Chapter 7: Sexual Selection
Chapter 7: Sexual Selection BIOL 515
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This 4 page Study Guide was uploaded by Erica Leonard on Thursday October 22, 2015. The Study Guide belongs to BIOL 515 at Kansas State University taught by Eva A Horne in Summer 2015. Since its upload, it has received 38 views. For similar materials see Behavioral Ecology in Biology at Kansas State University.
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Date Created: 10/22/15
Chapter 7 Sexual Selection Sexual Selection gt Characters contributing to finding amp keeping a mate are selected Darwin 1871 o Intersexual selection 1 gender chooses the other female choice 0 ntrasexua selection competition over 1 gender females within the other gender males 0 Parental investment differences in amount of energy materials time etc put into producing offspring Gametes gt Maximizes fitness Females produce few large gametes eggs Males produce many small gametes sperm 10 eggs 10000 sperm Low investment high potential high levels of sexual activity competition of mates High investment low potential low levels of sexual activity selection among mates 0000 I Example Pipefish Males choose largest and most ornamented female females who display for longer periods of time But males are limited to how many zygotes they can carry in their pouch ntrasexua Selection gt Competing for access to opposite gender gt Gaining copulations o Dominance amp fighting exclude others through conflict can lead to sexual dimorphism I Differences between gender males larger stronger w more weapons 0 Dominance amp hierarchies form linear rank system ordering individuals from most least dominant decides who gets first choice on females 0 Alternate male strategies how to safely avoid dominant male amp mate anyway I Mimic females males get close enough to dominant males nest to releases sperm at same time as DM and fertilize eggs I Satellite males wait quietly near displaying male amp intercept incoming females 0 Ensure use of males sperm I Male guarding Guard female from other males timing depends on whether females stores sperm amp sperm she decides to use Males lose weightfitness from guarding females and not leaving to eat I Displace or inactivate rival sperm sperm competition Quality of sperm based on mobility and numbers How many mates female had before male order depends Tactics 0 Remove rival male sperm from female 0 Seal rival male sperm off inside female 0 Stimulate female to eject rival male sperm 0 Produce quotkillerquot sperm Iepidopterans bigger sperm produced that attacks rival ales sperm and doesn t fertilize eggs 0 Advantages to females of multiple copulations I Why allow sperm competition Increase probability of Increase genetic diversity of Accumulate benefits from Increase diversity of mating o Interfere with rival male I Sexual sabotage reduces rival s fitness by Infanticide male destroys offspring of rivals o Occurs in males only kill nonkin brings females into estrous Intersexual selection gt one gender chooses the other female choice gt characteristics chosen 0 Material benefits qualityquantity of resources provided by males I Improve females survivalability to reproduce I Improve survival of offspring o Nuptial gifts foodvaluable substances presented to female during courtship birdsinsects I Prey seminal nutrients gland secretions body parts I Make males appear for desirable I Easier to copulate I Maximize amount of sperm I Parental investment to offspring Red backed spider 0 Male transfers sperm somersaults so abdomen can be eaten by spider increases copulation timeeggs fertilized eating male decreases chances of 2quot l mate if male survive to mate again ensures 100fetilization 0 Larger males are able to constrict abdomen in order to survive first copulation come back for 2quot l mating dies within 24hrs post mate 0 Mates that don t survive fertilize more eggs due to longer copulation time o Territory quality ampor size of area defended by male I Good nest or oviposition site low predation risk good forage o Sufficient sperm females are picky about mates I In some species females choose males that haven t mated recently occurs in species that package sperm with nutrients and other substances 0 Parental ability ability of male to defend ampor feed offspring choose based on character that correlates to good parental care I Large sizebetter defenderprovider I Large epaulettes better defenderintensity of courtship feeding effort I Quality of nutritional gifts ability to forage provide I Previous experience w male successful choosing him again 0 Other male qualities I Flashy colors red orange yellow can t be made by body Can indicate physical condition foraging ability or parasite load Bright males 9 better fathers feed offspring more 9 brighter sons pass more of females genes on I Song repertoire I Display objects birds that collect rare blue objects to display for females Female mate choice of traits offering no material benefit gt Why do females prefer flashy males gt Why do traits persist when they reduce male survival 0 Runaway selection coevolution of female preference amp male character I Female develops preference for male character sonscharacter daughters preference 0 Handicap principle I Male s exaggerated trait makes him less likely to survive I Female chooses him because he survives despite the quothandicapquot 0 Good genes females chooses male that can pass on the best adapted traits I Peacock 0 Females choose males w most eyespots on tail of those she visited 0 More eyespots 9 survived better healthier o More elaborate tail 9 heavier offspring 9 higher survival rate 0 Parasite load color or other traits indicates of parasites male has I Flashy males more resistant to parasites good genes for young healthierbetter parents 0 Symmetry animals with bilateral symmetry both sides equal proper development good genes good health I Female preference indicates resistance to mites I Birds regrow feathers after molting if they have mites9tai regrows unevenly 0 Genetic differences degree to which prospective mate has same genes I Major histocompatibility complex MHC region on chromosomes important in immune response antibody production I Avoid inbreeding I May increase offspring s resistance to disease by having more variable immune system 0 Sensory bias male traits evolved to take advantage of some preexisting bias of females I Females of genus Xiphophorus prefer males w long swords possibly evolved from female preference of large body size o Males increase total length to equal males w sword amp preference disappears o Prefer males with large bodies size not necessarily longer sword tail 0 Matechoice copying male becomes more attraction to female if another female is attracted to him first I Younger females learn what traits are best by observing older females in species I When allowed to choose female will choose same male as 1 female less experienced copy more experienced but not vis verse Male mate choice gt Males provide much care to offspring pipefish gt Female has mated before amp 1St male s sperm gains priority 13lined ground squirrels gt Females reproductive capacities are different amp predictable choose largest female because they can lay the most eggs Summary or sexual selection gt Two kinds 0 Intersexual selection female choice 0 Intrasexual selection malemale competition gt Differences based on initial differences on parental investments 0 Males Low investments amp max fitness by copulating w as many females as possible 0 Females High investments amp max fitness by choosing best male gt Many tactics for each depending on species amp circumstances gt Reversals of roles do occur
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