Biology Commons^™

Expression Analyses And Identification Of Key Molecular Participants In Plant Responses To Environmental Cues, Praveena Kanchupati

Electronic Theses and Dissertations

Plants constantly engage and interact with the environment and respond to the changes in conditions like temperature, water, and photoperiod, by regulating expression of genes of multiple regulatory and signaling pathways. Insight into these pathways and their participants has provided and will provide candidates to improve various agronomically important traits in crops through marker-assisted breeding and genetic manipulation. With this aim in mind, in the present study, I attempted to identify key candidate genes that are involved in the regulation of; i) plant response to low temperature stress, ii) plant roots’ response to soil moisture content and iii) flowering time. …

The Role Of Genomic Versatility In Multi-Niche Preferences Of Escherichia Coli, Gitanjali Nandakafle

Electronic Theses and Dissertations

Escherichia coli strains are naturally present as either commensals or pathogens in the gastrointestinal tract of mammals and some other vertebrates. Until recently, it was assumed that E. coli are solely associated with the gut and are unable to survive outside of a host for a long period of time, the basis of its use as an indicator organism. Recent reports suggest that E. coli can become naturalized to several tropical, subtropical or temperate soils and aquatic environments, where they have been isolated repeatedly. Several studies have shown that these strains are capable of surviving and proliferating in the environment …

Microbial Communities And Their Impact On Bioenergy Crops In Dynamic Environments, Brandon Monier

Electronic Theses and Dissertations

Native perennial grasses, such as prairie cordgrass (PCG, Spartina pectinata Link), and switchgrass (SG, Panicum virgatum L.) have a great potential as bioenergy crops, because they require fewer inputs, produce more energy, and reduce greenhouse gas emissions in comparison to annual cropping systems such as corn and soybean. SG has been selected by the U.S. Department of Energy for development as bioenergy crop, but studies have shown that PCG can outcompete switchgrass in terms of biomass production. These crops can also form associations with a wide variety of plant growth promoting microbes including arbuscular mycorrhial (AM) fungi. In CHAPTER 2, …

Regulation Of Local Auxin Metabolism During Soybean Nodule Development, Suresh Damodaran

Electronic Theses and Dissertations

Legume-rhizobia symbiosis leads to the development of secondary root organs called nodules. Rhizobia bacteria housed inside nodules assimilate atmospheric nitrogen and convert them into plant usable forms thereby reducing the need for fertilizer application in crop legumes like soybean. Nodule development is a coordinated process orchestrated by multiple plant hormones. In soybean, the auxin responsive gene expression was detected in nodule primordia and in the periphery of mature nodules, primarily in nodule vasculature. Auxin hypersensitivity reduces nodule formation in soybean and also polar auxin transport inhibition at the site of nodule development is not crucial for determinate nodule formation. Therefore, …

Surveillance Of South Dakota Mosquito Abundance, Infection Rate, And Insecticide Susceptibility, Geoffrey P. Vincent

Electronic Theses and Dissertations

The aim of this dissertation was to survey and evaluate the abundance, infection rate, and insecticide susceptibility of mosquito fauna present in South Dakota. Mosquito surveillance has been conducted across South Dakota to record and track potential West Nile virus (WNV) vectors from 2004 to 2017. The nuisance mosquito Aedes vexans was found to be the most abundant species overall in the state and most abundant in many of the regions. The WNV vector, Culex tarsalis, was found to be the second most abundant mosquito and the most abundant vector mosquito across the state. However, geospatial variation did exist between …

Identification Of Qtl Modifying The Activity Of The Tcb1-S Locus And Characterization And Sequencing Of Two Plutonium-Beryllium Induced Reduced Gametophyte Transmission Mutants In Maize, Merritt Bryer Burch

Electronic Theses and Dissertations

This thesis is split into two independent projects both involving the male gametophyte generation of maize. The first project looks at how pollen interacts with the female gametophyte to reduce its transmission in cross-incompatible reactions controlled by the unilateral cross-incompatibility system, teosinte crossing barrier 1. The second project explores two plutonium-beryllium induced male gametophyte mutants and attempts to uncover their genetic basis.

