Dissertationen zum Thema „Developmental ecological niche theory“

The aim of the study is to investigate a selection of picture books about the start of school to see how children's transitions from preschool to preschool class are depicted. This is to further investigate whether picture books can be used as a complement to transition activities. Through this study, we aim to gain more knowledge about whether the books in the study could serve as a complement to transition activities.  In total, six picture books have been processed using close-up reading as a method and the developmental ecological niche theory. Previous research shows that the transition between preschool and preschool class is a problem area where there are major shortcomings in the interaction between these different activities. Therefore, the study aims to investigate a transitional activity without collaboration requirements for the activities. The results show that the characters in the picture books place the greatest emphasis on the community rather than the teaching and education in school. The social interaction and emotions are close in the plot and are difficult to distinguish as they often reflect each other.
Syftet med studien är att undersöka ett urval av bilderböcker om skolstarten för att se hur barns övergångar från förskola till förskoleklass skildras. Detta för att vidare undersöka om bilderböcker kan användas som komplement till övergångsaktiviteter. Genom denna undersökning strävar vi efter att få mer kunskap kring huruvida böckerna i studien skulle kunna fungera som ett komplement till övergångsaktiviteter. Totalt har sex bilderböcker bearbetats med hjälp av närläsning som metod och den utvecklingsekologiska nischteorin.  Den tidigare forskningen visar att övergången mellan förskola och förskoleklass är ett problemområde där stora brister finns i samverkan mellan dessa olika verksamheter. Därav eftersträvar studien att undersöka en övergångsaktivitet utan samverkanskrav för verksamheterna.  Resultatet visar att karaktärerna i bilderböckerna lägger störst vikt vid gemenskapen snarare än undervisningen och utbildningen i skolan. Det sociala samspelet och känslor ligger nära i handlingen och är svåra att särskilja då de ofta återspeglar varandra.

This dissertation models occupational wage using a fusion of the economic model of supply and demand and an ecological theory of social groups. I argue that competition between different occupations for similar workers is a key element in determining the amount of labor supplied to occupations, and therefore also determines wages. The model places occupational groups in niches within a social space composed of the sociodemographic dimensions of age, education, race, and gender. Occupations compete in their niches for members with other occupations in the niche. High levels of competition lead to lower levels of supply, and, therefore, higher wages. This approach challenges a key assumption of current approaches to wage determination, namely that human capital dimensions are the only dimensions relevant to wage outcomes, and that the effect of these dimensions is constant and unidirectional. I address several lacuna evident in previous work. The model I present is the first truly structural model of occupational interdependence. The model treats the set of occupations holistically, as a interdependent system, rather than independently. In addition, I introduce price into the theory of community ecology, which has been heretofore ignored in this work. Finally, this dissertation presents a theory which may explain the so called dual labor market wage effect. Data is taken from nine consecutive years of the Current Population Survey (1983-1991). I estimate the rate of change of supply and demand in the occupational labor market using a simultaneous equations model which incorporates the effect of competition along multiple social dimensions. I estimate both unidimensional effects of competition along age and education and multidimensional effects of competition along age, education, race, and gender simultaneously.

