Generating ideas and then testing predictions are important parts of the scientific process. In this laboratory exercise, I begin by challenging students to think about the reasons that the number of species on an island will increase or decrease. In small groups, students discuss how species richness changes over time and how rates of extinction and colonization will change depending on island size, distance from the mainland, and number of species already on the island. Students will make and test predictions using model islands and bean “species” only after they have come up with their own ideas of how species number changes over time and made predictions in the form of a graph. Last, students go outside and test the effect of area on the number of species found on a nonisland “island” (such as a wooded patch between sidewalks). This quick exercise allows students to differentiate between hypotheses and predictions and introduces such terms as sample size and replication while allowing for discussions about when the data don't always match predictions.