AP Biology Free Response Question

Distinguish genetic drift from gene flow in terms of how they occur and their implications for future genetic variation in a population. Genetic drift, defined as the process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next, can increase or decrease variability within particularly small populations. Certain genotype/phenotype frequencies, for example, may be reduced or completely eliminated through chance events.

Examples Of genetic drift might include the founder effect, which consists of a select mount of individuals is separated from a larger population and eventually establishes a gene pool different from that of the source population, or the bottleneck effect, in which a severe drop in population size can leave some alleles overrepresented in survivors and others underrepresented. In contrast, gene flow is the transfer of alleles into or out of a population due to the movement of fertile individuals on their gametes.

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Unlike the random favoring of traits that comes about through genetic drift, gene flow can transfer alleles that improve the ability of populations to adapt to local notations, ultimately becoming a mechanism of natural selection. Adhering to the definition of natural selection, individuals with beneficial traits survive and reproduce more efficiently- thus increasing the flow of favorable genes throughout a population. In fact, it has become an increasingly important agent of evolutionary change in human populations.

Individuals moving into a population can bring new alleles into the gene pool whereas other alleles can be completely eliminated as other individuals leave the population. Genetic variation within future populations, thusly, increases drastically, due to the introduction of new traits and alleles. Although genetic drift and gene flow differ in the ways that they change allele frequencies, both are vital to the diffusion and domination of certain genes. 2. Microinstruction is the change in the gene pool from one generation to the next.

Describe three ways in which microinstruction can take place. The three main mechanisms that can cause allele frequency change include natural selection, genetic drift (chance events that alter allele frequencies), and gene flow (the transfer of alleles between populations). Although each of these mechanisms has distinctive effects on the genetic composition of populations, only natural selection consistently improves the match between organisms and their environment (adaptation).

Beneficial traits are passed down from generation to generation according to the principle that individuals that are better suited to their environment survive and reproduce better than those that are not suited to their surroundings. Similarly, genetic drift causes unpredictable fluctuations in allele frequencies from one generation to the next. Chance events, such as a flash flood or stampede, can leave some alleles overrepresented and others underrepresented or wiped UT completely.

In especially small populations, alleles that are overrepresented are passed along from generation to generation and become more dominant and numerous in the gene pool. Underrepresented alleles gradually die out in the gene pool and can be wiped out in an entire population. Finally, gene flow, the transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes, causes microinstruction by introducing new, random alleles to a population and eliminating others. New traits can dominate a population if a random influx of individuals occurs.

These genes can be passed from generation Mr.. Nekton’s December 3, 2014 to generation through sexual reproduction and the dominant genotypes/ phenotypes will be observed. 3. Evolution is one of the unifying themes of biology. Evolution involves change in the frequencies of alleles in a population. For a particular genetic locus in a population, the frequency of the recessive allele (a) is 0. 4 and the frequency of the dominant allele (A) is 0. 6. A) What is the frequency of each genotype (AAA, Ear AAA) in this population? What is the frequency of the dominant phenotype?

AAA- 36 % AAA- 16% regency of dominate phenotype: 84% b) How can the Hardy-Weinberg principle of genetic equilibrium be used to determine whether this population is evolving? The Hardy-Weinberg principle of genetic equilibrium can be used to determine whether this population is evolving because if all of the conditions for equilibrium are not met, it can be concluded that some form of evolution is occurring. To figure out whether or not these five conditions are properly met, one would have to analyze the genotype and phenotype frequencies of the population and compare them to the predicted results of Hardy Weinberg Equilibrium.

Fifth frequencies and data are very similar, it can be concluded that no evolution has occurred. On the other hand, if the calculated data differs significantly from the predicted results, one must infer that an outside force, such as mutations or natural selection, is acting upon the population and preventing it from being in equilibrium. In other words, by determining the genetic makeup of a population that is not evolving at a locus and comparing it to that of the real population, it is possible to determine whether or not if evolution is gradually occurring. ) Identify a particular environmental hanged and describe how it might alter allelic frequencies in this population. Explain which condition of the Hardy-Weinberg principle would not be met. Over the last 200 years, the evolution of the peppered moth has been studied diligently. Two types of peppered moth exist, the white-bodied moth and the black-bodied moth. Originally, a vast majority of peppered moths had a light coloration, due to the fact that this trait allowed them to camouflage perfectly against the light-colored trees and lichen surrounding them.

Dreadlocks moths, in contrast, acted as easy food targets for birds and were threatened greatly by predators. However, widespread pollution brought about by the Industrial Revolution in England caused the lichen to disappear and covered the light-colored trees with black soot from factories. This sudden environmental change provided a physical advantage to dark-colored moths, which could now blend into their surroundings, and put the light-colored moths at a disadvantage, now becoming the easily identifiable prey for the birds.

During this period of the Industrial Revolution, a rise in dark-colored peppered moths was observed whereas a decrease in lighthearted moths was also taken note of. Consequentially, the genetic frequencies of the recovered moth became more prominent as their desirable alleles dominated the gene pool (via the process of natural selection, in which the dark-colored individuals could survive and produce at a faster rate than other peppered moths, and thus their genes were handed down).

This is a clear violation of the third condition for Hardy-Weinberg Equilibrium, no natural selection. The differences in the survival and reproductive success of one peppered moth over the other, especially that caused by a sudden, man- made disaster, alters allele frequencies and causes one allele/trait to dominate a gene pool.