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## 7.1 Technical notes on the dynamical model

Population dynamics crucially depends on two factors: How fitness is transformed into a reproduction rate (assuming that the transformation is always monotonous, this still leaves open quite a number of possibilities), and whether or when species die out. The model used in CoopSim uses population shares rather than an integer number of individuals for each species (strategy). This means that species never die out, even though their population share might become arbitrarily small. The reproduction rate is determined by the score a strategy gains in the tournament divided by the average score. Thus the reproduction rate does depend on the payoff parameters. Both assumptions are to a certain degree arbitrary.

Evolutionary noise (which can be adjusted via the Background noise parameter in the simulation setup dialog) is modeled as random disturbance on the reproduction rate (not on the population share).