Charles Darwin's Theory of Evolution
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In The Origin of Species, Charles Darwin poetically entailed, "There is grandeur in this view of life . . .." Personifying Nature as the ultimate breeder, Darwin infers and hypothesizes what is arguably the most fundamental and profound scientific manifesto that governs what we now know about modern science and the science of discovering our past. His two theories of Natural Selection and Sexual Selection effectively bridge the gap that his predecessors could not. These concepts are imperative as their implications paved the way for Darwin's explanation of Evolution. The term "Survival of the Fittest" has been made synonymous with Darwinian ideology, yet to fully understand this idea we need to know what it truly means to be "fit." As discussed in class, being fit does not necessarily imply fitness on a physical or mental level. Rather, the principle entails how well-suited one is for its environment or a readiness for a species to adapt, whether to a new habitat or possibly changes in food, shelter, climate, etc. Through small, almost unnoticable change, over large periods of time, organisms develop physiological and/or anatomical features that invariably help the organism live or live easier. It is important to note that this does not infer that the process of adaptation takes place for the mere purpose of only "bettering" a species or self-improvement, rather modifications are a supplemental benefit. Darwin stated that, "if they be in any degree profitable to the individuals of a species, in their indefinitely complex relations to the organic beings and to their physical conditions of life, will tend to the preservation of such individuals . . .." In some cases this modification can be a detriment to a species. Take for example a species of like-moths in England preceding and during the Industrial Revolution. Before the manufacture of goods in large quantities, two types of moths, white and gray would rest on the bark of trees where birds would prey upon them. The barks of trees were mainly white, which helped the white moths immensely in that they were camouflaged from their predators. Conversely, the gray moths were clearly noticeable and were thus preyed upon heavily. With the advent of machinery, dust and smoke turned the barks of trees from white to gray, which shifted the predatorial tendencies from gray moths to white. Thus we are able to infer that while the adaptation of color was beneficial to a group of species for a certain extent of time, it does not guarantee that Mother Nature will not shift her favor at some other point in time.
Nature has an infinite supply of checks and balances at her disposal. The amount of food present in a location is key to determining how many organisms an environment can maintain. Those who may be better adapted to, for example, eat leaves on tall trees, such as giraffes, would have less difficulty surviving in a terrain containing tall trees. Climactic divergences of extreme frost or drought can severely wipe out a species ill adapted for that type of weather. Predation and epidemics can also scourge population when numbers of a species are too high. Darwin wisely noted in his work that, "there must be much fortuitous destruction, which can have little or no influence on the course of natural selection," those who do invariably survive however, were statistically the best-adapted species for their environment. If these "better" species continued under the same conditions, where slight modifications in the structure or habits give it an advantage over another species, and they were able to pass down these modifications to their offspring, the weaker like-species would eventually die off or assimilate with the flock. Evolution, therefore, is a result of the passing on of traits, usually on a small scale, over gradual periods of time. We are able to see this timeline of Evolution through the Fossil Record, although some sections may have eroded or been destroyed over the lapse of time. Seventeenth century English author John Dunne stated "No Man is an Island," and in a very literal and figurative definition it can be said that no single organism can survive without depending on something else. Yet, Nature dictates a precarious balance where no one entity can truly reign supreme over all others. As the population of species grows exponentially, the world only has a limited supply of resources to support the population. Using the law of Supply and Demand, there are simply not enough resources for all to survive. Thus the struggle for existence is ever pressing between prey and predator, individuals of a same species vying for the same nutrients and sustenance or even Darwin's example of a flower, struggling to exist at the edge of a desert. There were three major components of his theory of Evolution that he took from his predecessors and incorporated them along with his ideas and findings into a remarkable precedent in the science field. The first dealt with the issue of time, through the fossil record and looking at modern day animals he postulated that there was a development of life through time. That there was a correlation between the Megatherum and the modern-day armadillo, which led him to believe that there were changes over time to make what the modern day animal is now from its ancestors. Secondly, the Galapagos Island finches exemplified the idea of space and it also playing a role in adaptation and evolution. When Darwin examined the birds from the various islands in the Galapagos Archipelago he saw minute differences in the shape of their beaks. He thus concluded that like time, over a large space, small adaptations begin to occur to help the species out in their specific environments. Finally, he tied everything up with the unifying concept of Uniformitarianism, where large changes can be induced through the accumulation of small changes over time. As of now we've mainly discussed the adaptations by which individual organisms have evolved. Adaptations that provide some necessary function for it to live as best it possibly can. Darwin states that Sexual Selection depends, "not on a struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex. The result is not death to the unsuccessful competitor, but few or now offspring." This implies that the most virile of males will be able to mate more successively, more often and will produce more progeny to carry on his traits. These incitements, such as the love song of songbirds, the plumage of peacocks, the liveliest males will arouse the agency that decides the pairing of mates, primarily females. Charles Darwin correctly kept Sexual Selection markedly different from Natural Selection due to the major principle in that sexual selection allows for adaptations within a gender, specifically males, which have no practical use for the animal, except to entice a female. In the Descent of Man, Darwin points out that, "these characters are the result of sexual and not of ordinary selection, since unarmed, unornamented, or unattractive males would succeed equally well in the battle for life and in leaving a numerous progeny, but for the presence of better endowed males." Natural selection, as stated earlier, are adaptations by which the environment winnows out good and bad traits. Letting the "fittest" to its particular environment survive. Charles Darwin's journey on the H.M.S. Beagle, as a Naturalist, allowed the geologist an opportunity to accumulate mass quantities of data and research, from which he began to understand what his counterparts were missing about the issue of Evolution. His forerunners postulated a wide assortment of valid ideas, but each had major controversies that stemmed from flaws in their individual theories. By taking bits and pieces of these sources and examining it along with his findings and own ideas he was able to effectively show the "true grandeur in this view of life. . .." A life that has been and still will be ever changing. The human race live in times where we take leaps and bounds in science and other fields and the geographical space between people decrease allowing a cross-cultural mixing pot of ideas that will "change" our world. We in turn, have to adapt and to evolve if we truly are the top of the evolutionary chain.
Campbell, Biology 1998