HL 2 Biology

E.6b Reciprocal Altruism



  • evolution of altruism
    • natural selection should act against altruism
  • evolution of co-operation
    • group of animals helping each other  could be more suffecssful in overall struggle for existence
    • all of them will increase their chance of survival
    • yet increase cheating or manipulation disrupting relationships
  • true altruism – generally involves genetically related animals, with natural selection working at the level of alleles
    • e.g in honey bees, offspring a worker helps to rear => usually is her siblings/share some alleles
    • important to protect colonies => because worker’s alleles could survive or die with it
    • colonies will have died out if  => worker bees didn’t act altruistically to defend colony & rear young
    • workers with alleles that made them act non-altruisically will have disappeared
  • reciprocal altruism = benefitting nonrelatives at cost to self, possibly self-sacrifice
    • e.g. vampire bats

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