Try these parameter values:
Lots of Variation
Observe the above for each graph type.
Variation is important in determining the strength of natural selection. Populations with a large amount of variation can adapt quicker to changing environments. Populations with little variation change more slowly, and are more suseptable to extinction.
Natural selection may also effect the amount of variation in a population. For example, persistant selection in one direction (such as that seen to the right) can reduce the amount of variation in a population. This variation can only be replenished by mutation, which is the source of all new variation. Variance is a descriptive statistic which is a measurement of the amount of variation in a population.
Adjust the amount of variation to the right:
Note that as the amount of variation increases, the rate of selection is greater. When there is no variation (variance = 0), no selection can occur.
The trait in question is the color of the individual, where selection is acting against purple and for green.