This unit aims to help students understand how How natural selection can lead microevolution and results in populations that are better adapted to their environment. Students will first play like a bird that eat moths. Two phenotypes of moths are presented, and it is likely that students will eat mostly visible moths and therefore create a selective pressure. Then, students are guided to calculate allele frequencies based on the data they generated as birds that eat moths. Since the data are generated by students themselves, students are tend to have high motivations to find out what are the allele frequencies under the selective pressure they created. These calculations become more meaningful to students. This unit is one of the three topics under "Evolution > Natural Selection": http://ats.doit.wisc.edu/biology/ev/ns/ns.htm