Natural Selection and Evolution

    Natural selection is related to the phenotypes of an individual and how these traits affect their fitness. In theory, a phenotype that increases fitness will be passed on and become more prevalent in the population, yet there may be more to the genotype. Many phenotypes are influenced by more than one gene and there may be other factors that play into it, such as heterozygote advantage. Genes can be advantageous in some ways, yet lethal if they were combined with others. Natural selection may not always lead to evolutionary change because there are many factors that go into which phenotypes that are expressed. A phenotype may be advantageous to have, but it could be very difficult to track through the genotype.

    One way selection could happen without natural selection if there was a natural disaster, such as a drought, flood, hurricane, etc. A population can be almost all the way wiped out during a hurricane, except for a few individuals that may have gotten lucky just due to where they are located. Their survival has nothing to do with natural selection, yet their genes may become more prevalent in that population over time since they would be some of the few living members left. Another way selection might happen is through random mutations. A gene may be randomly mutated in a beneficial way for the organism and increase their fitness. It would not be due to natural selection because it would be a new, random gene that has been changed.