NDSU Repository

Search Results

Now showing 1 - 10 of 20

Curriculum design and assessment: the development of a nonmajor biology course-based undergraduate research experiences and its effects on students and instructors
(North Dakota State University, 2024) Falkner, William
The goals of nonmajor science education are to improve scientific literacy and produce pro-science attitudes. Together, these goals are expected to improve an individual’s ability to make evidence-based decisions based on newer understandings of the natural world as well as developing technologies. In a post-COVID-19 world, public understanding of science was brought to the forefront for public health but were also challenged by a deluge of misinformation to obfuscate these goals. General education science courses represent the last formal experience for our populace. Following a learning-science-by-doing-science approach, this dissertation describes the development, implementation, and assessment of a course-based undergraduate research experience (CURE) for nonmajor science students. The first objective of this dissertation was to review the outcomes and design elements of published CUREs. Through a systematic review of Biology-based CURE literature, several content, skill, and affective-based outcomes are identified resulting from eight proposed design elements. The second objective was to outline and highlight the decision-making process when designing a CURE for nonmajors. Here, historical perspectives on course design, both general and science-specific, are described and applied along with findings from the first objective to design a CURE for nonmajor biology students. The third objective was to survey graduate teaching assistants (GTAs) that instructed this nonmajor CURE to identify GTA benefits and challenges. Findings indicate that GTAs found CUREs to be beneficial to their current and future works and strongly believed this type of approach to nonmajor education is preferable to expository lab design. The final objective was to assess student scientific literacy and science attitudes after engaging with a CURE. Based on two surveys using a pre/post design, there were no significant differences between different laboratory course designs for neither literacy nor attitudes and only found some support between the association of scientific literacy and science attitudes. This dissertation demonstrates the complexity of cradle-to-grave course design, the difficulty in measuring large constructs such as scientific literacy and science attitudes, and implications for future evidence-based course design.
An Investigation of Student Understanding and Acceptance of Evolution
(North Dakota State University, 2021) Harding, Rachel Leigh Salter
Evolution is central to biology education and yet, it is often one of the most misunderstood and controversial topics that biology educators must teach. Research spanning the last four decades has shown that students continue to struggle, even with direct instruction, to understand the process of evolution by natural selection. In my first chapter, I found that students enrolled in non-majors geology course did not increase in their understanding of evolution, even after instruction. This followed similar findings from research occurring over 30 years in the past. Discipline-based education researchers have theorized that students’ persistent difficulties understanding evolution may stem from the conceptual challenges inherent to complex biological systems. To meet the needs of biology instructors, I developed a new teaching tool, a rapid response rubric (3R: Evolution), to provide more opportunities for formative assessment and feedback in large-enrollment courses. I found the 3R: Evolution provided direct and actionable feedback, allowing students to modify their understanding of evolution in large-enrollment courses and exhibit large increases in their knowledge from pre- to post-assessment. However, knowledge of evolution is not the only challenge to biology education: students must also accept evolution. A lack of evolution acceptance can emerge from various social, cultural, and epistemological factors including religiosity and regional impacts, knowledge of the nature of science, openness to experience, and evolution exposure. In this work, I present a path analysis to illuminate the direct causal relationships from these individual factors to evolution acceptance. I found that while religiosity was the largest casual predictor of acceptance, the other chosen factors, including knowledge of evolution, were all significant predictors of evolution acceptance. Even though evolution remains a difficult topic, this work shows that students can increase both their understanding and acceptance of evolution, using new curriculum and increasing exposure to evolution content across their school career.
Physiological Mechanisms Underpinning Growth and Aging in Wild Birds
(North Dakota State University, 2019) Sirman, Aubrey Erin
Life-history trade-offs have been well-documented within the literature through correlational and experimental studies. However, the physiological mechanisms underlying these trade-offs are less understood. Currently, there is great interest in shared mechanisms, specifically endocrine mechanisms, that might underlie the variation in life-history traits. Insulin-like growth factor-1 (IGF-1) may be one shared mechanism that is particularly important. IGF-1 is a metabolic hormone that is part of a highly conserved insulin-signaling pathway known to influence multiple life-history traits including growth and longevity across taxa, however, little is known about these trade-offs outside of laboratory populations. This dissertation focuses on the role of IGF-1 as a hormonal mechanism underlying the life-history trade-off between growth and aging in wild birds. While the causes of aging are not fully understood, telomere