Matching Items (6)
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- All Subjects: Biology
- All Subjects: ethics
- Genre: Masters Thesis
- Creators: Pratt, Stephen
Description
Coal bed natural gas (CBNG) production has become a significant contribution to the nation's energy supply. Large volumes of water are generated as a byproduct of CBNG extraction, of which this "product water" is relatively high in sodium. High sodicity reduces water quality and limits environmentally compliant disposal options for producers. Crop irrigation with CBNG product water complies with state and federal laws and is a disposal method that also provides a beneficial use to private landowners. However, this disposal method typically requires gypsum and sulfur soil amendments due to the high levels of sodium in the water, which can reduce soil infiltration and hydraulic conductivity. In this study, I tested a new product called Salt Extractor that was marketed to CBNG producers to ameliorate the negative effects of high sodicity. The experiment was conducted in the Powder River Basin of Wyoming. I used a random block design to compare the soil and vegetation properties of plots following application with CBNG product water and treatments of either Salt Extractor, gypsum and sulfur (conventional), or no treatment (control). Data was analyzed by comparing the amount of change between treatments after watering. Results demonstrated the known ability of gypsum and sulfur to lower the relative sodicity of the soil. Plots treated with Salt Extractor, however, did not improve relative levels of sodicity and exhibited no favorable benefits to vegetation.
ContributorsAdams, Shelly (Author) / Hall, Sharon (Thesis advisor) / Chew, Matt (Committee member) / Stromberg, Juliet (Committee member) / Arizona State University (Publisher)
Created2011
Description
Gene-centric theories of evolution by natural selection have been popularized and remain generally accepted in both scientific and public paradigms. While gene-centrism is certainly parsimonious, its explanations fall short of describing two patterns of evolutionary and social phenomena: the evolution of sex and the evolution of social altruism. I review and analyze current theories on the evolution of sex. I then introduce the conflict presented to gene-centric evolution by social phenomena such as altruism and caste sterility in eusocial insects. I review gene-centric models of inclusive fitness and kin selection proposed by Hamilton and Maynard Smith. Based their assumptions, that relatedness should be equal between sterile workers and reproductives, I present several empirical examples that conflict with their models. Following that, I introduce a unique system of genetic caste determination (GCD) observed in hybrid populations of two sister-species of seed harvester ants, Pogonomyrmex rugosus and Pogonomyrmex barbatus. I review the evidence for GCD in those species, followed by a critique of the current gene-centric models used to explain it. In chapter two I present my own theoretical model that is both simple and extricable in nature to explain the origin, evolution, and maintenance of GCD in Pogonomyrmex. Furthermore, I use that model to fill in the gaps left behind by the contributing authors of the other GCD models. As both populations in my study system formed from inter-specific hybridization, I review modern discussions of heterosis (also called hybrid vigor) and use those to help explain the ecological competitiveness of GCD. I empirically address the inbreeding depression the lineages of GCD must overcome in order to remain ecologically stable, demonstrating that as a result of their unique system of caste determination, GCD lineages have elevated recombination frequencies. I summarize and conclude with an argument for why GCD evolved under selective mechanisms which cannot be considered gene-centric, providing evidence that natural selection can effectively operate on non-heritable genotypes appearing in groups and other social contexts.
ContributorsJacobson, Neal (Author) / Gadau, Juergen (Thesis advisor) / Laubichler, Manfred (Committee member) / Pratt, Stephen (Committee member) / Arizona State University (Publisher)
Created2012
Description
Professional environmental scientists are increasingly under pressure to inform and even shape policy. Scientists engage policy effectively when they act within the bounds of objectivity, credibility, and authority, yet significant portions of the scientific community condemn such acts as advocacy. They argue that it is nonobjective, that it risks damaging the credibility of science, and that it is an abuse of authority. This means objectivity, credibility, and authority deserve direct attention before the policy advocacy quagmire can be reasonably understood. I investigate the meaning of objectivity in science and that necessarily brings the roles of values in science into question. This thesis is a sociological study of the roles environmental values play in the decisions of environmental scientists working in the institution of academia. I argue that the gridlocked nature of the environmental policy advocacy debates can be traced to what seems to be a deep tension and perhaps confusion among these scientists. I provide empirical evidence of this tension and confusion through the use of in depth semi-structured interviews among a sampling of academic environmental scientists (AES). I show that there is a struggle for these AES to reconcile their support for environmentalist values and goals with their commitment to scientific objectivity and their concerns about being credible scientists in the academy. Additionally, I supplemented my data collection with environmental sociology and history, plus philosophy and sociology of science literatures. With this, I developed a system for understanding values in science (of which environmental values are a subset) with respect to the limits of my sample and study. This examination of respondent behavior provides support that it is possible for AES to act on their environmental values without compromising their objectivity, credibility, and authority. These scientists were not likely to practice this in conversations with colleagues and policy-makers, but were likely to behave this way with students. The legitimate extension of this behavior is a viable route for continuing to integrate the human and social dimensions of environmental science into its practice, its training, and its relationship with policy.
