Natural+Selection+and+Genetic+Variation

Natural Selection and Genetic Variation   Darwin first proposed the theory of natural selection without a specific answer to the most pressing questions, how variations could continue in organisms through this concept. Variation just wasn't possible if all species were to become accustomed to their environment and adapt accordingly, this evolution would result in all genes blending and organisms being exactly the same. This remained a mystery until a few years later when Mendel introduced genes, a unit of heredity of specific DNA make up, which passed traits from parents to offspring. Through this thought Darwin came to the conclusion that quantitative characters, these characters were first seen as an either or, such as the color of eyes or flowers, one gene controlled that phenotype entirely. This idea was then replaced by the thought that these phenotypes were controlled by multiple loci. Variation also exists because populations are capable of interbreeding. Genetic variation is inherently preserved by mutation, natural selection, sexual recombination, genetic drift and gene flow. Mutation is a change in the DNA sequence, only those in cells that produce gametes can be passed on to offspring and mutations only affect a minority of the population. Sexual recombination is many possible mating combinations and genetics brought together by fertilization. Nearly all variation is due to the allele shuffling of sexual recombination. Natural selection is the variation of traits for organisms to fit into society. Those organisms most fit for the environment will produce more offspring, resulting in more offspring of further generations being fit for the environment. Genetic drift is variation of traits because of the decrease of organisms due to catastrophes, environmental factors and the founding of new civilizations. Gene flow is the affect of certain genes being added or subtracted to the community, gene flow has increased with more prevalent travel around the world.

A completely perfect organism cannot be produced by natural selection, although this process is responsible for making organisms better fit for their environment no organism will ever adapt perfectly to its surroundings. There are four reasons for this; the first being that evolution is limited by historical constraints. Evolution has occurred from a long line of ancestors. By evolving a species is not made completely from scratch, the original structure is just tweaked. The next reason is that organisms often compromise when it comes to adaptations, they can't have it all. This is the reason you have never seen a four legged bird as the bird traded its original two front legs for wings. Chance interacting with natural selection as occurrences affect the result of evolution. Lastly, natural selection can only edit existing variations. Through natural selections organisms do not have the ability to add eyes or sprout extra limbs, only to make an existing variation more prevalent. Organisms cannot be perfected through the selection of best fit genes, but a majority will be better off.