Many biological problems can be reduced to the description of a food chain model or a food web. In these systems, the biodiversity and coexistence of all species are vital issues to discuss. Three ecological models have been proposed in case of the existence of a reserved area, in order to understand multi-species interactions so as to prevent the slow extinction of some endangered species and to test the stability when the length of the food chain and size of the web models are increased. It is taken that the environment has been divided into two disjoint regions, namely, unreserved and reserved zones, where a predator is not allowed to enter the latter. The first model describes a four species food chain predator-prey model with prey refuge (prey in the reserved zone, prey in the unreserved zone, predator and top predator), with the predator being entirely dependent on the prey in the unprotected area. The second model addresses the same problem, but in addition, a third component in the chain partially depends on the prey in the unreserved zone. Finally, the last model investigates a four species food web system with a prey refuge and in this case, the fourth component can also feed directly on the prey in the unreserved zone. The boundedness, existence and uniqueness of the solutions of the proposed models are established. The local and global dynamical behaviours are investigated, with the persistence conditions of the models being elicited. The local bifurcation near each of the equilibrium points is obtained. The numerical simulations in MATLABR are used to study the influence of the existence of the reserved zone on the dynamical behaviour of the proposed models. It has been concluded that the role of the reserved area could be beneficial for the survival and stabilising of multi-species interactions.

Thesis (M.App.Sc.) -- University of Adelaide, School of Earth and Environmental Science, Discipline of Soil and Land Systems, 2004. / "March, 2004" Bibliography: p. 112-136.

Thesis (M.A.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains ix, 121 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 117-121).

Thesis (Ph. D.)--University of London, 1990. / Includes bibliographical references (leaves 555-577).

Our bodies contain a vast number and diversity of microbes. These microbes interact, and these interactions can define how microbes affect us. Microbial ecology and evolution, therefore, are important for both microbiology and human health. However, our understanding of microbial communities remains limited. There is a need for theory that dissects the complexity and identifies the key factors and processes affecting microbial groups. Here I develop realistic computer simulations and population models of microbial communities. My first project seeks to explain microbial communication (quorum sensing) and argues that quorum sensing is a way to infer when competing genotypes are no longer a threat. The second project proposes an evolutionary explanation for another major microbial trait: adhesion. I argue that adhesion is a weapon allowing cells to compete within microbial groups and push competitors out, particularly when growing on a host epithelium. The third project moves from microbes to the host and asks whether a host can control which microbes grow and persist inside it. I develop a model of the human gut epithelium and show that the gut architecture amplifies the ability of hosts to select helpful microbes over harmful ones using nutrient secretion. In addition to selecting particular microbial strains, a host will also benefit from stable symbiotic communities that behave in a predictable manner. But what determines whether host-associated communities are ecologically stable? My final project uses ecological network theory to show that ecological stability is likely to be a problem for gut communities that are diverse and contain species that cooperate with each other. However, I argue that the host should function as an ecosystem engineer that increases ecological stability by weakening the strong dependence of cooperating species upon one another. While host-associated communities are complex ecological systems, my thesis identifies key factors that affect their form and function.

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 2009. / Microbiology and Plant Pathology / unrestricted

The relative contributions of biome history and geological setting to historical assembly of species richness in biodiversity hotspots remain poorly understood. The tropical Andes is one of the world’s top biodiversity hotspots, and with its diverse biomes and the relatively recent but dramatic uplift, the Andes provides an ideal study system to address these questions. To gain insights into the historical species assembly of the tropical Andes, this study focuses on investigating patterns of plant species diversification in the Andean seasonally dry tropical forest (SDTF) biome. Three plant genera are used as study groups: Amicia (Leguminosae, Papilionoideae), Tecoma (Bignoniaceae), and Mimosa (Leguminosae, Mimosoideae). Species limits are re-evaluated to enable dense sampling of species and intraspecific diversity for phylogeny reconstruction for each group. Time-calibrated phylogenies for Amicia and Mimosa are presented and used to determine patterns of species diversification in time and space. For Tecoma, incongruence between nuclear and chloroplast gene trees precludes straightforward estimation of a species tree and this incongruence is attributed to possible reticulation caused by hybridization. Divergence time estimates and patterns of diversification for Amicia and Mimosa are compared with other Andean SDTF groups (Cyathostegia, Coursetia, Poissonia; Leguminosae) using isolation by distance and phylogenetic geographic structure analyses. Consistently deep divergences between sister species and high geographic structure across all five groups suggest that Andean SDTF lineages have persisted over the past 10 million years (My) with high endemism driven by dispersal limitation, caused by geographic isolation, following the most recent episode of rapid mountain uplift 5-10 My ago. This prolonged stasis of the Andean SDTF biome is in line with Miocene fossil and paleoclimate evidence. Finally, wider analyses of the contrasting evolutionary timescales of older SDTF and more recent high-altitude grassland diversity suggest that the exceptional plant species diversity in the Andes is the outcome of highly heterogeneous evolutionary histories reflecting the physiographical heterogeneity of the Andean biodiversity hotspot.

