Zoo 425 1st EditionExam # 3 Study Guide Lectures: 14 - 19Lec. 14 – 3/12• anisogamy - asymmetry in gamete size◦ sperm - small, energetically cheap to produce, produced throughout male lifetime, 300 million sperm/ml of ejaculate (3.5mL)◦ eggs - larger, contain mitochondria and extra nutrient stores (energetically costly)▪ in many species females have additional costs such as gestation, lactation, and offspring care ▪ offspring care isn’t always strictly maternal ▪ higher energetic cost in lactating than in offspring care ◦ males may maximize fitness (in terms of offspring produced) by fertilizing multiple females ◦ females may maximize fitness by finding the best mates for their limited eggs ◦ in general:▪ eggs costly, sperm cheap▪ males experience greater variance in reproductive success▪ on average, every female finds a male to fertilize her eggs▪ males should compete to fertilize limited female eggs ▪ females should be the choosier sex▪ have the limited resource (eggs)• sexual selection ◦ “Arises from the advantages that certain individuals have over others of the same species in exclusive relation to reproduction"▪ - Darwin ◦ sexual selection and natural selection▪ color patterns, songs, mating behaviors — often are used by predators and parasites to find prey/hosts as well▪ often used to explain the evolution of ornaments (elaborate)▪ ex. peacock’s tail▪ any characteristic of phenotype that affects reproductive success▪ behaviors: courtship, displays, infanticide▪ morphology: body size, characteristics of reproductive tract▪ physiology: composition of seminal fluids, mating pheromones ◦ intrasexual selection - within-sex (male-males/female-female)◦ intersexual selection - between sexes (male-female)◦ sexually selected if only one sex has inherited the trait ▪ any instance of sexual dimorphism • benefits of being choosy◦ direct benefits - females select particular males because they gain something directly from a good choice ▪ nuptial gifts - from males ▪ ex. nursery web spiders and hanging flies ◦ good genes - traits used by females to select a male us presumably an honest indicator of the male’s genetic quality ▪ coloration - less susceptible to disease/parasites ▪ male fighting ability ▪ symmetry - asymmetry indicates lower genetic quality, poor nutrition, etc ▪ developmental stability - how easily phenotype is perturbed by environment ▪ MHC-dependent mate preferences in humans • evolution of exaggerated traits ◦ Fischer’s runaway selection▪ once preference is linked to trait, because females are selecting males, their offspring will be born with males with this trait and females with preference for this choice▪ indicator used for choice and choice itself covary ▪ halts when runs into another selective pressure ▪ when it has consequences related to survival▪ not necessarily an indicator of good genes — indicator of female preference ◦ preference exists: good genes and sensory bias ▪ primate preference for red - attracted to food that’s red, leads to sensory bias ▪ sensory exploitation - exploiting previous bias in population for a sexual reproduction cue◦ handicap hypothesis - elaborate traits signal male quality bc only high quality males won’t die with the elaborate trait ▪ persist along with burden (cost) of elaborate trait ▪ more feasible if male chooses to utilize trait Lec. 15 – 3/17• mating system - species specific pattern of mate finding, reproduction, and parenting of offspring ◦ Drickamer◦ alt def: social system that describes how males and females come together to breed ◦ components/considerations:▪ number of sexual partners▪ timing and duration of association between males and females ▪ male vs female perspectives on the benefits/costs ◦ types:▪ monogamous - each breeding adult mates with only one individual of the opposite sex during breeding season▪ not necessarily life long▪ polygamy - general term for when one individual of either sex has more than one mate, pair bond is often absent▪ polygyny - one male mates with greater than one female during breeding season ▪ polyandry - one female mates with greater than one male during breeding season ▪ promiscuity - any individual may mate with greater than 1 individual, no real pair bond formation • forces to influence mating systems:◦ parental care▪ constrains options available to any species ▪ phylogenetic constraints▪ sometime depends upon resource distribution▪ components:▪ degree to which parental care influences offspring survival▪ number of times adults can expect to have reproductive opportunities during their lifetime ▪ tradeoff between current care and future reproduction ◦ ecological constraints: limiting resources, resource distribution, predation, parasitism, disease • game theory model of parental care◦ John Maynard Smith◦ parameters:▪ P0 , P1, P2, = probability of egg survival with increasing parental care ▪ P0 = no parental care▪ P1 = one parent cares▪ P2 = two parents care ▪ Ed = number of eggs laid by a female who deserts ▪ doesn’t contribute to offspring care ▪ Ec = number of eggs laid by a female who cares for offspring ▪ m = probability that a deserting male will mate againFemale cares Female desertsMalecaresFemalegets:EcP2 EdP1Male gets: EcP2 EdP1Maledeserts Femalegets:EcP1 EdP0Male gets:EcP1+ EcP1m—> EcP1 (1+m)EdP0 + EdP0m —> EdP0 (1+m)◦ 4 ESS outcomes:▪ both parents desert:▪ req. EdP0 > EcP1 or female will care ▪ req. P0 (1+m) > P1 or male will care ▪ EdP0(1+m) > EdP1▪ female deserts, male cares:▪ req. EdP1 > EcP2 or female will care▪ red. P1 > P0 (1+m) or male will desert▪ female cares, male deserts:▪ req. EcP1 > EdP0 or female will desert▪ req. P1 (1+m) > P2 or male will care▪ female and male care:▪ req. EcP2 > EdP1 or female will desert▪ req. P2 > P1 (1+m) or male will desert ▪ dependent upon costs/benefits ▪ assumes male cant reproduce while caring for offspring• ex. fish parental care◦ bony fishes◦ internal vs external fertilization◦ male or females parental care or none at all▪ 79% have no parental care at all▪ inc when external fertilization and and parent care ◦ male doesn’t desert bc as likely to procure mating opportunities◦ usually 1, P0 (1+m) > P1• mammals ◦ parental care: mostly female only (95% species) in 5% of species