With recent developments in Scottish education characterised by less prescriptive curriculum guidance, educators, and teachers in particular, are being presented with the opportunity to become more active participants in the curriculum innovation process (Scottish Executive, 2004). This thesis argues, however, that a more participatory curriculum innovation approach contrasts with the centrally-driven top-down curriculum projects that have held currency over the last 30 years; as such, the experiences of most teachers, and their managers, have not helped build the capacity to cope with and influence the curriculum innovation process. Following on, it is suggested there is an urgent need to develop curriculum innovation approaches that specifically set out to help educators construct these innovation-related capacities. The thesis proposes that a more participatory curriculum innovation approach may be achieved by extending concepts from current educational ‘change knowledge’ (Fullan, 1993) to include key principles from complexity-oriented theories (Biesta, 2010; Morrison, 2010). A complex ecological approach (CEA) is presented in which curriculum innovation efforts are portrayed as complex, self organising, emergent, non-linear and ambiguously bounded phenomena influenced by the ongoing interaction of contextual factors and personal capacities. The applicability of this complex ecological approach is explored by means of a case study focused on my personal curriculum innovation efforts in primary physical education (PE) over a twenty-four year period from 1987-2011 in two countries: England and Scotland. I provide a detailed retrospective analysis of the ‘Developmental Physical Education Project’ (DPEP) to explore the extent to which the macro, meso and micro contexts in which I worked and my personal capacities have influenced my curriculum innovation efforts over this twenty-four year period. In particular, the nature of my developmental PE innovation efforts, characterised as complex, self-organising, emergent, non-linear and ambiguously bounded is explored. Analysis reveals the important influence of different contextual factors on the nature of these innovation efforts, particularly the prevailing policy-making and policy-dissemination processes and the support of micro-level management. However, the most significant finding is the central role played by my personal capacities in shaping innovation efforts that, over time, are self-organising, emergent, ambiguously bounded and non-linear. In particular, the analysis highlights how six key capacities; reflection, inquiry, emotions, vision, knowledge and relationships, all played a key role in helping me cope with and influence the innovation process. Given these findings, the thesis concludes by proposing ways in which the CEA may help educators, and teachers in particular, better understand, negotiate and influence future curriculum innovation agendas.

The Unified Neutral Theory of Biodiversity has been advanced as a universal theory for species coexistence in forests worldwide, but few studies have examined its relevance to high-elevation, stressful environments. I established the Utah Forest Dynamics Plot (UFDP) in a heterogeneous subalpine forest at 3,091 m elevation on the Colorado Plateau to examine three underlying assumptions of neutral theory (functional equivalence, ecological equivalence, and habitat generality) and one prediction (the species abundance distribution). The UFDP comprises 27,845 stems ≥1 cm diameter at breast height of 17 species, 10 genera, and 6 families over 13.6 ha. The neutral model was a poor fit to the observed species abundance distribution, but I did not find the alternative lognormal model to provide a better fit. Using spatial pattern analyses of tree data, topography, and soil type, I found some limited support for the neutral theory assumptions of functional and ecological equivalency, with notable exceptions. Populus tremuloides, Pinus flexilis, and Pinus longaeva were characterized by non-neutral recruitment processes, and Abies bifolia and Populus tremuloides exhibited asymmetric competitive and facilitative interactions. The assumption of habitat generality was strongly contradicted, with all ten abundant species in the UFDP having habitat preference. In this subalpine temperate forest, species diversity and community structure are influenced more by habitat heterogeneity, species differences, and niche selection, with neutral processes playing a lesser role.

Two current positions in the field of human development are presented. On the one hand, Scarr' s theory abour the effects of genotype on environment is discussed. On the other hand, the ecological theory of Bronfenbrenner, which describes human developmenr as an interaction between the developing person and his/her environment. The author discusses some aspects of both positions that need furrher study in order ro prevent negarive effects and have a better understanding of child development, in third world countries.
El artículo presenta dos posiciones actuales que buscan explicar el desarrollo humano desde perspectivas diferentes. Por un lado, se presenta la posición de Scarr acerca de los efectos de los genotipos sobre el ambiente, donde el peso de la interpretación está dado en los aspectos hereditarios. Por otro lado, la teoría ecológica sustentada por Bronfenbrenner que define al desarrollo humano como una interacción entre la persona en desarrollo y su medio ambiente. La aurora discute algunos aspectos de ambas posiciones en los que sería importante profundizar para prevenir negativos y tener una mejor comprensión del desarrollo del niño, en países en vías de desarrollo.

