HL 2 Biology

E.6c Kin Selection

p. 334

<<Social organisms>>

  • e.g. Honey Bees
    • live in colonies of thousands of bees
    • work together for survival (*individual bees can’t survive unless colony survives)
    • colony = super-organism; natural selection acts at this level than on the individual bees
    • Levels of bees
      • Queen: fertile females; lays eggs; one per colony
      • Drones: fertile males; finds virgin females & mate; several hundreds per colony
      • Workers; infertile females; tasks (searching for food & rearing larvae); thousands
        • usually sacrifice their lives to protect colony, rear larvae even if they didn’t breed them =altruistic behavior
        • altruism:  actions that increase other individual’s lifetime number of offspring at a cost to one own survival & reproduction


  • 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

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