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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A World Without You

Patterson, Brian C 01 January 2018 (has links)
The following thesis is adapted from screenplay format. The document from which it derives serves as a shooting script for a film/video called A World Without You . The shooting script contains explicit scene description, camera set-ups that include angle and lens choices, dialog, and transitions - all the relevant instruction needed for anyone to reproduce the film with explicit similarity to its original. The thesis reflects a series of short videos I completed as research. In their finished state, the series of videos coalesce to a single film/video with a sixty-two-minute running time. That conglomeration emerged as a “shadow” or “inversion” of a twenty-minute, singlechannel video loop called Intermission For Deleted Acts, which served as centerpiece to my thesis exhibition. The script navigates themes of environmental catastrophe, companionship, survival, surveillance, and art practice. The following thesis attempts to keep the screenplay formatting intact to communicate both its functionality and aesthetic quality.
2

Mineralogical - Geochemical Investigation of two sections across the Permian-Triassic Boundary in the Continental Realm of the Southern Karoo Basin, South Africa

Coney, Louise 17 November 2006 (has links)
Student Number : 9902718G - MSc dissertation - School of Geosciences - Faculty of Science / The Late Permian (251.0 ± 0.4 Ma) mass extinction is universally acknowledged as the most consequential of the five major Phanerozoic mass extinctions. More than 90% of marine species, ~70% of terrestrial vertebrates, and ~90% of plant life were lost in a very short interval. The nature of the Permian-Triassic (P-Tr) boundary and the cause of the mass extinction associated with it have been the subject of extensive international debate. Possible causes for the P-Tr extinction include asteroid/comet impact, oceanic anoxia, volcanism, methane clathrate dissociation, or combinations of these causes. Geochemical studies of the P-Tr boundary have traditionally been focused on the marine realm, as the boundary in continental sections is typically difficult to pinpoint. One continental setting of the P-Tr boundary that has, however, received much attention is that in the main Karoo Basin, South Africa. The Karoo Basin is a large retro-arc foreland basin which accumulated sediment from the Carboniferous (300 Ma) through to the Early Jurassic (180 Ma) in southwestern Gondwana. Mineralogical and geochemical investigations across two palaeontologically well-constrained continental P-Tr boundary sections at Commando Drift Dam and Wapadsberg in the southern Karoo Basin of South Africa have been undertaken in order to aid in our understanding of this extinction event. The Commando Drift Dam section is also constrained palaeomagnetically. There is a change in paleosol colour across the P-Tr boundary from green-grey to red-brown, which is believed to reflect a change of oxidizing conditions at the P-Tr boundary. Quartz grains were examined for possibly impact-produced microdeformation features, but these were not found. Iridium concentrations are below the detection limit (by instrumental neutron activation analysis) and the sections could not be evaluated as to whether any significant enrichment has taken place at the P-Tr boundary. Major element chemical profiles are dominated by the signatures of carbonate nodular horizons in both sequences. Iron contents (and accompanying siderophile element abundances) increase across the palaeontologically-defined P-Tr boundary, followed by a decrease thereafter. The major element concentrations, together with the effects of weathering, largely control trace element distribution. Carbon isotopic results from the Commando Drift Dam section show a gradual decrease in values before the P-Tr boundary, with a larger negative excursion at the P-Tr boundary. Above the boundary, gradual recovery to initial ratios is observed, followed by another gradual decrease in values to the palaeomagnetically defined boundary. No evidence supporting an extraterrestrial impact extinction mechanism has been found. Rather, the carbon isotope data from this study support two gradual palaeoclimatic changes separated by a sudden change in the carbon isotopic content of the atmosphere. The size and nature of these excursions support the addition of large amounts of anoxic material into the atmosphere. This is proposed to have been caused by the multiple influx of carbon dioxide, methane and other greenhouse gases at various times and by different mechanisms. Such a release of carbon dioxide, methane and other greenhouse gases could have been caused by the coincident volcanic event (the formation of the Siberian Traps) and the episodic release of methane clathrates.
3

