Lecture 5Overview of Current Lecture- Biological Evolution- Sources of Genetic Diversity- Forces Preserving Genetic Diversity - Environmental Influences- Selection, Adaptation, Speciation- Evolutionary Stable Strategies I. Biological Evolution a. Change in the relative gene frequency within a population from one generation to anotherb. Gene frequency associated with a useful trait increasesi. MRSA – catch it at hospitals1. Methicillin = antibiotic resistant c. Evolution can involvei. Adaptations1. Minor changes (in our domesticated animals; dogs)ii. Speciation1. Non-interbreeding species II. Population Genetics a. The more diverse the genetics of a species population, the better the future of that species b. Hybrid vigor that results from selective breeding of long isolated animalsi. Ie: various breeds of cattle that are interbred produce bigger offspring 1. Angus and Zebu (brahma) c. Endangered animals – lack of genetic diversity is a serious problem III. Sources of Genetic Diversity a. Mutations – result in heritable changes in genetic materiali. Most are deleterious (bad)1. Hard to get rid of/remove from gene pool ii. It can take 104 generations to reduce an allele (gene group) to 1/3rd of the original iii. Identical mutations may be induced in other animalsiv. If there is genetic predisposition for Huntington’s chorea or cancer, and the predispositionis not expressed until after childbearing period, then the genetic predisposition is perpetuated 1. Susceptibility can often be unknown b. Recombination – sexual reproduction; shuffling the deck of DNA cardsc. Gene Flow – population of the same species possessing genetic variation moves in and breeds with the original species i. Genes of original species incorporate genetic changes brought in by newcomers PSYC 311 1st EditionIV. Forces Preserving Genetic Diversity a. Frequency Dependent Selection i. Predation – predators concentrate on most abundant phenotype, therefore the extremes of predisposition are favoredii. Reproduction – rare phenotypes most likely to be selected as a mate by all others within distribution b. Negative Assortive Matingi. Extremes of distribution (opposites) attractc. Gene Flow V. Environmental Influencesa. Example: English moths – pre/post Industrial Revolution i. Preservation of dominant and recessive genes 1. White moths were camouflaged and black moths were heavily predated upon untilthe soot from the Industrial Revolution covered the trees in the foresta. The black moths became camouflage and the white moths were predated upon 2. Selection pressures from the environment b. Example: skin/eye color in humansi. People closer to the equator have darker skin and eyes due to the amount of sunlight thereVI. Selection, Adaptation and Speciation a. Natural Selection: change in frequency of genotypes  phenotype survives/reproduces i. Stabilizing selection – norm favoredii. Directional selection – favors one extremeiii. Disruptive selection – favors both extremes/deselects norm b. Ecological niche – environment involving food, shelter, etc. that is available for exploitation by aspecies i. Galapagos had a lot of unoccupied niches upon formation c. Adaptive radiation – Darwin’s Galapagos finchesi. Perpetuation of plants through seeds ii. Competition – forces those less efficient at doing something to improve or die d. Speciation i. Major changes that result in new/different species 1. Reproductive isolating mechanisms a. Ensure that two different groups do not interbreedi. Courtship rituals in birds; evolution through sexual selection ii. Sympatric speciation – niche/behavior differences prevent interbreeding – still in same geographical location 1. Ie: caterpillars raised on apple trees and switched to pear trees – can they mate?2. Ie: Hirsch and Boudreau’s fruit flies iii. Allopatric speciation – environmental changes result in geographically separate habitats1. Prevents interbreeding 2. Ie: Grand Canyon squirrels VII. Evolutionary Stable Strategies a. Successful solutions (strategies) tend to be repeated across species i. Ie: migration, hibernation, flying b. Optimality theory – there can be “too much of a good thing” i. Ex: Irish Elk – Megalocerus – antlers over 12 feet from tip to tip 1. Extinct based on cost/benefit analysis 2. Related to mate selection c. Cost/benefit ratios – important factors relevant to survival i. Ex: lions vs. prey – costs/benefits of pursuit 1. Prey – cost of not