Evolution Charles Darwin Essay Example For Students

Evolution Charles Darwin Essay EVOLUTION TABLE OF CONTENTS PageINTRODUCTION .. 2DARWINIAN THEORY OF EVOLUTION 4THE THEORY OF BIOLOGICAL EVOLUTION:CONTRIBUTING ELEMENTS .. 7WALLACES CONTRIBUTIONS .. 13HARDY-WEINBERG PRINCIPLE . 15 COMPARISON: LAMARCK vs. DARWIN 16 DARWINS INFLUENCES 20METHODS OF SCIENTIFIC DEDUCTION 23LIMITS TO DARWINS THEORY 25MORPHOLOGICAL ; BIOLOGICAL CONCEPTS .. 27BIO-EVOLUTION: POPULATION vs. INDIVIDUALS . 29MECHANISMS FOR GENETIC VARIATION .. 31GENETIC VARIATION AND SPECIATION .. 35DARWINS FINCHES 37SPECIATION vs. CONVERGENT EVOLUTION .. 39CONCEPT OF ADAPTATION . 41PUNCTUATED EQUILIBRIUM 43VALUE/LIMITATIONS: THE THEORY OF BIOLOGICAL EVOLUTION . 45ALTERNATE EXPLANATIONS OF BEING 47CONCLUSIONS .. 48INTRODUCTIONTheories explaining biological evolution have been bandied about since the ancient Greeks, but it was not until the Enlightment of the 18th century that widespread acceptance and development of this theory emerged. In the mid 19th century english naturalist Charles Darwin who has been called the father of evolution conceived of the most comprehensive findings about organic evolution ever1. Today many of his principles still entail modern interpretation of evolution. Ive assessed and interpreted the basis of Darwins theories on evolution, incorporating a number of other factors concerning evolutionary theory in the process. Criticism of Darwins conclusions abounds somewhat more than has been paid tribute to, however Darwins findings marked a revolution of thought and social upheaval unprecedented in Western consciousness challenging not only the scientific community, but the prominent religious institution as well. Another revolution in science of a lesser nature was !also spawned by Darwin, namely the remarkable simplicity with which his major work The Origin of the Species was written straightforward English, anyone capable of a logical argument could follow it also unprecedented in the scientific community (compare this to Isaac Newtons horribly complex work taking the scientific community years to interpret2). Evolutionary and revolutionary in more than one sense of each word. Every theory mentioned in the following reading, in fact falls back to Darwinism. DARWINIAN THEORY OF BIOLOGICAL EVOLUTIONModern conception of species and the idea of organic evolution had been part of Western consciousness since the mid-17th century (a la John Ray)3, but wide-range acceptance of this idea, beyond the bounds of the scientific community, did not arise until Darwin published his findings in 19584. Darwin first developed his theory of biological evolution in 1938, following his five-year circumglobal voyage in the southern tropics (as a naturalist) on the H.M.S. Beagle, and perusal of one Thomas Malthus An Essay on the Principle of Population which proposed that environmental factors, such as famine and disease limited human population growth5. This had direct bearing on Darwins theory of natural selection, furnishing him with an enhanced conceptualization of the survival of the fittest the competition among individuals of the same species for limited resources the missing piece to his puzzle6. For fear of contradicting his fathers beliefs, Darwin did not publish his find!ings until he was virtually forced after Alfred Wallace sent him a short paper almos t identical to his own extensive works on the theory of evolution. The two men presented a joint paper to the Linnaean Society in 1958 Darwin published a much larger work (a mere abstract of my material) Origin of the Species a year later, a source of undue controversy and opposition (from pious Christians)7, but remarkable development for evolutionary theory. Their findings basically stated that populations of organisms and individuals of a species were varied: some individuals were more capable of obtaining mates, food and other means of sustenance, consequently producing more offspring than less capable individuals. Their offspring would retain some of these characteristics, hence a disproportionate representation of successive individuals in future generations. Therefore future generations would tend have those characteristics of more accommodating individuals8. This is the basis of Da!rwins theory of natural selection: those individuals incapable of adapting to change are eliminated in future generations, selected against. Darwin observed that animals tended to produce more offspring than were necessary to replace themselves, leading to the logical conclusion that eventually the earth would no longer be able to support an expanding population. As a result of increasing population however, war, famine and pestilence also increase proportionately, gener ally maintaining comparatively stable population9. Twelve years later, Darwin published a two-volume work entitled The Descent of Man, applying his basic theory to like comparison between the evolutionary nature of man and animals and how this related to socio-political development man and his perception of life. It is through the blind and aimless progress of natural selection that man has advance to his present level in love, memory, attention, curiosity, imitation, reason, etc. as well as progres s in k!nowledge morals and religion10. Here is where originated the classic idea of the evolution of man from ape, specifically where he contended that Africa was the cradle of civilization. This work also met with opposition but because of the impact of his revolutionary initial work this opposition was comparatively muted11. A summary of the critical issues of Darwins theory might be abridged into six concise point as follows:1 Variation among individuals of a species does not indicate deficient copies of an ideal prototype as suggested by the platonic notion of Eidos. The reverse is true: variation is integral to the evolutionary process. 