Lecture 13&14

Lecture 13&14 - POLYANDRY - several males mate with...

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EVOLUTION OF SEX; SEXUAL SELECTION A. THE EVOLUTION OF SEX SEX: Fusion of genes from more than one individual ASEXUAL REPRODUCTION -- reproduction without sex (e.g. by mitosis) SEXUAL REPRODUCTION: 1.Isogamy: fusion between gametes of equal size 2.Anisogamy: fusion of sperm and egg THE TWO FOLD-COSTS OF SEX IN DIPLOIDS: At meiosis, females throw away half their genetic material to produce a haploid egg Advantages of sex in haploids: 1.Conjugation allows the selfish spread of genes by imposing them on other individuals 2.Transformation allows for chromosome repair Advantages of sex in diploids: 1.Elimination of mutations by segregation and independent assortment 2.Sex allows the acquisition of alleles that confer resistance to disease In diploids, sex must confer a two-fold advantage to overcome the costs of meiosis B. SEXUAL SELECTION MONOGAMY - one male with one female
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Unformatted text preview: POLYANDRY - several males mate with the same female POLYGYNY - several females mate with the same male SEXUAL SELECTION - selection of traits that influence mating success Tenets of sexual selection: 1.Female reproduction is limited by amount of resources she can convert to eggs or young 2.Male reproduction is limited by the number of matings he can obtain FITNESS I. Survival II. Reproduction A.Fecundity selection (converting food into gametes/offspring) B.Sexual selection (differential mating success) 1.Intra-sexual competition a.Direct combat (greatest with polygyny) b.Sperm competition (greatest with polyandry) 2.Female choice a.On basis of male providing resources (more sons & daughters) b.On basis of male genetic quality (better sons & daughters) c.On basis of male attractiveness (sexy sons, choosy daughters)...
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