Behavioural scientists argue that ‘social learning' provides the link between biological phenomena and cultural phenomena because of its role in the ‘cultural transmission' of knowledge among individuals within and across generations. However, leading authors within the social sciences have proposed alternative ways of thinking about social life not founded on the Modern oppositions including nature-culture, biology-culture, body-mind, and individual-society. Similarly, the distinction between a domain of nature and a domain of nurture has also been extensively criticized within biology. Finally, advocates of ‘radical embodied cognitive science' offer an alternative to the representational-computational view of the mind which supports the conventional notion of culture and cultural information. This thesis attempts to integrate developmental systems theory, radical embodied cognitive science, and relational thinking, with the goal to bring the field of social learning closer to these critical theoretical developments. In Chapter 2, I find no justification for the claim that the genome carries information in the sense of specification of biological form. Chapter 3 presents a view of ontogeny as a historical, relational, constructive and contingent process. Chapter 4 uses the notions of environmental information, abilities, affordances, and intentions to make sense of behaviour and learning. In Chapter 5, I argue that the notion of social learning can be understood in terms of relational histories of development rather than in terms of transmission of information. I then report empirical studies investigating behavioural coordination and social learning consistent with this theoretical framework. Chapter 6 presents evidence that dyads in a joint making activity synchronize their attention constrained by their changing situation and that coordination of attention is predictive of implicit and explicit learning. Chapter 7 presents evidence that joint attention does not require gaze following and that attentional coordination is predictive of learning a manual task. Together, these theoretical and empirical studies suggest a new way of thinking about how humans and other animals live and learn socially, one that is consistent with critical theoretical and philosophical developments that are currently neglected in the literature on social learning.

This exploratory research study examines changes in food and foodways (food habits) among Arab migrant families in a small community in Tampa, Florida. It also explores how those families’ children may play a role in the process of change. Within this community, I conducted my research study at a private school, where I recruited families with children between the ages of eight and seventeen. In applying the ecological model of food and nutrition and the developmental niche theoretical framework, this research draws on qualitative methods, including structured interviews with parents; focus group discussion with parents; a food survey; and children’s focus groups that included engaging activities such as vignettes (role playing), free-listing and sorting, and one-day food menus. I used MAXQDA 18 software for qualitative data analysis, and the results show that the main factors aiding in post-migration food and foodways changes are time constraints (lifestyle), ingredients, and availability and accessibility of permissible food (halal). Parent did not mention their children as a main factor; however, they perceive influence of their children. Feeding practices such as rewarding, restriction, forcing, and family meals were emerging themes, and children express their agency around those practices. Children developed their own agency regarding food because of their social and physical environments. Older children perceived their influence on their families’ food and foodways by introducing food items to their own families.

The aim of this study is to get a deeper understanding, from a Swedish context, of how you can do social work with vulnerable and orphaned children in a developing country such as Uganda. We have investigated this through the example WEBALE, an NGO working in a context where among other things HIV/AIDS, poverty and a defective social safety net have led to social problems affecting children. Further, we have also aimed at acquiring a deeper understanding of what it is that motivates the volunteers and the director to work with vulnerable children at WEBALE. In order to fulfil this aim, the research has the following two key questions: What is the motivation for the teacher volunteers and the manager to work with vulnerable children at WEBALE? How do the teacher volunteers perceive the social work with the children in everyday life at WEBALE and what experiences do they have from this? The study is a field study with a phenomenological and ethnological approach. We were present at and took part in the everyday life of the informants at the school and orphanage in Uganda for eight weeks. The investigation uses a qualitative method where four interviews and participant observations were carried out. The results are analyzed in connection with theories on social work defining preventions and interventions, where theories on risk- and protection factors and the salutogenetic theory on SOC have been used. The analysis is also connected to theories on social work with children from a developmental-ecological and attachment-theoretical perspective. The results show what it is that motivates the volunteers and manager to work as volunteers in this specific contest through personal accounts of their background. Our observation is that the motivation of the volunteers and the manager to work with orphaned and vulnerable children is closely connected to their own background and childhood. The biggest reason for this kind of a life choice seems to be a sense of coherence and the largest motivating factor is that the work they do feels meaningful. The results further highlight the social work that is carried out and how the volunteers perceive their work at WEBALE. The study shows that the volunteers (who mainly consist of teachers) carry out what can be called social work, according to the definitions of interventions and preventions within various fields, such as health, education, emotional and behavioural development, ability to take care of oneself, social behaviour, family and social relations, and identity.

