Darwin's Theory of Natural Selection

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Charles Darwin revolutionized biology when he introduced The Origin of Species by Means of Natural Selection in 1859. Although Wallace had also came upon this revelation shortly before Origins was published, Darwin had long been in development of this theory. Wallace amicably relinquished the idea to Darwin, allowing him to become the first pioneer of evolution. Darwin was not driven to publish his finding, which he'd been collecting for several years before Wallace struck upon it, because he had "never come across a single [naturalist] who seemed to doubt to permanence of species" (Ridley, pp. 70). What follows are the key points of Darwin's Theory of Natural Selection taken directly from the two chapters concerning it in his book Origins. In chapter III of Origins Darwin sets up his discussion on Natural Selection by establishing the struggle for existence in nature. By this he means not only an individuals need to fend of enemies and survive its environment but also it's ability to create living, healthy, successful offspring. The first factor concerning this struggle is the ratio of increase in any given species. Darwin explains how this struggle must be occurring otherwise a single species would dominate the entire earth because every single one of it's offspring would survive. This is due to the fact that every species reproduces exponentially, a rate that would soon produce astonishing numbers if left unchecked. This does not happen however, because nature has a system of checks and balances. Although we may not be able to detect these checks, we can see their effects by the indisputable fact that one species doesn't completely dominate the planet. These checks consist of enemies eating the young or even adults, the rigors of weather or environment, and countless others. In this way birds, for example, cannot populate beyond their food supply, and the grains they feed on are held in check, because even though they may produce thousands of seeds only a few are able to reach maturity. Darwin goes on to show how all plants and animals compete and relate to each other in this struggle for existence. He does so by relating various personal observations that show the introduction of a different species of plant or animal can have a direct effect on the present survival of the indigenous species and even allow other foreign species to proliferate. This leads to interspecies survival, which Darwin considers the hardest struggle of all, and the one that may have the greatest effect on the evolution of a species through Natural Selection. It springs forth from the similarity in "habits and constitution". Plants and animals of the same species must compete for the same food and the same space to live in. Also, the original make-up of a plant or animal may give it an advantage to thrive in an ever-competitive environment. This brings us to Natural Selection and survival of the fittest that Darwin is most known for. Darwin begins chapter IV by comparing human selection to nature's ability to select, dubbing his theory Natural Selection, and explaining how imperceptible it is for us (at least science in his time) to examine the minute changes slowly taking place in nature. Variations in a species now come into play, and how these adaptations concern Natural Selection. Slight differences in an individual of a species will give rise to two situations. One is that it will be an injurious variation, which will definitely lead to the death of the individual because of the aforementioned struggle for existence. The other is a favorable adaptation in the individual's ability to gather nutrients, survive its enemies, survive its environment, etc. The chance of this individual surviving is greater than its less adapted competitors, however slight, which gives it a better chance of leaving progeny. These progeny will also have these abilities, increasing their chances of survival. Changes in the young can also bring about changes in the...
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