Identification of QTL Modifying the Activity of the Tcb1-s Locus
Teosinte crossing barrier 1 (Tcb1) is a unilateral cross-incompatibility system present in maize that provides a pre-zygotic pistil barrier to plants carrying Tcb1-s (strong allele) from pollen …

The Effects Of Acidic Conditions And Tannins On The Survival, Development, And Behavior Of Cope’S Gray Treefrog (Hyla Chrysoscelis), Caleb E. Dodd

Electronic Theses and Dissertations

As amphibians decline around the world, freshwater acidification resulting from pollutants and acid rain may be a contributor. The ability of organisms to cope with environmental changes is greatly mediated by behavior, and recent studies indicate that anthropogenic acidification impairs behavioral responses by impacting olfactory abilities of aquatic organisms. Responding appropriately to novel stimuli is important for individual performance and survival, and pollutants may cause organisms to behave maladaptively. In this study I sought to: a) determine whether the oviposition site choices of adult female frogs correspond with the pH and tannin conditions that maximize tadpole survival and performance in …

Leaping Behavior In Silver Carp (Hypophthalmichthys Molitrix): Analysis Of Burst Swimming Speeds, Angle Of Escape, Height, And Distance Of Leaps, Ehlana Stell

Electronic Theses and Dissertations

Silver Carp have rapidly expanded their range exploiting vulnerable habitats, disrupting fisheries, and inflicting unknown ecological damage. These fish have continued to spread into the Middle Mississippi River and the Tennessee River Valley and great effort is being expended to prevent Silver Carp from entering the Great Lakes and expanding further into the Ohio, Illinois, Missouri, and Tennessee Rivers. Using boat-mounted cameras, we recorded in situ video of invasive Silver Carp, Hypopthalmichthys molitrix leaps to measure their horizontal distance, height, and angle of escape as well as their burst speed. Video tapes of fish leaps were obtained from populations of …

Effects Of Hydrological Connectivity On The Benthos Of A Large River (Lower Mississippi River, Usa), Audrey B. Harrison

Electronic Theses and Dissertations

The effects of hydrological connectivity between the Mississippi River main channel and adjacent secondary channel and floodplain habitats on macroinvertebrate community structure, water chemistry, and sediment makeup and chemistry are analyzed. In river-floodplain systems, connectivity between the main channel and the surrounding floodplain is critical in maintaining ecosystem processes. Floodplains comprise a variety of aquatic habitat types, including frequently connected secondary channels and oxbows, as well as rarely connected backwater lakes and pools. Herein, the effects of connectivity on riverine and floodplain biota, as well as the impacts of connectivity on the physiochemical makeup of both the water and sediments …

The Evolution Of Peristenus (Hymenoptera: Braconidae): Taxonomy, Phylogenetics And Ecological Speciation, Yuanmeng Zhang

Electronic Theses and Dissertations

Parasitoid wasps are ecologically and economically important as biological control agents. However, little is known about the diversity, distribution and biology of most hymenopteran parasitoids due to their small size, morphological conservatism, and complex life styles. The focus of my PhD research was to investigate the evolution and speciation of euphorine braconid wasps, using a combination of multilocus phylogenetics and population genomic techniques combined with traditional taxonomy. The three data chapters of my dissertation are divided into different taxonomic ranks of euphorine braconids, focusing on genera, species, and populations. For chapter 2, I built a multilocus phylogeny of the tribe …

Evolution And Distribution Of Phenotypic Diversity In The Venom Of Mojave Rattlesnakes (Crotalus Scutulatus), Jason Strickland

Electronic Theses and Dissertations

Intraspecific phenotype diversity allows for local adaption and the ability for species to respond to changing environmental conditions, enhancing survivability. Phenotypic variation could be stochastic, genetically based, and/or the result of different environmental conditions. Mojave Rattlesnakes, Crotalus scutulatus, are known to have high intraspecific venom variation, but the geographic extent of the variation and factors influencing venom evolution are poorly understood. Three primary venom types have been described in this species based on the presence (Type A) or absence (Type B) of a neurotoxic phospholipase A2 called Mojave toxin and an inverse relationship with the presence of snake venom metalloproteinases …

Biodiversity And Evolution In The Guiana Shield, South America, Andrew Michael Snyder