The use of renewable energy as part of the solution for stabilising global warming has been promoted in industrialised countries for the past three decades. In the last ten years, China, a non-democratic and less-developed state, has implemented non-hydro alternative energy sources through top-down, technology-oriented measures and expanded its renewable energy capacity with unprecedented speed and breadth. This phenomenon seems to contradict to the principle of orthodox environmental governance, in which stakeholder participation is deemed as necessary condition for effective policy outcomes. Given that little research has been conducted on environmental politics in an authoritarian context, I first set out to explore the role of the Chinese state in enabling transformation of the renewable energy sector and to understand the ways in which policy elites seek to introduce developmental state and ecological modernisation strategy in the policy area. Second, by adopting principal-agent theory, I explicate how the governance mechanisms have been deployed and how challenges of the expansion of the sector in the governance system with a large territory have being mitigated. Based upon news reports, policy documents, and interviews with 32 provincial officials, business leaders, academic researchers, and NGO practitioners in two subnational governments, I argue that the renewable energy development in China is governed through a hybrid mode of environmental policy model that uses, upon the existing developmental state regime, ecological modernisation as a policy paradigm, which is partially incorporated in the process. Ultimately, I examine in this thesis the possibility of an alternative form of environmental governance in which renewable energy can be diffused in a less-participatory manner, with more direct controls and target-oriented state intervention measures. This thesis challenges the orthodox assumption that the inclusive mode of governance are the only capable form of environmental governance that reaches desired policy outcomes of renewable energy deployment.

Cette thèse s’intéresse aux liens entre réseaux d’interactions en écologie, espace et temps. On assiste à un changement croissant de représentation d’un communauté d’espèces, d’un ensemble d’espèces à un ensemble d’espèces et leurs interactions : un réseau d’interactions. On s’attachera alors à élaborer les prémisses d’une théorie spatiale des réseaux, en développant des méthodes, des modèles et en les appliquant sur des données écologiques. La thèse s’articule autour de quatre chapitres. Dans un premier chapitre, on se penchera sur le problème de comparaison de réseau en différents points du temps et de l’espace. Nous étendrons les mesures de diversité, jusque-là développées pour des abondances uniquement, aux réseaux avec abondances des espèces et des interactions. Nous nous attacherons à définir des indices à plusieurs niveaux d’agrégation des noeuds dans le réseau et montrerons l’intérêt de la méthode sur des données de réseaux trophiques. Dans un deuxième chapitre, nous nous intéresserons au développement d’une théorie des méta-communautés qui modélise explicitement l’espace comme un réseau spatial et la communauté comme un réseau d’interaction. Nous définirons la notion de capacité de persistance de la méta-communauté. Dans un troisième chapitre, nous nous intéresserons aux problèmes d’inférence d’interactions sur des données de sol d’ADN environnemental le long d’un gradient d’altitude dans les Alpes. Nous montrerons que la méthode proposée permet d’estimer l’influence des variables environnementales et de reconstruire un réseau d'interaction cohérent vis-à-vis de la littérature. Dans un quatrième chapitre, nous nous intéresserons à la combinaison d’abondances provenant de différents marqueurs d’ADN environemental et montrerons l’efficacité de la méthode proposée pour obtenir des meilleurs données d’abondances sur des données de plantes
This thesis focuses on the links between interaction networks, space and time. There is a paradigm shift in community ecology concerning the representation of a species community : from a collection of species towards species and their interactions, represented by an interaction network. We aim to build the bricks for a spatial network theory, by developing new methods, new models and applying it on ecological data. This manuscript contains four chapters. In a first chapter, we extend the diversity indices, built on Hill numbers, to network diversity indices. We define diversity indices across species aggregation levelsand show the interest of this method on a trophic network data set. In a second chapter, we develop a spatially explicit meta-community theory, with various kind of interactions. The theory contains a stochastic and a deterministic meta-community model. We then define the notion of meta-community persistence capacity. In a third chapter, we focus on network reconstruction from environmental DNA data along an environmental gradient.We show that the proposed method allows to evaluate the influence of environmental variables on community and infer a network in agreement with the literature on soil interactions. Finally, in a fourth chapter, we develop a method to combine environmental DNA data coming from different primers and show the efficiency of the method to better estimate plant abundances

