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A model of the chemostat involving two populations of microorganisms competing for two perfectly substitutable, growth limiting nutrients is developed. To describe nutrient uptake, a general class of functions is used which allows for the effects that the consumption of one resource may have on the consumption of the other. It includes as a special case the model studied by Waltman, Hubbell and HSu [21] in which they generalize Michaelis-Menten functional response for a single resource to two perfectly substitutable resources. It also generalizes the model studied by Leon and Tumpson [12] where the consumption of each resource is unaffected by the consumption of the other. Analytical methods are used to obtain information about the qualitative behaviour of the model. Interesting similarities are found between both the local and global behaviour in this model and in the model for perfectly complementary resources. / Thesis / Master of Science (MS)

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Like much of the world, the United States is currently experiencing intense growth, especially in and around its cities. Unfortunately, this growth is often at odds with the natural environment. In order to reduce the demand of foreign energy resources designing with "green" or ecologically responsive design objectives in mind is vital. We may think of cars and factories as the most obvious enemies of the environment, but buildings consume half of the energy used world wide. The idea of this thesis project was to explore the possibilities of sustainable strategies.That is to develop an energy intensive building based on ecological principles as design tools that demonstrate the economic value of sustainability, and to highlight an energy intensive building type as an example of energy-responsive-living that actually 'looks good'. / Master of Architecture

The family Soricidae, encompassing shrews, represents a diverse group of small (head-body length 30-178 mm) omnivorous or carnivorous mammals distinguished by unique morphological and physiological traits. Ecologically, shrews are dominant small predators, significantly impacting invertebrate populations. Their foraging strategies are diverse, with species adapted to fossorial, psammophilic, scansorial, semiaquatic, semifossorial, and terrestrial guilds. High metabolic rates necessitate nearly constant food intake, influencing their prey selection and feeding behaviors. Physiologically, shrews exhibit adaptations for thermoregulation, with Soricinae generally having higher mass-specific metabolic rates compared to Crocidurinae, who can enter torpor to conserve energy. These metabolic differences are crucial for their ecological distribution and competition dynamics, particularly in regions where the ranges of subfamilies overlap. Size plays a crucial role in shaping the biology of species, influencing aspects such as behavior, energy balance, thermoregulation, locomotion, and reproductive strategies. This study explores the ecological drivers of size variation with the family Soricidae. Using extensive skull and body measurements from a comprehensive literature review and detailed ecological data, this research examines the relationship between size and ecological factors such as foraging guild, biome, elevation, and venom presence. Larger sizes are observed in semiaquatic guilds and those with venom, while terrestrial species are generally smaller. Biome-related size variations align with metabolic and thermoregulatory adaptations. Additionally, range latitude and elevation significantly correlated with minimum and maximum size measures. These findings underscore the importance of ecological and evolutionary factors in shaping size within Soricidae, providing insights into niche partitioning and species coexistence in insectivorous mammal communities. Competition is a critical driver of speciation and adaptation, significantly shaping ecological communities. This study investigates the predictors of potential competition among shrew species using morphological character displacement as a proxy. I collected skull length (SL) and head-body length (HBL) data for 456 and 457 shrew species, respectively, from an extensive literature review. Using spatial analyses and linear modeling, I examined the relationship between character displacement and factors such as species richness, elevation, and distance from the equator across 1,000 shrew assemblages worldwide. The findings indicate that character displacement, and thus potential competition, increases with the number of shrew species, elevation, and distance from the equator. Conversely, the number of shrew genera negatively correlates with character displacement. Interestingly, the number of non-shrew insectivorous mammal species did not consistently predict competition levels. This study underscores the importance of morphological, ecological, and abiotic factors in shaping competition and adaptation in shrews. The complex interplay of these factors allows for the coexistence of numerous morphologically similar species, highlighting shrews as an ideal taxon for studying morphological diversification and niche differentiation.

Assignment (MPhil)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: From 1954 to 1993 the Rooibos Control Board, a statutory one-channel marketing system, regulated the rooibos industry. In 1993 the industry was deregulated and competition between different role players in the industry emerged. In this study competitiveness is analysed from both a historical as well as a modem -day perspective. Modem economic theory defines that competition is good for all industry and that it leads to economic development. In the case of the rooibos industry, one could be inclined to think that the unique character of the product and the fact that the Control Board had established a marketing mechanism would limit competition and rivalry in the post -Control Board era. Inthis study it was determined that deregulation in this industry coincided with very intense price-driven rivalry in the export market whilst very little rivalry occurred in the domestic market. The information for this thesis was obtained from published Annual Reports of the Rooibos Control Board and from personal interviews with the main role players in the industry. Two strategies that could enhance the competitiveness of this industry are recommended: 1. Repositioning rooibos as a gourmet health tea. 2. Improving supply chain coordination within the industry. / AFRIKAANSE OPSOMMING: Verbetering van die Mededingendheid van die Rooibos Industrie Vanaf 1954 tot 1993 het die Rooibos Beheerraad, 'n statutêre enkelkanaal bemarkingsorganisasie, die rooibosindustrie gereguleer. In 1993 is die bedryf gedereguleer en kon mededinging tussen verskillende rolspelers plaasvind. In hierdie studie word mededinging uit beide 'n historiese sowel as moderne perspektiefbestudeer. Moderne ekonomiese teorie stel dit dat mededinging tot voordeel van alle industrieë is en dat dit lei tot ekonomiese ontwikkeling. In die geval van rooibos sou mens geneig wees om te dink dat die unieke karakter van die produk en die feit dat 'n bestaande bemarkingskanaal alreeds bestaan, mededinging sou beperk in die post-Beheerraad tydvak. In hierdie studie is bevind dat deregulering gepaard gegaan het met intense prys-gedrewe mededinging in die uitvoermark, terwyl die binnelandse mark bykans geen mededinging ervaar rue. Die inligting vir hierdie tesis is verkry uit gepubliseerde Jaarverslae van die Rooibos Beheerraad en deur persoonlike onderhoude wat gevoer is met rolspelers binne die bedryf Twee strategieë word voorgestel waarmee die bedryf meer mededingend gemaak kan word: 1. Produk herposisionering as 'n gourmet gesondheidstee. 2. Verbeterde koordinasie binne die voorsieningskettings.