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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 Presentation
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Cannibalism: is it ever a good idea?
Sara GarnettKBS 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
Explaining Altruism?
Some behavior seems unexpected if only individual survival and reproduction matters
Kin selection helping relatives can benefit individual depending on circumstances
Why Cannibalism?
Straightforward costs and benefits as behavioral strategy – what are some?
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?
Spadefoot Toads
Spadefoot Toads
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
Resources in Environment
Plant detritus (“general” food resource)
Tadpoles from three families
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
Compiling Data (Rounds 2 and 3)
Group Member
# General Resources
Eaten
# Green Tadpoles
Eaten
# Red Tadpoles
Eaten
# Blue Tadpoles
Eaten
Total Resources
Eaten
Off to the “pond!”
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?
Discussion Questions
Did your individual success always correlate with family success? What does this tell you about evolution by natural selection?
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?
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
Other Cannibalism Studies
Any questions?
