ZOL 313 Week 12
ZOL 313 Week 12 ZOL 313
Blue Mountain State
Popular in Animal Behavior
Popular in Animal Science and Zoology
This 6 page Class Notes was uploaded by Elaine Foster on Monday April 27, 2015. The Class Notes belongs to ZOL 313 at Michigan State University taught by Dr. Dyer in Fall. Since its upload, it has received 149 views. For similar materials see Animal Behavior in Animal Science and Zoology at Michigan State University.
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Date Created: 04/27/15
ZOL 313 Animal Behavior Reproduction 0 Questions about sex 0 Why reproduce sexually Sex is expensive 0 Twofold genetic cost 0 Other costs time feeding etc What benefits make up for costs 0 Commonly cited genetic variation among offspring 0 Why is sex ratio 1 1 There seem to be more males than necessary or at least more sperm than necessary 0 Why so many males 0 Human males 300 million sperm per ejaculation 200 ejaculationsyear 50 years 3x1012 spermlifetime 0 Human females 0 Maximum 20 pregnancieslifetime 0 Why are the sexes so different Males amp females often differ in size color weapons ornaments and behavior 0 Evolution of sex differences drivers 0 Anisogamy the fundamental difference between the sexes Anisogamy not same size gametes What it is 0 Female large costly rare gametes 0 Male small cheap numerous gametes Consequences produces different limits on reproductive success R8 of males amp females 0 Females need more resources to produce gametes o Males need mating opportunities 0 Primary sex ratio Males Females at birth 11 for many species 0 Operational sex ratios biased Skewed toward an excess of males at time of mating 0 After fertilization males can more readily mate again 0 Also female spatial aggregation synchrony in estrus cycles Consequence of OSR variation in male mating opportunities 0 Limits on reproductive success Bateman s principle 0 Male amp female RS optimized in different ways 0 Females acquire resources Relevant traits foraging habitat selection migration etc o Males increase mating opportunities Relevant traits outcompeting other males 0 This sets the stage for sexual selection ZOL 313 Animal Behavior 0 Sexual Selection 0 Works by differential success of inherited variants O O O O Defined by what variants are selected Sexual selection may target one sex but both sexes play a role Secondary sexual characteristics ie not reproductive tracts Commonly seen in species under intense sexual selection antlers plumes etc Such traits are costly Not essential for reproduction Paradox two kinds of sexual selection 0 Direct competition intrasexua selection 0 Competition mediated by choices of opposite sex intersexua selection Outcomes of sexual selection Direct competition intra o Weaponry body size aggression behavioral tactics Mate attraction inter depends on female choice strategies 0 Ornaments elaborate displays Male combat selection for competitive traits Northern elephant seals 0 Fighting is a way of life 0 Costs of fighting are huge but benefits of winning are potentially huge Male competition alternative strategies ln populations where males gain high RS by fighting for females some males don t fight but instead sneak or accept subordinate status The puzzle if being subordinate or sneaking is a lowerpayoff strategy why isn t it eliminated by natural selection 0 Hypothesis 0 Individual optimality no chance of winning take chances on lowpayoff strategy 0 Game theoretical subordinate strategy does just as well lower payoffs but lower cost Sperm competition Context multiple mating by females 0 Traits involved 0 Specialized genitalia o Mate guarding 0 Large number of sperm Female responses to male competition Are females passive bystanders 0 Honey Bee Queen mating sign copulation plug 0 Queens mate 1520 times in 10 min so it s not a good plug o If she mates only one time she dumps sperm and mates again 0 Plug is actually a bull seye to make next mate s job easier 0 Northern Elephant Seals 0 Females resist attempts by sneaks to copulate o Attracts attention of dominant male ZOL 313 Animal Behavior 0 Female choice inter Females are expected to be choosier in general 0 Less benefit of mating multiple times 0 Bigger cost of making bad mating decisions There are costs of being choosy Criteria of female choice o Direct benefits 0 Indirect benefits good