BIOL10010 Practical Report 2 PDF

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BIOL10010 Practical Report Tianyou Lan (992486)

Context: The change of phenotypic and allelic frequencies was measured when the selection pressure on a virtual population of koi fishes was altered and monitored using the PopGen Fishbowl program.

Aim: To investigate the effect of selection on a virtual koi fish population.

Hypothesis: That the results from reducing the genotype relative fitness of q 2 to 0 should be in Hardy-Weinberg Equilibrium.

Method: 1. Select one genotype to select against before running the experiment. 2. Open up the PopGen Fishbowl simulation by following this link: http://virtualbiologylab.org/ModelsHTML5/PopGenFishbowl/PopGenFishbowl.html 3. Set the parameters as the following:

4. Run the experiment for ten generations and record the results in the table below

5. Using the data collected, calculate the allelic frequency for p for each of the generations, and enter the values in the table below:

6. Show the change in allele frequency overtime and compare the population in HardyWeinberg Equilibrium to the population using an appropriate graph. 7. Then, use an appropriate statistical test to see if the population is in Hardy-Weinberg Equilibrium after ten generations of selection.

Results: Genotype selected against: rr (white)

Null hypothesis: there is no significant difference between the observed and expected values, and any observed difference are due to error and chance.

Findings: It was found that the selection affected the population of koi fish, and that there was an increase in the R allele over the ten generations, which in turn represents the decrease of the r allele.

χ = ∑ (O – E) = 3.33 2

2

E Degrees of Freedom = 2 - 1 = 1 Probability range = 0.05 – 0.10

Due the probability being greater than 0.05, we accept the null hypothesis and hence the underlying genetic hypothesis that the results are in Hardy-Weinberg Equilibrium. However, the probability range being close to that of significant symbolises that there the decrease in the r allele might not be associated with the selection.

Discussion: 1.

What effect did selection have on the frequency the genotype you selected against?

The selection led to a decrease in the frequency of the rr genotype, starting at 0.24 at generation zero and ending up at 0.12 at generation ten.

2.

What would you predict to be the outcome if you were to keep running this experiment to 50 generations?

From the results recorded, it’s likely that there will be a continuous decrease in the genotype selected and an increase in the R allele over time, and the frequency of the r allele will be reduced b drastically by generation 50.

3. Name the type of selection you have modelled in Part 4 of the practical and comment on the effect it would have on a distribution curve of phenotypes. The type of selection that was modelled is directional selection. This is when an extreme phenotype is favoured over the others and causes the allele frequency to shift over time in favour of the extreme phenotype. This shifts the distribution curve away from the mean by favouring individuals with the extreme phenotype.

4. How does selection shape microevolution? Give an example where it has shaped human evolution. Microevolution refers to the change in allele frequencies within a population that occurs over time

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Studies: do your finding agree with previous studies? If not, why? Methodology: could the procedure and program have been improved?

Conclusion: -

Hypothesis: do the findings support the hypothesis? If not, why? Implications of findings: how does selection enhance the effects of other forces of microevolution?

References: 1. EB Editors, (2017, November 5). Directional Selection, Stabilizing Directional and Disruptive Selection. https://biologydictionary.net/directional-selection-stabilizing-directionaldisruptive-selection/ 2. Wilkin, D., Akre, B. (2015, December 11). Natural Selection and Populations – Advanced. https://www.ck12.org/book/ck-12-biology-advanced-concepts/section/10.36/...