Evolution Honors Option: Darwin and Natual Selection

Charles Darwin is a well known contributor to the theory of evolution. Many know that he went to the Galapagos islands and noticed variation in the animals there. People also know that he came back and wrote the famous book, On the Origin of Species by Means of Natural Selection. What people do not know commonly are the gaps that fill those events.

The dapper, Charles Darwin
http://pterosauria.files.wordpress.com/2011/02/charles-darwin.jpg

Darwin set sail on a ship called "the Beagle" which was on a trip to around the South American coast. Darwin was on the ship to find evidence to support natural theology. With all the fossil evidence, variation of species, and other observations, Darwin had a lot to contemplate! Once he returned back to England, he thought about and researched information about his hunches, until he came up with the theory of evolution as "descent with modification." This means that every organism is related and has descended from an ancient common ancestor. The main concept of descent with modification is the theory of natural selection. The Theory of Natural Selection has four parts, or postulates, that encompass the idea:

1. There is variation among individuals of a species.

2. Some of these variations are heritable.

3. In every generation, more offspring are produced than are able to survive.

4. Some of these offspring live and some do not survive. (Natural Selection occurs)

Here, an article describes a “real life” example of natural selection. “The theory of natural selection clearly explains how features such as the sharp teeth of the tiger, the thick fur of the polar bear and the camouflage of the moth evolved. When the ancestors of polar bears colonised the Arctic, for instance, those with thicker fur would have had a better chance of surviving and producing more offspring than those with thinner fur” (Wilson). The Arctic is obviously cold and polar bears that live there would benefit from thicker fur. Variation in the polar bear population would include bears having thinner fur and thicker fur. This trait would be a heritable one that would be passed on to offspring. More baby bears are produced than can survive, but the ones with thicker fur have a better chance of survival and reproduction.

The same principles can be applied to the microorganism, Bacillus anthracis. Anthrax can be treated with three different drugs: ciprofloxacin, doxycycline and penicillin. Bacillus anthracis has variation in each population. Some of these variable traits are hereditary and then passed on to offspring. Usually variation can be seen in the strains of Bacillus and whether or not the strain is resistant to the antibiotic. More Bacillus are produced than can survive. The antibiotic of choice will kill some of the organisms, but not others. The ones that survive are more resilient and have acquired an advantageous heritable trait. Even though the theory was very controversial for a very long time, it is now well established in the field of evolution.