Phylogenetic Analysis: How Old are the Parts of Your Body?

Abstract

According to the National Academy of Sciences, biology students in the USA are not being adequately prepared for successful futures. Of paramount concern is a lack of sufficient training in quantitative and computational skills, which are needed to compete effectively for an array of educational and occupational opportunities. In this paper, we introduce a classroom exercise that invites students to solve a simple biological problem and illustrates the need for a computer-assisted strategy to arrive at a solution. The exercise invites students to consider the question “How old are the parts of your body?” Some features of the human body are more ancient than others. For example, our bodies have both hair and backbones, but backbones arose much earlier in evolutionary history. Our exercise relies upon MEGA 4.0, a free, visually appealing, and intuitive computer program that allows students to gather DNA or protein sequences from electronic databases, then use them to infer phylogenetic trees. Student-inferred phylogenies are used to explore the relative order in which diverse aspects of the human form evolved. In the process, students are trained to use powerful features of MEGA and encouraged through group discussion to consider additional applications of the technology they have learned. Our lesson plan includes a brief video, a web site with essential terminology and links for further exploration, a hands-on experience using MEGA, and a follow-up discussion.