Evolution explains both the unity and the diversity of all organisms, and developing students' ability to represent and communicate evolutionary relationships is an important component of a complete biology education. We present a series of student-centered, exploratory activities to help students develop their tree-thinking skills. In these activities, students use complementary phenotypic and molecular data to explore how to build phylogenetic trees and interpret the evolutionary relationships they represent. This learning module is designed to engage students in the process of science, provide them with active learning experiences using online bioinformatics tools, and foster their appreciation for the evolutionary connections across the tree of life.

A lesson plan on the phylum Tardigrada is presented in a storytelling workbook that introduces the evolutionary concepts of adaptive radiation, speciation, divergence, and “tree-thinking” through narrative, transitional art, contemplative coloring, and data searches, which can be enhanced with microscopy wet labs. Students gain insight into the invertebrate world of the highly adaptable, ubiquitous microorganisms known colloquially as “water bears,” generating a microevolutionary and macroevolutionary perspective through a narrative that includes an introduction to the TimeTree database.

I offer comments on two recent articles in The American Biology Teacher by Davenport and colleagues addressing the interpretation and construction of phylogenetic trees. The “tree-thinking” literature suggests that students need to acquire a clear understanding of the meaning of phylogenetic tree diagrams. To this end, I provide clarifications of terminology and address the problematical status of “ancestors.” Cladograms are not genealogies viewed from a distance, but empirical hypotheses of relationship based on the distribution of shared derived character states. I describe an exercise employed in an introductory systematics course that emphasizes the empirical activities of character delimitation and formation of groups based on those characters.

Evolution is a fundamental principle in biology, yet students, teachers, and the public at large all too often misunderstand the way it works. I introduce a hands-on exercise that emphasizes tree-thinking and phylogenies to organize biodiversity. During the activity, students observe and investigate the patterns and processes of macroevolution by first building unique specimens through gradual, stepwise changes in characters. They then switch specimens with another group and, by observing shared characters, hypothesize the evolutionary relationships of the specimens by drawing phylogenies. The exercise has been used for several years, and pretest–posttest results confirm that it significantly improves student understanding of macroevolution and phylogenetics.