Teaching undergraduate students to draw phylogenetic trees: performance measures and partial successes

Abstract

Abstract Background An in-depth understanding of the process and products of evolution is an essential part of a complete biology education. Phylogenetic trees are a very important tool for understanding evolution and presenting evolutionary data. Previous work by others has shown that undergraduate students have difficulty reading and interpreting phylogenetic trees. However, little is known about students’ ability to construct phylogenetic trees. Methods This study explores the ability of 160 introductory-level biology undergraduates to draw a correct phylogenetic tree of 20 familiar organisms before, during and after a General Biology course that included several lectures and laboratory activities addressing evolution, phylogeny and ‘tree thinking’. Students’ diagrams were assessed for the presence or absence of important structural features of a phylogenetic tree: connection of all organisms, extant taxa at branch termini, a single common ancestor, branching form, and hierarchical structure. Diagrams were also scored for how accurately they represented the evolutionary relationships of the organisms involved; this included separating major animal groups and particular classification misconceptions. Results Our analyses found significant improvement in the students’ ability to construct trees that were structured properly, however, there was essentially no improvement in their ability to accurately portray the evolutionary relationships between the 20 organisms. Students were also asked to describe their rationale for building the tree as they did; we observed only a small effect on this of the curriculum we describe. Conclusions Our results provide a measure, a benchmark, and a challenge for the development of effective curricula in this very important part of biology.