Life Science 15: Concepts and IssuesLecture 5: Nurturing nature: the power of culture1/24/12I. The four ways that evolution can occurII. Sexual selection: NS can create sex differencesIII. The norm of reaction illustrates the relationship between nature and nurture.What is an evolutionary successful organism?-an organism with greater reproductive success than other indivs in the pop.Critical to assessing fitness is understanding that it is measured:- relative to other genotypes/phenotypes in the population- in a specific environment- by reproductive successThere is no absolute successThere is only relative successThis success is quantified as fitness.Fitness is the relative reproductive success of a phenotype or genotype. Alleles that confer the highest fitness on the individuals carrying them will increase their market share in a population over time.What do we expect fitness to do over time?It should increase. But it doesn’t!Should it eventually reach a maximum? No.Does evolution create optimal solutions? No.How does evolution occur?1. natural selection – nonrandom elimination of alleles- variation- heritable- differential reproductive success2. mutation- can change allele frequencies directly by altering the DNA: one allele changed to another- Chernobyl and radiation- mutations- can be passed down to children if in sex cells3. gene flow- within a population, some individuals leave or new individuals arrive, thus changing the overall allele frequencies- via airplanes, etc…4. genetic drift- a random change in allele frequencies- influential on smaller populations- like islandsEvolution can occur via one of four agents: mutation, migration, drift, or natural selection.Sexual Selection:- costly traits: high likelihood of mortality and high likelihood of mating- natural selection increases these features- a trade off.- Peacocks- Friggit birds with big red puffy chests (color goes away after mating)- Antlers on deer- Maybe, if they’re alive and have these features, they’re a high quality male?Nature vs. Nurture:- is there human nature? What does that mean?- how you’re born and you can’t change it- Show someone a snake: sweat, heart rate increases, fear- Show someone a gun: babies don’t know to fear guns by instinct- Why is this opposite to the actual risk?Where does culture come in?- rhesus monkeys born in captivity have no snake fear- but… learn fear quickly, even only if seeing video of another monkey afraid of a snake- and… don’t learn fear of flowers even after seeing a videoNot all fears are learned with equal ease.Show someone from New Guinea a snake- adult is not afraid- when growing up, they learn which snakes are poisonous- they modify our innate fear and capitalize on our big brain’s ability to alter theprogram.Himalayan rabbit: genes specify coat color, and temperature will change the color.Siamese cat: temperature sensitive genesPhenotype: the observable qualities of an organism (morphology, behavior, etc.)Genotype: the internal state of hereditary factorsGenotype does not determine the phenotype, but influences it.What is a norm of reaction?- the set of all phenotypic expressions possible for a given genotype if raised under all possible different environmental conditions.Ex. Body size hinges on amount of food eaten.The slope tells you how important the environment is to the genotype. Steep norm of reaction:-The environment is important in determining the phenotypeFlat norm of reaction:-The environment doesn’t influence the phenotype much.-Ex. Eye colorWhat would a genetic determinist predict a norm of reaction would look like?-A flat lineA norm of reaction describes the interaction between nature and nurture in producing