Natural Selection is prevalent throughout life science learning standards across K-12 contexts. Additionally, undergraduates who are interested in the fields of biology and education must also be well informed on the topic, as it is foundational to some biology research and necessary to touch upon within elementary and secondary classrooms. This pilot study explores the understanding of undergraduate preservice teachers' understanding of evolution mediated by a simulation called SEPUP, which explains evolution within generations of bird populations. By utilizing this simulation, we were able to identify how students engaged with a simulation to think about natural selection. Through analyzing student artifacts, findings suggest that employing a simulation to teach natural selection afforded students' a positive learning experience which likely could not have been easily achieved otherwise. This work provides recommendations for technology usage (e.g. creating meaningful reflection questions which target content) and development (e.g. ensure simulations provide a clear scope and scale around time) for evolution simulations.