Natural Selection Experiment

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Since the publication of Darwin’s “On the Origin of Species” in 1859, natural selection has been widely accepted by the scientific community as the engine that drives evolution, or the change of frequency of heritable characteristics in a population over time. Natural selection results in the survival of the fitter individuals of a given population, and therefore the increase in frequency of the genes that produced the adaptive phenotype. For natural selection to occur, there are three conditions that must be met. First and foremost, there must be variation in a population. If no variation occurs, then no individual will have a phenotype that is any more adaptive or maladaptive than another. Second, the variable trait must be heritable. …show more content…
However, natural selection is not the only process that can drive evolution. Natural selection is a non-random sorting process, however, other mechanisms, such as genetic drift, a random sorting process, can also lead to the evolution of a population. Genetic drift may lead to a change in the frequency of alleles in a population, however the change will be unpredictable. In this experiment, we will be emulating the processes of both natural selection and genetic drift to model the evolution of a population of weevils. The “weevils” in this experiment will have three distinct phenotypes, each varying in size, shape, and color. We predict that when modeling natural selection, the weevils indicating a phenotype of blue, flat, and large, will decrease in frequency, or go extinct in our population. The size and shape of this phenotype allows it to be more easily grabbed and preyed upon by a chicken predator (as modeled by one of the lab partners). We predict that when modeling genetic drift, a non-random process, we will see no pattern as to which phenotypes will increase or decrease in frequency.

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A rapid decrease in the phenotype happened very early, after the first generation, however, extinction didn’t take place until after the sixth generation (our final generation). The dark phenotype thrived the most under these conditions, overall increasing in frequency in the population. In our genetic drift model, we also saw the extinction of the indigo phenotype. In this model, the extinction actually occurred one generation earlier than in the natural selection model. Even though it does appear looking at the change of frequencies in this model was a measured increase in the dark frequency and decrease in indigo frequency, if we were to repeat this experiment several times, we would expect the result to be different each time, as this is a random process. There are many possible sources of error in this experiment. One such source, may be our improvement as predators throughout the experiment. As we continued picking up marbles throughout the trials, we became much more efficient and able. This would make the biggest difference between the natural selection and genetic drift trials. Even though we had the disadvantage of the blindfold in the genetic drift trials, because we were much more experienced predators in these trials, that may have negated to effect of the blindfold to some

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