Which evolutionary mechanism creates new alleles

Genetic drift is a random change in allele frequencies that occurs in a small population. When a small number of parents produce just a few offspring, allele frequencies in the offspring may differ, by chance, from allele frequencies in the parents. This is like tossing a coin. If you toss a coin just a few times, you may, by chance, get more or less than the expected 50 percent heads or tails. In a small population, you may also, by chance, get different allele frequencies than expected in the next generation.

In this way, allele frequencies may drift over time. There are two special conditions under which genetic drift occurs. They are called bottleneck effect and founder effect. Founder Effect in the Amish Population. The Amish population in the U. How has this affected the Amish gene pool? Forces of Evolution The conditions for Hardy-Weinberg equilibrium are unlikely to be met in real populations.

Mutation Mutation creates new genetic variation in a gene pool. Gene Flow Gene flow occurs when individuals move into or out of a population. Genetic Drift Genetic drift is a random change in allele frequencies that occurs in a small population. Bottleneck effect occurs when a population suddenly gets much smaller. This might happen because of a natural disaster such as a forest fire.

By chance, allele frequencies of the survivors may be different from those of the original population. Mutations may be harmful or benign, but they may also be beneficial. For example, a mutation may permit organisms in a population to produce enzymes that will allow them to use certain food materials.

Therefore, natural selection tends to remove the less-fit individuals, allowing more-fit individuals to survive and form a population. Another mechanism of evolution may occur during the migration of individuals from one group or location to another.

When the migrating individuals interbreed with the new population, they contribute their genes to the gene pool of the local population.

This establishes gene flow in the population. Gene flow occurs, for example, when wind carries seeds far beyond the bounds of the parent plant population. As another example, animals may be driven off from a herd. This forces them to migrate to a new population, thereby bringing new genes to a gene pool.

Gene flow tends to increase the similarity between remaining populations of the same species because it makes gene pools more similar to one another. Another mechanism for evolution is genetic drift, which can occur when a small group of individuals leaves a population and establishes a new one in a geographically isolated region. For example, when a small population of fish is placed in a lake, the fish population will evolve into one that is different from the original.

Fitness of a population is not considered in genetic drift, nor does genetic drift occur in a very large population. Another mechanism for evolution is natural selection, which occurs when populations of organisms are subjected to the environment. The fittest creatures are more likely to survive and pass their genes to their offspring, producing a population that is better adapted to the environment.

The genes of less-fit individuals are less likely to be passed on to the next generation. The important selective force in natural selection is the environment. Environmental fitness may be expressed in several ways.

Mutations occur at random in the genome, but mutations of large effect are often so bad for the organism that the organism dies as it develops, so mutations of smaller effect or even neutral mutations are theoretically more common in a population. The variation that is created in a population through the random process of mutation is called standing genetic variation, and it must be present for evolution to occur.

Mutation is the raw stuff of evolution because it creates new heritable phenotypes, irrespective of fitness or adaptation. But mutation combined with one of the other mechanisms of evolution genetic drift , natural selection , non-random mating, and gene flow can result in meaningful changes in allele frequencies in a population.

Evolution by genetic drift occurs when the alleles that make it into the next generation in a population are a random sample of the alleles in a population in the current generation. By random chance, not every allele will make it through, and some will be overrepresented while other decline in frequency regardless of how well those alleles encode for phenotypic suitability to the environment, so sometimes drift reduces the average fitness of a population for its environment.

Populations are constantly under the influence of genetic drift. The random drifting of allele frequencies always happens, but the effect is subtle in larger populations.

Genetic drift in a population can lead to the elimination of an allele from a population by chance. In each generation, a random set of individuals reproduces to produce the next generation. The frequency of alleles in the next generation is equal to the frequency of alleles among the individuals reproducing. Do you think genetic drift would happen more quickly on an island or on the mainland?