dynamics (length and change in length) are a potentially important mechanism underlying lifespan. To investigate the role of IGF-1 as a hormonal mechanism underlying the life-history trade-off between growth and aging in Franklin’s gulls (Leucophaeus pipixcan) and house sparrows (Passer domesticus). In Franklin’s gulls, dietary restriction reduced growth rate and IGF-1 levels but did not impact telomere dynamics. However, there was a significant negative correlation between IGF-1 levels and telomere length at the end of the post-natal growth period. In house sparrows, we found that nestling growth rates varied with respect to year, but IGF-1 levels did not. Telomere dynamics were not related to growth rates or IGF-1 levels, suggesting that during post-natal growth nestlings may be able to mitigate or even delay costs to later life stages. Finally, when exogenous IGF-1 was administered to house sparrow nestlings during the post-natal growth period, nestling growth was impacted but only in some years. Exogenous IGF-1 increased growth and final mass in 2016 and final mass in 2018. There was a trend suggesting experimental birds had shorter telomeres in 2016. Similarly, in 2018, experimental birds had significantly shorter telomeres than control birds. These effects were not observed in 2017, suggesting that trade-offs between growth an aging might only be visible under certain environmental conditions, which may vary with respect to year.
Alignment of Genetic Variation, Plasticity, and Selection, and the Effects of Cost of Plasticity
(North Dakota State University, 2021) Berdal, Monica Anderson
Phenotypic expression depends on both the underlying genetics and the environment the phenotype is expressed in, i.e., plasticity. Adaptive theory predicts that selection should align with the dimensions of most genetic variation and plasticity because this will increase the evolutionary rate of a population, meaning that a population would reach its fitness optimum faster than if they were misaligned. Alignment with selection is only predicted if there is directional selection, and not under stabilizing selection. In addition, only adaptive plasticity is predicted to align with both selection and genetic variation, with the proportion of the plastic variation consisting of adaptive plasticity determining how well aligned plasticity should be. In the first chapter of this dissertation, I outline the evolutionary consequences of the relationship between selection, genetic variation, and plasticity, as well as what the predictions are for their alignments and how to estimate them. In my second chapter I empirically test the alignment between selection, among- and within-individual variation (used as proxies for genetic variation and plasticity respectively) for three behaviors in a wild population of deer mice (Peromyscus maniculatus). I found that selection, among- and within-individual variation were all misaligned, and that there was very little variation in all three behaviors. This could indicate that the behaviors have already reached their fitness optimum due to previous selection pressure. Consequently, this population might not be able to adapt to environmental change. In my last chapter I investigate the cost of plasticity in response to a predatory cue on reproductive outputs in isogenic lines of the banded cricket (Gryllodes sigillatus). Plasticity is assumed to have associated costs which would affect its alignment with selection and genetic variation. I found no evidence for cost of plasticity in G. sigillatus, and in addition there was no genetic variation in plasticity among the lines. Again, previous selection might drive the population’s mean plasticity to its fitness optimum, reducing the variation and the costs of plasticity, making it harder to detect.
Evidence of Climate Niche Creation in the Northern Great Plains: The History of Invasion, Population Genetics, Competitive Effect, and Long-Term Trends of Invasive Poa Pratensis L.
(North Dakota State University, 2016) Dennhardt, Lauren Alexsandra
Understanding the mechanisms of invasion is critical in order to control an invasive species. Poa pratensis L. (Kentucky bluegrass) is an invasive species that has been present in the northern Great Plains (NGP) for over 100 years, but has become a dominant species in the mixed grass region recently. My dissertation seeks to answer one critical question—why has P. pratensis become such a successful invasive species in the NGP? I first asked if the invasion was caused by adaptation and/or propagule pressure. I screened the genetic fingerprint of invasive P. pratensis in the NGP along with measuring the genomic content of wild plants and compared them to common cultivars. I found virtually no overlap between lawn cultivars and invasive P. pratensis populations. This was further supported by a narrow range of genomic content in wild individuals compared to the lawn cultivars. I also found no evidence of geographical patterning which is consistent with the hypothesis that local adaptation is not pervasive in P. pratensis. I then asked whether P. pratensis was a strong competitor compared to dominant plant species native to the tallgrass prairie. I studied competitive effect between Poa pratensis, Nassella viridula, Pascopyrum smithii, and Bouteloua gracilis through a species-pair competition experiment. Based on the relative interaction indices, P. smithii and P. pratensis were competitive against B. gracilis, and P. smithii was competitive against N. viridula. Additionally, P. pratensis was facilitated by all three species in the experiment. This study indicates that P. pratensis may be somewhat competitive. Finally, I asked whether the increase in the frequency of P. pratensis in the NGP may be attributed to environmental factors. In order to understand long-term correlations between P. pratensis invasion and environmental variables, I resampled plots that were previously sampled for species composition in 1978, 1979, and 1999. I found that P. pratensis levels did increase across plots and was corrrelated with higher levels of precipitation. My research indicates that increased precipitation in the NGP as a result of climate change is correlated with P. pratensis invasion in the NGP.
