Humboldt-Universität zu Berlin - Department of Biology


Inga Ubben-Lother, Annette Upmeier zu Belzen

Phylogenetic trees - Models of and for Evolution

Phylogenetic trees serve both as models of existing hypotheses about evolutionary relationships among organisms and as models for the prediction of new hypotheses (Mahr, 2008, 2009; Passmore, Svoboda Gouvea, & Giere, 2014). In the first case, phylogenetic trees are used as a medium whereas in the second case their use is methodical (Gilbert, 1991; Mahr, 2009). According to the framework of model competence (Grünkorn, Upmeier zu Belzen, & Krüger, 2013; Upmeier zu Belzen & Krüger, 2010) handling phylogenetic trees occurs on three different levels: description (level I) and explanation (level II) of phylogenetic trees as medial aspects and the more elaborated use for prediction and inquiry purposes (level III) as methodical aspects. In contrast to science, most phylogenetic trees in German biology textbooks are presented in a medial scenario (Ubben, Nitz, Rousseau, & Upmeier zu Belzen, 2015) neglecting the promotion of students’ model competence on level III (Grünkorn, Upmeier zu Belzen, & Krüger, 2013; Upmeier zu Belzen & Krüger, 2010).
Most students do only use superficial features of phylogenetic trees without understanding the underlying meaning - their representational competence with phylogenetic trees is on a low level (Halverson & Friedrichsen, 2013). Their tree thinking ability, namely interpreting phylogenetic trees and comparing several representations, is poorly developed (Halverson, 2011).
Despite the highly visual character of phylogenetic trees, only one study dealt with their visual perception so far (Novick, Stull, & Catley, 2012). Hence, the present study investigates how participants visually perceive phylogenetic trees and how visual perception and verbal reasoning correspond with each other during tree reading. Furthermore, the model character of phylogenetic trees and their use as a medium and as a method, respectively, lead to the question whether the scenario in which a phylogenetic tree is presented influences visual perception and verbal reasoning. For this purpose we test pre-service biology teachers from Berlin who are about to finish their own studies in order to start teaching at school. Their eye movements (fixations, scan paths) while solving multiple choice items about tree thinking are recorded with eye-tracking technology. Every item is followed by retrospective think aloud to document their justification of how they solved an item (verbal reasoning). In order to investigate the influence of the medial and methodical use of a model, phylogenetic trees are presented either in a medial or methodical scenario. Again eye movements and verbal data are recorded as described. Verbal reasoning is now coded according to the seven levels of representational competence by Halverson and Friedrichsen (2013).
Understanding and dealing with phylogenetic trees as models of and for evolution is inseparably connected to the understanding of evolution (Omland, Cook, & Crisp, 2008). Nevertheless only little is known so far about processing phylogenetic trees. Hence our study will contribute to a better understanding of processes during tree reading with the aim of improving teaching phylogenetic trees.