PSY1 8 - Sexual Reproduction Why Is There Sex? Hedge...

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Sexual Reproduction
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Why Is There Sex? z Hedge against environmental change z No current reason for humans ± phylogenetic inertia z Protection against pathogens ± Red Queen hypothesis
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Gametes (Sex Cells) Released 1-2 /month 40 - 600 million per ejaculate
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The Sexes and Sexual Selection z ³)HPDOH´ ± sex that makes the larger parental investment per gamete. z ³0DOH´ ± sex that makes the smaller parental investment per gamete. z Sexual selection ± a type of natural selection in which members of one sex compete for reproductive access to members of the other sex. z The means of competition can be structural or behavioral, and often lead to sexual dimorphism .
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Sexual Dimorphism z In most of animal kingdom, females are much bigger than males. z One major exception is in species with proportionally large brains. z In those species, males compete for females with displays of strength and prowess. z Females choose mates based in part on these displays ± Overt female choice ± Cryptic female choice
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Sexual Selection: Male Behavioral Displays
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Rough-and-Tumble Play in Rhesus Juveniles
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Sexual Selection: Male Structural Displays
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Experimentally Exaggerated Sexual Dimorphism: Widow Birds
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Incitement
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Mating Systems z Monogamy - pair-bonding z Polygamy ± one animal has many mates ± Polyandry ± one female mates with many males ± Polygyny ± (harem) ± one male mates with many females z Promiscuity
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Mating Systems in Birds and Mammals
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Polyandry
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Lion Mating: Pride Polygyny
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Promiscuity in Chimpanzees
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Some Features of Human Mating System I z Monogamy w/ Some polygyny z Male > Female Preference for sexual variety ± More diverse arousal patterns z Fetishes z Exhibitionism z Criminal patterns: rape, child sexual abuse ± Numbers of partners - - males are: z less picky about people z less careful about circumstances
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Mating systems: Standard Cross-Cultural Sample (186 Cultures) z Most human cultures allow polygyny z In those cultures, polygyny is restricted to the well-to-do minority, and most men in these cultures have only one wife. z Overall, the vast majority of marriages are monogamous. z In every society studied to date, female extramarital sex is considered an offense against her husband, and is often grounds for murder of wife and/or lover. Monogamy
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This note was uploaded on 01/25/2011 for the course PSYCH 41855 taught by Professor Fridlund during the Winter '10 term at UCSB.

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PSY1 8 - Sexual Reproduction Why Is There Sex? Hedge...

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