In this simulation of natural selection, learners use binder clips in three different sizes to represent the diversity of beak sizes in a bird population. They use the "beaks" to collect food--if they collect enough to survive and/or reproduce, they and possibly their offspring play the next round. In the subsequent rounds, the food supply changes, putting an adaptive pressure on the population. Learners track how the population changes over time and see possible speciation in progress. This activity is more advanced than the classic bird beak activity in that the different sizes of clips represent birds that are not only adapted to different food, but also have different caloric requirements to survive and reproduce.