Abstract:

Xavier University of Louisiana (XULA), a minority serving undergraduate institution based in New Orleans, Louisiana (US), is a nationally recognized leader in science education. To serve all students, faculty work collaboratively to determine the most effective approaches of teaching. In this context, the latest 2025 NAEP (National Assessment of Educational Progress Program) report has highlighted the continuing downward trend of the US high schoolers in reading, science, and mathematical skills, attributed in part to disengagement in learning. To address this urgent problem, instructors of our two freshman level courses have developed experiments to strengthen students’ skills in microscopy, observations, data recording, and performing calculations in a collaborative learning environment.

The first module focused on the compound microscope and usage of hemocytometer to determine the concentrations of stock solutions. Fresh and aged cultures of 3T3 fibroblasts stained with Trypan Blue were used to teach counting and distinguishing between colorless live cells versus blue sick/dying cells with damaged membranes. Students also learned loading samples and performing calculations. Next, students prepared their own fungal spore stock solution and its dilutions. They then worked in pairs to perform the counting and CFU/mL determinations. Comparisons of results showed that there was little variation between any two lab partners within every section, with average number of spores/square between 30-38 and the average concentration being 3.6 million CFU/mL. Students reported enjoying these experiments since they could actually “see” the distributed fungal spores and compare results with others.

In the second module, students were introduced to the stereomicroscope and noted its differences with compound microscopes. For actual experimentation, the nematode worm C. elegans was used. Briefly, instructors crossed wild type worms with a double recessive mutant (dumpy for a short and stubby phenotype and unc, for uncoordinated movement) to obtain heterozygous F1 progeny with wild-type phenotype. The F1 worms (hermaphrodites) were then allowed to self-fertilize to obtain the F2 generation. The main goal of this experiment was for students to place the resulting F2 plates on a transparency sheet circle and record actual numbers of the four possible phenotypes. They worked in pairs to maintain the plates' orientation. The F2 plates were set to obtain a recombination frequency (RF) of ~ 42-44% for both recombinants; Dpy non-Unc (only dumpy) and Unc non-Dpy (only unc). It was clear that students were very engaged and what was remarkable was that every section, the RF fell within half a percentage point with average RF = 43.5% for a total of 3240 worms scored. As instructors, we were overjoyed since these are freshman students who had never worked with C. elegans and without knowing in advance the expected RF values, were able to obtain such excellent results. Students also calculated the map distance, determined that dumpy and unc were linked but not closely linked and did the Chi Square test.

These results support the hypothesis that engaging students in experiments where they observe, count, and analyze their own results positively impacts their learning and helps build their confidence in mathematical and comprehension skills. Additional analysis of assessment data and survey results will be discussed in the presentation.

Keywords:

Curricular reforms, Assessment, Student-learning.