Electronic Theses and Dissertations

The neotropics are characterized as the most species rich region in the world. Unfortunately, the region's unparalleled biodiversity has not protected it from ongoing threats such as agriculture, mining, logging, oil extraction, and climate change. I studied the biodiversity and evolution of the herpetofauna of South America in order to investigate the influence of historical geological and climatological events in shaping extant neotropical diversity, particularly the Guiana shield. For my research, I set out to explore the processes involved in shaping the remarkable extant diversity using anuran amphibians as models. With my dissertation, I provide a comprehensive review of the …

Behavioral And Disease Ecology Of Gopher Tortoises (Gopherus Polyphemus) Post Exclusion And Relocation With A Novel Approach To Homing Determination, Johnathan Napier

Electronic Theses and Dissertations

In the wake of human expansion, relocations and the loss of habitat can be stressful to an organism, plausibly leading to population declines. The gopher tortoise (Gopherus polyphemus) is a keystone species that constructs burrows it shares with 362 commensal species. Frequent exclusions and relocations and long generation times have contributed to G. polyphemus being State-designated as Threatened in Florida. Prior studies have indicated that G. polyphemus may possess homing behavior and thus be able to counteract stressors due to relocation and exclusion. I radiotracked a cohort of G. polyphemus for 11 months following excavation, relocation, and exclusion due to …

The Ecology Of Land Managers In Riparian Restoration, Lisa Buie Clark

Electronic Theses and Dissertations

While previous studies in restoration ecology have focused on the efficacy of direct management actions, the driving forces on management decisions (e.g., managers' characteristics or attitudes, environmental conditions) and the indirect impacts on restoration outcomes from management decisions (such as whether to collaborate) are quantified here for the first time. As a case study, I used data from 244 sites across the riparian Southwest US where the invasive shrubby tree Tamarix sp. was removed using various different methods. I surveyed and interviewed the 45 land managers who were responsible for the removal projects to determine their characteristics, attitudes, and …

An Examination Of Beta Diversity Indices And Their Predictors In Two Large-Scale Systems, Philip Schroeder

Electronic Theses and Dissertations

Biodiversity is what conservation biology was developed to conserve. It is the physical manifestation of life as a concept and, be it for practical or idealistic reasons, all conservationists seek to protect or, in some cases, enhance it. Because of its monolithic importance to the field, much effort has been expended trying to better measure and understand it. Recently, greater attention has been paid to the partition of diversity; the observation that the total diversity of a system (γ) can be broken down into within-site diversity (α) and between-site diversity (β). In particular, it has been noticed that the β …

The Algz/R Two-Component System Is Responsible For Attenuation Of Virulence In Pseudomonas Aeruginosa, Danielle A. Williams

Electronic Theses and Dissertations

Pseudomonas aeruginosa is an important opportunistic pathogen. Many P. aeruginosa virulence factors are regulated by the AlgZ/R two component system. AlgZ is the sensor histidine kinase which phosphorylates AlgR, the response regulator. AlgR activates transcription of different gene targets based upon its phosphorylation state. The genes that encode AlgZ and AlgR are transcribed in an operon. While regulation of algR expression has been well studied, regulation of algZ expression has not. Using a pilW mutant in concert with algZTF-lacZ transcriptional fusion, we conducted a transposon mutagenesis to identify algZ regulators. We identified an unknown autoregulatory loop. The type …

Examining The Understanding Of Inquiry-Based Learning And Teaching Among Undergraduate Teachers And Students, Maren Hudson

Electronic Theses and Dissertations

One of the main aims of inquiry is to engage students as active, not passive, participants in science. The purpose of this study is to describe science educators’ and students’ views about inquiry-based instruction in order to better understand and improve implementation of evidence-based teaching strategies. Inquiry-based techniques have been shown to improve student understanding of scientific concepts, yet, there continue to be challenges in implementing these techniques. This research project utilizes Q Methodology, a research method that captures both common and disparate measures of subjectivity, to identify commonalities and defining viewpoints about inquiry-based teaching and learning. Three significantly different …

Effects Of Acute Sepsis On Renal Structure And Sympathetic Innervation In Mice, Tuqa Alkhateeb