Thesis (M.S.)--University of Tennessee, Knoxville, 2010. / Title from title page screen (viewed on July 20, 2010). Thesis advisor: Paul Ayers. Vita. Includes bibliographical references.

Text in Afrikaans / Die samelewing heleef tans groot veranderinge. Die kerk en gesinslewe word heide daardeur geraak. Al meer druk word op gesinslewe geplaas en daardeur verander gesinne se hehoeftes. Een van die grootste hehoeftes van gesinne is 'n hehoefte aan diepteverhoudings, medemenslike erkenning, emosionele sekuriteit en interpersoonlike intimiteit. Die kerk moet hierdie hehoeftes kan raaksien en aanspreek. Vir 'n hediening aan gesinne en deur gesinne, is dit noodsaaklik dat die gemeente opnuut weer God se plan met die gesin herontdek; die gemeente moet die gesin as 'n ekosistemiese eenheid verstaan en die ontwikkelingsfases en emosionele prosesse binne 'n gesinsisteem moet in ag geneem word. In hierdie studie word die selgemeente gehruik om moontlike antwoorde te hied vir die hehoeftes van gesinne. Die hevinding van hierdie studie is dat die selgemeente oor die potensiaal heskik om vir die gesin 'n ware tuiste te hied waar gelowige gesinne toegerus en opgehou kan word vir hulle roeping in die gemeente, die samelewing en die wereld. Die selgemeente kan 'n moontlike model vir 'n gesinshediening wees. / The church and family are both affected by the immense changes in society. Family needs change under the pressure of these changes. Among the greatest family needs are a relationship with depth, acknowledgement from fellow-man, emotional security and interpersonal intimacy. The church must recognise these needs and address them. A ministry to families must firstly rediscover God's plan for the family; secondly the family must be seen as an ecosystemic unity; thirdly development and emotional phases in the family must be understood and managed. I used the cell church model as a basis to develop a structure for family ministry. I found the cell church model to be essentially a relationship model. I came to the conclusion that the cell church model has the potential to be a genuine home for family; to be a basis from which the family can be built up and from which the family can be equipped for their calling. Thus, I found the cell church model to be a possible model for family ministry. / Philosophy, Practical & Systematic Theology / M. Th. (Practical Theology)

Text in Afrikaans / Die samelewing heleef tans groot veranderinge. Die kerk en gesinslewe word heide daardeur geraak. Al meer druk word op gesinslewe geplaas en daardeur verander gesinne se hehoeftes. Een van die grootste hehoeftes van gesinne is 'n hehoefte aan diepteverhoudings, medemenslike erkenning, emosionele sekuriteit en interpersoonlike intimiteit. Die kerk moet hierdie hehoeftes kan raaksien en aanspreek. Vir 'n hediening aan gesinne en deur gesinne, is dit noodsaaklik dat die gemeente opnuut weer God se plan met die gesin herontdek; die gemeente moet die gesin as 'n ekosistemiese eenheid verstaan en die ontwikkelingsfases en emosionele prosesse binne 'n gesinsisteem moet in ag geneem word. In hierdie studie word die selgemeente gehruik om moontlike antwoorde te hied vir die hehoeftes van gesinne. Die hevinding van hierdie studie is dat die selgemeente oor die potensiaal heskik om vir die gesin 'n ware tuiste te hied waar gelowige gesinne toegerus en opgehou kan word vir hulle roeping in die gemeente, die samelewing en die wereld. Die selgemeente kan 'n moontlike model vir 'n gesinshediening wees. / The church and family are both affected by the immense changes in society. Family needs change under the pressure of these changes. Among the greatest family needs are a relationship with depth, acknowledgement from fellow-man, emotional security and interpersonal intimacy. The church must recognise these needs and address them. A ministry to families must firstly rediscover God's plan for the family; secondly the family must be seen as an ecosystemic unity; thirdly development and emotional phases in the family must be understood and managed. I used the cell church model as a basis to develop a structure for family ministry. I found the cell church model to be essentially a relationship model. I came to the conclusion that the cell church model has the potential to be a genuine home for family; to be a basis from which the family can be built up and from which the family can be equipped for their calling. Thus, I found the cell church model to be a possible model for family ministry. / Philosophy, Practical and Systematic Theology / M. Th. (Practical Theology)