Natural Selection: Survival of the Fittest
Courtland Blanding
BIO-111C-01

Abstract:
Natural selection is the theory that competition exists within species, determining which species live to have off spring, and pass their traits on to those offspring allowing them to have the necessary traits to live. This theory was founded by Charles Darwin over 150 years ago and is now one of the basis for understanding how species change over time and adapt to their surroundings. Natural selection is composed of three different types which are directional selection, disruptive selection, and stabilizing selection. This paper also gives examples of each type of natural selection. Sexual selection is also a small part of natural selection where the female chooses who it will mate with leaving some species without a mate to pass on traits with. Natural selection does not only effect animals it effects the human race as well, by passing on certain traits that has allowed the human race to live so long. Even though natural selection is a big aspect in the science of evolution, quite a few scientists and paleontologists believe there isn’t enough evidence to support Darwin theory.
One of the greatest and most important influence on the science of evolution is the concept of natural selection which was discovered by Charles Darwin over 150 years ago (Pagel M 2009). Darwin collected a vast number of facts from a wide range of fields and also took notes from other naturalists to try and prove his hypothesis correct (Pagel M 2009). Charles Darwin’s theory was not taken seriously until many years later, but today natural selection is the basis for our understanding of how species change over time and adapt to their surroundings (Pagel M 2009). Since the beginning of time members of all species have been competing with each other for the resources that are required for them to survive. Natural selection is the theory that competition exists within species, determining which species live to have off spring, and pass their traits on to those offspring allowing them to have the necessary traits to live. A trait is a particular characteristic, in this case to survive. Natural selection also show the probability that a certain individual will contribute genes to the next generation.
Natural selection is usually broken down into three types of selection which are directional selection, disruptive selection, and stabilizing selection. Directional selection is when selection pressures favor on extreme of the trait distribution (Heather Scoville 2010). Changes in weather, climate, and food availability usually are the reasons for directional selection. In directional selection the average of the population will shift. For instance, the giraffes with short necks were unable to reach as many leaves as the long necked giraffes. The result of the neck length shifted to favor the giraffes with the longer necks. Humans have had a profound influence on their environment and the species around them. The human race is able to breed plants or breed animals which is called artificial selection. Human interactions also have a big part in directional selection, because hunters take out a lot of a certain species and usually go for the larger animals causing the smaller population to be greater (Heather Scoville 2010).
Disruptive selection is when the average form of the trait is selected against while either extreme is unaffected. For example, the peppered moths in the rural areas were almost all a very light color (Heather Scoville 2010). However, these same moths were very dark in color in industrial areas. Very few medium colored moths were seen in either location. It seems that the darker colored moths survived predators in the industrial areas by blending in to the polluted surroundings. The lighter moths were seen easily by predators in industrial areas and were eaten (Heather Scoville 2010). Disruptive selection is usually the rarest