PCB 4674 SPRING 2013 REVIEW QUESTIONS FOR EXAM 3 FROM SECTION III.A.1. ONWARD(See also the Clicker Questions for this section of the course)1. What do we mean by "concerted evolution"? What empirical evidence do we have that it is an important element of the evolutionary process?Definition: the process through which Sequences in gene families evolve togetherregardless of the number and location of gene copiesEvidence-- rRNA 18S and 28S sequences are identical across all repeats, non- transcribed regions similarand yet all are VERY different among species-- α hemoglobin sequences differ between pairs of species by ~ 10% yetα1 and α2 vary by one amino acid substitutionwithin most species 2. Describe briefly how gene families originate.Gene FamilyA group of genes related in function and, apparently, in origin , aligned in tandem clusters and usually repeated in the genome Formation of gene clusters and duplicates – selection for divergence, hemoglobin are good example; once evolution path starts it just gooes.3. What is the evidence that nucleotide sequence variation within the antigen recognition site of the human MHC gene has been driven by natural selection? - Replacement rates (nonsynonymous) exceed synonymous rates at the antigen recognition site - Extraordinary levels of polymorphism4. Distinguish Trivers’ principle from Bateman’s principle and describe what they suggest about how sexual selection is likely to operate in males and females.Batesman’s principle – Whichever gender has the steeper relationshipbetween reproductive success and mating successwill be the gender in which sexual selection is strongerIn general, male reproductive success tends to increase with mating success over a broader range of mating success than is the case for females. This generates the stronger pressure of sexual selection in males.- Triver’s - Whichever gender invests MORE per gamete is likely to be the limiting resource for reproduction and will be the object of sexual selection in the OTHER gender. (Energetic cost per gamete)“ Sperm are cheap, ovum are not” 5. Enumerate the factors that drive female choice among potential mates. In that light, speculate about the circumstances under which you might expect males to be extremely “choosy” in discriminating among females as potential mates? If males were extremely discriminating, would you expect females in that species to remain extremely discriminating? Why or why not? a) Direct benefits (nutrition, nest site and care, care of young)b) No direct benefits (good genes, sexy sons, sensory bias)Males would be choosy if the male does all the work for the eggs (Seahorse – post- fertilization investment). Also if the male incurs a cost in the mate choice process.Females might be choosy bc of a big invest in gametes; choosy based on males ability to help them. 6. What do we mean when we say two genes are paralogous? What do we mean when we say two genes are orthologous? Homologous: common evolutionary origin-Paralogous: derived from gene duplication event- Orthologous: derived from a speciation event7. Which among the lines of evidence from which we deduce that the continents move is the most persuasive? Is any single line of evidence sufficient to falsify the notion that the positions of the continents are fixed and immovable or do we need all of those lines of evidence to convince the skeptic?1. Ocean floor sediments are young (100- 200 my; about 50% are less than 65 my)a. Younger than the continentsb. Material near the ridges is younger than materialfurther from the ridgesc. Oceanic mountains are igneous basalt whereas continental mountains are folded, sedimentary rock2. Magnetic field bands and reversals occur symmetrically and in parallel on either side of oceanic ridges 3. Changes in the position/orientation of magnetic poles in rocks of different agesPaleomagnetism is the most persuasive, although no single line of evidence is going to convince the skeptic.8. Which is the most persuasive line of evidence that humans were one cause, even if not the only factor, in the Pleistocene mass extinctions? Pleistocene extinctions in North American mammals were selective with respect to body size and/or, likely, reproductive rate: Body mass between 10 and 32 kg: 20%Body mass between 32 and 1000 kg: 50%Body mass over 1,000 kg: 100% - Megafauna did NOT disappear on New Zealand or other oceanic islands until the arrival of humans.9. We discussed character transformation, the process through which adaptive evolution modifies a structure or a gene product for a novel purpose (e.g. electric organs and antifreeze proteins in fishes, tendrils in climbing vines). We saw many cases of independent adaptive evolution in which the same phenotypic result emerged through co-option of different structures (the examples above) or through different paths (e.g. loss of wings in ant castes, paedomorphosis in salamanders). We can also see this same theme of independent, different evolutionary solutions to the same ecological challenge if we think about mechanisms of malaria resistance in humans (e.g. sickle cell trait and G6PD alleles), tolerance of toxic compounds in insects (e.g. sequestering toxins or detoxifying them biochemically), and antibiotic resistance in pathogenic bacteria (e.g. different mechanistic processes). Return to our discussions of population genetics and speculate about why adaptive evolution might take different paths to the same end in different populations or species. - Whatever mutation someone happens to have; could be multiple mutations and genetic drift eliminated some and left one for selection to act one; could be that genes pushed the organism down one path hitchhiked to a freq. when they were