Darwin and Evolution Assignment Example | Topics and Well Written Essays - 750 words

Darwin and Evolution - Assignment Example Prior to Darwin, though some naturalists had speculated about modification of species, they failed to explain why and how species change. They also believed that evolution began with the special creation of only a fixed number of species. Partly influenced by Thomas Malthus' essay on the Principle of Population and stimulated by a letter from Alfred Russel Wallace, in 1859 Charles Darwin discussed in detail the evolution of species through natural selection in his famous work titled On the Origin of Species, which totally revolutionized the previous concepts of evolutionary biology. Natural selection refers to a process in which species compete and struggle for their survival according to the limited resources and conditions of their natural environment with different adaptive abilities. As individuals in a population are not same due to difference in inherited characteristics, nature only selects those individuals that are best suited to the environmental conditions, and thus rest o f the population dies over time. As all the offspring in a population acquire characteristics from their ancestors, produced more than nature can support and have different reproductive characteristics, only those organisms will survive that are better adapted to the living conditions. This means that organisms with higher reproduction ability will remain due to higher probability of their descendants to survive, and other will eventually become extinct due to less survival rate of their offspring with the passage of time. Since environmental conditions are different from place to place, there will be variation in characteristics of species at different locations. Darwin concluded that populations extending over large areas or through migration might have been isolated resulting in variation of their characteristics according to varying environments. Over long periods of time, they may have diverged or evolved into separate species different from each other. For instance, Darwin fou nd that finches he observed on the Galapagos Islands were similar to one another than they were to finches of the mainland. He also noticed that some varieties were only existent on the archipelago islands. So, he proposed that all species might have descended from a common ancestor and increase in number of species occurred through evolutionary natural selection over time rather than special creation. Question Two Darwin and other naturalists believed that variations among individuals of a species were due to mixing of traits from both male and the female. He was not aware of the heredity mechanism and different traits were regarded to be the result of blending of characteristics through generations over time. However, the concept of blending inheritance failed to describe the survival of variety as they descended through generations with time. It also failed to describe the maintenance of specific characteristics in varieties and that how new species would emerge through blending. It was 1866, when Gregor Mendel published his experimental findings on garden peas. To experiment with pure seeds, he selected a self pollinating plant. He experimented with garden peas that were different from each other in many characteristics such as their flowers were either red or white, had green or yellow seeds, and tall or dwarf. After cross-breeding generations having different characteristics, he observed that descendants from each cross possessed characteristics of only one of the parents and blending did not happen. Mendel concluded that instead of blending of certain fluids, heredity from parents was passed on to offspring through independent discrete units, particles or factoren, which were later termed as genes. The characteristic that appeared in a descendant after cross breeding was termed