(Sail) Study Help Only Essays - Charles Darwin, Biological Evolution

(Sail) Study Help Only On the voyage of the Beagle (1831-1836) Darwin collected and described thousands of animals and plants. In South America he observed the adaptations of organisms to a variety of habitat from jungle to grassland to mountain habitats. In the temperate regions the species resembled more closely the species of the tropical regions of South America rather than the corresponding species of the temperate regions of Europe. For example, in the grasslands of Argentina there are no rabbits, however, there are rodents that resemble rabbits; these rodents are unrelated to European rabbits but are similar to other rodents in South America. Moreover, the fossils in South America are dissimilar to European fossils but have similarities with extant (i.e. currently living) plants and animals in South America. Darwin was particularly intrigued by the finches on the islands of Galapagos which are located approximately 500 miles from the mainland of South America. These finches, although unique to these islands, were clearly related to mainland species. There were 14 different species or genera of Galapagos Finch and their bills were adapted for particular diets. Darwin amassed these and other data including observations on variability in domestic animals (for example, dogs) which had been brought about by generations of selective breeding. As well as drawing on his own observations, Darwin drew from the work of Linnaeus, Cuvier, Hutton, Lyell, Malthus and Lamarck. In the hierarchial classificatory system of Linnaeus there is a tacit acknowledgement of relatedness, for example, species belonging to one genus have more in common with each other than they do with species belonging to another genus. Linnaeus was a creationist - as evidenced by his egotistical proclamation God creates, Linnaeus arranges. Cuvier, also a creationist, was a comparative morphologist (he described the similarity/dissimilarity in anatomy of diverse animals). Cuvier founded the science of paleontology and described the differences between the fossil flora and fauna in different strata of rock: he observed that the more recent strata had fossils that more closely resembled extant organisms. Cuvier believed that the discontinuities between fossils in different strata were brought about by catastrophes such as floods which caused the extinction of ma ny species living at a particular time. This interpretation of earth's history is termed catastrophism and was also held by many contemporary geologists. By contrast, Hutton and subsequently Lyell held that geological processes are slow and subtle but that over prolonged periods of time (millions of years) these can lead to major changes; implicit in this viewpoint is an age for the earth radically different from the 6,000 years of the biblical creationists. Other key influences on Darwin were Malthus who had concluded that war and famine were inevitable as the human population grew more rapidly than available resources, and Lamarck who had proposed a theory of evolution based on a continuous process of gradual modification due to acquired characteristics. Both Darwin and Wallace brought together a multitude of facts including the geographical distribution of organisms, comparative morphology of living organisms and their fossil precursors. They postulated that long-term environmental changes including movement of land masses and changes in climate could have served in the process of natural selection over many generations with the result that diverse species arose from ancestral types. Darwin termed this descent with modification (the term evolution was introduced later, as was the tautology survival of the fittest). Darwin's ideas can be summarized in his own words from The Origin of Species: As many more individuals of each species are born than can possibly survive, and as consequently there is a frequently recurring struggle for existence, it follows that any being, if it vary in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of survival and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form. In assessing the contribution of Darwin and Wallace it should be noted that the key role in heredity of the nucleus, chromosomes and DNA were not demonstrated until 1892, 1903, 1943, respectively. Also, the Darwin-Wallace theory of evolution was developed without an appreciation of Mendel's work on inheritance (ironically, Mendel had written to Darwin with

I, Too essays

I, Too essays Title Black race is integral in America ParaphraseIm American (American pride). I represent the other half, and now you ignore me but I am getting stronger, and soon I wont be sent away, and then you will see how beautiful I am and regret sending me away because I too am American. Figurative language Darker brother is a symbol of the black race. Brother brings to mind the idea of America s a family. He is the other half of the integral relationship of brotherhood. Send me away when company comes brings about the idea of an embarrassing part of the family not to be talked of (for example a drunken step uncle). But I laugh and grow stronger -instead of letting the attempts to ostracize him ferment anger, he shakes it off and uses it for motivation for becoming more recognized, respectable, and qualifiedto become a more valuable member of the family. Tomorrow Ill be at the table, tomorrow represents a time in the near future when blacks will have equality. The table represents accomplishment, for it is where one is served. This can also mean the simple fact that he who sends the black man away or hides him today will still have to see him tomorrow. The table represents accomplishment and serves as a place of coming together (black and white). Tone The tone towards the black audience is uplifting and encouraging. It is intended to arouse feelings of support and pride for the black movement. Although towards any racist whites who read it, the tone is admonitory. This message is a polite warning of impending equality in spite of all attempts to stop the black movement. ...