Evolution in biological radiations; insights from the Triassic archosaur radiation

Hoffman, Devin Kane Fodor 29 June 2022 (has links)
Adaptive radiations, or evolutionary diversifications, are the evolutionary divergence of a single lineage into many different adaptive forms. They play a critical role in the history of life as groups of organisms speciate and fill new ecological roles over geologically rapid time intervals. There is currently no agreed upon operational unit, timeframe, or amount of divergence for organisms to be considered to have undergone an adaptive radiation. Additionally, the paucity of both comparative and fossil studies has limited the utility of the adaptive radiation in framing macroevolutionary questions, such as, is ecological and morphological diversification simultaneous? An ideal fossil clade to test this question is the Archosauriformes (crocodylians, birds, and their closest relatives). Archosauriforms radiated following the end-Permian mass extinction and their lineage diversification through the Early to Late Triassic is well documented in the literature. Prior to the end-Permian mass extinction, these reptiles were both species poor and ecologically limited, but by the Late Triassic they dominated terrestrial ecosystems in both species abundance and ecological breadth. However, continued environmental instability following the end-Permian extinction has led to the hypothesis that ecological expansion of archosauriforms lagged behind the diversification of lineages. The first chapter of my dissertation uses a Middle Triassic archosauriform tooth assemblage from Tanzania to reconstruct dietary specialization, estimated by morphological disparity of teeth. In addition to comparing tooth disparity of isolated and in situ teeth, this also provides a lens for comparing the timing of dietary specialization and species diversification. I found the archosauriforms to be faunivorous with little morphological disparity amongst the teeth. The second chapter uses an Early Triassic reptile tooth assemblage from South Africa to reconstruct the dietary specialization of archosauriforms early in their radiation to compare the amount of morphological disparity and lineage diversity. I use methods from Chapter 1 and integrate 3D morphometrics to better capture shape. I described several tooth morphotypes including six new to the locality. The morphological and dietary differences were minimal, indicating a greater species diversity than ecological diversity. The third chapter is a description of a new pseudosuchian archosaur taxon from the Middle Triassic of Tanzania. As species descriptions form the basic data unit of macroevolutionary analyses, this assists future studies of the archosauriform radiation. I recover this new taxon as the oldest known aetosaur. This species provides insights into the evolution of an armored carapace in crocodylian-line archosaurs and shows morphology related to armor evolved prior to the evolution of an herbivorous diet. / Doctor of Philosophy / There is an incredible diversity of life on Earth, but this is a small fraction of the life that once existed on our planet. The fossil record provides us a window into the past to reconstruct the history of life on our planet. Two of the patterns we see in the fossil record are rapid drops in biodiversity called mass extinctions, and rapid increases in biodiversity called biological radiations. Both of these events are often related and mass extinctions are followed by biological radiations throughout earth history. A particularly interesting case is the end-Permian mass extinction, not only because it is the largest extinction event, but also because the subsequent radiation was delayed by continuing environmental instability. An ideal group of animals to study in this time period are the archosaurs, the group of reptiles including crocodylians, birds, and their extinct relatives. Archosaur reptiles went from very few species before the extinction, to dominate ecosystems for the next 200 million years. However, we do not know if the radiation of many archosaur species occurred at the same time as they filled new roles in their communities. The first two chapters of my dissertation focus on using fossil teeth to reconstruct the diets of archosaurs at a single location. My first chapter describes teeth from the Middle Triassic (247-237 million years ago) of Tanzania. I measured the shapes of these teeth and used that to help assign them to diets. Doing this I found there were more species than types of diets indicating the radiation of species may have occurred before specialization of life habits. In the second chapter where I describe a reptile tooth assemblage from the Early Triassic (252-247 million years ago) of South Africa. I added additional methods for measuring tooth shape, found several different types of teeth (likely different species) but mostly similar diets, indicating again a delay in life habit specialization. In my third chapter I name a new species of archosaur reptile from the Middle Triassic of Tanzania. This new species helps us to understand how heavily armored plant eaters evolved in early crocodylian relatives during the archosaur radiation.
4

