Darwin's Postulates

Inheritance

The natural selection theory states that evolution is dependent on the ancestors of a species. Variability in traits is directly related to the descendant populations that came before. Currently, we can observe how past traits in our family influence our genetic traits now. An example of this is eye color. If a child's parents both have a dark/brown eye color it is very likely that the child will also have dark/brown eye color.
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Heredity: Crash Course Biology #9

Variation

Variations are defined as genetic happenings that cause the individuals and species to have different characteristics from each other. These genetic variations take place within the gene pool, the stock of different genes in an interbreeding population. Although variation is closely related to evolution, it's process is more about the recombination of already existing information in the gene pool. Examples of genetic variation can be color, size or shape of the certain body part of an organism.

Differential Survival

This postulate relates closely to Darwin's theory of natural selection and survival of the fittest. Natural selection is the survival and reproduction of individuals to a certain characteristic . Survival of the fittest explains that in an environment only those that posses the best characteristics will be able to survive. Because these are the species that survive, they will reproduce and thus the population will grow.
Proof of evolution that you can find on your body

Extinction

According to Darwin, the extinction of species have happened gradually and continuously along the passing of time. Individuals not fitted to survive in the changing conditions have disappeared one by one until an entire species group becomes extinct. This process is very slow compared to the production of a new species and marks the progress of an extermination. Although normally this is a natural process altered by ecological factors, now human are impacting species greatly and causing mass extinctions.

Bibliography

Charleswood, B. (2009, November 1). Darwin and Genetics | Genetics. Retrieved April 04, 2016, from http://www.genetics.org/content/183/3/757


Darwin, C., & Quammen, D. (2008). On the origin of species. http://www.talkorigins.org/faqs/origin.html


Polonis, L. (2015, January/February). Ch1. Adaptation by Natural Selection. Retrieved April 04, 2016, from http://www.wwnorton.com/college/anthro/bioanth/ch1/chap1.htm


Raup, D. M. (1994). The Role of Extinction in Evolution. Tempo and Mode in Evolution, 91, 6758-6763. doi:http://www.pnas.org/content/91/15/6758.full.pdf