Essay - Evolution & Genetic Drift Evolution and Genetic Drift the Variety...

Evolution & Genetic Drift

Evolution and Genetic Drift

The variety of human attributes evident in society comes as a result of the variety of alleles that direct ***** expression ***** ***** genotypes. This expression results in very different phenotypic traits that form the b*****is of human *****dividuality. Based upon these *****, a person may be more or less likely to adapt well to their environment. When viewed over a long enough time period, the frequency of allele distribution results in more or ***** advantageous phenotypes. Those phenotypes that are less adaptive to the surroundings make it harder for that individual to survive. This is the bas***** ***** natural selection, where desirable tra*****s are selected ***** ********** upon the advantages that ***** phenotype confers. This is also the reason for changing allele frequencies, as those gene variants that are ***** helpful to the organism become (***** time) less common in ***** population. "These ever-present and interacting forces of... genetic drift *****...***** selection work to differing degrees to shape populations." (Lewis 242).

Although there are only two alleles for a particular gene in any given ***** (one on each matching chromosome), ***** are usually many possible alleles for a trait within a populati*****. ***** allele ***** aren't *****, the population is said ***** be in a state of Hardy-Weinberg equilibrium. This is often not the case, however, as various positive character*****tics allow ***** that allele frequency to grow, and numbers of deleterious alleles to decline (and sometimes vice versa). There are many re*****ons for changing allele frequencies within a population. These include nonr*****om mating (where one chooses a spouse b*****sed upon some nonrandom process), migration and ***** drift, among others.

Underpinning evolution ***** natural selection is the concept of ***** flow. When various alleles move through the population based upon migration patterns and mating, the allele ***** are spread ***** the population. Generally, gene flow contributes to greater genetic diversity, however, in ***** circumstances, genetic diversity ***** be reduced, as ***** the ***** with genetic *****.

Lew***** (247) says that "genetic drift occurs when a subset of a ***** cont*****ins ***** gene frequencies than ***** larger population because it is a small sample." Over time, evolution and natural selection will ***** together to make the gene pool of a *****er population different from that of the ***** allele d*****tribution. This is especially ***** in c*****es where a small community has a lot of intermarriages (as in many religious communities). This mat*****g ***** a ***** sample can lead to a ***** ***** frequency ***** one would see in ***** larger sample.

The cause of *****tic drift is, essentially, the decline in numbers of a small population, leav*****g ***** remaining individuals ***** replenish the genetic stock. Since there is less allelic variation in this subsample, the ensuing generations will have ***** genetic ***** as well. "Genetic drift occurs when ***** population size plummets, due either to migration, ***** a ***** dis*****ter ***** isolates small pockets ***** a population, or to the consequences of human