Advances in medical technology have altered the need for certain types of surgery to be performed in traditional inpatient hospital settings. Less invasive surgical procedures allow a growing number of medical treatments to take place on an outpatient basis. Hospitals face growing competition from ambulatory surgery centers (ASCs). The competitive threats posed by ASCs are important, given that inpatient surgery has been the cornerstone of hospital services for over a century. Additional research is needed to understand how surgical volume shifts between and within acute care general hospitals (ACGHs) and ASCs. This study investigates how medical technology within the hospital industry is changing medical services delivery. The main purposes of this study are to (1) test Clayton M. Christensen’s theory of disruptive innovation in health care, and (2) examine the effects of disruptive innovation on appendectomy, cholecystectomy, and bariatric surgery (ACBS) utilization. Disruptive innovation theory contends that advanced technology combined with innovative business models—located outside of traditional product markets or delivery systems—will produce simplified, quality products and services at lower costs with broader accessibility. Consequently, new markets will emerge, and conventional industry leaders will experience a loss of market share to “non-traditional” new entrants into the marketplace. The underlying assumption of this work is that ASCs (innovative business models) have adopted laparoscopy (innovative technology) and their unification has initiated disruptive innovation within the hospital industry. The disruptive effects have spawned shifts in surgical volumes from open to laparoscopic procedures, from inpatient to ambulatory settings, and from hospitals to ASCs. The research hypothesizes that: (1) there will be larger increases in the percentage of laparoscopic ACBS performed than open ACBS procedures; (2) ambulatory ACBS will experience larger percent increases than inpatient ACBS procedures; and (3) ASCs will experience larger percent increases than ACGHs. The study tracks the utilization of open, laparoscopic, inpatient and ambulatory ACBS. The research questions that guide the inquiry are: 1. How has ACBS utilization changed over this time? 2. Do ACGHs and ASCs differ in the utilization of ACBS? 3. How do states differ in the utilization of ACBS? 4. Do study findings support disruptive innovation theory in the hospital industry? The quantitative study employs a panel design using hospital discharge data from 2004 and 2009. The unit of analysis is the facility. The sampling frame is comprised of ACGHs and ASCs in Florida and Wisconsin. The study employs exploratory and confirmatory data analysis. This work finds that disruptive innovation theory is an effective model for assessing the hospital industry. The model provides a useful framework for analyzing the interplay between ACGHs and ASCs. While study findings did not support the stated hypotheses, the impact of government interventions into the competitive marketplace supports the claims of disruptive innovation theory. Regulations that intervened in the hospital industry facilitated interactions between ASCs and ACGHs, reducing the number of ASCs performing ACBS and altering the trajectory of ACBS volume by shifting surgeries from ASCs to ACGHs.

