Ethology—the study of animal behavior—combines the observational skills of a natural historian with modern insights from ecologists, geneticists, and especially evolutionary biologists. In this unit, students discover more of the behavior repertoire of betta fish by observing their responses to several stimuli. Based on students' observations they will describe the bettas' world as they sense it, and within that context explain the evolutionary basis for their behaviors. After completing the exercise, students will have the opportunity to develop and carry out an experiment that explores some other aspect of behavior in greater detail.