Meeting Abstract

P3.101  Jan. 6  Misunderstanding the Unambiguous: Student Misconceptions in Phylogenetic Systematics BEI, D*; HOESE, WJ; California State University, Fullerton; California State University, Fullerton dbei@fullerton.edu

According to Hennig, one goal of phylogenetic systematics is to express the relationships of all organisms in a form that cannot be misunderstood. Cladograms are unambiguous diagrams of hypothetical relationships among select taxa. Unfortunately interpreting cladograms can be difficult for biology students. We investigated introductory college biology students� understanding of cladograms both before and after instruction. We used open-ended interviews to uncover major trends in conceptual difficulties. Using these interviews we developed a written survey and a directed interview. Before instruction most students had seen cladograms in textbooks, but few students had interpreted them. Several students interpreted a cladogram of vertebrate diversity as a food web diagram. Most students read from left to right at the tips of the diagram, and many students interpreted closeness of relationships by taxon proximity at the tips of the cladogram. Many students labeled the direction of time differently, depending on the style and orientation of the cladogram. After instruction many students shared new misconceptions. These included �ladder� thinking in which extant animals evolve into other extant animals as they progress up the �main branch.� Many students also thought that any given taxon is most closely related to the previous taxon on this �ladder.� In addition, this study shows that many pre-instruction conceptions were unchanged after instruction. Many students still have incorrect ideas about the direction of time on a cladogram, and think proximity at the tips implies closeness of relationships. Addressing both pre and post instruction misconceptions will allow us to teach cladogram interpretation more effectively, and take one step closer to accomplishing Hennig�s goal.