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Created by: Walbert, Savannah

Evolution is the change, over multiple generations, of allele frequencies in a population or species in response to the environment. Evolution occurs as a result of the process of natural selection, a concept proposed by Charles Darwin in 1859.

Natural Selection

The theory of natural selection states that the variation of traits within a species or population results in different levels of success for individual organisms to survive and reproduce. Those with traits that increase their likelihood of survival or reproduction are more likely to pass on those traits to a higher number of offspring causing the frequency of those favorable traits to increase. Organisms with traits that increase their likelihood of survival or reproduction are said to be more "competitive" than those with less favorable traits. Which trait ends up being more advantageous depends on the environment that organism is in. This leads to species being more well suited to their environment. Given enough time and over a large number of generations this process has lead to the diversity and unity of species we see on the planet today. It has taken roughly 3.8 billion years for one common ancestral organism to diversify into the 8.7 million species estimated to be present on the planet today.

Charles Darwin

<meta charset="utf-8">On the Origin of species by means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life
Charles Darwin
(better known as simply the Origin of Species) by Charles Darwin is the book that introduced the idea of evolution caused by natural selection to the world. Charles Darwin wrote this book mostly based on his research and evidence he gained on his 5 year trip aboard the HMS Beagle in the 1830's. The most widely known evidence Darwin gathered during this time was that of the Galapagos Finches. Darwin noticed that the populations of finches on the different islands had differing beak sizes which were relatively proportional to the type of food they chose to eat. Darwin had more or less developed his theory of natural selection by 1844 but was reluctant to introduce a theory which came into such contrast with the teachings of the Christian church. In 1858 Alfred Russel Wallace developed essentially the same theory as Darwin and they came to an agreement to publish the theory together as co-authors. The theory was immediately accepted by most in the scientific community but Darwin certainly did receive backlash from the religious community. While Darwin and Wallace's theory is more widely accepted today there is still large number of people who disagree with it because of their religious beliefs.

Galapagos Finches


<a href="https://evolution.berkeley.edu/evolibrary/article/evo_02">https://evolution.berkeley.edu/evolibrary/article/evo_02</a>






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