Bhavi Patel 3/29/12 Natural Selection Lab1. How did the allele frequencies in your population change over the course of the experiment? Why did these changes occur?In the beginning of the experiment, we had 3 birds with large sized beaks (AA alleles), 3 birds with small sized beaks (aa alleles), and 6 birds with medium sized beaks (Aa alleles), this meant that 50% of the birds had A alleles and 50% of the birds had a alleles on both the wet and dry islands. On the wet island, the frequency remained the same after the first generation. However, in the second generation the frequency of the A allele was 62.5%, for the third generation it was 79.2%, for the fourth generation it was 66.7%, and for the fifth generation it was 91.7%. This showed that over generations the frequency of the A allele increased in the population and the frequency of the a allele decreased, this means that the birds on the wet islandtend to have a population with birds with large sized beaks. The “A” allele was naturally selected for because a larger beak size can lead to better food sources, therefore on the wet islandthe individuals had a higher survival and reproduction rate with the large sized beak.2. How did the allele frequencies on the other island change? Why was it different from your island?In the beginning of the experiment, we had 3 birds with large sized beaks (AA alleles), 3 birds with small sized beaks (aa alleles), and 6 birds with medium sized beaks (Aa alleles), this meant that 50% of the birds had A alleles and 50% of the birds had a alleles on both the wet and dry islands. In the first and the second trials the frequency of the A allele was high on the dry island, it was 83% on the first one and 71% for the second trial. The frequency of the A allele decreased after this, for the third trial it was 33%, for the fourth trial it was 13%, and for the fifth trial it was 4%, while the frequency of the a allele increased. This showed that over generations the frequency of the a allele increased and the birds on the dry island tend to have a population with birds with small sized beaks. This is because birds on the dry island needed a small beak size to survive because it enables them to access more available food sources, ultimately leading to individuals having better adaptions. Therefore on the dry island the individuals had a better adaption with the small sized beak and on the wet island the individuals had a better adaptation with the larger sized beaks. The allele frequency was different from my island because of the distribution of the resources and the type and quality of the food available on each island. In addition to this, we see the difference in the two populations because of genetic drift due to feeding patterns and behavior. The allele frequency depends on behavior in terms of how aggressive the birds were to get their food using their beaks because first the birds follow their genetic behavior according to the type of beaks and then over time due to experience the birds learn how to get their food using different strategies for survival.3. Which island would you expect to have stronger natural selection, and why? Is this evident in your results? How so?I would expect the dry island to have stronger natural selection because there is less food andtherefore more competition for resources is present. This is seen in my data because for strong natural selection to be present, the population must have drastic change in the frequency of certain traits in the population. On the dry island, we see that after the initial experiment of having 50% A allele and 50% of a allele on both islands, the frequency of the A allele increases drastically for the first generation of offspring, the percentage goes from being 50% to being 83% while on the wet island the percentage of each allele remains the same as the initial. This shows that there seems to be a stronger natural selection on the dry island. 4. The population size on each of our islands was pretty small compared to real population sizes. How might small population size have affected our results (what would be differentif we used a much larger population size and scaled up the food supply and island size accordingly)?The small population made the effects of genetic drift on the allele frequencies is more noticeable because the changes were more drastic. However, if the population was much larger the effect of genetic drift would be much less because there would be steady change in the allele frequency over each generation in the population. 5. Imagine there is an island where all the birds have small beaks (only allele a existed). Eventually, mutation leads to the existence of a second allele A. Over time, this A allele becomes more common, how/why might that happen?For natural selection to occur, there needs to be an increase in fitness and if the allele increases over time then it is more fit, therefore since the allele A existed overtime, it had stronger natural selection. This could happen because maybe on that particular island the birds with small beaks had more competition therefore their survival rate and their reproduction rate were low and the birds with the A allele or the big beaks had a higher survival and reproduction rate and leading to birds with the A allele to have a higher frequency overtime in the population. 6. Imagine there's another island that has no clipbirds on it because it's so far away. After feeding successfully, two clipbirds from an island with a high diversity manage to reach that new island and lay a bunch of eggs there, giving rise to an entire population. Do you think the first generation of birds born on the new island would start out with approximately the same allele frequencies as the old island? Why or why not?This scenario is known as the Founder Effect. To figure out if the first generation of birds born on the new island would start with the same allele frequencies as the old island, I made the following table:Parent Allele Likelihood of leaving Island Offspring (F1) A aAA=AA (.25)(.25)= 0.0625 1 0AA=Aa (.25)(.5)=.125 3 1AA=aa (.25)(.25)=.0625 1 1Aa=Aa (.5)(.5)=.25 1 1Aa=aa (.5)(.25)=.125 1 3aa=aa (.25)(.25)=.0625 0 1According to this table, the likelihood of having the same population is .0625+.25= 0.3125, sincethis is for AA=aa and Aa=Aa. The probability that one would see the first generation to start