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Life Science 3C03

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Life Sciences
Brett Beston

22/12/2012 08:47:00 LECTURE 1 Sexual Selection • Intersexual – one sex choosing mates from another sex [mainly females choosing males] • Darwin o Natural selection: adaptive changes to certain environment o Distinction in sexual selection – things not adaptive at all– ex. peacock tail o costly/increases predation yet this adaptation is selected for o Natural selection favours short length o Sexual favours long length Two components • Intra/inter sexual Bateman’s principle • Differences in investment drives selective pressures • Large variance between reproductive success is the result Female mate choice • What limits female reproductive success? o Access to nutrients/resources – survival • Lose a lot if they pick wrong parent Ability to invest • Age – older males are more likely to invest • Preference for good financial o women value it more than men detection of earning capacity • ornamentation o experiment – high ornamentation/status and low ornamentation/status [medium status as well] o tested what was biasing mate choice o attractiveness or status?  Females mainly chose men of high status  Good cues for providing for offspring  Males mainly chose attractive females Preference for willingness to invest • La cerra study o Found male with child most attractive Why do animals have sex? Sex is expensive • Mixing genes can actually also be costly Sex is beneficial • May clear up/mask “bad” genes in a gene line • Allows for wider array of genotypes Red Queen Hypothesis o Sex/recombination helps introduce genes that may increase survival • Corn smut o Evolution allows some corn to survive • Req queen o We always have to be changing since environment is o Asexual oranisms are more susceptible to parasites o Sexual organisms – decrease in variation decreases parasite resistance • Muller’s ratchet o With recombination, can’t create linaeage that’s free from mutation o Without it, can’t put favourable mutations together o Bet-hedging – greater amount of diversity in offspring of sexual organism than asexual o Avoiding putting all fruits in one basket • Some animals can switch between being sexual and asexual depending on environment Evolution of Mating Systems • Switch being turned on and off in voles • Dopamine is important for engagement of mongomous relationship • D2 receptor activation – pair bonding • D1 – pair bonding inhibited [so, dopamine release inhibits pair bonding] Monogamy and the puzzle of monogamous males • Males want to maximize reproductive success so they mate with as many females as possible Monogamy • Males have a lot to lose in social monogamy as he may be raising offspring that potentially wont be his Dungflies • Competition for eggs is so high that mating lasts up to 30 minutes • They take any opportunity to mount female – to maximize reproductive success • Longer copulation[10 min or longer], fertilization rate was 80% or above • They also want to mate LAST “sexy son hypothesis” • there is no difference in survival between the offspring of the two groups [hot or not = same survival] • does not support the good gene model of mate choice as the males in hot group don’t have higher survival rating • the sons of attractive fathers have higher survival rate than sons of non-attractive o the females choose more attractive males, produce attractive sons, so there is indirect fitness [for her offspring] Females have a choice to be monogamous or polygamous Ecological Factors • Limits of reproductive success = access to resources • Resource dispersion – females will go where resources are, where females are, the males will go Polygyny and Resources • if a male has more than one “dot” of resources, it is possible that the females will be more open to polygamous relationships • stronger males, maintain greater territories and have greater opportunity for female access polygny threshold model • female disperses according to resources [if males are present, that’s good – if not, they move on] How the PTM works • 4 males, 4 territories to choose from • first female that arrives and asses males, goes for male with largest amount of resources = maximizes reproductive success nd • 2 female --- go for smaller resourced male, she may get MORE resources at the end of the day because she won’t have to share them with other females [compared to male with largest resources]  MONO Female choice of territories • female would choose D over A because higher fitness in A • A VS C – equal fitness so there should not be any bias PTM example More shade, more survival Good territories have more shade and a few females First female gets all the help from the males in raising – second female does it on her own Limitations of the PTM Model assumes females accurately assess the territories Assumes the females don’t cooperate – it may affect decision choices though Infants receive less aggression when theyre with their mother than on own – more survival if parent is present Fraternal care in bluegill sunfish – higher hatching success If parent is engaging in parental care, theyre not reproducing [in most cases] Fathers more willing to do work for offspring lose more weight 22/12/2012 08:47:00 Lecture 2 What is parental care? • More common with male parental care than female • No parental care is the highest Evolution of parental care • Long lived birds are less likely to risk sacrificing themselves because they have more mating opportunities • Short lived