The biological diversity on planet Earth is astounding. Understanding the origins of this diversity, and how it is maintained, are the twin goals of ecology and evolutionary biology. An early and oft-repeated insight in this investigation is that that similar organisms cannot coexist indefinitely. Theory predicts that individuals and species will compete for limited resources and whichever has even a slight advantage will drive all others extinct in a process known as ‘competitive exclusion’. By diversifying, species avoid competition, thereby ‘stabilizing’ their coexistence. Yet natural systems often display levels of diversity that are surprisingly high, given this theory and investigations of how the similarity of coexisting species is maintained have received much less attention. Using a combination of field studies and experiments I demonstrate that highly similar species of freshwater amphipods may compete for resources without resulting in competitive exclusion. These findings suggest that there exist a range of interactions among Hyalella amphipods, ranging from strong stabilizing effects due to ecological trade-offs, to weakly stabilizing effects, to a total lack of stabilizing effects among various pairs of species in this system. These findings demonstrate how the relative strength of stabilizing forces may vary among coexisting species. Although much effort has been dedicated to enumerating and classifying the ways in which ecological and evolutionary forces promote diversity among species, there has been far less attention paid to mechanisms such as convergent evolution, habitat filtering, competition for non-substitutable resources, and non-ecological speciation, among others. I surveyed current theory that may explain the high levels of similarity among species often found in natural systems. I describe how several ecological and evolutionary mechanisms may operate to promote the coexistence of similar species and present results from new theoretical combinations of mechanisms to demonstrate how they may further act in concert with one another.
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The purpose of the current study was two-fold. Firstly, to explore and describe how school staff members, learners and parents collaborate to prevent violence at two urban secondary schools and secondly, to help school staff members, parents and policymakers to gain a better understanding of the complex and multi-faceted problem of addressing school violence, which should result in guiding them to adopt effective strategies to prevent violence. The ecosystemic perspective, which is an integration of ecological and systems theories combined with the typology of violence, was the theoretical lens through which the phenomenon of adolescent learner violence was viewed. The study was rooted in the sociological interpretative research paradigm and a qualitative descriptive and exploratory case study design was employed. Multi-method data collection strategies (individual, dyad, triad and group interviews; document reviews) were employed to obtain trustworthy data from the three population units of analysis (school staff members, learners and parents) at the two selected urban secondary school sites situated in Johannesburg, South Africa. The inductive qualitative content analysis of the framework approach was used to give a transparent account of the data analysis process. Constant comparative analysis was employed to discover the emergent themes. The main research findings were interpreted by relating the results to the research purpose, the socio-ecological theoretical framework and the existing knowledge base on collaborative strategies for violence prevention. The findings of the current study suggest that family-school collaboration in violence prevention is especially important for families with adolescent children. Adolescence is characterised by many physical and psychological changes and development. Adolescents strive to find their independence and establish their own identities. However, this experimentation may lead to risk-taking or antisocial behaviour. Contrary to current belief, the findings of the current study suggest that adolescent learners want their parents to be involved in their lives and that parents want to support their children’s education but may lack the know-how. The learners explicitly expressed their need for the support and guidance of both their parents and also the school staff members in withstanding the peer and societal pressures that can result in their acting in aggressive or violent ways at school. To promote the positive development of all young people, the school staff members and most centrally young people and their families, must actively work together to establish positive and effective family-school collaborative partnerships as part of their violence prevention strategies. Copyright
Dissertation (MEd)--University of Pretoria, 2010.
Curriculum Studies
unrestricted

