A Role-Playing Exercise That Demonstrates the Process of Evolution by Natural Selection: Caching Squirrels in a World of Pilferers
Riechert, Susan E., Leander, Rachel N., Lenhart, Suzanne M., The American Biology Teacher
We introduce a strategic role-playing exercise that is based on the)act that the strategies animals use in storing food for periods of famine differ in the degree to which the cache is successfully relocated and defended from pilferers. This highly engaging board game offers high school and college students a clear understanding of the process of natural selection.
Key Words: Evolution; quantifying natural selection; role-playing exercise; misconceptions.
The theory of evolution by natural selection provides a unifying framework for understanding and integrating the immense body of knowledge available on biological systems. Thus, the National Research Council (1996) recognized that our students should have a firm grasp of how natural selection functions both in maintaining traits and in leading to change in species over time. Yet this is a difficult concept for the instructor to convey, in particular because many students come in with alternative conceptions of the diversification of life. In fact, college entry tests indicate that the process of evolution by natural selection is misunderstood by the majority of students. Bishop and Anderson (2006), for instance, found that incoming students to a biology course for nonmajors understood only that evolution is a process that leads to gradual change of species over time in response to environmental conditions. A common misconception was the idea that evolution by natural selection is a need-driven adaptive process. Students further lacked understanding of the relationship between natural selection and both trait variation and differential reproductive success in populations.
Readings, lectures, film presentations of examples, discussions, and even debates about evolution are important in setting a foundation for this concept. These are frequently used teaching strategies in high school and college biology courses. However, students have a much higher investment in learning something in which they are actively engaged. The National Academy of Sciences (NAS) recognized this fact in their 1998 guide to teaching about evolution. The activities listed above were referred to as merely setting the stage for developing student understanding. The NAS concluded that actually acting in the play is necessary for students to develop a firm understanding of this difficult topic. In a study that compared rote versus active learning of evolutionary concepts, Nehru and Reilly (2007) found that active learning significantly increased understanding of such natural-selection concepts as differential reproductive success, phenotypic variation, and changes in the distributions of individuals that possess heritable traits over generations. Here, we introduce a role-playing exercise in which students act as squirrels procuring food for times of famine, thus gaining a firm quantitative conception of the process of natural selection and its potential to lead to trait frequency changes within populations.
"Caching Food for Times of Famine" is an exercise presented under a behavior unit of the Biology in a Box project, which provides grade-level-appropriate exercises and permanent materials to school systems throughout Tennessee and, recently, in some school systems in neighboring states. Powerpoint and pdf versions of all exercises as well as materials lists and suggested readings are provided at the project's website (http://biologyinabox.utk. edu). In collaboration with the National Institute for Mathematics and Biological Synthesis (NIMBioS), many of the exercises incorporate math, demonstrating the quantitative nature of biology
* Evolutionary Framework: Caching Food for Times of Famine
This exercise is based on the fact that animals such as birds and squirrels experience a feast-or-famine existence: a relatively short period of food abundance is followed by a long period of food scarcity Many animal species solve this problem by caching food items that are not prone to decay (Figure 1; Smith & Reichman, 1984; Balda & Kamil, 1989, 1992; HadjChikh et al. …