Effects of the Late Permian mass extinction on Chondrichthyan palaeobiodiversity and distribution patterns

Koot, Martha Beatrijs January 2013 (has links)
The Late Permian mass extinction occurring at 252.6 ± 0.2 Ma is the most severe Phanerozoic extinction event and was preceded and followed by additional disturbances. Patterns and processes of extinction and recovery of marine vertebrates have been little studied compared to marine invertebrates. This project focuses on Chondrichthyes, which, together with other marine fish, appeared to have been relatively unaffected by the extinction, while most of their supporting ecosystem collapsed. This study explores the authenticity of extinction among chondrichthyans and possible explanations for the observed patterns, because extinction severities on the taxonomic and ecological levels may be decoupled or the quality of the fossil record may be variable. The presented analyses are based on a newly compiled database that supercedes older compilations. It is supplemented by material obtained from numerous localities globally, which includes newly described taxa. Hence, this study attempts to be the most up-to-date and comprehensive analysis of patterns and trends in chondrichthyan diversity and distribution that is currently available. The data demonstrate that, despite some variability in the Permian–Triassic chondrichthyan fossil record, the Lopingian record is shown to be of adequate completeness and, furthermore, range-through genus diversity is not significantly correlated with the number of taxonomic occurrences. Genus diversity declined from the mid-Guadalupian following an increasing extinction rate, which intensified throughout the Lopingian and thus supports a combined overall extinction as a result of the end-Guadalupian and Late Permian events. Furthermore, global distribution of chondrichthyan diversity shifted away from tropical regions and particularly the Boreal Sea gained in diversity, tracking extinction and recovery in marine benthic invertebrates in both time and space. No significant dependence of extinction on taxonomic structure or palaeoecological traits exists, which suggests proportional losses, except during the end-Smithian crisis. Also, a significant size decrease is absent among Permian/Triassic boundary-crossing taxa, suggesting selective loss of large-sized chondrichthyans rather than adaptive size decrease. Ultimately, the Hybodontiformes, Neoselachii, Xenacanthiformes and Holocephali are identified as the survivors, which possessed a varying combination of characteristics such as moderate body-size, adaptation to brackish/freshwater environments, benthic or generalist littoral (clutching) feeding behaviour, and a wide palaeogeographic range.
5

The Mycelim Connection

Zedell, Axel January 2016 (has links)
Humans used to be a part of nature, now we have become a force of nature. Our culture is based on infinite growth on a planet with finite resources. Its obvious that we need to change our lifestyle, in a radical way.Its not enough to drive a prius, buying organic food, or as an architect draw buildings with green roofs.We need a radical change of our lifestyle because we are facing radical change of our climate.Our impact is so great, occurs with such a speed and on a global scale that we have set of a mass extinction. My project consists of two parts.1: To apply a system, based on the unique properties of fungi, today.I want a site that is dead and polluted. 2: A site that will work as a testing ground, preparing us for a very harsh future. Alberta, CanadaOil sand mines the size of United Kingdom. Where a brutal mining process leaves a destroyed landscape behind. I see this landscape as a good preview of the future of our planet.I have formed a system that uses this extreme condition as an asset. The system will not only heal the landscape, it will also produce essential products such as food, fuel and material. All from fungi.The system is a network of fungi farms, growing through the land in patterns inspired by how fungi grows. / Människor brukade vara en del av naturen, nu har vi blivit en naturkatastrof. Vår kultur är baserad på evig tillväxt på en planet med begränsade tillgångar. Det är uppenbart att vi behöver ändra vår livsstil på ett radikalt sätt. För vi kommer snart att möta radikala ändringar av vårat klimat.   Svamp är en fascinerande livsform. Den var den första organismen att bosätta sig på jordens landmassor för 1.5 miljarder år sedan. Svamp kan leva utan ljus, kan leva i extremt förorenade miljöer och är en perfekt partner för att möta radikal klimat. Mitt projekt består av två delar. Att applicera ett system på oljesand gruvorna i Alberta, Kanada. Detta för att förbereda oss på en global ekologisk kollaps.
6

