NetLogo User Community Models
by Iain Weaver (Submitted: 01/16/2010)
WHAT IS IT?
This is a replication of Per Bak's model of punctuated equilibria in evolution, as presented in "How Nature Works", and "Punctuated equilibrium and criticality in a simple model of evolution".
HOW IT WORKS
Species are arranged in a circle and assigned a single, random value between 0 and 1 to represent their fitness. Each time step, the species with the lowest fitness and it's two neighbors are selected for mutation, and they are each assigned a new random fitness.
HOW TO USE IT
Setup creates a ring of num-species species, and assigns them a random fitness value.
The plot "Fitness" plots a point for each species at their corresponding fitness.
"Species History" shows the mutation activity of the species selected by the species-plot slider.
"Population History" shows mutation activity across the whole population. Each point shows where a mutation occurs, allowing us to track the region of activity over time. The "Species History" could be found by examining points along a vertical line on this plot.
THINGS TO NOTICE
"Species History" plot:
Additionally, the history neighboring species can be seen to have some similar features, gradually transforming into different shapes for more distant species.
CREDITS AND REFERENCES
Phys. Rev. Lett. 71, 4083 (1993): Bak and Sneppen - "Punctuated equilibrium and criticality in a simple model of evolution"
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