Electronic Theses and Dissertations

Sympathetic nerves are important for renal physiology and sepsis pathophysiology. A recent study showed sprouting of sympathetic nerves in spleen of septic mice. This study was done to test if renal sprouting of sympathetic nerves also happens and to investigate renal morphology in septic mice. Cecal ligation and puncture (CLP) was used to induce sepsis and kidneys were removed for evaluation. Bowman’s space was diminished with cortical bubble cells present suggestive of acute renal pathology, however, renal function was unchanged. Acute sepsis did not affect either renal sympathetic innervation or non-neuronal cholinergic cells. Mouse kidneys had more epinephrine (EPI) than …

Enemy Exacerbation: Effects Of Predator Stress On Sulfate Lethality In Freshwater Amphipods (Gammarus Minus), Trevor Chapman

Electronic Theses and Dissertations

Predator cues can influence how aquatic organisms respond to anthropogenic contaminants. This study examined the effects of predator cues on behavior, metabolic rate, and sulfate (as Na₂SO₄) toxicity in amphipods (Gammarus minus). Predator cues included alarm cue (macerated conspecifics) and kairomone from mosquitofish (Gambusia affinis). Amphipods decreased activity and increased time in refuge when exposed to alarm cue, and increased time in refuge when exposed to kairomone. While median lethal concentrations (96-h LC₅₀) were not influenced by predator cues, analysis of dose response curves indicated that kairomone exposure increased amphipod …

Regulation Of Haplid Phenotypes In Ustilago Maydis By Ammonium Transporters And Components Of The B Mating Locus., Rena Margaret Wallen

Electronic Theses and Dissertations

Fungi that can switch from budding to a filamentous infectious state have evolved mating type loci. Ustilago maydis, the maize pathogen, must mate with compatible partners possessing different alleles at two mating type loci for successful host infection. The a locus encodes pheromones and receptors, while the b locus encodes subunits of a heterodimeric transcription factor that regulates expression of virulence genes. Mating is triggered by environmental signals, including nutrient deprivation. My goal was to determine the fate of nitrogen starved haploid cells without a compatible mating partner. On solid low ammonium media, wild-type U. maydis filaments. I examined …

A Study Of Salmonid Growth In Two Southern Appalachian Headwater Streams, Joshua Argo

Electronic Theses and Dissertations

This study sampled salmonid populations in two headwater streams in East Tennessee, Briar Creek and Left Prong Hampton Creek. Length and weight data were used to calculate the growth of these populations to determine if significant variation exists between isolated brook trout populations. Slope comparisons concluded that there was a difference in growth between brook trout populations of these streams (p

Range-Wide Prevalence And Impacts Of Pseudocercosporella Inconspicua On Lilium Grayi And An Assessment Of L. Superbum And L. Michauxii As Reservoirs, Cindy L. Barrett

Electronic Theses and Dissertations

Lilium grayi (Gray’s Lily), a southern Appalachian endemic species, is threatened by a Lilium-specific fungal pathogen, Pseudocercosporella inconspicua. The disease is characterized by tan lesions that can cause early senescence, while also lowering seed production and viability. This project tested for P. inconspicua conidia and accessed health at nine locations. The disease was present and ubiquitous across the range of L. grayi. Through identification of P. inconspicua conidia in the field, L. superbum (Turk’s Cap Lily) was identified as an additional host, while L. michauxii (Michaux’s Lily) was disease-free. However, infection was inducible in both species. With …

Inclusive Teaching Strategies: An Evaluation Of Course Structure And Summative Assessment In Introductory Biology, Oluwaseun O. Agboola

Electronic Theses and Dissertations

Several active learning strategies have been used when increasing the structure of a course as increasing course structure has been known to improve student learning in introductory STEM courses. Much has been studied on the value of frequent formative assessment; however, few studies have evaluated the effective modes of delivering summative assessment. This study examines the use of summative assessment as an inclusive teaching practice to improve first generation college student success in introductory biology and also uses faculty surveys to find out how instructors structure their introductory biology course and why they are structured that way. Final exams were …

Effects Of Predatory Cues On Copper Sensitivity And Metabolic Rate In Gambusia Affinis, Melissa N. Campbell

Electronic Theses and Dissertations

Organisms living in aquatic environments are subject to a number of stressors from natural (temperature, predation, food availability) and anthropogenic origins (pesticides, metals, etc). Natural stressors may amplify the effects of contaminants and increase an organism’s sensitivity to them. Understanding the impact of these combined factors is therefore essential for the practical management of contaminants. This study sought to examine how predatory cues affect copper tolerance in the mosquitofish, Gambusia affinis. The influence of predatory cues on fish metabolic rate was also evaluated to gain insight on any interactive effects between the natural stressor and copper. Alarm cues, chemicals released …

