Lecture 8 Outline of Last Lecture I. MutationsII. Natural Selection Outline of Current Lecture I. Adaptive trade offsII. Sexual selectionIII. Gene FlowIV. Genetic DriftCurrent Lecture Anthro 1031st editionNatural selection can only work with traits that are present - cannot miracu-lously create a perfect being that is completely adapted to its environmentAdaptive "trade offs" - Husky vs. greyhoundHusky has short, stout legs to conserve body heat and paws safe from freez-ingGreyhound has longer legs that helps it chase down foodIt's an adaptive trade off for the husky - it doesn't have longer legs to help it catch food, but its short legs protect it from the coldA 'problem' for Darwin...Maladaptive traits?Don't improve survivalHow can theory of natural selection explain traits that don't help the species?These 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.Ex: Male peacock's big, bright tail inhibits it from flying and also makes it very noticeable to predatorsEx2: Male Irish elk has enormous antlers that make it very dif-cult to walk through the forest without hitting into thingsDarwin's answer: sexual selectionThe big tail of the peacock does not help it survive, but it is favored by the female species and so its alleles are passed onSexual dimorphism:Sexes have two different morphsMales are bigger than females, have bigger teeth than females (in baboons, and many other species)Polygyny - single male mates with many females (ex: gorillas, deer)Baboons are polygynous so males have to be bigger and stronger to beat other males for the females. They became sexually dimorphic because malesneeded to have bigger teeth or other advantages to battle other males.Gibbon's are monogamous pairs, so there is no need to be dimporhic - there is no intense male-male competition. Each male has one female, vice versa.Gene flow:Demes - a subdivision of a population consisting of closely related people, typically breeding within the groupPeople tend to mate more within their population than outside their popula-tionGene flow - genes flow from one population to anotherGene flow example: Two separate populations combine (80% red, 30% red) leads to 50% red population.Genetic drift - allele frequencies drift aimlesslyPopulation that is 50% red, 50% blue. Population splits into two populations, one that is 33% red and another that is 67% red. Has nothing to do with nat-ural selection. They just drifted randomly.Founder effect - small subset of population leaves (ex: colonists leaveEngland and found Jamestown). They become the founders for a new population.Bottleneck - large population that becomes diminished (cheetah population becoming lower as they are hunted) bottleneck shape - go from large amount to small amount. Lots of inbreeding in cheetahs because there is less diversity among remaining cheetahs.Random loss of alleles - flood comes and kills off town; those alleles are lost, not from unfitness, but by poor luckGenetic drift depends largely on the size of a populationSmall population has 16% red fish, that fish is lost and new population has 0% red fishLarge population has 33% red fish, after a change there is still 33% redfishLoss of certain traited organism in small population has greater effect than loss of certain traited organism in large populationEpigenetics:-all cells have same DNA......but become different kinds of cells-different 'gene expression'-activate parts of genome ("turn on")-deactivate ("turn off")-"Epigenome" - sum total of all genomes that say what genes should be turned on and which shouldn'tStem cell can become anything-it gets a signal telling it to become part of the nervous system, so some genes become expressed and others are deactivatedEvolution:-change in allele frequency over time-change in gene expression over time-regulatory genesThings like diet can affect genes - Change in gene expression over time, but not a change in the genesEnvironmental circumstances can change expression of genes over timeAncestral ape led to modern humans and modern chimpanzeesDifferent expression of the same gene? Reason for why we look differ-ent from chimpanzeesFor next class:Microevolution and macroevolution:-micro - evolution within a species-macro - evolution of a new