Short- and Long-Term Effects of Environmental Variability on the Ecophysiology of a Solitary Bee
(North Dakota State University, 2022) Earls, Kayla
Environments can vary across seasons. One characteristic of spring in temperate regions is fluctuations in temperature. Sudden bouts of low temperature can have lasting effects on ectotherms that rely on ambient temperature. For developing insects, being unable to avoid or manage these low temperatures puts them further at risk. For example, Megachile rotundata undergo active development in the spring. Exposure to low temperatures as pupae for short periods does not decrease survival but does affect adult morphology. Pollination services may also be affected if temperatures are too low to promote flight in adults. The overall question is what are the short- and long-term physiological effects of temperature in pupae and adults? The first objective of this dissertation is to investigate the long-term effects of low temperature stress by measuring flight performance, reproductive output, and offspring characteristics. After receiving a constant low temperature for a week, females were less likely to nest and changed their offspring investment. Additionally, offspring of bees exposed to fluctuating low temperature stress were more likely to enter diapause despite being early in the season. The second objective was to test if oxygen consumption across temperatures generated a thermal performance curve as a short-term effect in M. rotundata pupae. Results indicate that oxygen consumption scales non-linearly like a thermal performance curve; however, the negative slope at high temperatures was not observed. The third objective was to determine how microclimate conditions affect flight initiation in M. rotundata adults. Two different activity boxes were designed to measure environmental variables and to manipulate cavity temperature. The first activity box measured several environmental variables and showed that even at very close proximities, M. rotundata experience different temperature conditions. In the other activity box design, internal cavity temperature was manipulated to increase early in the morning. Results show that increasing the cavity temperature promoted earlier flight and at lower ambient temperatures. This dissertation shows that the life stage an insect experiences a thermal stress can affect short- and long-term effects on physiology and life history in M. rotundata.
Low Temperature Stress in the Alfalfa Leafcutting Bee, Megachile Rotundata
(North Dakota State University, 2017) Torson, Alex S.
Dramatic changes in ambient temperature can have a significant impact on insect physiology throughout development. The accumulations of the deleterious physiological effects throughout low temperature exposure are collectively known as chill injury. The mechanisms underpinning the downstream physiological consequences of chill injury such as oxidative stress, perturbations in ion homeostasis, and changes in metabolism have yet to be elucidated. Brief, daily pulses of increased temperatures have been shown to repair and/or protect against the continued accumulation of chill injury, leading to an increase in survival across several insect taxa. Until recently, no transcriptomic-level assessments of gene expression during low temperature stress had been conducted. In this document I present a comparison of low-temperature stress response mechanisms across life stages in the alfalfa leafcutting bee, Megachile rotundata. RNA-seq, qPCR and oxidative stress assays were used to determine the physiological effects of low temperature exposure on two life stages: one adapted for low-temperature exposure and one that is not. Differential expression analysis revealed distinct gene expression profiles between life stages. The lack of overlap in expression profiles suggests different mechanisms are driving the response. Furthermore, an overlap in the functional classes of differentially expressed transcripts suggest that the response may be physiologically robust, even though the response is variable at the level of gene expression. Gene expression suggests oxidative stress may be a critical component in chill injury response and recovery. Antioxidant activity and lipid peroxidation, a common proxy for oxidative stress, were assessed in both life stages. M. rotundata’s ability to cope with an induced oxidative stress did not vary between treatments in either life stage. Furthermore, a lack of statistical differences between treatments in lipid peroxidative do not support the hypothesis that the benefits of fluctuating temperatures are, in part, due to reduction in oxidative stress.
The Influence of Body Size on Metabolic Rates, Scaling, Telomere Dynamics, and Metamorphosis in Megachilid Bees
(North Dakota State University, 2021) Grula, Courtney Corinne
