This worksheet is designed to accompany an activity through www.pbs.org. The link needed is included on the sheet. The materials needed for use are able to be printed from the PBS site, thus the activity can be used by teachers without student computer access. It is a great intro activity for an evolution unit. To be clear, PBS designed the activity. This is just a student sheet to accompany the activity, as there was not one available on the PBS site. I have also included a description of how I use this activity in my classroom, along with general pacing recommendations.