Fig. 1

Schematic representation of evolution as described in class as the consequence of the independent, factual, observable processes of replication, variation, and selection. The diagram is to be drawn in stages during the course of the class, not revealed in its entirety at the beginning. First to be drawn is a, representing the mating of two individuals of the same species. b Variation, resulting from recombination (in this case of sexually reproducing organisms), in the offspring of mates shown in a. c Selection is depicted by crossing out some of the variable offspring; in this case, the light-gray shaded individual is the only survivor. d The light-gray shaded survivor of the previous bout of selection has found a mate and they have their own offspring, which include two light-gray shaded offspring, depicting the change over time of the properties of the population