genes 0 Fisher s runaway o Sensory drive Direct benefits 0 Choice of male provides resources 0 Food territory paternal care lower disease risk more sperm protection 0 Nest building Sticklebacks o Zigzag dance 0 Nest physical protection male s investment cleaning fighting predators aerating eggs 0 Similar in weaver birds fresh green nests are preferred Indirect benefits 0 Traits that don t provide material gain 0 Ex bower birds males build nests for attracting mate but no eggs are laid there 0 Good genes 0 Hypothesis Male provides only sperm Benefit accrues to offspring Better genes better offspring quality Traits that predict good genes should be chosen 0 Evidence from guppies see graphs Females prefer larger body size amp brighter color Daughters of large males are larger and more fecund Another factor predation risks 0 Parasite resistance 0 Hypothesis Males vary in parasite resistance Males traits correlate with parasite resistance Adaptive function Phylogenetic history 0 The puzzle of mate copying o Guppies How it works Benefits 0 Maybe environment has changed 0 History preexisting sensory bias 0 Swordtails Females prefer male w long sword When did male trait amp female preference originate 0 Experiment 0 Glue fake sword on platyfish males ZOL 313 Animal Behavior Mating Systems 0 Platyfish females prefer sworded males Indicates that the female preference was there before male trait evolved o Fisher s Runaway Process RA Fisher 0 Hypothesis Male trait has no inherent benefit to male Preferences and trait became associated because of accidental genetic correlation between two heritable traits Offspring receive genes for preference and genes for male trait 0 Definition pattern of association between males and females relative to mating amp offspring care 0 Parental care Name Malefemale Sex providing care Examples association Monogamy 1 female 1 male Both Many birds Polygyny gt1 female 1 male Females Many mammals some birds Polyandry 1 female gt1 male Males sometimes Some birds many both insects Polygynandry gt1 female gt1 male Both or only males Some birds some fish Promiscuity gt1 female gt1 male Neither or only Many fish females chimpanzees ZOL 313 Animal Behavior 0 Why do svstems vary among species 0 Conflict of interest between males amp females in what maximizes RS 0 Calls for Game Theory 0 What determines outcome that evolves Male Cares Deserts o Monoqamv in birds 0 More than 90 of bird species are socially monogamous o Males amp females form stable pair for duration of breeding season sometimes longen Female Cares Deserts Monogomy amp Polyandry polygynandry Polygyny Promiscuity 0 Both parents can help rear offspring 0 But 0 Benefits of Genetic diversity Mammals o Advantage of heterozygosity at the Major Histocompatibility Complex 0 Polygyny Ideal for male Three types 0 0 DNA fingerprinting studies find high levels of ExtraPair Copulation EPC Both sexes stray and both do it secretly Why For female ideal mate is different from you at the MHC locus MHC and Mate Choice in humans Measuring preference the tshirt experiment Males wore tee shirts around for a week then pieces of the tshirts were given to women to smell and judge on how good they smelled Resource defense polygyny Males defend resources needed by females Males that offer better resources attract several mates Why should female settle w already mated male There are costs 2nd female gets no help from male have to share territory What are the benefits 0 Polygyny threshold Hypothesis if territory is good enough share ZOL 313 Animal Behavior Primary if r39quot 39 39 Jarquot 39 39 l in P j I as Addiiiilninelll Female fitness ifquot 39lll39emiriilinifr qlMlEllllll y 0 Female defense polygyny Males defend aggregated females Why should females gather together rather than dispersing so as to secure attention of single male Costs Predation o Lek polygyny origin Afrikaans Polygyny based on female choice males gather to display Defend territory w no resource Little aggression What favors evolution of leks H1 Hot Shot hypothesis good male attracts other males who seek to intercept females H2 Hot Spot hypothesis both males and females aggregate in certain parts of environment H3 female discrimination against solitary males benefit of comparison lt most likely hard to test
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