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Clemson BIOL 3350 - Competition and Sexual Selection
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BIOL 3350 1st Edition Lecture 17 Outline of Last Lecture I. Sexual SelectionII. Why Sexual Reproduction?III. Origins of Sex Differences: AnisogamyIV. Daily Energetic Investment in GametesV. Anisogamy and Mating Efforts in FruitfliesVI. Reproductive Success in Male versus Female Function in Bladder SnailsVII. Bateman’s PrinciplesVIII. Not Sex-specific: Investment SpecificIX. Takes More Than Insemination for SuccessX. Alex Joseph and His Nine WivesXI. Mating SystemsXII. Sexual Dimorphism in ApesXIII. Sexual Dimorphism in HumansOutline of Current Lecture I. Sperm competition as a function of mating system: nonhuman primatesII. Male-Male Competition in HumansIII. Bateman’s PrinciplesIV. Alternative Male StrategiesV. Male Reproductive Tactics: InfanticideVI. Female Counterstrategies to InfanticideVII. Parental – Investment TheoryVIII. Sexual Selection and Mate ChoiceIX. Sexual Displays can be costlyThese 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.X. How does the good-genes model work?Current LectureI. Sperm competition as a function of mating system: nonhuman primatesa. Tests size varies with mating systemb. Chimps produce 200 times more sperm than the harem-living gorillasc. Human are intermediateII. Male-Male Competition in Humansa. Concluded that this kind of inter-tribal violence was adaptive in terms of sexual selection because it ended up in higher reproductive successb. Men compete in many ways to attract matesi. Risky sportsii. Brawlsiii. Jealousy-induced fights with other meniv. Competition for statusc. Men engage in a variety of tactics to retain matesi. Societal-level mate guardingii. Sexual jealousyIII. Bateman’s Principlesa. Males have higher variance in RS than femalesb. Males have higher variance in mating success than femalesc. A stronger relationship between RS and MS among males than females: sexual selection gradientd. The graph with the steeper line has the higher rate of sexual selection because there is more benefit in that set that on the other sete. Argue that these principles are not always truef. Females redback spiders take part in sexual suicideg. Diminishing returns – means that the graph increase at first and then levels off atthe toph. Male harem-living primates have an optimum reproductive success around 4 females (bell curve graph)i. Trade-off for choosinessi. Emphasis on more matesii. Emphasis on mate selectionj. When should males emphasize mate selection?i. Female-biased OSRii. High paternal investmentiii. High variation in female qualityk. Will not always do better if mate morel. Female-biased OSR - Numerically more females than males; or males are investing much more than femalesi. The investment of males is the limited resourcem. High variation in female quality – really low and really high fertility femalesn. Basically found that there is a need for more researcho. Should not assume that humans all follow this patternp. Polygamous societies are more common than monogamous societiesq. Only 16% are strictly monogamousr. Only 1% is polyandrous (one female and multiple males)s. A lot of variation within these stats – need finer detailIV. Alternative Male Strategiesa. Commonly see alternative males strategies (i.e. some males are territorial while some hangout on the outside and sneak in at the right time)b. During development, orangutans have two different ways to develop – one is much larger than the otherc. Hormonal suppression when a flanged male dies, a nearby unflanged male develops male secondary sexual characteristicsV. Male Reproductive Tactics: Infanticidea. Lactational amenorrhea – when females are lactating and nursing frequently, their ovulatory cycle is suppressed so if a male comes in and kills a child, then thefemale will be able to reproduce againi. A hypothesis that this is an adaptive strategy if the male kills kids other than its ownb. Death of infant accelerates return to sexual receptivityc. Data:i. 85% of deaths follow takeover by new maleii. unweaned infants primarily targetediii. rarely done by sexually active males in groupiv. 45-70% of cases males mated with same femalesVI. Female Counterstrategies to Infanticidea. Infanticide is not reproductively beneficial for femalesb. Females have evolved counterstrategiesi. Paternity confusionii. Male friends1. Females groups male2. Male protect femaleVII. Parental – Investment Theorya. Emphasized the relationship betweeni. Investment of resources in gametes and other forms of careii. Sexual competitionVIII. Sexual Selection and Mate Choicea. Intrasexual Selection – competitive interactions within members of the same sexto gain access to the other sexi. typically (but by no means exclusively) male-male competitionb. Intersexual Selection – mate choice; selection of mates with goal of producing high-quality offspringi. typically expressed as female choice of a mating partnerIX. Sexual Displays can be costlya. Females like males that are loud and produce fast clucksb. But the bats that prey on these frogs have cued into that trait and also prefer those calls à eat the male frogs which pushes the trait in the other directionX. How does the good-genes model work?a. Red spots are produced by carotenoidsi. This trait is costly to produce but is a reflection of male health and ability to surviveii. Red spots show that the males are more fitb. There is a benefit to both the sons and daughters of the


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Clemson BIOL 3350 - Competition and Sexual Selection

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