Bioee 1780 1st Edition Lecture 18Outline of previos lectureI. Types of selectionA) Kin selectionB) Individual selectionC) Group selectionII. Behaviors are traitsIII. SociabilityA) Cost and benefit of sociabilityB) DarwinIV. Kin selectionA) Hamilton’s ruleB) Cornell crowsC) Maternity assuranceOutline of current lectureI. The evolution of sexA) Paradox of sexII. Sexual selectionA) AnisogamyB) Certainty of paternityCurrent lectureI. The evolution of sex*Two types of reproduction: asexual and sexual*Hermaphrodites: produce both male and female gametes*Recombination: forming new allelic combinations in offspring (during meiosis)A) Paradox of sex*There is a cost to sex… asexual organisms can reproduce faster*Plus females must produce twice the offspring to have the same future reproduction success*Muller’s Ratchet: In asexually reproducing populations as the entire genome is passed on, deleterious mutations accumulate (genetic load)*In sexual reproduction, unfavorable mutations are purged by natural selection*Without sex, mutations must arise sequentially in the same lineage. With sex, 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.independent mutations can be brought together in recombinant offspring*Red Queen effect: evolutionary arms race between host and parasite-Sex allows for rapid evolution by reshuffling alleles, but they never really get anywhereI. Sexual selection*Sexual selection is a special subset of natural selection*Example: corkscrew duck penises and confusing duck vaginas*Example: birds of paradise dance and display bright colorsA) Anisogamy: the fusion of two dissimilar gametes (leads to different male and female investment)*Example: “penis fencing” so the winning male can swim away without having to shoulder female responsibilities/costs*Sperm are cheap, eggs are costly (females typically invest more)* Male reproductive success tends to be more variable than female reproductive Success*Females-Limited by their own energy and ability to produce eggs*Males-Limited by access to females-Males who mate with more females sire more offspring-Common strategy: mate with as many individuals as possible*Usually there are more willing males than female at any given time (creates a strange ratio)B) Certainty of paternity: *Females know that their offspring are their own, but males may not know who inseminated their woman (therefore, they may not want to investas much in offspring that may not be theirs)*Around Ithaca, between 8% and 28% of the offspring of backyard birds are not the male’s-How many humans do you think are secretly fathered by someone other than their social father? The best guess is somewhere around
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