Evolution 1 - Selection and fitness

The simulation below illustrates a simple evolutionary process. In the beginning a small population of individual exists, each individual belonging to a particular strain. Each strain has a strain specific fitness that remains fixed during the process. Strains are distinguished by color and their fitness is marked on the fitness axis (bottom of window, scroll down if not visible). The size of symbols on the axis quantifies the relative amount of individuals for a corresponding strain.

As the simulation proceeds individuals reproduce stochastically with a propensity given by the fitness. When a capacity value (200) for the population is reached individuals also die with a uniform probability. Because strains with a larger relative fitness reproduce more frequently they slowly take over the entire population and the average fitness of the entire population (red moving dot on axis) increases on average. When a strain goes extinct, it can never come back.