BIOL 112 1nd Edition Lecture 8 Outline of Last Lecture I What causes microevolution a Natural selection b Genetic drif c Gene flow d Mutation e Non random mating Outline of Current Lecture II Exam prep III Natural selection revisited IV Important notes about NS V Sexual selection NS for mating VI Sexual selection a tradeof VII How genetic variation is maintained Current Lecture Exam Prep o Chapters 22 24 last day of lectures for test on Monday 8 16 2013 o Learning objectives eCampus o Class notes o Relevant sections of the book covered in class o Homework quizzes eCampus o BRING CALCULATOR Lecture o Non random mating Ex Inbreeding mating between close relatives increase homozygosity at variable loci increase in deleterious recessive alleles becoming homozygous Natural selection revisited Fig 23 13 o Modes of selection Stabilizing selection selects against extremes Directional selection Typical pattern during adaptation 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 Disruptive selection acts against intermediate phenotypes polymorphic population Important notes about NS o 1 Smallest unit NS acts on is the individual Selection of phenotype selection of genotype Afecting genetically encoded phenotypes o 2 Smallest unit that NS can change is population Changes allele frequencies o 3 NS is not due to chance Happens all the time The selective pressure can be due to a change event o 4 NS doesn t select for adaptation of future benefit Selects what is useful for the present o 5 NS strictly intra specific Each species has its own niche and particular challenges Diferent species are not subject to the same selective pressures o 6 NS can t make the perfect organism Historical constraints Adaptation involves compromise Sexual selection NS for mating success o Good example of where adaptation involves compromise Balance between characteristics that increase reproductive success vs nonsexual fitness survival o Sexual selection sexual dimorphism Sexual diferences between males and females o 1o sexual dimorphism diferences directly related to reproduction ex Genetalia gonads o 2o sexual dimorphism Diferences in characteristics not essential for reproduction ex Features hairs Within a species or population there are 2 types of sexual selection operation o Intra sexual competition between members of the same sex o Inter sexual individuals of one sex are choosey about selecting a member of the other sex usually females choosey Sexual selection a trade of o Pros reproductive success increases o Cons survival decreases ex Advertising to predators energetically costly to some sexual structures ex Large tail of peacock How is genetic variation maintained o Heterozygotes get diferent phenotypes every time o 1 Diploidy NS acts on phenotype but a phenotype can be encoded by heterozygotes ex A A A a phenotypically
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