While research on microbiomes has increased rapidly over the last decade, sequencing costs and some course structures (e.g., lecture only, online, and hybrid) have often prevented students from exploring microbiome community data. In this lesson, students have the opportunity to use an online application to analyze one of 17 different microbiome datasets that were collected to determine the effect of different treatments on the microbiome of bean beetles (Callosobruchus maculatus). The lesson begins with a series of presentations on the natural history of bean beetles, the importance of microbiomes, and approaches to community analysis of microbiomes. Students then work individually or in small groups to analyze an assigned or self-selected microbiome dataset. Then, students present the results of their analysis in the form of a written research report or an oral presentation. This lesson is easily adaptable to different course levels and course contexts, providing a wide range of students with the opportunity to explore microbiome datasets.

Primary Image: Female bean beetle (Callosobruchus maculatus) and a recently laid egg on an adzuki bean (Vigna angularis) with images of Petri dishes with bacteria cultured from a homogenate of eggs (left) and the adult bean beetle (right). Photographs taken by Lawrence Blumer.

Phylogenetic trees are branching diagrams that display hypothesized relationships among species, higher taxa, or genes. The term “tree thinking” has been coined to describe the ability to correctly interpret phylogenetic trees. Tree thinking tends to be introduced to biology students during their first-year courses, as phylogenetic trees are prevalent throughout the biological literature. Traditional lectures can be used to introduce students to phylogenetic trees, phylogenetic terminology, and tree thinking. However, without guided, active learning exercises, students may achieve only a shallow understanding of tree-thinking. This active learning exercise was developed to teach students to use a web-based phylogenetics program to build a phylogenetic tree and test a hypothesis about the evolution of toxicity and bright coloration in the Neotropical frog family Dendrobatidae. Dendrobatidae includes the colorful and toxic poison dart frogs and the cryptic and typically nontoxic rocket frogs. In this exercise, students build a phylogenetic tree of the dendrobatid frogs using DNA sequences from GenBank and use the resulting tree to determine if toxicity and bright coloration evolved once or multiple times in the group. Students will also learn about Müllerian and Batesian mimicry as they work through this exercise and find examples of species that display both phenomena.

Primary Image: Dendrobates tinctorius (Dyeing Poison Dart Frog), a toxic frog species from northern South America. Photo by Michael Gäbler, CC BY 3.0.