonly expressed form of evolution, and for Darwin the most radical at the time. The concept is rather easy to grasp. If individuals within a species differ genetically from one another, and some of those differences affect an individual's ability to survive and reproduce in its environment, then in the next generation the "good" genes that lead to higher survival and reproduction will have relatively more copies that the not-so-good genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately this process produces organisms that are well-adapted to their habits and way of life.

6. The last are non-selective measures of evolutionary change. An example here might be the random changes in the proportion of genes caused by the fact that different families have different numbers of offspring. Theses changes may have nothing to do with adaptation. These are probably the least important features of evolution because they don't have the molding power of natural selection. Genetic drift may also play some non-adaptive role in small populations which would account for some non-adaptive features of DNA change.

Some of these, of course, are intimately connected. In order to be a scientific theory, it must be testable and make verifiable predictions, and evolution has accomplished both. There is no one moment when a theory becomes fact, however.

In addition to this, Darwinism can also be supported by what is known as "retrodictions": facts and data that aren't necessarily predicted by the theory of evolution but make sense only in light of the theory of evolution. This may include patterns of species distribution and other concepts related to biogeography and continental drift.

There are several ways to help make the case for evolution as a mechanism for change. They are:

1. Fossil evidence
2. DNA
3. Biogeography
4. Embryology
5. Vestigial Traits
6. Dead Genes

Interestingly, Darwin considered his best evidence of evolution at the time to be Embryology - which is by far the least discussed aspect of evolution, but one that still holds true. Most pre-natal doctors are no longer educated on how the subject relates to evolution.