2 The fundamental struggle in nature occurs within single species population to obtain food, interbreed, and resist predation. The struggle between different species (ie. fox vs. hare) is less consequential. 3 The only variations pertinent to evolution are those which are inherited. 4 Evolution is an ongoing process which must span many moons to become detectably apparent. 5 Complexity of a species may not necessarily increase with the evolutionary process it may not change at all, even decrease. 6 Predator and prey have no underlying purpose for maintenance of any type of balance natural selection is opportunistic and irregular12. THE THEORY OF BIOLOGICAL EVOLUTION: CONTRIBUTING ELEMENTSThe scientific range of biological evolution is remarkably vast and can be used to explain numerous observations within the field of biology. Generally, observation of any physical, behaviourial, or chemical change (adaptation) over time owing directly to considerable diversity of organisms can be attributed to biological evolution of species. It might also explain the location (distribution) of species throughout the planet. Naturalists can hypothesize that if organisms are evolving through time, then current species will differ considerably from their extinct ancestors. The theory of biological evolution brought about the idea for a record of the progressive changes an early, extinct species underwent. Through use of this fossil record paleontologists are able to classify species according to their similarity to ancestral predecessors, and thereby determine which species might be related to one another. Determination of the age of each fossil will concurrently indicate the rate of evolution, as well as precisely which ancestors preceded one another and consequently which characteristics are retained or selected against. Generally this holds true: probable ancestors do occur earlier in the fossil record, prokaryotes precede eukaryotes in the fossil record. There are however, significant missing links throughout the fossil record resulting from species that were, perhaps, never fossilized never!theless i t is relatively co mpatible with the theory of evolution13. It can be postulated that organisms evolving from the same ancestor will tend to have similar structural characteristics. New species will have modified versions of preexisting structures as per their respective habitats (environmental situations). Certainly these varying species will demonstrate clear differentiation in important structural functions, however an underlying similarity will be noted in all. In this case the similarity is said to be homologous, that is, structure origin is identical for all descended species, but very different in appearance. This can be exemplified in the pectoral appendages of terrestrial vertebrates: Initial impression would be that of disparate structure, however in all such vertebrates four distinct structural regions have been defined: the region nearest the body (humerus connecting to the pectoral girdle, the middle region (two bones, radius and ulna are present), a third region the hand of several bones (carpal and metacarpal, and !region of digits or finger s. Current species might also exhibit similar organ functions, but are not descended from the same ancestor and therefore different in structure. Such organisms are said to be analogous and can be exemplified in tetrapods, many containing similar muscles but not necessarily originating from the same ancestor. These two anatomical likenesses cannot be explained without considerable understanding of the theory of organic evolution14. Jack Londons To Build A Fire: Theme EssayThe integral relevance for employment of the Hardy-Weinberg principle is its illustration of expected frequencies where populations are evolving. Deviation from these projected frequencies indicates evolution of the species may be occurring. Allele and genotype frequencies are typically modified per each successive generation and never in ideal Hardy-Weinberg equilibrium. These modifications may be the result of natural selection, but (particularly among small populations) may simply result from random circumstance. They might also arise form immigration of individuals form other populations where gene frequencies will be unique, or form individuals who do not randomly choose mates from their wide-ranged species26. COMPARISON: LAMARCK vs. DARWINDespite the lack of respect lamarckian theory was dealt at the hands of the early evolution-revolutionaries, the enormous influence it had on numerous scientists, including Lyell, Darwin and the developers of the Hardy-Weinberg theory cannot be denied. Jean Lamarck, a French biologist postulated the theory of an inherent faculty of self-improvement by his teaching that new organs arise form new needs, that they develop in proportion to how often they are used and that these acquisitions are handed down from one generation to the next (conversely disuse of existing organs leads to their gradual disappearance). He also suggested that non-living matter was spontaneously created into the less complex organisms who would evolve over time into organisms of greater and greater complexity. He published his conclusions in 1802, then later (1909) released an expanded form entitled Philosophie zoologique. The English public was first exposed to his findings when Ly ell popularized them wi!th his usual flair for writ ing, but because the influential Lyell also openly criticized these findings they were never fully accepted27. Darwins own theories were based on those of older evolutionists and the principle of descent with modification, the principle of direct or indirect action of the environment on an