Biological Sciences Undergraduate Works
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- ItemOpen AccessHerbivory resistance to generalist feeder Trichoplusia ni of faba bean (Vicia faba) exposed to salinity stress(2025-03) Lavallée-Shrupka, Caleb; John Markham (Biological Sciences); Kevin Fraser (Biological Sciences); Renault, Sylvie; Avila-Sakar, GermanPlants are often exposed to multiple stress factors simultaneously. Exposure to one stress can exacerbate or mitigate the response to a subsequent stress. While salinity and herbivory can impair growth and physiological function individually, their combined effects remain poorly understood. To investigate this interaction and determine if salt tolerance influences resistance to herbivory, Vicia faba (cv. Broad Windsor) plants were grown under salinity (0, 50, 75, 100 mM NaCl) and exposed to cabbage looper (Trichoplusia ni) herbivory. Gas exchange parameters (photosynthesis, stomatal conductance, transpiration) were not significantly affected by salinity after 11 days of treatment. After 20 days, salinity did not affect plant height, stem biomass or water content of most tissues but significantly reduced root and lateral leaf biomass. Total phenolic compounds and total soluble proteins in the leaves were also unchanged. Elemental analysis revealed that salinity significantly increased Na and Cl concentrations in all three tissue types (leaves, stems, and roots), with the highest accumulation in roots. Salinity significantly increased the concentrations of macronutrients (N, P, K, Ca, and Mg) and micronutrients (Fe, Mn, Cu, Zn, and Mo) in the leaves, suggesting efficient nutrient retention in photosynthetically active tissues. Constitutive resistance to herbivory was not significantly affected by salinity. However, induced resistance was significantly impaired in salt-treated plants. Together, these findings indicate that V. faba exhibits moderate tolerance to salinity, maintaining gas exchange and nutrient homeostasis under salt stress while minimizing growth impairments. The compromised induced resistance highlights the vulnerability of inducible defenses and suggests that salinity may force a tradeoff between preserving physiological function and sustaining inducible defences against herbivory. These results emphasize the importance of considering stress interactions when evaluating plant defence.
- ItemOpen AccessAcute effects of quinoline and 2-methylquinoline on electrical activity of great pond snail (Lymnaea stagnalis) neurons(2025-04) Tramley, Cameron; Tomy, Gregg (Chemistry); Markham, John (Biological Sciences); Fry, MarkPolycyclic aromatic compounds (PAC) are organic compounds found ubiquitously in the environment and originate naturally or anthropogenically. They are persistent, bioaccumulative, and toxic (PBT). PACs have been found to modulate voltage gated ion channels in fish cardiomyocytes. Many studies have examined PACs effects, however, there is growing concern about a less studied class of PACs: hetero-polycyclic aromatic compounds (HPACs). Quinoline and its derivative 2-methylquinoline are two-ringed HPACs found in high concentrations in sediment and tissues of fishes from the Great Lakes. Studies investigating synthetic quinoline derivatives used in the pharmaceutical industry have shown HPACs modulate voltage gated sodium, calcium and potassium ion channels in cardiomyocytes of fishes and mollusk neurons. We therefore designed a study investigating the acute neurobiological effects of quinoline and 2-methylquinoline on Great Pond Snail (Lymnaea stagnalis) neurons, a model with a large easily accessible central nervous system and well conserved ion channels. Electrophysiological characteristics were measured by performing suction electrode experiments on the right internal nerve of the right parietal Lymnaea stagnalis ganglion. Extracellular recordings before and after application of various quinoline or 2-methylquinoline concentrations were used to determine the frequency of right parietal nerve activity which we normalized as percent of control. The extracellular recordings revealed that quinoline affects right parietal nerve activity in a dose dependent manner. Quinoline caused a statistically significant effect on right parietal nerve activity at 1000 nM, but not 100 nM, and 10 nM, with mean percent of control values being 89.2 ± 4.3%, 103.9 ± 4.6% and 99.9 ± 3.5% respectively. 2-Methylquinoline had no statistically significant effect on right parietal nerve activity at 1000 nM. These experiments highlight the importance of understanding the neurobiological effect of PBT environmental contaminants quinoline and 2-methylquinoline, as well as demonstrate the utility of suction electrode recordings as an electrophysiology technique to evaluate acute neurotoxicity of environmental contaminants.
