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Lecture 4 (Chapter 1-2 - Jan28) - PSYCH 2TT3

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McMaster University
Brett Beston

PSYCH 2TT3 2013 Lecture 4 January 28 2013Modern Theoretical Framework for Animal BehaviourSelfish Gene approach to ethologythe sociobiological notion that genes associated with behavior are the units upon which natural selection actsNatural selection favours those genes that increase the expected relative reproductive success of their bearersfrom the genes perspective thats all that matters Sociobiology and Selfish Genes Evolution of antipredator behaviour in guppiesLow and high predation poolsPopulation structure of guppies is ideal to be studied o Most studied are fish from Trinidad and TobagoLow and high predation pools that empty into oceansGuppies can be found upstream and downstream in waterfallswaterfall acts as a natural barrier to predatorsHigh and low frequency streams can occur close to one another o Very likely that these guppies share some ancestral data o Characteristic differences can be observed in guppiesPhysical Characteristics distinct between two populations o KillfishLow risk to guppiesCan only eat the smaller ones Once guppies reach a certain size they are safe from killfishFewer offspring but larger in sizeFemales invest more in each individual offspring to maximize chance of growth and survival o High predation sites close to ocenPredators are pikes and pike ciclidsCan eat guppies of any size to adults are not safe eitherFemale guppies offspring are different o Small offspring are hateches and few might survive o Trinidad GuppiesDifference in coloration between males and femalesmale more colorful used to attract a mate and indicates quality in male colorful demonstrates health better genes etcFemales like to search for colorful food at the bottom of the pondpredisposition toward color coloration within the male plays off of a sensory bias that females haveFemales consistently select male of brightest coloration even down to 4 difference between two guppies always select more colorfulsexual selectionDownside to colormakes them more obvious to predators Handicap Hypothesisif male is able to survive despite handicap colorful attracts predators he must be superiorHigh poolslow predation more colorful more offspring smaller earlier age of reproductionLow poolshigh predation more drab in color less offspring larger later age of reproductionSmall predator can prey on small fish onlyLarge predator prey on adultsEffects on malecolor age at maturity body size and behaviourDoes predation risk affect guppy group size o Swimming in pools is a tactic that fish employ to avoid predation o Thought therefore that it would attract predators but this is actually advantageous o Known benefit to be in pools 1
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