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Cannibalism: is it ever a good idea?

Cannibalism: is it ever a good idea?. Sara Garnett KBS K-12 Summer Institute June 29, 2012. Agenda. Introduction to broader questions Game rules Play game Compile data and draw conclusions Follow-up discussion. Competition. Central to evolution by natural selection.

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Cannibalism: is it ever a good idea?

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  1. Cannibalism: is it ever a good idea? Sara Garnett KBS K-12 Summer Institute June 29, 2012

  2. Agenda • Introduction to broader questions • Game rules • Play game • Compile data and draw conclusions • Follow-up discussion

  3. Competition • Central to evolution by natural selection

  4. Explaining Altruism? • Some behavior seems unexpected if only individual survival and reproduction matters • Kin selection  helping relatives can benefit individual depending on circumstances

  5. Why Cannibalism? Straightforward costs and benefits as behavioral strategy – what are some?

  6. Costs and Benefits of Cannibalism • Benefits • Provides cannibal with meal • Eliminates potential competitor • Costs • Higher risk of injury if more evenly matched • May increase risk of disease • Other indirect costs?

  7. Spadefoot Toads

  8. Spadefoot Toads

  9. Basic Game Rules • Several resources in “desert pond” • You will be a tadpole from one family • One minute to forage using stirrers and cup • 15 food items necessary to survive • Several rounds to simulate different conditions

  10. Resources in Environment Tadpoles from three families Plant detritus (“general” food resource)

  11. Game Rounds • Round One: Compete for general food on volleyball court • Round Two: Compete for resources on volleyball court using family strategy • Round Three: Compete for resources on half of volleyball court using family strategy

  12. Compiling Data (Rounds 2 and 3)

  13. Off to the “pond!”

  14. Discussion Questions • Compare the results for rounds 2 and 3. Give a brief description of the patterns and propose an explanation for the results. • Do any of the results surprise you? Why might this be?

  15. Discussion Questions • Did your individual success always correlate with family success? What does this tell you about evolution by natural selection?

  16. Discussion Questions • What sorts of traits or behaviors would you expect to see in species that tend to be cannibals? Why might these be useful?

  17. Study Results • Carnivore tadpoles spend less time around siblings than omnivores • Carnivores taste tadpoles and tend to release siblings • Carnivores prefer to consume non-siblings if given a choice • Preference is weaker with increased hunger

  18. Other Cannibalism Studies

  19. Any questions?

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