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by: Zenia Mason


Marketplace > Georgia State University > Psychology > Psyc 1100 > INTRO TO BIOPSYCH PSYCH 1100 REPRODUCTION AND SEXUAL SELECTION WEEK 6 7 NOTES
Zenia Mason
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About this Document

This set of notes covers all information on reproduction and sexual selection lectured on at the end of week 6, and throughout week 7 in intro to biological psychology.
Intro to Biological Psychology
Ken Sayers
Class Notes
intro, to, Bio, psych, Biological, Psychology, 1100, reproduction, sexual, selection, week, 7, 6




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This 8 page Class Notes was uploaded by Zenia Mason on Monday October 10, 2016. The Class Notes belongs to Psyc 1100 at Georgia State University taught by Ken Sayers in Fall 2016. Since its upload, it has received 10 views. For similar materials see Intro to Biological Psychology in Psychology at Georgia State University.




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Date Created: 10/10/16
Reproduction and Sexual Selection MALE PRIMATES MAY DIFFER FROMFEMALE IN THE SAME SPECIES  Larger body size  Larger canine size  More elaborate coloration HUMAN MALE AND FEMALE DIFFER IN SOME TRAITS  Male moderately larger in terms of body size  Canines similar in size  Sex-species characters that appear at puberty AND MALES ALSO DIFFER FROM FEMLES IN MANY NON- PRIMATES…  Antlers of male deer  Tail of male peacock o Bird of Paradise o White-eyed Peacock o The females find the largeness or bright colors of the male feathers attractive  Mane of male lion  Bright coloration of male cardinal EXPLAINING MALE ADORNMENT  The descent of man and selection in relation to sex (1871)  Secondary sexual characteristics o Traits that serve no purpose in survival per se, but reflect competitive ability and attractiveness to mates TERMS  Intrasexual competition o Competition among members of the same sex  Sexual Selection o A form of natural selection acting on variation in the ability of individuals to compete with others of their own sex and to attract members of the opposite sex  Usually expressed as: o Male-male competition (males have less choice in hopes of not having to compete for the likes of females) o Female choice  Bowerbird males build bowers to attract females, which choose their mate based on the quality of the construction  Males do a dance with feathers to show off, and the females choose based on that as well SEXUAL SELECTION  Competition over access to mates (generally stronger in males)  Selection for choice of mates (generally stronger in females) WHY IS MALE-MALE COMPETITION SO FEIRCE?  Greater variation in reproductive success than in females  The losers lose big time WHY ARE FEMALES (ESPECIALLY MAMMALS) SO CHOOSY?  Females bear the energetic burden of pregnancy and lactation  Reproductive potential- Maximum number of offspring an individual can produce (lower in females than males) 2 HUMAN REPRODUCTIVE POTENTIAL  Maximum number of offspring each individual has  Female o First wife of Feodor Vassilyev, 18 century Russian peasant o 69 offspring o 16 pairs of twins o 7 sets of triplets o 4 sets of quadruplets  Male o Moulay Ismail Ibn Sharif, Sultan of Morocco (1672-1727) o 888 offspring o > 500 wives o Males are generally less choosy  Ex. Toad mating with a researcher finger  Ex. Beatle mating with a beer bottle PREDICTIONS  Ovulating females are “limiting resources” for male reproduction  Reproductive mistakes costlier to females FEMALE FACTORS THAT INFLUENCE MALE COMPETITION  Grouping  Breeding? o Male-male competition is limited to short slice of the year if there is  Interbirth interval o Period of time between on average, of when a female gives birth  time between next birth. It can heighten the male competition, if the time between is longer.  Breeding synchrony? o If yes, difficult for one male to monopolize 3 o Humans lack breeding season or obvious signs of ovulation OPERATIONAL SEX RATIO f  (m)(Sm) / (f)(S )  m= # of males  S = period when males ready to mate m  F= # of females  S f period when females ready to mate  A larger operational sex ratio predicts greater male- male competition  Papio ursinus Chacma baboon SOME TERMS  Monogamy o Two individuals having exclusive access to one another for some period of time; female has one mate for one breeding season  another for the next  Polygamy o Bonded relationships over a period of time  more than one mate 1. Polyandry- one female mates with more than one male 2. Polygyny- male(s) mate with multiple females 3. “Promiscuity”- general (and culturally-loaded) term for having multiple sex partners MONOGAMY AND POLYGYNY AS RELATED TO HABITAT QUALITY  Polygyny Threshold Model o When the fitness and territory quality equate in both females 4 o The difference in territory quality that equates the fitness of the monogamous/ polygynous female  measure of habitat equality  Territory Quality- Food or general resources available; territory quality is greater in monogamous female o When the resources (that the male has associated with him) are great enough, it can make up for being a polygynous wife, and encourage it SEXUAL DIMORPHISM  When the sexes differ in body or canine size  Usually males are larger (especially in Gorillas)  Sexual dimorphism provides an indirect indicator of degrees of “effective polygyny” or amount of male- male competition (with some caveats) PRIMATE BREEDING SYSTEMS RELATED TO DIMORPHISM AND TESTES SIZE  Body size dimorphism greatest in single-male groups, lowest in monogamous  Canine dimorphism greatest in single male and multi- male groups, lowest in monogamous  Relative testes size greatest in groups with multiple males o The competition itself for females is having a physiological effect on the males’ testosterone and behavior  sometimes prenatally SEXUAL DIMORPHISM AND DEGREE OF MALE-MALE COMPETITION: CAVEATS  Phylogenetic factors o (e.g. lemurs) that constrain the genetic sexual dimorphism that we see (or for the males to grow larger sexual body sizes females larger than males) 5  Social Factors o (Turtles, seals)  Competition is by doing aquatic displays instead of fighting  the males are smaller than females because of these aquatic display and that’s how females choose them o This constrains body size with the males  Ecological factors o (e.g. terrestrial monkeys, some birds)  the environment you live in may limit the dimorphism you have o In birds, there are slight differences in the M/F like in bill length  this contributes to competition for food, and the size SPERM COMPETITION  When females mate with more than one male, testes size and sperm per ejaculate in males’ increases  Relative testes size highest in multi-male, multi-female group, moderate in monogamous groups, and lowest in single-male groups o There is competition of sperm in individual males in females to fertilize the eggs.  “sperm plugs”  Humans- relatively few signs of significant sperm competition HORMONES  Chemicals released by glands which influence the behavior of other distant cells  Bind to target receptors and initiate changes in the associated cells MARMOSETS  New World monkeys with cooperative breeding system 6  Males carry and feed infants  High reproductive ate: 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 scent of their own infant  Prolactin levels inversely related to testosterone levels  Human males exposed to infants show reduced testosterone and increased prolactin  Oxytocin and vasopressin linked with “pair bond” formation and infant care behaviors in female and male rodents, marmosets, and humans o Monogamous prairie voles will abandon their comparatively faithful ways when oxytocin and vasopressin are blocked. They have a large number of receptors for these hormones compared to the polygynous montane vole; workers have implicated differences in specific genes as an underlying factor (eg. Avpr 1 a) o Montane voles which are similar are not monogamous TO SUM  How does human mating behavior compare or contrast with nonhuman animals? o Humans like other mammals in males’ mate with anything possible. o Competition (usually between males) and mate choice (usually by females)  Both of these are the two avenues for how sexual selection works o 7 o Sexual selection helps explain physical and behavioral differences between males and females of the same species 8


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