4 Fundamental Truths of Evolution
The 4 Postulates
Darwin developed a total of four individual postulates. There are:
- The potential for a species to increase in number
- The heritable genetic variation of individuals in a species due to mutation and sexual reproductionVariation is heritable
Competition for limited resources
The proliferation of those organisms that are better able to survive and reproduce in the environment.
"the potential for a species to increase in number"
Nature compensates for the fact that many species face multiple hardships throughout their lives and thus not all organisms reach reproductive age by making species have more offsprings than those that are needed to maintain a population. An excellent example of this would be fish who will lay up to thousands of eggs since most will be eaten or starve to death before they reach reproductive age. An example that I like to think that relates to this is Nemo (Pixar character), who lost all his siblings since they were eaten by a shark when they were still eggs and nonetheless there were still bountiful clownfish in the sea. A more concrete support for this same argument would be a study conducted in 1977 in which researches found that around 80% of the finch population did not reach reproductive age, nonetheless, finch population is still thriving and growing today. Thus we are able to prove the first postulate and see that regardless of the competition out there, since there are a lot of offsprings, populations will continue to grow.
"the heritable genetic variation of individuals in a species due to mutation and sexual reproduction"
Darwin was aware of the variability between species but was unable to understand how it occurred. Now that we have improved technology we can perform advanced research which has revealed to us that variation in the genes is created through mutation (genes are altered through DNA replication, DNA damage, repair, or recombination), and though sexual reproduction where there is independent assortment of genes. Something interesting to observe is that the gene variation follows an interesting bell shaped curve. Traits such as height follow this pattern. An example has been provided in the image found below.
"competition for limited resources"
Competition in nature is seen everywhere: when we kill a fly, when a lion eats a zebra, when a bird flies faster and gets the last sip of water. All of these are examples of competition. Competition is seen as the limitation of supply of at least one source in nature (food, water, territory). If a species is constantly loosing this biological warfare it is likely to adapt in order to survive or else it will die. This is referred to as the "Competition exclusion principle." Nonetheless, adaptation isn't a voluntary process, it can take years before a species evolves through natural selection. This idea is closely related to the idea of natural selection which will be explained in the next postulate.
"the proliferation of those organisms that are better able to survive and reproduce in the environment"
Finally, Darwin's last postulate relates to his theory of "survival of the fittest" which is based on the fact that we live in a savage world in which those who are best adapted to their environment will live more than those who are not and thus they will have a greater opportunity to reproduce and pass on their "super genes" to successive generations. Traits that help a species be better adapted to their environment are referred to as "adaptations." It is important to keep in mind that natural selection is a process through which biological evolution occurs. It isn't biological evolution itself. An example of this would be the now extinct species referred to as "tiktaalik." Tiktaalik was a cross between a fish and a land animal because it evolved to have 4 legs and could thus evade water predators by seeking refuge on land. Although tiktaalik are now long dead, they are responsible for the adaptation of legs. Without them, no four legged animals would exist! An image of how tiktaalik very possible looked is found bellow.
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University of Chicago. (n.d.). Tiktaalik roseae. University of Chicago. Retrieved April 5, 2016 from <http://tiktaalik.uchicago.edu/>.
University of Evansville faculty. (n.d.). Natural Selection. University of Evansville. Retrieved April 5, 2016 from <http://faculty.evansville.edu/de3/b32003/lecture%20summaries/selection.pdf>.