individual organism, and a wavering belief in Lamarcks doctrine that new characteristics acquired by the individual through use or disuse are transferred to its descendants. Darwin basically built around this theory, adding that variation occurs in the passage each progressive generation. Lamarcks findings could be summarized by stating that it is the surrounding environment that has direct bearing on the evolution of species. Darwin instead contested that it was inter-species strife the will to power or the survival of the fittest28. Certainly Lamarck was looking to the condition of the sexes: the significantly evolved difference of musculature between male and females can probably be more easily explained by Lamarckian theory than Darwinian. There was actually quite a remarkable similarity between the con clusions of D arwins grandfather, Erasmus Darwin and Lamarck Lamarck himself only mentioned Erasmus in a footnote, and with virtual contempt. The fact is neither Lamarck nor Darwin ever proposed a means by which species traits were passed on, although Lamarck is usually recalled as one of those hopelessly erroneous scientists of past it was merely the basis for his conclusions that were hopelessly out of depth the conclusions were remarkably accurate29. DARWINS INFLUENCESIn 1831 a young Charles Darwin received the scientific opportunity of lifetime, when he was invited to take charge f the natural history side of a five year voyage on the H.M.S. Beagle, which was to sail around the world, particularly to survey the coast of South America. Darwins reference material consisted of works of Sir Charles Lyell, a British geologist (he developed a concept termed uniformitarianism which suggested that geological phenomena could be explained by prevailing observations of natural processes operating over a great spans of time he has been accused synthesizing the works of others30) who was the author of geologic texts that were required reading throughout the 19th century including Principals of Geology, which along with his own findings (observing the a large land shift resulting from an earthquake), convinced him of geological uniformitarianism, hypothesizing for example, that earthquakes were responsible for the formation of mountains. Dar win faith!fully maintained this method of interpreting facts by seeking explanations of past events by observing occurrences in present time throughout his life31. The lucid writing style of Lyell and straightforward conclusions influence all of his work. When unearthing remains of extinct animals in Argentina he noted that their remains more closely resembled those of contemporary South American mammals than any other animals in the world. He noted that existing animals have a close relation in form with extinct species, and deduced that this would be expected if the contemporary species had evolved form South American ancestors not however, if thereexisted an ideal biota for each environment. When he arrived on the Galapagos islands (islands having been formed at about the same time and characteristically similar), he was surprised to observe unique species to each respective island, particularly tortoises which possessed sufficiently differentiated shells to tell them apart. !F rom these observations he concluded that the tortoises cou ld only have evolved on the islands32. Thomas Robert Malthus was an English economist and clergyman whose work An Essay on the Principal of Population led Darwin to a more complete understanding of density dependent factors and the struggle in nature. Malthus noted that there was potential for rapid increase in population through reproduction but that food cannot increase as fast as population can, and therefore eventuality will allow less food per person, the less able dying out from starvation or sickness. Thus did Malthus identify population growth as an obstacle to human progress and pedalled abstinence and late marriage in his wake. For these conclusions he came under fire from the Enlightment movement which interpreted his works as opposing social reform33. Erasmus Darwin, grandfather of Darwin, was an unconventional, freethinking physician and poet who expressed his ardent preoccupation for the sciences through poetry. In the poem Zoonomia he initiated the idea that evolution of an organism results from environmental implementation. This coupled with a strong influence from the similar conclusions of Lamarck shaped Darwins perception on the environments inherent nature to mould and shape evolutionary form34. METHODS OF SCIENTIFIC DEDUCTIONEarly scientists, particularly those in the naturalist field derived most of their conclusions from observed, unproven empirical facts. Without the means of logically explaining scientific theory, the hypothesis was incurred an educated guess to be proven through experimentation. Darwin developed his theory of natural selection with a viable hypothesis, but predicted his results merely by observing that which was available. Following Lyells teaching, using modern observations to determine what occurred in the past, Darwin developed theories that only made sense logical from the point of view of the human mind (meaning it was based on immediate human perception) but decidedly illogical from a purely scientific angle. By perusing the works of Malthus did Darwin finally hit upon his theory of natural selection not actually questioning these conclusions because they fit so neatly into his own puzzle. Early development of logical, analytic scientific theo ry did not occur u!ntil the advent of philosophe r Rene Descartes in the mid-17th century (I think therefore I am35). Natural selection was shown to be sadly lacking where it could not account for how characteristics were passed down to new generations36. Philosophy Essays