Evolution By Mackenzie Rodgers
Charles Darwin Charles Robert Darwin was born on February 12, 1809 in Shrewsbury, England. He the second son of five children to Robert Waring Darwin and Susannah Wedgwood. In 1831 Charles Darwin, age 22, signed on as a naturalist with the H.M.S. Beagle for a 5 year trip around the world. During his trip he studied the natural history and biology of multiple Pacific islands and South America. He was especially interested in the Galapagos Islands. As he explored these islands he met fascinating animals and plants. He collected many Samples. He learned how to tell which island the turtles came from based on their size, shape, neck and leg length.
Darwin’s Return to England When Darwin returned to England he continued to study the specimens he collected on his trip. His Finch collection was studied by experts and concluded it contained 13 different species. He read an article that presented the idea of a population reproducing faster than the food could supply. He argued that populations are kept in check because some organisms can’t reproduce. Darwin's theory of evolution had a tremendous impact on religious thought. Many people strongly disagreed the idea of evolution because it conflicted with their religious beliefs.
Natural Selection Darwin observed a process known as artificial selection and believed that, in nature, animals that reproduced were selected by the environment. Oramismswith the characteristics to survive in in their environment could produce more offspring than individuals with out those traits. He called this process natural selection. Scientists now define natural selection as the process in which characteristics that enhance survival and reproduction are continued. Eventually they replace less beneficial characteristics.
Adaptations in Natural Selection These mentioned characteristics are called adaptations. Adaptations are features that allow some members of a species or population to survive and reproduce more frequently. They are part of the variations in the population. Darwin proposed that variations appeared randomly and without design. If a new variation appeared it would allow its bearer to produce more offspring with the adaptation.
Another scientist of natural selection Jean Baptiste Lamarck also studied natural selection. He suggested one species could make another grow. He suspected that some force causes an organism to generate new structures to meet biological needs. He believed, once formed, they continued to develop with use and were passed on to offspring. We now know these are called acquired characteristics and are not passed on to offspring.
Mutations Mutations are alterations in DNA structure and may be helpful, harmful, or have no effect at all on the organism. Mutations have can be seen occurring in large populations through long periods of time making enough variations for natural selection to happen. Mutations, then, create new genetic material adding to the gene pool.
Evidence Supporting Natural Selection in Genetics Darwin’s ideas have been greatly modified but are still the backbone of the theory. The chromosome theory of heredity helped to show the way variations could be inherited and maintained in a population. Only hereditary variations have any meaning in the evolution process. Hereditary variations are the products of an organism’s genes. There are two major sources of variability required for evolution, mutations and genetic recombinations.
Other variations Other variations in diploid organisms include diploidy, the shuffling of chromosomes, and crossing over, the exchange of genetic material between homologous chromosomes. With these variations trillions of recombinations are possible. An about limitless number of variety in hereditary types is possible. New mutations can occur and form new genotypes that produce new phenotypes. The new phenotypes are subjected to natural selection which eliminates some gene combinations for the populations gene pool.
Works Cited • BSCS. “Chapter 9.” Biology. Barbra C. Resch. Ninth Edition. Kendall/Hunt Publishing Company:2002, N.D. 222-232. • Dennis O'Neil. “Darwin and Natural Selection.” Early Theories of Evolution. Dennis O'Neil. N.D., 5/23/12. Internet. 5/25/12. < http://anthro.palomar.edu> • N.A. “Charles Darwin.” Lucid Café. N.A. N.D., n.d. Internet. 5/24/12. http://www2.lucidcafe.com • University of Michigan. “Evolution and Natural Selection.” Global Change. N.A., Ben van derPluijm. N.D., 10/10/10. Internet. 5/24/12.http://www.globalchange.umich.edu