Body size is related to many aspects of a bee’s life history including foraging distance and pollination efficiency. Megachile rotundata, and Osmia lignaria are agriculturally important, solitary pollinators. Adult body size in solitary bees is variable because it is determined by the quantity of food available to the developing larva. The goal of this dissertation was to determine the effect of body size on metabolic rates, scaling, telomere dynamics, and entry into metamorphosis. Body size was manipulated under laboratory conditions by manipulating the amount of food provided during the final larval stage. First, I tested the effect of body size on allometry and amount of energy produced, measured indirectly through CO2 emission. The power required during flight was predicted using biomechanical formulas. I found larger bees had higher absolute metabolic rates at rest and during flight. Smaller bees had higher mass-specific metabolic rates at rest, but not during flight. As bees increased in size, their thorax and abdomens became disproportionately larger, while wings became disproportionately smaller. Smaller bees had more power available during flight as demonstrated by flight biomechanical formulas. Next, I measured telomere length in M. rotundata and O. lignaria throughout development. I also measured telomere length across a variety of body sizes, and life stages in both bee species, and found that body size does not affect telomere length. I found that telomere length increases in later life stages in both bee species. Lastly, I determined the cue for metamorphosis in M. rotundata by determining the critical weight. Entry into metamorphosis involves the insect’s ability to monitor its size. I found the cue for metamorphosis in M. rotundata is a critical weight which is influenced by nutritional condition. This was confirmed by declines in Juvenile Hormone titers, and upregulation of genes involved in metamorphic molts. This study found smaller-sized bees are not always at a disadvantage. Smaller bees had increased flight performance based on flight biomechanical formulas, did not show differences in telomere length based on body size, and enter metamorphosis at small sizes. Advantages to small body size may be a response to declines in resource availability.
Examination of Age at Death Methods and the Effects on Estimation Accuracy when Applied to Computed Tomography Scans and Virtual Models of Mummies
(North Dakota State University, 2015) Schanandore, James
Three-dimensional (3D) medical imaging provides a method to non-invasively examine the sub-surface structures of a mummified body, particularly the skeleton. The unique nature of both natural and anthropogenic mummification processes causes inconsistencies for estimating accurate age at death for a particular mummy or group of mummies. These inaccuracies are compounded when age at death methods are used in relation to 3D virtual models. There is a need for the examination of methods being used in mummy case studies and how they are being applied to the 3D virtual models. My research encompassed three studies that addressed the relationship of and the variability when estimating age at death of mummies using radiological imaging. In one study, 146 published case studies were examined for which methods were used to estimate age at death. This study found that articles often provided an assessment of age, but many failed to specify the methods used to calculate the estimated age, and if specified methods were limited to certain areas of the body. In a second study, a cohort of age at death methods was applied to a sample of 17 adult mummies and it was determined that some methods do not transpose well and consequently provided inaccurate age at death estimations when applied to 3D virtual models. Modifications to traditional osteological approaches for age estimation were sometimes necessary due to the presence of soft tissue and post-mortem changes to the body. This study proposes that more methods are needed that utilize the tools available for radiological images in order to limit the variability of transposing a traditional age at death method to virtual 3D models. In the third study, the rim height of the auricular surface was measured using computed tomography scans of 97 living or recently deceased individuals’. These measurements targeted areas around the edge of the surface, for example the height of the apex above the surface. The rim height above the surface produced models that can accurately predict age at death.
Developmental Effects on Immunity: Hormonal and Proteinase Control
(North Dakota State University, 2016) Booth, Kimberly Katie
Insects are ubiquitous, diverse, and able to combat infections despite their lack of adaptive immunity. Insects have a robust innate immune system that is divided into two branches, cell-mediated and humoral. Activation of cell-mediated immune responses results in phagocytosis, nodule formation, and encapsulation by the insect’s immune cells, hemocytes. Activation of humoral immunity results in the production of anti-microbial peptides (AMPs) and phenoloxidase (PO). Insect immune responses can be plastic with development. However, research on how and why insect immunity changes with age as insects develop within a larval developmental stage (instar) is limited and contradictory. In my dissertation research, I answer two main questions: 1) how do immune responses vary within an instar and 2) what drives changes in immunity within an instar? My dissertation research showed that humoral immune responses are more robust at the beginning of the 5th and final instar in Manduca sexta (tobacco hornworm) compared to responses from animals later within that instar. Many changes occur within an instar that could affect immunity. For example, I found that protein expression of matrix metalloproteinase (MMP) in immune tissues of M. sexta decreases throughout the 5th instar. Though MMPs are involved in immune responses in other insects, MMP was not found to be immunostimulatory in M. sexta. Another important factor that changes within an instar is the level of juvenile hormone (JH). JH, a developmental hormone that prevents early molting, peaks early and decreases within an instar until molting. I determined that JH is necessary to survive an infection, control bacterial growth in hemolymph (insect blood), and mount an AMP activity immune response. My dissertation research has established that there is a development-immunity link, and that the naturally fluctuating levels of JH may mediate the effect of development on immunity.

Filters

Settings

Sort By

Results per page

Search Results