Biol 1209 writing assignment

8 August 2016

Lake Malawi’s cichlid male population of fish are tested on their ability to build bowers to attract the female population. Altering this extended phenotype, or ability to build bowers resulted in no change of mating, but males that built successful bowers showed to be less aggressive with other males in the population. This is important in maintaining polymorphic populations (Magalhaes, 2014). In my self-created scenario, the focus is on the small male population of cichlid fish. The male cichlid fish ability to build successful bowers is dominant while not building successful bowers is recessive within the population.

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After a recent hurricane wiped out the cichlid population food source, the male population has been tested on their ability to find other food for the female population. The ability includes better strength and speed. Female cichlid fish find this new ability to more attractive than building successful bowers because of this environmental change. The purpose of this study is to determine natural selection and to see if the male population of cichlid fish will be altered due to the changes in their environment. Null Hypothesis: The male population of cichlid fish will not have an altered allele frequency due to changes in the environment.

Alternative Hypothesis: The male population of cichlid fish will have an altered allele frequency due to changes in the environment. Methods: PopG software was used to perform this experiment. The data listed below are the settings used for each trial of each different figure. Figure 1 Population size =100 Fitness values AA =1. 0 Aa = 1. 0 aa = 1. 0 Mutation Rate A>a =0. 03 a>A = 0 Migration = 0 Initial allele frequency = 0. 5 Number of generations = 100 Figure 2 Population size = 100 Fitness values AA = 1. 0 Aa = 1. 0 aa = 1. 0 Mutation Rate A>a = 0 a>A = 0 Migration = 0.8 Initial allele frequency = 0. 5 Number of generations = 100 Figure 3 Population size =100 Fitness values AA =0. 5 Aa = 1. 0 aa = 0. 6 Mutation Rate A>a =0 a>A =0 Migration = 0 Initial allele frequency = 0. 5 Number of generations = 100 Figure 4 Population size =100 Fitness values AA =1. 0 Aa = 1. 0 aa = 1. 0 Mutation Rate A>a =0 a>A = 0. 001 Migration = 0 Initial allele frequency = 0. 5 Number of generations =100 Results: The frequency of alleles of the male population of cichlid fish is shown in the graphs below. Each figure consists the average of five trials.

In figure 1 a mutation that takes over the recessive alleles in the male population of cichlid fish causes the allele frequency to become a rate of 0. 116. Figure 2 shows the effect of migration at a rate of 0. 8 on the male cichlid fish population. The parameter of migration makes the average allele frequency 0. 366. Figure 3 involves a change in the fitness of both the homozygous dominant and recessive alleles of the male cichlid fish. Their fitness are decreased to 0. 5 and 0. 6 and that results in an average of 0. 496 for the allele frequency.

The last figure, figure 4, involves another mutation, but over the dominant alleles at a rate of 0. 001. The average after this new mutation is 0. 318. Figure 1. This graph depicts the average allele frequency value of male cichlid fish when a new mutation that goes from dominant to recessive arises in the male population after the hurricane hit Lake Malawi. Over five trials the average allele frequency after this mutation is shown to be 0. 116. Figure 2. This graph depicts the average allele frequency of male cichlid fish when their population migrates at a rate of 0. 8 after the hurricane decreased their food source.

Over five trials the average allele frequency with this change in the migration rate is 0. 366. Figure 3. This graph depicts the average allele frequency of male cichlid fish when the change of fitness in the homozygous dominant (AA) and the homozygous recessive (aa) are decreased to 0. 5 and 0. 6 based on their ability to find food sources after the hurricane hit. The average value over five trials is shown to be 0. 496. Figure 4. This graph depicts the average allele frequency of male cichlid fish when a mutation that goes from recessive to dominant arises within the population at a rate of 0. 001.

The average value over five trials is shown to be 0. 318. Discussion: From the data we can conclude that different traits or parameters can effect a population in many different ways. It can decrease or increase a population depending on the trait. After a hurricane hits Lake Malawi the cichlid fish male population must adapt to the new factors that have been put upon them. Mutation within the population supports the fact that it can cause dominant and recessive allele frequency to decrease. Migration causes the allele frequency to lower as well due to movement of the population after the hurricane.

The cichlid male fish with a higher fitness are more suitable for their environment, but when their fitness is lowered, their allele frequency decreases. This decrease puts the more fit fish on top making their trait more favorable to pass onto other generations. In this experiment since the fitness was lowered there was a decrease in the allele frequency. The overall results show that the null hypothesis is rejected because the results support the alternative hypothesis that the male population of cichlid fish will have an altered allele frequency due to changes in their environment, in this case a hurricane.

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