class3.final

class3.final - SEXUAL SELECTION SEXUAL SELECTION • Darwin...

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Unformatted text preview: SEXUAL SELECTION SEXUAL SELECTION • Darwin argued that sexual selection, “depends on the advantage which certain individuals have over other individuals of the same sex and species in exclusive relation to reproduction” – Trait is sexually selected if it confers an advantage over same-sex rivals but is not necessary for survival or for reproduction in the absence of rivals – Sexual selection is a subset of natural selection (artificial category) and operates according to same mechanism (differential gene replication) Why have sexes at all? • Pathogens – Especially problematic with long generation times – Do not want to ‘train’ pathogens to your offspring – Why few species clone • Solution: mix up genes (protein variability) with sex WHY 2 SEXES? Gametes are haploid (1/2 DNA of zygotes) Greater gamete size = greater survival probability but lower # that can be produced “Anisogamy” 2 gamete sizes Female defined as sex that produces larger gametes PARENTAL INVESTMENT THEORY • Trivers (1972) predicted that the sex with the greater typical parental investment in offspring becomes a limiting resource for the reproductive success of the opposite sex – PI defined as any cost associated with raising offspring that reduces parent’s ability to produce or invest in other offspring – Females of most species make larger typical parental investment than do males • Bateman’s data with fruit flies PARENTAL INVESTMENT THEORY...
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class3.final - SEXUAL SELECTION SEXUAL SELECTION • Darwin...

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