Essay on Evolution

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Essay on Evolution

There are many mechanisms that lead to evolutionary change. One of the most important mechanism in evolution is natural selection which is the differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Natural selection occurs when a environment makes a individual adapt to that certain environment by variations that arise by mutation and genetic recombination. Also it favors certain traits in a individual than other traits so that these favored traits will be presented in the next generation. Another mechanism of evolution is genetic drift. Genetic drift is a random change in a small gene pool due to sampling errors in propagation of alleles or
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The most precise and powerful method for comparing DNA from two species is DNA sequencing which determines the nucleotide sequences of entire DNA segments that have been cloned by recombinant DNA techniques. This type of comparison tells us exactly how much divergence there has been in the evolution of two genes derived from the same ancestral gene. In 1990, a team of researchers used PCR(polymerase chain reaction) a new technique to compare a short piece of ancient DNA to homologous DNA from a certain plant. Scientists have also compared the proteins between different species such as in bats and dolphins. The oldest type of evidence has been the fossil record which are the historical documents of biology. They are preserved remnants found in sedimentary rocks and are preserved by a process called pretrification. To compare fossils the ages must be determined first by relative dating. Fossils are preserved in strata, rock forms in layers that have different periods of sedimentation which occurs in intervals when the sea level changes. Since each fossils has a different period of sedimentation it is possible to find the age of the fossil. Geologists have also established a time scale with a consistent sequence of geological periods. These periods are: the Precambrian, Paleozoic,
Mesozoic and the Cenozoic eras. With this time scale, geologists have been able to deduce which