- ItemOpen AccessEvaluating Nitrogen Utilization Strategies in Chlamydomonas reinhardtii(2025-04) Tibule, Miku; Doering, Jennifer (Biological Sciences); Markham, John (Biological Sciences); Lee, Jae-HyeokNitrogen (N) is a common, yet essential macronutrient required for nucleic acid and amino acid synthesis for cell growth and biomass of photosynthetic eukaryotes which includes algae and plants. Understanding how organisms strategically use N for growth will allow development of economical use of N fertilizer being invested into croplands, which in return mitigates anthropogenic contribution to environmental pollution. This honours thesis explores N-use strategies by examining the N-sensing mechanisms within Chlamydomonas reinhardtii to investigate its necessity for optimal growth under N-limited and N-repleted conditions through comparative growth within individual N source provision of NH4Cl, KNO3, and urea. Using photobioreactor and nitrogen quantification experiments, I obtained biomass productivity data and residual N within the cultures, which allowed for an understanding of algal growth under various N-source concentration conditions. Through a comprehensive data analysis of growth biomass OD and residual N concentrations, my study uncovered that there is a regulatory mechanism of C. reinhardtii that allows for a reduction in N consumption rate under extreme N limitation stress, which in turn allows the algae to shift its metabolic priorities to internal N-use. These insights contribute to the existing literature by highlighting the significance of the N-sensing mechanism within C. reinhardtii, for N-use strategies, discovering a temporal switch in metabolic function, and offering potential further investigations into how the algae prioritize cellular N contents for growth and cellular division. Ultimately, this study provides a deeper understanding of N assimilation and cellular use, paving the way for future research and developments in the field.
- ItemOpen AccessRegulation of gene expression by growth differentiation factor 15 in the developing mouse and human neocortex(2025-04) Mohamad, Ruby; Docker, Margaret (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Xing, LeiThe evolution of the neocortex, specifically its expansion, is the key advancement that made higher cognitive abilities possible. Humans today have a neocortex that constitutes up to two-thirds of their overall brain mass. This expansion reflects increased and prolonged activity of neural progenitor cells (NPCs), which give birth to neurons during fetal cortical development. Growth differentiation factor 15 (GDF15) is a cell-extrinsic signal that has previously been found to promote basal progenitor proliferation, one of the main classes of NPCs critical to human brain development and evolution. Previously, the Xing Lab discovered several potential downstream targets that could be regulated by GDF15 in the fetal human neocortex, including Dachshund Family Transcription Factor 1 (DACH1), Glypican 6 (GPC6), Semaphorin 5A (SEMA5A), and Shroom Family Member 3 (SHROOM3). All of which have been reported to have various roles in neurodevelopment. In this study, we manipulated GDF15 levels in the developing mouse and human neocortex to understand its regulatory effect on the potential downstream targets. My range-finding experiment indicated a concentration-dependent increase in mRNA levels of the downstream targets, with the most increase observed in fetal human neocortical tissue incubated with 100ng/ml recombinant human GDF15 protein. Knockout of the GDF15 gene in embryonic mice revealed decreased mRNA levels of all the downstream targets. Furthermore, adult GDF15 knockout transgenic mice exhibited a decrease in interneuron and deep-layer neuron numbers. My findings are consistent with the notion that GDF15 regulates NPC proliferation through these downstream targets, contributing to long-term effects on neuron abundance in the adult brain.
- ItemOpen AccessMeasuring the Active Learning Gains of Students In Undergraduate Biology Labs Using Peer Review(2025-03) Bantel, Joseph; Joy Stacey (Biological Sciences); Tamara Kelly (York University); Debets, CassandraThe peer-review process allows students to engage in the valuable exercise of critically thinking about how they generate and judge the validity of an idea. This is a cornerstone of the scientific community and a core component of biological sciences. Some students in undergraduate studies routinely underperform in the traditional educational experience and benefit greatly from active learning. In a first-year introductory biological science course at the University of Manitoba, I studied the population by using an online peer-review platform called Peerceptiv to study the standardized learning gains of different demographic groups of students to determine if any subgroups experienced a disproportional benefit in this learning exercise compared to any others. I hypothesized that peer-to-peer feedback on scientific graphing would raise the measurable graded assignment scores of URM students in undergraduate biological science, and therefore predicted that there would be no significant difference between URM and non-URM students' graded performance after peer-to-peer input. Students in certain groups did have higher learning gains over the course of the semester when averaged however, these results were not significantly different from the rest of the population. Overall, the reception of the exercise was very positive in student perceptions with 79% of respondents saying that it helped them understand the concepts they learned about. The strongest response was from students saying that getting reviews of their work was the most useful, with 87%. Ultimately, this study shows that students learn from the peer review process and have learning gains associated with it however, additional testing is necessary to definitively say which groups may or may not benefit the most from this activity.