Quantifying the Biogeochemical Impact of Land Plant Expansion in the Mid Devonian and Implications in Marine Anoxic Events

Smart, Matthew Stephen 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The evolution of land plant root systems occurred stepwise throughout the Devonian, with the first evidence of complex root systems appearing in the mid-Givetian. This biological innovation provided an enhanced pathway for the transfer of terrestrial phosphorus (P) to the marine system via weathering and erosion. This enhancement is consistent with paleosol records and has led to hypotheses about the causes of marine eutrophication and mass extinctions during the Devonian. To gain insight into the transport of P between terrestrial and marine domains, presented here are geochemical records from a survey of Middle and Late Devonian lacustrine and near lacustrine sequences that span some of these key marine extinction intervals. Root innovation is hypothesized to have enhanced P delivery and results from multiple Devonian sequences from Euramerica show evidence of a net loss of P from terrestrial sources coincident with the appearance of early progymnosperms. Evidence from multiple Middle to Late Devonian sites (from Greenland and northern Scotland/Orkney), reveal a near-identical net loss of P. Nitrogen and Carbon isotopes from a subset of these lakes confirm elevated input of terrestrial plant material concurrent with P perturbations. Terrestrial P input appears to be episodic in nature, suggesting land plant expansion was driven by an external catalyst in the study region. All sites analyzed are temporally proximal to significant marine extinctions, including precise correlation with the Kačák extinction event and the two pulses associated with the Frasnian-Famennian (F/F) mass extinction. The episodic expansion of terrestrial plants appears to be tied to variations in regional and global climate, and in the case of the F/F extinction, also to atmospheric changes associated with large scale volcanism. Using P data presented here as an input into an Earth system model of the coupled C-N-P-O2-S biogeochemical cycles shows that globally scaled riverine phosphorus export during the Frasnian-Famennian mass extinction generates widespread marine anoxia consistent with the geologic record. While timing precludes land plants as an initiating mechanism in the F/F extinction, these results suggest they are implicated in every marine extinction event in the Mid to Late Devonian.
7

Carbon and nitrogen isotope records of the Hirnantian glaciation

LaPorte, Dan F 10 March 2009
The Hirnantian mass extinction was the second largest of the Phanerozoic. A global sea level fall resulting from a glaciation on Gondwanaland caused significant changes in ocean circulation patterns and nutrient cycling that is recorded as a worldwide positive δ13C excursion.<p> In chapter 2, carbon and nitrogen isotope profiles were reconstructed from two North American carbonate platforms in Nevada and one in the Yukon with the purpose of gaining a better understanding of proximal to proximal gradients in δ13C values from Hirnantian epeiric seaway sediment. Positive δ13C excursions are recorded in bulk inorganic and organic carbon fractions from all three sections, and in graptolite periderms from one section. A larger positive excursion is recorded in the proximal sediment (7) compared to proximal sediment (3-4). This gradient appears to reflect differences in surface water dissolved inorganic carbon δ13C values across epeiric seas. These findings are consistent with the carbonate weathering hypothesis, that predicts larger positive δ13C shifts in proximal settings of tropical epeiric seas resulting from changes in the local carbon weathering flux caused by the exposure of vast areas of carbonate sediment during glacioeustatic sea level fall and restricted shelf circulation. A 2 positive excursion in δ15N is interpreted to result from increased ocean ventilation, greater partitioning of atmospheric oxygen into downwelling surface waters, oxygen minimum zone shrinkage, and declining denitrification rates. This allowed for upwelling of recycled nitrogen with high 15N values into the photic zone that forced exported organic matter from the photic zone to higher 15N values, consistent with the observed positive shift in 15N during the Hirnantian glaciation. This study presents a conceptual model to explain secular changes in δ13C and δ15N during the transition from a greenhouse to icehouse climate.<p> The second focus of this research, presented in chapter 3, was on improving the chemical and analytical methods for δ18O analysis of biogenic apatites. The technique applies cation exchange chromatography that allows for small sample sizes of apatite (200 µg) to be used for chemical conversion to Ag3PO4. The precision (0.15, 1) of δ18O analysis obtained using a Thermal Conversion Elemental Analyser Continuous Flow Isotope Ratio Mass Spectrometer (TC/EA CF-IRMS), and the ability to collect multipe isotopes (O, Ca, Sr, REE) using a cation exchange column, makes this technique valuable for high-resolution, multi-isotope studies of biogenic apatites.
8

