Common Evolution Homework 2

Common Evolution Homework NAME: BS 162 FS 23 The Esatina salamanders ( Ensatina eschscholtzii ), shown above, live along the West Coast of North America from Vancouver to Baja California. We will be focusing two populations: 1. individuals that live in Northern California and represent a more ancestral population 2. individuals that live in Southern California. Researchers have found that these all individuals of this salamander species have two color phenotype, either red or blotchy. Genetic analysis has shown that this color difference is linked to the Ensatina melanophore gene (EM Gene). There are 2 alleles present for this gene in the current population. The R allele at this locus results in a red phenotype while the B allele at this locus results in a blotchy phenotype dominated by black, brown and orange coloration. This gene has a co-dominant inheritance pattern, meaning that individuals that are heterozygous for this gene, having the genotype “ RB ”, are red and blotchy. GENOTYPE RR BB RB The research group is interested in whether this population in Southern California is experiencing evolution on the body coloration. The research group will be using the Hardy-Weinberg Equation to test whether evolution is occurring on the EM gene. Q1a. What is the null hypothesis for this study? Katie Ret es The null hypothesis is that there is no evolution on the Em gene for the Salamander species

Q1b. What is the alternative hypothesis for this study? As part of your summer internship in California, you categorize 100 salamanders collected from several populations across Southern California. You count 50 red and 37 blotchy individuals, the rest are red and blotchy. Q2a. Using these data you collected as an intern, determine the observed genotype frequencies for the 3 possible genotypes and write them in the appropriate spaces. Show your work below. RR= BB= RB= Q2b. Calculate the allele frequencies for the two alleles. Show your work and clearly label the values with the appropriate allele letter. Q2c. Use the Hardy-Weinberg equation to calculate the expected genotypic frequency for this population. And then complete the table below. ° Genotyp es # Observed in population # Expected in population O- E RR RB BB Q2d. Based on your calculations, do you support your null or alternative hypothesis? Explain your answer. Having noted the lack of red and blotchy individuals, you do some research about the environment and the predators and other organisms that live in the areas where these salamanders are found. You notice that on the Western side of the distribution toward the coast, these salamanders co-exist with a species of newt (pictured below) that look awfully similar to the RR salamanders. These newts are also known to be poisonous when eaten, so the predators in the area leave them alone. The ground is mostly rocky or sandy in these areas. Alternative hypothesis for the Salamander species ? Study would be , a evolution happening on the Em gene 50 100 = . 50 37/180 = - 37 13/100 . 13 RAlleles = 50 + 50 + 15= 113/200 Rallele Frequency = - 565 BAIleleS=3713713 = 87/200 Ballele frequency = . 155 P 12 + 2pq + qr2 = 1 50 >2 18 RR = P 12 = ( . 565(r2 = - 32 13 19 c6 RV = 2 pq = 2( . 565)( . 135) = - 19 37 19 18 (r = 912 = ( . 135)12 = - 19 les , it's supported because there is a larger difference /w the expected and Observed . The number of heterozygotes is much lower than expected . 113 to 19 . (

Q3c. What event could occur if this pattern continued for 20 or more generations in Southern California? Explain your answer in 1 sentence. Q4 Considering your latest conclusions about the salamanders, explain each of the principles of evolution by selection listed in the left column. In the right column, explain in one sentence how each concept would be represented in this specific case. Principle One sentence explanation Does variation exist for skin coloration pattern in this population? Explain any variation. What is the origin of the variation? (How/why is there variation) Is the variation for skin coloration pattern heritable ? How would we test for this? How was selection a factor in the skin coloration pattern? What is the evidence that the population of salamanders is evolving (remember definition of evolution)? Q5. In the table above, you have shown that this case is evolution by natural selection. Explain in 1-2 sentences how we know it is not genetic drift AND that it is not gene flow. The event thac could occur would be two species that are no longer interbreeding . Yes , color variation For red , blotchy , red and blotchy in the Salamanders . A mutation in the EM gene caused more than one type of Skin Coleration I dont know which is which Yes , accociated with a gene . we do breeding expirements and expect two red Parents to have red offspring . Red dominate by coast because it gave Protection from Preditors who thought they were poisiness . blotchy dominated because inland because they blend into avoid Preditors . Population was not HWE . There was change in expected and the observed Phenotypes Could be explained by change in allele Frequencey over time .

Disease biologist working near you in California have noticed that a large number of salamanders dying. The disease biologists discover that a virus that is causing “wasting” symptoms in some salamanders that leads to death, but some salamanders survive. The biologists realize that the salamanders that are surviving the disease have a mutation called IM2 which produced proteins that result in an immune system that is better than other salamanders at fighting viral infections. One of the biologists says, “Wow. It is a good thing that there are some individuals that adapted to this viral infection and developed the IM2 mutation so that the entire species of salamanders doesn’t become extinct.” Q6. How do you respond to the comment to educate your co-worker about evolution? A complete answer would include 2 misconceptions and an explanation of each misconception. Above is a phylogenetic tree showing the evolutionary relationships of the several of the major families of amphibians as we understand them today. Genetic drift is a random change Frequency . But this case wasn't random . It was driven by Preditors who were less likley to find and eat Salamanders that were blotchy in the Inland . and were reluctent to eat Salamanders that were red in coastal areas out of fear that they were posinous . This is n't gened flow , because gene flow involves populations that are genetically istant from eachother for a consented period of time before they begin to reproduce with each other . No new alleles were introduced to the population , no gene Flow . Individuals can adopt on a population level . Salamanders did not develop a mutation because they needed it to fight a disease . The mutation already exsisted in the pipe elation due to random changes in the nucleotide Sequence of the Salamanders . Evoluti on by natural Selection doesn't necisarily lead to good things Natural selection results from a Selection of a particular trait that provids an advantage in a distinctive enviornment ↑