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UM BIOB 272 - Sexual Selection
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BIOB 272 1st Edition Lecture 27Outline of Last Lecture Natural Selection and AdaptationI. Cross-fertile Maize and TeosinteII. Pesticides and Herbicides in SelectionIII. Resistance to Pesticides in HousefliesIV. Key Concepts- Selection in WildV. Adaptationa. Adaptation with Quantitative Charactersb. Complex AdaptationsVI. Three Potential Fates of a Duplicated GeneVII. Paralogous Gene vs Orthologous GeneVIII. NeofunctionalizationIX. Case Study: Evolution of Snake VenomsX. Complex Adaptations may involve: - Regulatory NetworkXI. Example of a Regulatory Hierarchy: Hox genesXII. Changes in Limb PatterningXIII. Mutations to Gene NetworksXIV. Key Concepts- AdaptationsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Outline of Current Lecture Sexual SelectionI. Adaptation Continueda. Forelimb Geneticsi. Dpp, BMP2, Mm E, MmPrx1, Bat Eii. Shhb. Additional AppendagesII. SEXa. Asexual Reproductionb. Eukaryotic Sexual ReproductionIII. Female Contributions to ReproductionIV. Cost of SexV. Disadvantages of Asexual ReproductionVI. Consequences of Sexual ReproductionVII. Sexual SelectionVIII. Sexual DimorphismIX. Clicker Question- What is a female? What is a Male?X. AnisogamyXI. Why does Sexual Selection OccurXII. Unequal Investment- Unequal Limits on Male and Female FitnessXIII. Rough Skinned Newts Example of Gender Asymmetry= InvestmentXIV. Two Categories of Sexual Selectiona. Male-male competition (intrasexual selection)b. Female Choice (intersexual selection) Current LectureSexual SelectionI. Adaptation Continueda) Forelimb Geneticso BMP2- digit enhancer, MmPrx1= forearm enhancer in mice1. Change in expression of Dpp= flys2. Change in expression of BMP2= same gene (both Dpp and BMP2) just expressed differently= changes in morphology- need many other co-items to exist with it= OROTHOLOGSo Shh- limb loss1. Presence/absence of limbs= switch with the hedgehog geneo Limb loss= expansion of trunk- due to expansion of Hoxo Snakes- hind limb reduction through down regulation of Shhb) Additional Appendages1. Mutations to gene networks can produce additional appendageso Ectopic expression (start growing at the wrong time) expression of Shh triggers new limbc) Key Points:- Ancient regulatory networks determine body patterning - Reveals a universal genetic toolkit derived from common ancestry with extensive modification, often through gene duplication.- Subtle changes can generate tremendous diversity in morphological form.II. SEX: Creation of new genetic combinations (i.e., genetic recombination) Viruses, Prokaryotes (bacteria, archea, etc.), Eukaryoteso Genetic recombination is not necessary for reproduction. Clonal reproduction is an effective mode of reproduction used by many organisms.b) Asexual Reproduction: produces an exact copy of a genetic individual (clone)o Found in all prokaryotes and many eukaryotes (i.e. aspens, protozoans) o All female asexual animals: mourning gecko and aphidc) Eukaryotic Sexual Reproduction: produces progeny through meiosis and generallyfusion of gametesIII. Female Contributions to Reproduction:o Females provide most of the resources for reproductiono Why should a female allow a male to contribute 50% of the genes to their progeny?= more varianceIV. Cost of Sex= a twofold costo Clonal female will produce more offspring (4)o Sexual Female (male and female) will have less progeny (2) but more genetic varianceV. Disadvantages of Asexual Reproductiona) Cannot rapidly create new genotypes by recombinationb) Harmful mutations become linked to beneficial mutations cannot be removed and may slowly accumulate (Muller’s Rachet)VI. Consequences of Sexual Reproductiono Disadvantages:1. Twofold Cost2. Search Cost3. Reduced Relatedness4. Disease Transmissiono Advantages1. Recombining beneficial mutations2. Novel Genotypes3. Removal of deleterious mutation4. Faster evolutionVII. Sexual Selection: differential fitness due to variation in mating success (competition for mates)o Darwin on Sexual Selection:1. Sexual selection depends on the success of certain individuals over others of the same sex...2. The sexual struggle is of two kinds: in the one it is between the individuals of the same sex, generally the males, in order to drive away or kill their rivals, the females remaining passive; while in the other, the struggle is likewise between the individuals of the same sex, in order to excite or charm those of the opposite sex, generally the females, which no longer remain passive, but select the more agreeable partners.3. Lastly, we have distinct evidence …. that the individuals of one sex are capable of feeling a strong antipathy or preference for certain individuals of the other sex.VIII. Sexual Dimorphism: Different traits in males and femalesIX. Clicker Question- What is a female? What is a Male?o Defined relative to gamete sizeX. Anisogamy: sexual reproduction involving the fusion of two dissimilar gameteso Larger gametes= femaleo Smaller gametes= maleXI. Why does Sexual Selection Occuro Unequal reproductive investment: females usually invest more in offspring than males, even in species with no gestation or parental careo Sperm=cheap , Eggs=costlyXII. Unequal Investment- Unequal Limits on Male and Female Fitnesso Investment differences can extend past fertilization- gestation and paternal careo Females: limited by number of eggs (access to resources)o Males: limited by number of mates (access to females)o Sexual selection will be strongest in the sex with the highest variance in reproductive successo Males should compete for mates= high risk of failure, but big payoff for winnerso Females should be choosy= variance is low but each offspring costly, so don’t waste effort on dud dads*Sexual selection should usually be stronger in malesXIII. Rough Skinned Newts Example of Gender Asymmetry= Investmento No parental car, both sexes can mate multiple timeso Gender asymmetry in breeding successo Captured all animals from a single pond following matingo Hormonally induced egg-layingo Performed DNA paternity analysiso Found females= not very big variance, but always reproduced1. Males= high variance, but didn’t always reproduce= fitness more dependent on number of mates2. Asymmetry in success = property of investmentb) Sygnathidae- pipefish and seahorses= men carry the babys through pregnancy= large investment= opposite graph then with


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