Monday, May 16, 2011

Evolution Essay

Evolution is the theory that all living forms came from ancient ancestors. Through a series of mutations, genetic drift, migration, and natural selection today’s descendants show an amazing amount of similarities and diversity. Evolution on a small scale is called microevolution, relating to the changes that occur such as insects becoming resistant to pesticides. Macroevolution refers to the grand scale. It is associated with extinction, change, stability, and lineage. At the time of its “birth”, it was a controversial subject. Charles Darwin was the first to formalize the theory of evolution, but before him there were more scientists interested in it.

Charles Darwin was born in England and originally planned to take up a career in medicine. When that didn’t work out, he switched to divinity in Cambridge. Later he took a five year excursion on the HMS Beagle. During his time on board Darwin read the “Principles of Geology” that stated there was geological evidence of ancient animals. While on the Galapagos Islands he noticed that the finches on the each island were closely related but different in big ways. When he returned, he theorized evolution based on natural selection. Twenty years later he and Alfred Russell Wallace discussed evolution openly. In 1859 he published his extremely controversial ideas. Darwin was attacked for his theory, particularly by the Church. But his ideas became widely accepted.

Darwin’s own grandfather, Erasmus Darwin, was a prestigious physician, botanist, naturalist, poet, and philosopher. He believed that all modern creatures had originated from “one living filament”, a common ancestor. Erasmus did not come up with natural selection, but he did believe in competition and sexual selection. He believed that the strongest males reserved the right to mate, therefore passing on satisfactory traits. He used an integrative method of research, bringing together multiple branches of science to come to his conclusion. Some of his ideas were alike to those of Jean Baptiste Lamarck. Lamarck is an obscure character in evolutionary history as he was ostracized and his theories were not recognized by his colleagues. He was in the army, then worked as a botanist in the royal gardens. In 1793, Lamarck was appointed professor of invertebrates. At the time there was little research on insects. He wrote a series of books about invertebrate zoology and paleontology. Although other scientists in his day hinted at the possibility of evolution, Lamarck declared it forthright. He was discredited by his peers and died a poor man. However, Charles Darwin and others respected his as a great zoologist and the forerunner of evolutionary theory. Georges Cuvier was a colleague of Lamarck’s that forsake him. He was a brilliant mind, but he did not share Lamarck’s theory of evolution, going as far as to discredit him. Cuvier had studied mummies of cats and ibises brought back from Egypt by Napoleon. Finding no difference from current day animals, he had decided evolution was false. He later studied elephants and mammoth fossils, determining that mammoths were different from living elephants in their day. This led to the important idea of extinction.

Macroevolution is evolution on a grand scale. Instead of focusing on a single branch, macroevolution focuses on that chunk of the tree. It identifies patterns and transformations, then figures out how and why it happened. Mutation, migration, genetic drift, and natural selection are basic mechanisms that apply to both micro- and macroevolution to determine these patterns.For 3.8 billion years mutations have been passing through the filter of natural selection, creating stronger and more resilient descendants.  Changes and extinctions that have happened over the years are all part of macroevolution. Some changes take place slowly, this is called stasis. An example of this is the c┼ôlacanth, a fish hauled onto a ship in 1938, it was thought to be extinct for 70 million years. Extinction is an important part of evolution. Every species has a chance that it will become extinct. Microevolution is an even more important part of the evolutionary theory. As previously discussed, it is evolution on a small scale. It is the changes in animals to adapt to their habitats and the changing environment. Microevolutionairy changes can be seen by changes in gene frequency. A few of the mechanisms that affect these changes are mutation, migration, genetic drift, and natural selection. If a random cell is mutated, for example if a  yellow bird has some purple chicks and the rest are yellow. The genes in the yellow bird would have been mutated to produce purple chicks. If the purple chicks moved to another island, and the yellow birds on that island immigrated to the island that purple birds had previously inhabited, that is known at migration, or gene flow. When a mutated gene is passed to more offspring and out numbers the original colored offspring it is called genetic drift. As for natural selection, it means that the more well equipped animals are the most likely to survive. For example if the purple birds lived in a purple tree they would be more likely to survive than their yellow relatives in a purple tree. A test for preformed on sand colored and dark colored mice, showing that each mouse matched the color of their corresponding habitats. When put in the other’s habitat, they were put into more danger.

Ideas about evolution extend to different types of science as well. Biochemistry is also interested in this topic. It shows that there is a surprising amount of evolutionary evidence within the human body, bacteria, and fungus. An e.coli bacteria can become mutated and glow under a black light, showing an evolutionary change. As human fetuses grow within their mother’s wombs they are changing in evolutionary ways. There is fossil evidence that supports the evolutionary theory. Paleontologists have found and studied different species of fossils and have concluded that some fossils found were related to fossils found prior to the dig, or after. These fossils just had changes to them, evolution it could be said.

The most convincing arguments for evolution seem to be fossil evidence and the evidence that the fossils have evolved from other, previous fossils. Seeing how Darwin’s finches different from each other although they are the same bird, it makes sense to believe that evolution is plausible. Human are even evolving. Jaws are becoming shorter and their is less room for wisdom teeth in their mouths. Looking back into history, there is also the thought about Native Americans who lived in Arizona or the indigenous people of the Arctic. Their constitutions must have been completely different to be able to survive such extreme conditions. When thinking about dogs, crows, and spiders that can procreate with different dogs, crows, and spiders in their species it’s hard not to believe in evolution. This idea of speciation is a rather convincing idea.


All Information Was Taken From

Understanding Evolution. 2011. University of California Museum of Paleontology. 22 August 2008 <http://evolution.berkeley.edu/>.

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