ContributorsAppleton, Caroline (Author) / Minteer, Ben (Thesis advisor) / Chew, Matt (Committee member) / Armendt, Brad (Committee member) / Arizona State University (Publisher)
Created2012
Description
Aggregation is a fundamental principle of animal behavior; it is especially significant tohighly social species, like ants. Ants typically aggregate their workers and brood in a central nest, potentially due to advantages in colony defense and regulation of the environment. In many ant species, when a colony must abandon its nest, it can effectively reach consensus on a new home. Ants of the genus Temnothorax have become a model for this collective decision-making process, and for decentralized cognition more broadly. Previous studies examine emigration by well-aggregated colonies, but can these ants also reach consensus when the colony has been scattered? Such scattering may readily occur in nature if the nest is disturbed by natural or man- made disasters. In this exploratory study, Temnothorax rugatulus colonies were randomly scattered in an arena and presented with a binary equal choice of nest sites. Findings concluded that the colonies were able to re-coalesce, however consensus is more difficult than for aggregated colonies and involved an additional primary phase of multiple temporary aggregations eventually yielding to reunification. The maximum percent of colony utilization for these aggregates was reached within the first hour, after which point, consensus tended to rise as aggregation decreased. Small, but frequent, aggregates formed within the first twenty minutes and remained and dissolved to the nest by varying processes. Each colony included a clump containing the queen, with the majority of aggregates containing at least one brood item. These findings provide additional insight to house-hunting experiments in more naturally
challenging circumstances, as well as aggregation within Temnothorax colonies.
ContributorsGoodland, Brooke (Author) / Shaffer, Zachary (Thesis advisor) / Pratt, Stephen (Thesis advisor) / Pavlic, Theodore (Committee member) / Arizona State University (Publisher)
Created2023
Description
The molt from pupae to adult stage, called eclosion, occurs at specific times of the day in many holometabolous insects. These events are not well studied within Lepidopteran species. It was hypothesized that the eclosion timing in a species may be shaped by strong selective pressures, such as sexual selection in the context of male-male competition. The daily timing of eclosion was measured for six species of nymphalid butterflies. This was done by rearing individuals to pupation, placing the pupa in a greenhouse, and video recording eclosion to obtain the time of day at which it occurred. Four species exhibited clustered eclosion distributions that were concentrated to within 201 minutes after sunrise and were significantly different from one another. The other two species exhibited eclosion times that were non-clustered. There were no differences between sexes within species. The data support a relationship between the timing of eclosion each day and the timing of mating activities, but other as of yet undetermined selective pressures may also influence eclosion timing.
ContributorsSencio, Kaylon (Author) / Rutowski, Ron (Thesis advisor) / McGraw, Kevin (Committee member) / Pratt, Stephen (Committee member) / Arizona State University (Publisher)
Created2017
Description
One of the most pronounced issues affecting the management of fisheries today is bycatch, or the unintentional capture of non-target species of marine life. Bycatch has proven to be detrimental for many species, including marine megafauna and pelagic fishes. One method of reducing bycatch is illuminated gillnets, which involves utilizing the differences in biological visual capabilities and behaviors between species of bycatch and target fish catch. To date, all studies conducted on the effects of net illumination on bycatch and target fish catch have been conducted at night. In this study, the effects of net illumination on bycatch, target fish catch, and market value during both night and day periods at Baja California Sur, Mexico were compared. It was found that i) net illumination is effective (p < 0.05) at reducing bycatch of finfish during the day and at night, ii) net illumination at night is more effective (p < 0.05) at reducing bycatch for elasmobranchs, Humboldt squid, and aggregate bycatch than during the day, iii) time of day did not have an effect (p > 0.05) on sea turtle bycatch, and iv) net illumination did not significantly (p > 0.05)affect target catch or market value at night or during the day. These results suggest that net illumination may be an effective strategy for reducing finfish bycatch in fisheries that operate during the day or across 24 h periods, and is especially effective for reducing elasmobranch, Humboldt squid, and total bycatch biomass at night.
ContributorsDenton, Kyli Elise (Author) / Senko, Jesse (Thesis advisor) / Neuer, Susanne (Thesis advisor) / Pratt, Stephen (Committee member) / Arizona State University (Publisher)
Created2021