BIOL 112 1nd Edition Lecture 7 Outline of Last Lecture I. What causes microevolutiona. Natural selectionb. Genetic drifc. Gene flowd. Mutation e. Non-random matingOutline of Current Lecture II. Exam prepIII. Natural selection revisitedIV. Important notes about NSV. Sexual selection-NS for mating VI. Sexual selection-a tradeofVII. How genetic variation is maintained Current Lecture- Exam Prepo Chapters 22-24 (last day of lectures for test on Monday, 8-16-2013)o Learning objectives (eCampus)o Class noteso Relevant sections of the book covered in classo Homework quizzes (eCampus)o BRING CALCULATOR- Lectureo 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 adaptationThese 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 NSo 1) Smallest unit NS acts on is the individual  Selection of phenotypeselection of genotype- Afecting genetically encoded phenotypeso 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 evento 4) NS doesn’t select for adaptation of future benefit Selects what is useful for the presento 5) NS strictly intra-specific Each species has its own niche and particular challenges Diferent species are not subject to the same selective pressureso 6) NS can’t make the perfect organism  Historical constraints  Adaptation involves compromise- Sexual selection-NS for mating successo Good example of where adaptation involves compromise Balance between characteristics that increase reproductive success vs. non-sexual fitness (survival)o Sexual selectionsexual dimorphism Sexual diferences between males and femaleso 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 operationo Intra-sexual: competition between members of the same sexo Inter-sexual: individuals of one sex are choosey about selecting a member of the other sex (usually females choosey)- Sexual selection-a trade ofo Pros: reproductive success increaseso 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 timeo 1) Diploidy NS acts on phenotype but a phenotype can be encoded by heterozygotes (ex. A/A=A/a