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Item Student Interpretations of Phylogenetic Trees in an Introductory Biology Course(North Dakota State University, 2013) Dees, Jonathan AndrewPhylogenetic trees are a common visual representation in biology, and the most important visual representation used in evolutionary biology. Thus, phylogenetic trees have also become an important component of biology education. We sought to determine what forms of reasoning are utilized by introductory biology students to interpret taxa relatedness on phylogenetic trees, what percentage of students correctly interpret taxa relatedness, and how these results alter in response to instruction and over time. Our students demonstrated a tendency for counting synapomorphies and nodes, rather than more common misinterpretations found in current literature. Students also struggled mightily with correctly interpreting phylogenetic trees, including many who exhibited memorization of correct reasoning. Broad initial instruction achieved little for phylogenetic tree understanding. More targeted instruction on evolutionary relationships improved understanding, but to a still unacceptable level. It appears these visual representations, which can directly affect student understanding of evolution, represent a formidable challenge for instructors.Item Effects of Phylogenetic Tree Style on Student Comprehension(North Dakota State University, 2017) Dees, Jonathan AndrewPhylogenetic trees are powerful tools of evolutionary biology that have become prominent across the life sciences. Consequently, learning to interpret and reason from phylogenetic trees is now an essential component of biology education. However, students often struggle to understand these diagrams, even after explicit instruction. One factor that has been observed to affect student understanding of phylogenetic trees is style (i.e., diagonal or bracket). The goal of this dissertation research was to systematically explore effects of style on student interpretations and construction of phylogenetic trees in the context of an introductory biology course. Before instruction, students were significantly more accurate with bracket phylogenetic trees for a variety of interpretation and construction tasks. Explicit instruction that balanced the use of diagonal and bracket phylogenetic trees mitigated some, but not all, style effects. After instruction, students were significantly more accurate for interpretation tasks involving taxa relatedness and construction exercises when using the bracket style. Based on this dissertation research and prior studies on style effects, I advocate for introductory biology instructors to use only the bracket style. Future research should examine causes of style effects and variables other than style to inform the development of research-based instruction that best supports student understanding of phylogenetic trees.