cannibalism: is it ever a good idea?
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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. - PowerPoint PPT PresentationTRANSCRIPT
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Cannibalism: is it ever a good idea?
Sara GarnettKBS K-12 Summer Institute
June 29, 2012
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Agenda
Introduction to broader questions Game rules Play game Compile data and draw conclusions Follow-up discussion
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Competition
Central to evolution by natural selection
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Explaining Altruism?
Some behavior seems unexpected if only individual survival and reproduction matters
Kin selection helping relatives can benefit individual depending on circumstances
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Why Cannibalism?
Straightforward costs and benefits as behavioral strategy – what are some?
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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?
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Spadefoot Toads
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Spadefoot Toads
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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
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Resources in Environment
Plant detritus (“general” food resource)
Tadpoles from three families
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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
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Compiling Data (Rounds 2 and 3)
Group Member
# General Resources
Eaten
# Green Tadpoles
Eaten
# Red Tadpoles
Eaten
# Blue Tadpoles
Eaten
Total Resources
Eaten
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Off to the “pond!”
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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?
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Discussion Questions
Did your individual success always correlate with family success? What does this tell you about evolution by natural selection?
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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?
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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
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Other Cannibalism Studies
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Any questions?