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Texas ISD School Guide
Texas ISD School Guide







Short Stories for Teachers

Charles Darwin's Theory of Evolution by Natural Selection
By:S. Tanna <webmaster@ans2000.com>

Charles Darwin is today known for his theory of evolution by natural selection. He developed this theory over a number of years after returning on a 5 year (1831 to 1836) round the world voyage on HMS Beagle. The outline of the theory was first presented in a paper read to the Linnean Society by Charles Darwin's friends, Sir Charles Lyell and John Dalton Hooker (Darwin himself was unable to attend this presentation of his work because of the recent death of his infant son from scarlet fever) on July 1st 1857. Darwin then presented his ideas to a wider public, and at considerably greater length, in his classic 1859 book, "On the Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life", which today is usually referred to simply as "On the Origin of Species".

Many people misunderstand what Darwin's theory is about. Perhaps the most common error is that it is a theory of the origin of life ("abiogenesis"), that is not the case - Darwin's theory does not deal with that matter, but rather is only about how successive generations of organisms change over time ("evolution"). Another common point of confusion about Darwin's work is that he was the first person to propose the idea of evolution - this is far from the case - evolutionary ideas date back to at least the 6th century BCE (e.g. the Greek philosopher Anaximander). Instead Darwin's great insight was "natural selection", which is an explanation of how evolution works to produce new species and to create organisms suited to their environments.

Although of course there are many details and fine points behind the idea of natural selection, the basic idea behind it is beautifully simple. It begins with the observation that children tend to be similar to their parents. From that observation one can state that whatever heritable traits are better at helping organisms to survive and reproduce will tend to become more common in a population, whereas harmful heritable traits will gradually become less and less common. Of course, random changes to heritable traits ("mutations") may also occur, but these too will tend to become or less common depending on whether they are helpful or harmful. Finally, when we consider the immense age of the Earth, this provides enough time for the accumulation of tiny improvements in beneficial heritable traits to produce a great variety of different organisms - in fact all life on Earth.






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