Characterization of the Molecular Mechanisms of Noise Stress on Developmental Plasticity in Gryllus bimaculatus & Co-teaching and Peer-Led Team Learning in Undergraduate Introductory Biology Courses Toward Expanding Participation in STEM for All

Abstract

As part of my training as a Discipline Based Education Researcher (DBER), I gained human subjects educational research experience as well as traditional biology research experience in the laboratory setting. This dissertation explores both my biology education research and traditional developmental biological research. The first and second projects focus on biology education research, examining how Peer-Led Team Learning (PLTL) and modifying introductory biology course instructional design can influence student outcomes in undergraduate Biology education. The third project examines how anthropogenic noise affects the developmental biology of the two-spotted field cricket Gryllus bimaculatus using a genetic approach. Peer-Led Team Learning (PLTL) is an active learning model that has been shown to be beneficial for student learning. Using a longitudinal approach, this study focuses on understanding the trajectory of students over the course of five years to examine the potential long-term effects of PLTL. We assessed the relationship between PLTL participation and student outcomes like earning a C+ or better in introductory biology and graduation rates in any major and STEM specific majors. PLTL participation was associated with a higher likelihood of passing introductory biology with a grade of C+ or better with URM and first-gen status being associated with lower odds. When considering the percentage of students who achieved a C+ or better, both URM and non-URM students who participated in PLTL had significantly higher rates of earning a C+ or better. A performance gap was observed between URM and non-URM students in the non-PLTL groups. A similar relationship was observed in first-generation students, with students who participated in PLTL outperforming their non-PLTL peers with a similar gap in the non-PLTL group. Analysis disaggregated by sex showed that PLTL benefitted both male and female students in a similar manner. Students who completed a STEM degree showed similar trends with performance gains across URM status, sex, and first-generation status. These results suggest that PLTL participation continues to promote positive student outcomes and mitigate structural barriers for success in STEM. We also examined how instructional strategies may influence student learning trajectories. Introductory biology is often seen as a gateway course in which students tend to compartmentalize information for performing well on exams without considering the connection between foundational content and the content of more advanced courses. There also exists a discrepancy between what advanced course instructors expect foundational courses to cover, and student retention of that knowledge. We investigated whether a co-teaching model in the introductory biology course can bridge the divide between these contexts. We involved the instructor for the genetics course in the instruction of genetics content in the introductory classroom, and measured student performance using a course assessment by implementing 20 items that typically appear on exams in the genetics course into the introductory course’s exam. The implemented items directly aligned with the exam objectives of the introductory course. Following a nonequivalent control-group design, one year of introductory biology served as our control group which had the typical instruction with one instructor, with the genetics items implemented. Our treatment group was a population of students in the following year with the genetics instructor teaching the introductory content and genetics items implemented. We used an open-ended survey to measure students’ impression of the experience, opinions on diversity of instructors, and whether they thought including upper division course instructors in introductory biology instruction was a good idea. The results indicated that students who were taught by the genetics instructor improved at a greater rate than their peers in the control group. Students reported positive impressions of the experience, and several mentioned a need for increased diversity in instructor identities. Anthropogenic noise levels are increasing as humans continue to expand their usage of land and natural resources. Noise pollution has been recognized as a source of environmental stress with associations with detrimental health impacts on humans and other organisms. Invertebrates in particular use sound for many biologically relevant processes like mate selection, therefore, increased noise levels may work to impede those processes. We investigated the developmental and genetic impact that roadside noise exposure has on the cricket species Gryllus bimaculatus. Crickets were exposed to 24-hour playbacks of roadside noise or silence in our trials. We compared the developmental timings, body size, and expression profiles of adult crickets from the two experimental treatments. There was a significant decrease in the time to adulthood of crickets exposed to chronic noise stress. We hypothesized that the adult physiological differences were due to differential gene expression patterns as a result of the environmental stimulus of chronic noise. Male and female cricket brains and gonads were dissected and examined to identify any significant differences in gene expression under the experimental conditions. Female brains and male gonads were found to have the highest numbers of differentially expressed genes that included genes like heat shock factor, ryanodine receptors, among other genes involved in cell signaling pathways. GO term enrichment analysis revealed significant enrichment of pathways linked to stress response, energy metabolism, and protein interactions suggesting that noise stress may alter both cellular stress responses but also metabolic processes in a tissue and sex specific manner. Though this dissertation describes three distinct projects, they work together to contribute to our understanding of both biological systems and the systems through which biology is taught and learned by undergraduates