An interdisciplinary course on evolution and sustainability increases acceptance of evolutionary theory and increases understanding of interdisciplinary application of evolutionary theory.

Background: Although evolutionary theory is foundational and integrative in modern biology, there remains widespread lack of acceptance among U.S. residents. An interdisciplinary approach to teaching evolutionary theory at the undergraduate level has many advantages, such as giving students a context for learning about evolution and application of evolutionary theory to other academic disciplines and everyday life. While there are foundational examples of interdisciplinary approaches to teaching evolutionary theory, there are few examples of courses with application of evolutionary theory to issues of sustainability, such as conservation or global climate change. We build on the practical and theoretical work of others to create an interdisciplinary course on evolutionary theory for non-science majors, with ties to sustainability. Our course is taught in three modules, with extensive readings and hands-on lab activities. The first module is focused on honey bee biology, with hands-on beekeeping experiences; the second module on native plants and community education on sustainability; and the third module on the evolution of the subjective human experience of free will. Results: We found that students in our course experienced an increased acceptance of evolutionary theory. We found that students also met the course leaning objectives, of basic knowledge of evolutionary theory and application of evolutionary theory to other disciplines, assessed through group and individual major assignments. We also found that students had an expanded perspective on interdisciplinary application of evolutionary theory, assessed through closed-ended survey questions and analysis of open-ended writing. Conclusions: Students in our course experienced an increase of acceptance of evolutionary theory and an expanded perspective on interdisciplinary application of evolutionary theory, despite the fact that many students were not science majors. Supplementary Information: The online version contains supplementary material available at 10.1186/s12052-023-00188-4.

An Active Learning Intervention Based on Evaluating Alternative Hypotheses Increases Scientific Literacy of Controlled Experiments in Introductory Biology.

Scientific education provides a set of tools to make sense of a complex world by teasing out complicated cause-and-effect relationships, such as the elimination of effects of confounding factors in controlled experiments. There is evidence that depth of understanding of controlled experiments is lacking among undergraduate science students despite exposure to controlled experiments in courses. To examine the understanding of controlled experiments, we developed a two-tiered assessment that includes closed-ended and open-ended questions, with three types of questions, i.e., (i) a scientific scenario about a flawed drug study, (ii) an everyday-life scenario about flawed thinking regarding product effectiveness, and (iii) a direct question about explaining controlled experiments. Consistent with previous findings, we demonstrated that large percentages of students in introductory biology courses at both a research-intensive institution and a primarily undergraduate, minority-serving institution failed to recognize the need to account for confounds. Based on these findings, we tested the hypothesis that scientific literacy could be improved through a course-based intervention using an active learning framework focused on science as a process of evaluating alternative hypotheses. We found start-to-end-of-semester improvement in students' identification of unaccounted confounds with a scientific scenario in an intervention course but not in the control course. Interestingly, students in both the control and intervention courses showed improvement when tested with a scenario based on everyday life. The study findings suggest that a concerning number of college students may not account sufficiently for uncontrolled variables in real-life situations, and we present a widely applicable instructional strategy that improves on this broadly relevant scientific reasoning skill.

Complex and non-redundant signals from individual odor receptors that underlie chemotaxis behavior in Drosophila melanogaster larvae.

The rules by which odor receptors encode odors and allow behavior are still largely unexplored. Although large data sets of electrophysiological responses of receptors to odors have been generated, few hypotheses have been tested with behavioral assays. We use a data set on odor responses of Drosophila larval odor receptors coupled with chemotaxis behavioral assays to examine rules of odor coding. Using mutants of odor receptors, we have found that odor receptors with similar electrophysiological responses to odors across concentrations play non-redundant roles in odor coding at specific odor concentrations. We have also found that high affinity receptors for odors determine behavioral response thresholds, but the rules for determining peak behavioral responses are more complex. While receptor mutants typically show loss of attraction to odors, some receptor mutants result in increased attraction at specific odor concentrations. The odor receptor mutants were rescued using transgenic expression of odor receptors, validating assignment of phenotypes to the alleles. Vapor pressures alone cannot fully explain behavior in our assay. Finally, some odors that did not elicit strong electrophysiological responses are associated with behavioral phenotypes upon examination of odor receptor mutants. This result is consistent with the role of sensory neurons in lateral inhibition via local interneurons in the antennal lobe. Taken together, our results suggest a complexity of odor coding rules even in a simple olfactory sensory system.

Translation of sensory input into behavioral output via an olfactory system.

We investigate the logic by which sensory input is translated into behavioral output. First we provide a functional analysis of the entire odor receptor repertoire of an olfactory system. We construct tuning curves for the 21 functional odor receptors of the Drosophila larva and show that they sharpen at lower odor doses. We construct a 21-dimensional odor space from the responses of the receptors and find that the distance between two odors correlates with the extent to which one odor masks the other. Mutational analysis shows that different receptors mediate the responses to different concentrations of an odorant. The summed response of the entire receptor repertoire correlates with the strength of the behavioral response. The activity of a small number of receptors is a surprisingly powerful predictor of behavior. Odors that inhibit more receptors are more likely to be repellents. Odor space is largely conserved between two dissimilar olfactory systems.

Membrane topology of the Drosophila OR83b odorant receptor.

By analogy to mammals, odorant receptors (ORs) in insects, such as Drosophila melanogaster, have long been thought to belong to the G-protein coupled receptor (GPCR) superfamily. However, recent work has cast doubt on this assumption and has tentatively suggested an inverted topology compared to the canonical N(out) - C(in) 7 transmembrane (TM) GPCR topology, at least for some Drosophila ORs. Here, we report a detailed topology mapping of the Drosophila OR83b receptor using engineered glycosylation sites as topology markers. Our results are inconsistent with a classical GPCR topology and show that OR83b has an intracellular N-terminus, an extracellular C-terminus, and 7TM helices.

The molecular basis of odor coding in the Drosophila larva.

We have analyzed the molecular basis of odor coding in the Drosophila larva. A subset of Or genes is found to be expressed in larval olfactory receptor neurons (ORNs). Using an in vivo expression system and electrophysiology, we demonstrate that these genes encode functional odor receptors and determine their response spectra with 27 odors. The receptors vary in their breadth of tuning, exhibit both excitation and inhibition, and show different onset and termination kinetics. An individual receptor appears to transmit signals via a single ORN to a single glomerulus in the larval antennal lobe. We provide a spatial map of odor information in the larval brain and find that ORNs with related functional specificity map to related spatial positions. The results show how one family of receptors underlies odor coding in two markedly different olfactory systems; they also provide a molecular mechanism to explain longstanding observations of larval odor discrimination.