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.

Darwin traveled all around the world and observed different species in different places thanks to the beagle. Darwin was inspired by the books of Charles Lyell and was convinced that uniformitarianism (the late 18th century theory of James Hutton that the natural forces now changing the shape of the Earth's surface have been operating in the past much in the same way.  The most important implication is that the Earth is very old and that the present is the key to understanding the past.) provided the correct understanding of the earth’s geological history.  The combination of his observations and knowledge of the theory of uniformitarianism were critical in leading Darwin to understand evolution. Most importantly his observations in the Galapagos islands were also very critical in forming in his theory. It was there that he began to understand the mechanism of evolution for plants and animals.

What is special about the Galapagos is the fact that it has species of animals that are found no where else in the world, although some are similar in South America. What was most important to Darwin was the fact that the birds were much different from one island to another. He came to the conclusion that the reason they were different is because of the environment. Darwin found 13 different species of finches. The main difference between each species was the shape of their beaks, and this was associated with the diet that the finch had (each finch basing its diet on different foods). Thus Darwin concluded that when the original south American finches reached the islands, they dispersed to different environments where they had to adapt differently. each finch came about because nature had selected those who could eat the best.

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This is process has come to be known adaptive radiation (Where species originate from common ancestor, and differentiate because of different environments). Darwin then came to understand that all populations have members that are somewhat different. Those members with some variation that can give them a slight advantage in staying alive long enough to successfully reproduce are the ones that pass on their traits more frequently to the next generation. 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. Technological advancements then took place reducing the pollution level making the lichens whiter than before, and thus the situation reversed again and the black moths died out and the white moths survived. This is a clear example of  natural selection, and it has also been noticed to take place in Detroit Michigan.

Other evidence of natural selection is within plant evolution observation through fossils. British researches hypothesized a reason for which plants with leaves evolved. 400 million years ago a primitive form of plants colonized the land, and none had leaves. Instead they stems with bristles or spines. 40 million years later plants suddenly evolved with leaves. It is thought that this has to do with the leaves of atmospheric oxygen and carbon dioxide of those times. It has been found that during this time period levels of carbon dioxide dropped by 90 percent as those of the oxygen rose. This was due to the plants, which took in carbon dioxide and extracted carbon for their own growth, and expelled oxygen as a waste gas. As there was less carbon dioxide the plants had to come up with a way to be more efficient in taking in the gas. The early stem plants had fewer stomata than the modern ones (the stomata is the opening through which gases are taken in or expelled). One thing to keep in mind is that as there was high CO2 levels when the plants first came, there was a greenhouse effect which would’ve not been good for plants with leaves, as it would’ve overheated them because of the large surface area the leaves would take up. As carbon dioxide levels dropped so did the greenhouse effect, thus lowering the temperature and thus reducing the overheating danger. This incited plants to develop leaves, which increased the number of stomata they had, and thus having a higher efficiency. The appearance of leaves takes place at the same time as the reduction of CO2 levels. This is clear evidence of evolution by natural selection.

Two other great expmaples of natural selection are in the observation of horses and antibiotic resistance in hospitals. Horses will not be discussed but are mentioned to arise some curiosity and incite the reader to do research.

Antibiotic resistance is a problem that is now being faced by all hospitals. What is tended to be done in the hospitals is that everything is “sprayed” with antibiotics so as to make sure that there is a minimum of disease causing microbes around. The result of this is the strongest that have survived these chemicals have survived to pass on their genes, thus making a new population that is stronger and more capable of facing the antibiotics without dying. This is an increasing danger to the public health. Tuberculosis, gonorrhea, malaria, and other diseases are just a few of the diseases that have become hard to treat with antibiotic drugs. This evolution that is taking place is due largely to the increasing use of antibiotics.

Some facts (taken from: )

• 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.