Vegetation Community Changes In Two National Forests In The Pineywoods, East Texas, Trisha L. Williams

Electronic Theses and Dissertations

Despite extensive research into forest succession, little research has been directed to long-term studies. The fundamental properties of succession remain unclear and further research into terrestrial vegetation and an accounting of drivers in specific ecosystem types is required. This study addresses change in plant communities from five ecosystem types in two east Texas National Forests over a 20-year period. An analysis of 30 sample stands yields results due to various ecosystem drivers of vegetation change and uncovers plant community responses in multiple ecosystem types over this period. This research provided three key results: 1) that vegetation composition change occurs more …

Social Dynamics, Network Structure, And Information Diffusion In Fish Shoals., Matthew Jerome Hasenjager

Electronic Theses and Dissertations

Animal populations are often highly structured, with individuals differing in terms of whom they interact with and how frequently they do so. The resulting pattern of relationships constitutes a population’s social network. In this dissertation, I examine how environmental variation can shape social networks and influence information flow within them. In Chapter I, I review the history of social network analysis in animal behavior research, and discuss recent insights generated by network approaches in behavioral ecology. I focus on the fields of: social learning, collective behavior, animal personalities, and cooperation. Animal network studies are often criticized for a lack of …

Function Of The Enterobactin Operon Of A. Actinomycetemcomitans In The Presence Of Catecholmines And Iron., Taylor Johnson

Electronic Theses and Dissertations

Background: Aggregatibacter actinomycetemcomitans (Aa) possesses a two-component system, QseBC, which is key in biofilm formation/virulence and is activated in the presence of iron-catecholamine complexes. Aa does not synthesize enterobactin, a catechol-based siderophore, yet possesses the machinery for recognition and uptake. We hypothesize that Aa is able to acquire iron by catecholamine mediation through the enterobactin receptor/transporter. Methods: By insertional mutation, we attempted to delete the enterobactin permease from the genome using suicide vector pJT1. A growth curve of truncated mutant ΔfepA was also conducted to observe growth in the presence of iron and catecholamines. Statistical significance was determined by ANOVA …

Small Rho Gtpase Family Member Cdc42 And Its Role In Neuronal Survival And Apoptosis, Noelle Christine Punessen

Electronic Theses and Dissertations

Neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Alzheimer's and Parkinson's disease are caused by a progressive and aberrant destruction of neurons in the brain and spinal cord. These disorders lack effective long term treatments, and existing options focus primarily on either delaying disease onset or alleviating symptomology. Dysregulated programmed cell death, known as apoptosis, is one of the most significant contributors to neurodegeneration, and is controlled by a number of different factors. Rho GTPases are a protein class with recognized importance in proper neuronal development and migration, and have more recently emerged as regulators of apoptosis and neuronal survival. …

The Effect Of Parental Population Density On Offspring Immune Function, Dana Davis

Electronic Theses and Dissertations

It is well known that an individual's environment, genetic code, and gene by environment interactions have an effect on its overall phenotype. However, there is a growing body of work that shows that parents can have an effect on their offspring's phenotype beyond the inherited genetic code. Studies have shown that parents may affect their offspring through physiological mechanisms such as egg provisioning and epigenetic effects and through behavioral mechanisms such as maternal care. In many of these cases, the parental effect is triggered by an environmental cue. Previous work has shown that density can impact immune function and cuticle …

Mucking About: Hydrologic Regime And Soil Carbon Storage In Restored Subtropical Wetlands, Alicia Huber

Electronic Theses and Dissertations

Wetlands are extremely important ecosystems that have declined drastically worldwide, continue to be lost, and are threatened globally. They perform a number of important ecosystem services such as flood control, provide habitat for many species, and have aesthetic and recreational value. Wetlands are also important to the global carbon (C) cycle. Wetland soils are especially effective C sinks because they have high primary productivity and low decomposition rates due to flooded, anoxic conditions. Increased recognition of wetlands' value has led to more ecological and hydrological restoration of degraded wetlands to mitigate the effects of wetland destruction. Hydrological restoration, which attempts …