birds like robins are more likely to sacrifice for their offspring • Minimize risk to self if long lived • Minimized risk to offspring if short lived • If Jay finds nest of another bird, it will hunt the chicks • Feeding rate drops after the presentation of jay song • They are not willing to tip off the location of their young – few visits to their young • After song is played, thrush isn’t visiting nest but going into opposite direction • Robins don’t decrease feeding as much as thrush [more willing to sacrifice kids’ lives] William’s principle • Addresses whether or not natural selection should favour the evolution of parental care • Takes into account when parental care should be maximized Why should you care? Maternal parental care • Tends to be more common • In nest on the left, if all the eggs are hers, she has a reproductive gain of “5” • If one egg is not the males, the male on the left has less success because he’s losing something by parenting an offspring that is not his Why maternal care? Why do we see paternal care? he’s missing out on increasing reproductive success Paternal care: stickleback • Can gain a lot from caring for young • The costs – growth rate is reduced [they spend energy caring for young] – not a huge cost • For females, she has greater cost in trying to rear young [females tend to be smaller so they grow a lot slower] o He egg production will be affected [reduced reproductive success] o Less foraging opportunities for females, affects survival Paternal care: fishes • Measures costs associated with future reproductive in males and females • Both parents received same benefit for helping but female has greater cost • Its advantageous for males to rear their young in these fishes Parental care: male water bugs • Males don’t have much a cost by taking on eggs on their back – survival is not really affected • For females, they have less reproductive success while taking care. She will have less mating opportunities Discriminating parental care • Parental care in two related animals o Byproduct of where they’re living o Cliff have more complex calls and are better at distinguishing between different calls Adoption: gulls • Sometimes kids leave own nest and are adopted in most cases [may be because parents aren’t taking good care of them] • Because of adoption, parent loses some fitness [0.5 fitness loss as a result of adoption] • Why would they do this ?? o Very simple recognition [if it’s in my nest, it’s mine] o Begging behaviour in kids [basically being forced to feed them based on fixed action pattern, they can’t help but respond] o They may end up NOT feeding their biological kids, and the cost is higher [1 cost] – better to just feed all kids [0.5 cost] Adoption: goldeneye duck • If a lot of young present, maybe the few that die are not the biological kids o There is a potential benefit in the dilution effect in predators o Less of a cost because they don’t have to feed them o Basically, parents don’t want to make mistake Brood parasitism • Cuckoo have increased begging behavior than other birds [red mouth, louder call] • Blue = parasitism occurring • Less chance of being fed if parasite is smaller • Larger parasite, more chances of being fed • If small bird dumps egg in large bird nest, lower chance of survival [offspring will be smaller] Why tolerate parasites? • If foreign egg is similar to native egg, higher chance of survival • Parent either raise all OR abandon all eggs and build new nest o If it’s late in mating season, not good idea to leave eggs • If female have options, she will more likely abandon the eggs in her nest • Environmental conditions o If later in season, they just put up with raising the cuckoo birds – not enough time Mafia hypothesis • Some parasites actually monitor behavior of hosts • They use retaliation tactics Why tolerate? Arms race • Some hosts win, like blackbirds – strong tactics may have been developed and cuckoo’s tend to avoid them • Blackbirds are more likely to abandon all eggs • Fairy wren – cover parasite eggs with twigs and lay own eggs on top 22/12/2012 08:47:00 Human parental investment Allocation of Parental investment Who do you think the baby is most similar to? • Looked at reactions as people saw a child • Everyone present in the room tends to make similarity comments that the child looks like the father – there’s a bias in this case • “badging” – may be evolutionary – being able to link children to their father o if the child doesn’t look like parental father, may remove self from situation What baby are you? • Got members to submit photo of themselves and their son at different ages • Were most correct when comparing father and child at 1 year old Parent-offspring conflict • As cost goes up, life time reproductive success goes down [graph] • Each offspring is 0.5 related to parent, reduces the parents wanting to help offspring • Want to maximize reproductive success • From a child’s perspective, if parent is incurring a cost, it doesn’t matter to them • The cost for offspring at each point is HALF of what parent actually experiences • Max = when straight line is longest • A child would benefit more if they receive more resources from parent • There’s a gap between what a parent SHOULD give to maximize success and what the offspring actually WANTS  conflict Parent favoritism and siblicide • There is a hierchy of how parents treat their offspring • Some parents disrupt sibling rivalry, some support it Parental disciplining • MB parent + MB offspring = allow offspring to kill each other • BFB parent + BFB offspring = lowest rate of siblicide Parental favoritism and siblicide • Parental investment is reduced when eggs are hatched at the same time • Androgens – make older siblings more aggressive Why do parents play favoriits Insurance • Trade-offs o In panda, live longer if taking care of one offspring o They use second offspring as insurance policy Environmental uncertainty • Core offspring and marginal offspring [handicapped in multiple ways, generally smaller, parents only hold on to them if there is a good year, they will have enough resources ] • Asynchrony in egret laying eggs is said to be adaptive – benefits parental reproductive success • It’s not just an advantage to lay chics at the same time and let them figure it out – the parents need to give it TO them • Survivors increased with exaggerated asynchrony • Normal vs exaggerated – normal results in the lowest amount of food brought Brood reduction and humans • Twin conceptions are more common than one child = vanishing twin • Extra egg is said to be insurance, incase something is wrong with the other egg. Evaluating the reproductive value of offspring • Caroternoid – indicator of health • If colour was more conspicuous in darkness, received more food • If you remove orange feathers, get fed less • B and d = controlled conditions [slide 32] Magpie assessment of offspring value • 17-20 days of age, must recognize child will reach reproductive age, so parent invests more Behavioural ecology and Kinship Interactions and fitness Theories proposed to solve the problem of altruism • Altruistic individuals lose reproductive success but it benefits the group as a whole Hamilton’s rule • B > C But… • About 1% of genome is different between each individual An evolutionary stable strategy • Hamilton vs brown? Altruism example • More adult females in the population, most signaling from them as well • Male adults signal far less than expected • Males tend to move much further away – bias in relatedness of males and females to others • It makes sense for females to be more likely to make signals – they are more likely to be around relatives • Alarm calling varies depending on relatedness Recognition system Kin discrimination Kin recognition models • You are near/in my nest, you must be my kin Rule of thumb • A gooses mechanism for recognition is very vague Code breaking Matching models • Match others to gage some degree of relatedness • Depends on how individual matches the internal representation of what a relative should look like Template matching • Look for visual/chemical cues in environment • It would be advantageous for the carnivores to avoid relatives • Cannibals use taste test models – they spit out what is believed to be relatives • Observed behavior over 24 hour period – over 48 hours, the cannibals end up eating EVERYONE [including kin] Facial similarity and trust • Take photo of subjects then ask to play a game against someone else • Merged participants face with another • two players take turn choosing to take larger share or pass to other player [allowing other player to share or not] • recorded steps that were trusting or not trusting Learned kin discrimination • Females are very sensitive to the smell of mhc • Attracted to males with dissimilar set of mhc alleles 22/12/2012 08:47:00 Cooperation is not guaranteed • Benefits are not guaranteed with this behaviour Range of cooperative behaviours • Females take 3 hours from beginning to end of birth – they need help • They hold their wings, clean and lick new born pups, make sure they don’t drop to the floor • “bat midwives Paths to Cooperation Reciprocity Game theory • Mathematical tool for decision making when there is a benefit Games and economic behaviour • How to countries to behave towards each other during war • Bombs were used as threats rather than actually weaponry • Both sides revealed depth of their nuclear capabilities • Nobody wanted to attack due to MAD – if one decided to use weapons, other country would retaliate, and nobody would survive Game theory and cold war • Could attack from anywhere in the world, this made things tense Game theory and behavioural ecology • Applied game theory to evolution of reciprocity Prisoner’s dilemma • Non-zero-sum – someone always gains benefit after playing game [don’t leave empty handed] The story Dilemma slide 23 - 26 • Looks at years they would get free [years of life get back if not going to jail] • No matter what player A is going to do, the best action player B can do is DEFECT --- always get most profit from that behaviour o Looking out for self So why do people cooperate when they can look out for only themselves? • Slide 28 - Suckers payoff – player B gets punished • If cooperation both ways has a higher benefit, it should be favoured Iterated Prisoner’s Dilemma • Repeating the dilemma game = iteration • End point of one iteration is starting point of another • First game, they should cooperate – second, they should defect • If you know defection is going to happen, you should make the decision to defect Instablity of Prisoner’s Dilemma • If no fixed end, player’s can develop strategies that are more complex • ‘if, when” rational o “if she corporates then I will, otherwise, I’ll defect on next trial” Axelrod’s Experiments Analysis of Some Simple strategies • Always defective optimizes for person always looking out for themselves • Always cooperates optimizes for both people • Expected scores • Average outcome for random is actually better than cooperating • Long term, alway
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