Carbon and nitrogen isotope records of the Hirnantian glaciation

LaPorte, Dan F 10 March 2009 (has links)
The Hirnantian mass extinction was the second largest of the Phanerozoic. A global sea level fall resulting from a glaciation on Gondwanaland caused significant changes in ocean circulation patterns and nutrient cycling that is recorded as a worldwide positive δ13C excursion.<p> In chapter 2, carbon and nitrogen isotope profiles were reconstructed from two North American carbonate platforms in Nevada and one in the Yukon with the purpose of gaining a better understanding of proximal to proximal gradients in δ13C values from Hirnantian epeiric seaway sediment. Positive δ13C excursions are recorded in bulk inorganic and organic carbon fractions from all three sections, and in graptolite periderms from one section. A larger positive excursion is recorded in the proximal sediment (7) compared to proximal sediment (3-4). This gradient appears to reflect differences in surface water dissolved inorganic carbon δ13C values across epeiric seas. These findings are consistent with the carbonate weathering hypothesis, that predicts larger positive δ13C shifts in proximal settings of tropical epeiric seas resulting from changes in the local carbon weathering flux caused by the exposure of vast areas of carbonate sediment during glacioeustatic sea level fall and restricted shelf circulation. A 2 positive excursion in δ15N is interpreted to result from increased ocean ventilation, greater partitioning of atmospheric oxygen into downwelling surface waters, oxygen minimum zone shrinkage, and declining denitrification rates. This allowed for upwelling of recycled nitrogen with high 15N values into the photic zone that forced exported organic matter from the photic zone to higher 15N values, consistent with the observed positive shift in 15N during the Hirnantian glaciation. This study presents a conceptual model to explain secular changes in δ13C and δ15N during the transition from a greenhouse to icehouse climate.<p> The second focus of this research, presented in chapter 3, was on improving the chemical and analytical methods for δ18O analysis of biogenic apatites. The technique applies cation exchange chromatography that allows for small sample sizes of apatite (200 µg) to be used for chemical conversion to Ag3PO4. The precision (0.15, 1) of δ18O analysis obtained using a Thermal Conversion Elemental Analyser Continuous Flow Isotope Ratio Mass Spectrometer (TC/EA CF-IRMS), and the ability to collect multipe isotopes (O, Ca, Sr, REE) using a cation exchange column, makes this technique valuable for high-resolution, multi-isotope studies of biogenic apatites.
9

Uranium Isotope Variations Across Key Evolutionary Intervals in Geological History

