Biological Psychology Exam 2 Study Guide – Fall 2017 READ POWERPOINTS!!! Lecture 5: Reproduction and Sexual Selection - Secondary sexual characteristics: o Traits that serve no purpose in survival per se, but reflect competitive ability andattractiveness to mates. (Charles Darwin)  Appear around puberty - Sexual selection – o A form of natural selection acting on variation in the ability of individuals tocompete with others of their sex and to attract members of the opposite sex.  Competition over access to mates - Stronger in males  Selection for choice of mates - Stronger in females. o Idea, common eo Type of natural selection that is used to explain attractiveness and competition tomates - Male-male competition o Greater variation in reproductive success than females o The losers lose big time o Males are less choosy o Males competition for access to female  Strong - Female choice o Females bear the energic burden of pregnancy and lactation o Reproductive potential  The maximum number of offspring an individual can produce - Lower in females than in males o Female choosing mates  Strong - Variation in reproductive success o Passing of genes onto the next generation in a way that they can also pass onthose genes  Higher in males than females o Higher in males vary in species and population o Reproductive successes… amount of offspring o Greater variation = more male-male competition  Males are larger than females o Currency for natural selection - Variation in reproductive potential o The maximum number of offspring an individual can produce Lower in females than in males o Higher in males than females, variants - Operational sex ratio o (m)(Sm) / (f) (Sf)  M = number of males  Sm = period when males are ready to mate  F = number of females  Sf = period when females are ready to mate - Predicts greater male-male competitiono The number of sexually active male over sexually active female  Higher – higher competition  Lower – low competition o Predicter of male-male competition o Related to polygamy - Mating systems o Monogamy  One partner o Polygamy (multiple partners)  Polyandry - One female mates with more than one male  Polygyny - Males mate with multiple females  Promiscuity - General (and culturally loaded) term for having multiple sexualpartners- Polygyny threshold modelo Monogamy and polygyny as related to habitat quality  Fitness and territory quality - Fitness is how well something is doing o Offspring, survival, reproductive success- Amount of habitat quality increase that is required to increase orequate the fitness of the monogamous or polygynous female. o Gordon O’Ryan  Reproductive fitness with habitat quality - First or second mate  If a female is sharing a territory with a male and another female, if habitatquality is high, you can increase fitness. - The equal of habitat and fitness- Sexual dimorphismo When the sexes differ in body or canine sizeo Usually, males are larger o Provides an indirect indicator of the degrees of effective polygyny or the amountof male to male competitiono Body size is greatest in single male groups, lowest n monogamous o Canine size greatest in single male and multi-male groups, lowest in monogamouso Relative teste size greatest in groups with multiple males  Caveats - Phylogenetic factorso Same size in male and female  Lemurs - Social factorso Competition is not fighting, ritualized swims or dances o Females can be larger than male  Turtles or seals - Ecological factors o Ground life  Monkeys o How males and females differ  Body size, canine size Social system - Sperm competition o When females mate with more than one male, testes size and sperm per ejaculatein males increaseo Relative teste size highest in multi-male, multi-female groups, moderate inmonogamous groups, and lowest in single male groups o Sperm plugs Prevent sperm from other males from penetrating o Humans  Relatively few signs of significant sperm competition o Females mate with multiple males near ovulation Males have very large testes to produce a lot of sperm - Sperm plug, part of the semen makes a plus so sperm of othermales can’t penetrate o Sperm competition Competition of sperm to fertilize sperm Missing from the study guide…*Male primates may differ from females in the same species - Larger body size, larger canine, more elaborate coloration *Human males and females differ in some traits- Males moderately larger, canines similar in size, sex-specific characters that appear atpuberty. *And males also differ from females in many non-primates - Antlers of male deer, tail of a male peacock, a mane of a male lion, bright coloration of amale cardinal. *The extinct Irish elk - Huge antlers why?o Because of allometric growth *Intrasexual competition - Competition among members of the same sex. *Predictions - Ovulating females are limiting resources for male reproduction - Reproductive mistakes are costlier to females. *Female factors that influence male competition- Grouping, breeding season, interbirth interval, breeding synchrony (if yes, difficult forone male to monopolize), humans lack breeding season or obvious signs of ovulation. *Hormones - Chemicals released by glands which influence behavior of other distant cells - Bind to target receptors and initiate changes in the associated cells. *Marmosets - New world monkeys with cooperative breeding system- Males help carry and feed infants - High reproductive rateo Females give birth to twins multiple times per year. *Hormonal influences on male marmoset parental behavior - High levels of testosterone when exposed to scent of sexually active female - Reduced testosterone when exposed to the scent of their infant - Prolactin levels inversely related to testosterone levels - Human males exposed to infants show reduced testosterone and increases prolactin *Oxytocin and Vasopressin - Linked with pair bond formation and infant care behaviors in female and male rodents,marmosets and humans - Monogamous prairie voles will abandon their comparatively faithful ways when oxytocinand vasopressin are blocked. - They have a large number of receptors for these hormones compared to the polygynousmonotint vole; workers have implicated differences in specific genes as an underlyingfactor*To sum- How does human mating behavior compare and contrast with nonhuman animals?- Competition (usually