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Describe in detail the main ideas behind Darwin's theory of evolution by natural selection and describe in detail three pieces of evidence that support this theory.

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Introduction

Describe in detail the main ideas behind Darwin's theory of evolution by natural selection and describe in detail three pieces of evidence that support this theory By Bakor Al-tayar Darwin's theory of evolution is the idea that all species of living things are connected as they all have a common ancestor. The general theory stresses a undirected "decent with modification". In other words more complex creatures naturally evolve from simpler ancestors over time. The main mechanism of this evolution is the mutations. These are random and most of the time they are not beneficial, but when they are beneficial (by aiding survival) they are preserved by natural selection and are passed on to offspring. Over time these beneficial mutations accumulate and can result in making a new species. The idea of evolution existed well before Darwin, the Greek philosopher Anazimander proposed the idea of evolution, Darwin added the idea of natural selection, the mechanism through which evolution works. Natural selection works so as to preserve and accumulate minor advantageous genetic mutations. Imagine a species of animals that live in the mountains and need strong leg muscles to be able to move up and down the hills with ease and without being tired. Now imagine one member of this species had a mutation which allowed it to use its energy more efficiently, in such a way that by eating the same amount of food as the other members it could use more energy out of the food. ...read more.

Middle

Thus these traits become more common in the population, and the population evolves. This was called descent with modification. Darwin did not believe that the environemtn was producing variations, rather he thought that the variations already existed and nature just selected those that could survive best. In the finch case, it selected the more efficient beaks against the less efficient ones. This was called: "survival of the fittest". An example of natural selection is among the peppered moths, near English industrial cities. These insects have varieties that vary in wing and body coloration from light to dark. A natural pollution indicator is the lichen on trees, which turns black when there is high pollution, this also turns out to be moth food, and moths are bird food. When England started to get more industrialized, (burning fuels for energy) the lichens turned darker and darker. Before the industrialization period the lichens were white, and 98% of the moth population was clear white, and 2% was black. The black moth on white lichens were easy targets for predators such as birds. The black moth was selected against. After the industrialization period the lichen turned black and the white moth became an easy target for the predators and soon enough 2% of the population became white and 98% was black moth. ...read more.

Conclusion

* About 70 percent of bacteria that cause infections in hospitals are resistant to at least one of the drugs most commonly used to treat infections. * Some organisms are resistant to all approved antibiotics and must be treated with experimental and potentially toxic drugs. * Some research has shown that antibiotics are given to patients more often than guidelines set by federal and other healthcare organizations recommend. For example, patients sometimes ask their doctors for antibiotics for a cold, cough, or the flu, all of which are viral and don't respond to antibiotics. Also, patients who are prescribed antibiotics but don't take the full dosing regimen can contribute to resistance. * Unless antibiotic resistance problems are detected as they emerge, and actions are taken to contain them, the world could be faced with previously treatable diseases that have again become untreatable, as in the days before antibiotics were developed. Peniclin for instance is being made weaker. The way that penicillin works is by destroying the cell wall of bacteria, but some bacteria have now evolved so that the penicillin can't destroy it's cell wall and thus has become too strong for penicillin. There is nothing that can be done against it so as to put a full stop the phenomenon, but there can be measures taken to slow down the process. Having higher hygiene levels, by cleaning sewages and washing one's hands more often. The cleaner a society the less risk there is of infection. 1 http://killdevilhill.com/darwinchat/shakespearew/207.html ...read more.

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