January 2018 (has links)
abstract: There is a growing body of evidence that the evolving redox structure of the oceans has been an important influence on the evolutionary trajectory of animals. However, current understanding of connections between marine redox conditions and marine extinctions and recoveries is hampered by limited detailed knowledge of the timing, duration, and extent of marine redox changes. The recent development of U isotopes (δ238U) in carbonates as a global ocean redox proxy has provided new insight into this problem. Reliable application and interpretation of the δ238U paleoproxy in geological records requires a thorough understanding of the reliability of δ238U recorded by bulk carbonate sediments. In this dissertation, I evaluate the robustness of δ238U paleoproxy by examining δ238U variations in marine carbonates across Permian-Triassic boundary (PTB) sections from different paleogeographic locations. Close agreement of δ238U profiles from coeval carbonate sections thousands of kilometers apart, in different ocean basins, and with different diagenetic histories, strongly suggests that bulk carbonate sediments can reliably preserve primary marine δ238U signals, validating the carbonate U-isotope proxy for global-ocean redox analysis. To improve understanding of the role of marine redox in shaping the evolutionary trajectory of animals, high-resolution δ238U records were generated across several key evolutionary periods, including the Ediacaran-to-Early Cambrian Explosion of complex life (635-541 Ma) and the delayed Early Triassic Earth system recovery from the PTB extinction (252-246 Ma). Based on U isotope variations in the Ediacaran-to-the Early Cambrian ocean, the initial diversification of the Ediacara biota immediately postdates an episode of pervasive ocean oxygenation across the Shuram event. The subsequent decline and extinction of the Ediacara biota is coincident with an episode of extensive anoxic conditions during the latest Ediacaran Period. These findings suggest that global marine redox changes drove the rise and fall of the Ediacara biota. Based on U isotope variations, the Early Triassic ocean was characterized by multiple episodes of extensive marine anoxia. By comparing the high-resolution δ238U record with the sub-stage ammonoid extinction rate curve, it appears that multiple oscillations in marine anoxia modulated the recovery of marine ecosystems following the latest Permian mass extinction. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018
10

The biodiversity loss crisis in Southeast Asia

Nilsson, Louise January 2019 (has links)
Denna kandidatuppsats gör en ansats till att belysa biodiversitetsproblematiken i Sydostasien, som är ett område med mycket hög artrikedom som samtidigt hotas av en intensifierad förlust av arter. Fyra ’biodiversitet hotspots’ omger Sydostasien, vilka indikerar platser med hög artrikedom vilka sammanfaller med hög förlust av habitat. Det största orsaken till förlust av biologisk mångfald i Sydostasien är omvandlingen utav artrika naturtyper till monokulturodlingar, och expansionen av jordbruk och urbana områden. För att undersöka den pågående biodiversitetsforskningen genomfördes en systematisk litteraturanalys av publicerade artiklar från 2010-2019. Vad litteraturanalysen kom fram till var att flera problem, socioekonomiska samt miljöproblem intensifierar varandra, liksom fattigdom och förlust av biologisk mångfald. Internationellt samarbete krävs för att stoppa exploateringen av de värdefulla arter och naturtyper som går förlorade till fördel för den globala handeln med produkter som kommer från området. Medel för att stoppa denna biodiversitetskatastrof måste riktas till forskning och organisationer som arbetar i området. Vi bör genast agera på ett globalt plan för att förhindra förlusten av biodiversitet samt dess tillhörande ekosystemtjänster, detta skulle kunna tacklas genom att vi rör oss ifrån den antropocentriska och emot den ekocentriska natursynen. / This bachelor thesis focuses on the biodiversity loss problematics in Southeast Asia, since it is one of the most species rich places on Earth, coupled with the highest rate of loss of species. Four biodiversity hotspots encompasses Southeast Asia which implies areas of high endemism coupled with high rates habitat loss. This thesis aim to understand what current research in the field focuses on and what ways of protecting biodiversity in the area that exists. The main driver of biodiversity loss in Southeast Asia as well as in the rest of the world, are land-use alterations; forests and natural habitat being converted to monoculture plantations, as well as agricultural- and urban expansions. Through a systematic literature review of scientific material from 2010-2019, the biodiversity research in Southeast Asia is reviewed. What the literature review concluded was that an array of environmental- as well as socioeconomic problems intensifies each other in the area, such as poverty and biodiversity loss. International cooperation to halt biodiversity loss and the global demand for products produced in the area which greatly damages ecosystems needs to be addressed urgently. Actions to halt the mass-extinction of species and their connected ecosystem services needs to be taken by providing means to organizations and to scientists that work in the area and could possibly be addressed by moving from anthropocentrism towards a biocentric nature view.

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