Chapter 22 Notes
Chapter 22 Notes BSC 114
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This 2 page Class Notes was uploaded by Rebecca Sharp on Saturday April 30, 2016. The Class Notes belongs to BSC 114 at University of Alabama - Tuscaloosa taught by Stevan Marcus in Winter 2016. Since its upload, it has received 9 views. For similar materials see Principles Of Biology I in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 04/30/16
Evolution is any change across multiple generations in the phenotypes of a population, it’s most simply defined as the change in frequency of alleles over time. An organism’s phenotype results from the unique combination of genes it has as well as enviormental factors and interactions between the two. Mutations and natural selection are the two main driving forces of evolution. o Natural selection is a concept that gets tossed around a lot in pop culture, so for biological purposes it’s defined as the process by which individuals born with traits that help them reproduce more or survive better end up surviving over individuals born with traits that don’t. Darwin offers a definition of evolution as descent with modification. Before Darwin, the predominant belief was that God had created everything perfectly speciated as they were. o The study of fossils lay a solid groundwork for evolution. Georges Curvier, a paleontologist, thought that changes in the earth’s appearance were from slow gradual changes that were still going on in the present (a principal called uniformitarianism, invented by Lyell). He advocated a view called catastrophism, which said that each boundery between layers (also called strata) was caused by a catastrophic event. The story of Darwin; Darwin tried out college and decided it wasn’t really his thing, he tried studying medicine and failed and then tried theology and hated it, so he got on a boat instead for a five year trip around the world with Captain Robert. It was on that voyage that Darwin laid eyes on the Galapagos islands, and first saw the finches. The finches looked alike, but had beaks specific to their various diets and lifestyles. This was where he first put together the idea that adaptation was closely related to evolution. He wrote his essay on natural selection as the mechanism of descent with modification in 1844, but didn’t go public until he found out in 1858 that Alfred Russel Wallace had developed the same theory. He quickly finished the Origin of Species and published it the next year. o The Origin of Species explained 3 major topics; the unity of life, the diversity of life, and the match between organisms and their enviorement. o There’s natural selection and then there’s artificial selection. Artificial selection is when humans choose specimans with desired traits and breed specifically for those desired traits; like dog breeds. There were 2 major things that Darwin saw and drew conclusions from. He saw that that members of a population often vary phenotypically, and concluded that individuals with traits that gave them an advantage were more likely to reproduce than other individuals. He also saw that all species can produce more offspring than their enviorment can support and many of the offspring died as a result, and concluded that the unequal ability of individuals to survive and reproduce will lead to a sort of arms race between nature’s carrying capacity and accumulation of favorable traits. It’s important to remember that individuals do not evolve, populations do. Girrafes did not evolve longer necks by stretching them out over the course of thier lives. There are 4 types of data that can document evolution. They are; direct observations, homology, the fossil record, and biogeography. o Homology is similarity resulting from a common ancestor, for example, arms in humans, legs in cats, flippers in dolphins, and wings in bats, all result from a common ancestor. Vestigial structures are another example of homology, like pelvises in whales or itsy bitsy arms on T Rexes. Biogeography is the scientific study of the geographic distribution of species. This is for studying how thing got to where they are. Endemic species are species that are only found in one part of the world. Islands often have many endemic species Evolution is still working feverishly today and is evidence in things like pesticide resistence in insects and drug resistence in viruses. Convergent evolution is the evolution of similar features in distantly related groups. This happens when groups independently adapt to their enviorment in the same way. This does not provie information on ancestory. For example, the sugar glider and the flying squirrel. One is a marsupial. One is a squirrel. 99.9% of all the species that have ever existed on the earth are extinct. There have been 3 major extinctions that have had drastic major impacts on evolution. o The Cretaceous-Paleogene Extinction happened 65.5 million years ago. 75% of all species that existed on the earth at the time became extinct. Most non-avian dinosaurs became extinct. Mammals and birds took over. o The Triassic-Jurassic Extinction was 205 million years ago. 70-75% of all species that existed on the earth at the time became extinct. Mostly everything except the dinosaurs died. o The Permian-Triassic Extinction happened 251 million years ago and about 96% of all the species that existed on the earth at the time became extinct. Evolution is a theory with as much weight as the theory of gravity and the theory of relativity.