Darwin's 4 Postulates of Evolution

By: Fernando Lobo

1. Variation among individuals within species

There is variation among the same species. The variation may be genetic, which may be displaying diverse physical characteristics for the specific species. Certain variations in species flourish due to natural selection, but similar species may have different characteristic due to different habitats. A perfectly clear example, are the Galapagos's finches. They are the same species, but they have variation in their beaks due to different food sources since they live on different islands.
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2. Some of the variation is heritable

In most cases, this variation is inheritable due to the fact that certain characteristics of the variation help species in certain things. This is basically natural selection in the works, where the best characteristics are inherited, and the rest die out. A great example of heritable characteristics is the long neck on a giraffe. Since their food source is up on a high tree, only giraffes with long necks will reach and eat the food to survive. So as they continue to reproduce, only ones with favorable characteristics will prevail.
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3. In every generation, more offspring a reproduced than can survive

Every generation eventually reproduces to a point where not all the offsprings can survive. This may be due to food availability, for example. It is this way, that only offsprings with favorable characteristics will survive to keep reproducing. For example, lions. As the pack continues to grow, their food availability will diminish, since their is not enough food for all of them. Only the strongest, fastest, and most agile hunters will be able to get the food and continue to reproduce.
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4. Non-random survival and reproduction

Only the species with the best traits will survive. Species with the best traits have favorable reproduction rates, since they can better adapt to situations. These special offsprings can survive climate better, gather food better, and basically survive on their own better. A very clear example is the one of the Arizona Desert Mice. These creatures only survive if their fur matches the sand, since they will be less visible to airborne predators. Therefore, only mice with the specific colors will survive and reproduce.
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Buffalo State University. (n.d.). Ch 3. Darwinian Natural Selection. Retrieved April 04, 2016, from http://faculty.buffalostate.edu/penaloj/bio405/outline3.html

Evansville University. (n.d.). Natural Selection. Retrieved from http://faculty.evansville.edu/de3/b32003/lecture summaries/selection.pdf


Benard, M. F. (n.d.). Desert Pocket Mouse. Retrieved April 07, 2016, from https://www.flickr.com/photos/21670394@N07/3497297534

Galapagos Islands: Darwin Inspiration - PRE-TEND Be curious. (2015). Retrieved April 04, 2016, from http://www.pre-tend.com/galapagos-islands-darwin-inspiration/