In a changing environment sex benefits individuals as

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In a changing environment, sex benefits individuals as sex generates more variation in offspringIn a stable environment, more variation is not useful, and so asexual reproduction is favoredLottery principle and Red Queen principle as environmental (short-term) benefits of sexRed Queen Hypothesis and evolutionary change: “It takes all the running you can do, to stay in the same place”oEvolutionary arms race with infectious diseasesoDiseases “invent” new keys; hosts “change the locks”Lottery Principle: Sex is like the lottery. By picking different numbers on each ticket rather than the same numbers, you increase your odds of winning/ being successfulHow sexual reproduction places different selective forces on males vs. femalesSelective forces on males and femalesoDoes not impact females as muchoHigh-quality males are very successfuloLow-quality males are not successfuloThe best for a male to increase his reproductive success is to mate with as many females as he canoThe best way for a female to increase her reproductive success is to mate with high-quality males so that high-quality offspring is producedoSex-role reversed species swap roles (males carry offspring and females compete for males)Distinction between intrasexual selection and intersexual selectionoIntrasexual – Ex. Horns which males use to fight to compete for femalesoIntersexual – Ex. Peacock feathers on male to attract femalesWhy males usually compete for access to females (rather than vice versa)Males compete for females because female investment in offspring is usually higherTo maximize their fitness, females choose mates that will sire the best offspringWhich sex has higher potential fitnessMales can mate with as many females as they can to produce as many offspring as they can which will result in a very high fitness
Which sex has higher average fitnessFemales have a higher average fitness because they can be choosyRelationship between sexual selection and parental investmentIf females have higher investment in offspring, they will be more choosyIf males have higher investment in offspring, they will be more choosyIf both have a high investment, both sexes compete for matesMuller’s Ratchet: Asexual Lineage Accumulates Harmful MutationsSexual recombination “breaks the ratchet”Continually creates new genotypes with fewer harmful mutations“Rubies in the rubbish”Advantages and disadvantages of living in a groupAdvantages:oSafety in numbers, group hunting, cooperationDisadvantages:oConflict can occurGroups can protect each other and their youngLiving in groups can also be expensive
oCompetition for food can increase because pressure on local food supplies is greatoCommunal living may facilitate the spread of contagious diseases and parasitesSocial animals usually live in groups characterized by some form of structure. Some individuals may dominate others (dominance hierarchy), manifested in access to

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