BIOL 3350 1st EditionExam # 2 Study Guide Lectures: 8-14Lecture 8 (February 3)What is selection?Mechanism of evolution. Genetic Drift is another type. Selection acts on phenotypes and the genes that produce them.What is the difference between stabilizing selection and directional selection? Use real life examples if applicable.Stabilizing:- Mice that were too dark on the light environment, had low survival à selection was acting against them- Selection is stabilizing the representation of coat colors so that it matches the environment- Saw that the mechanisms of selection (predation acting against survival) stabilized selectionDirectional:- Selection is acting against one extreme and is changing allele frequencies in the population- The environment drives changes in phenotypes- Ex: if new predator is introduced, the environment is changed, and pressure for a different kind of phenotype occurs- Before the drought – variation in beak depth- After drought – beak depth shifted to a higher value due to the change in the environment- Change in the mean value of the traits shows that selection has occurred à the mean is higher, which means directional selection has occurred- Force of selection is driving towards larger beaksLecture 9 (February 10)What are paralogous genes? Differentiate paralogous from psuedogenes.-Paralogous genes – function copies of genes that originated from divergence in function from another gene-Paralogous = functional; Pseudogene = non-functionalWhat is a current idea on the evolution of trichromatic color vision in primates?- Original condition à mutation à produce 2 different alleles à another mutation à 3 different alleles- Female can be trichromat (if have two different alleles on the same chromosome) or dichromat (if have two of the same allele)- Gene duplication error in OWM which created two different alleles on the same chromosome- Found L and M pigments in both NWM and OWM are almost identical à were present in the same common ancestorLecture 10 (February 12)What are the assumptions of Hardy-Weinberg Equilibrium?-Large population size to ensure no effects of genetic drift-No natural selection-No mutation-No migration-Random mating with respect to genotypesWhat does it mean when you are able to reject the null hypothesis, or HWE?Deviation of observed genotype frequencies from expected HWE genotypes frequencies means that evolution is occurring at that locus.Lecture 11 (February 19)How do we measure natural selection?- Fitness is the currency of natural selection- Absolute fitness = W = probability of survival x reproductive outputo Contribution of phenotype to the next generationWhat components are needed to calculate the change in allele frequency due to selection?- ∆p = change in frequency of A1 allele in response to natural selection- ∆q = change in frequency of A2 in response to natural selection- If ∆p = 0 then locus is in HWE and no evolution is occurring - If ∆p > 0 then the relative frequency of A1 is increasing- If ∆p < 0 then the relative frequency of A1 is decreasingLecture 12 (February 24)What is overdominance?- A1A2 heterozygote has highest fitnesso Both alleles remain in the population over timeo The less fit genotypes stay in the population because need parents of two homozygotes in order to produce heterozygoteso Still have genotypes that are not the most fit maintained in the population due tothe overdominanceWhat is underdominance?- Both homozygotes have higher fitness than heterozygoteso Hard for population to maintain both alleles since heterozygote condition is deleteriouso Equilibrium is unstable – which ever allele ends up above 0.5 will be favoredo Allele A1 will either go to 0 or 1o The mean population fitness is the lowest when allele A1 is at 0.6o When A1 is low, then A2 will be favored and will go to extinctiono When A1 is close to fixation, the equilibrium will go to fixation in the other directiono Selection acts on individualso Equilibrium is reached when population wide fitness if at a very low pointLecture 13 (March 3)What is the difference between zygotic gene flow and gametic gene flow?- Zygotic gene flow – when an animal moves from one habitat to anothero Ex: mountain lions grow up and move thousands of miles to another habitat- Gametic gene flow – haploid gametes moveo Ex: marine coral throughout their gametes all at one time to disperse themWhat are some of the consequences of migration?-Migration is homogenizing variability between populations- increases variability within a population but makes both populations more similar to each other-Slows down the rate at which populations because genetically differentiated form one another-New combinations of pre-existing traits can be generated by recombination with introduced genotypes-Can cause deviations from HWE until new equilibrium is reachedLecture 14 (March 5)What is genetic drift?- Genetic drift – random change in allele frequencies across generationso Change is not directed with respect to phenotypeo Small populations are more subject to chance events o Certain alleles become more or less common by chance aloneWhat is a population bottleneck?- Population size is drastically reduced due to some type disease or natural disaster- Remaining survivors do not carryall the allelic diversity o the original population- The small amount of genetic diversity due to the small population size will eventually lead to fixation – random at which allele becomes