La capacité à répondre aux changements environnementaux est cruciale pour l’établissement et la persistance des populations dans un système hétérogène. Les processus sous-jacents à cette capacité peuvent prendre différentes formes. La grande diversité génétique (et phénotypique) découlant de la reproduction sexuée est un des processus permettant à une population de répondre aux différentes conditions environnementales par la survie d’au moins quelques individus. D’autre part, les processus épigénétiques, en permettant la modification du patron d’expression des gènes, contribuent également à la variation phénotypique. Ces variations peuvent survenir accidentellement (épimutations) ou en réponse à un stimulus environnemental (plasticité). Les processus épigénétiques représenteraient ainsi une alternative à la variation génétique pouvant expliquer le succès écologique des organismes génétiquement identiques. Toutefois, les génotypes ne répondent pas tous de la même façon aux conditions environnementales ; certains génotypes sont considérés comme généralistes et peuvent s’acclimater à une vaste gamme de conditions environnementales alors que d’autres sont plutôt spécialistes et restreints à un type d’environnement donné. L’objectif général de cette thèse est de mettre en évidence certains des processus responsables de la persistance des organismes asexués en déterminant les relations entre la variation épigénétique, la variation phénotypique et les stratégies écologiques. Pour ce faire, des hybrides asexués Chrosomus eos-neogaeus, un poisson à reproduction clonale, ont servi de modèle biologique. Se reproduisant par gynogenèse, les lignées clonales (génotypes) doivent faire face aux mêmes variations environnementales que les espèces parentales sexuées. De plus, la répartition géographique de chacune des lignées suggère la présence de génotypes généralistes et spécialistes. L’analyse de ces lignées en milieux naturels et en milieux contrôlés a permis de décortiquer l’influence des variations génétique, environnementale et épigénétique sur la variation phénotypique. Dans un premier temps, les modèles de stratégies généraliste et spécialiste ont été testés de manière empirique : (i) des analyses génétiques ont permis d’inférer les processus historiques expliquant la diversité et la répartition actuelle des lignées clonales ; (ii) l’analyse du patron de ii méthylation de différentes lignées a permis de déterminer l’importance relative des sources de variations épigénétiques selon les fluctuations environnementales et de les associer à une stratégie écologique : une importante influence de l’environnement ou une plus grande stochasticité dans l’établissement des marques épigénétiques étant associées à la plasticité phénotypique ou au bet-hedging, respectivement ; et (iii) le rôle de la plasticité phénotypique dans la diversification de niches écologiques a été souligné par la comparaison de la variation de la morphologie trophique en milieux naturels et contrôlés. D’autre part, le second volet de cette thèse a permis d’associer un coût (détection d’une instabilité développementale) à la plasticité phénotypique et d’élaborer une hypothèse sur l’existence d’un handicap démographique nécessaire afin d’expliquer la situation contre-intuitive concernant la coexistence des organismes gynogènes et de leurs hôtes sexués. La compréhension des différents mécanismes sous-jacents au succès écologique des organismes face aux variations environnementales permet ainsi une meilleure évaluation de leur potentiel évolutif et fournit des outils supplémentaires pour leur protection face à un environnement changeant.
The capacity to cope with environmental changes is crucial to the establishment and persistence of populations. The processes underlying such a capacity can take different forms. The high genetic (and phenotypic) diversity arising from sexual reproduction is one process that allows to cope with different environmental conditions through the survival of at least a few individuals. On the other hand, epigenetic processes, allowing the modification of gene expression, are also responsible for phenotypic variation. Epigenetic changes may occur accidentally (epimutations) or in response to an environmental stimulus (plasticity). Thus, epigenetics would represent an alternative process to genetic variation to explain the ecological success of genetically identical organisms. However, genotypes are not equally capable of coping with environmental changes. Some genotypes are generalists and can acclimatize to a wide range of environmental conditions, whereas other genotypes are specialized and restricted to narrow environmental conditions. The general objective of this thesis is to highlight the processes responsible for the persistence of asexual organisms by determining the relationship between epigenetic processes, phenotypic variation and ecological strategies. To achieve this, the clonal hybrid fish Chrosomus eos-neogaeus were used as a biological model. By reproducing by gynogenesis, the clonal lineages (genotypes) are distributed among the same environments than the sexual parental species. Moreover, the geographical distribution of the lineages suggests the presence of generalist and specialist genotypes. The analysis of these lineages in natural and controlled conditions allowed to disentangling the influence of genetic, environmental and epigenetic variations on phenotypic variation. On the one hand, generalist and specialist strategies were empirically tested: (i) genetic analyses were used to infer the historical processes explaining the diversity and the current distribution of the clonal lineages; (ii) the comparison of methylation patterns in different lineages allowed to determine the dynamism of the epigenetic processes according to environmental fluctuations and to associate them with an ecological strategy: an important environmental or stochastic effect on epigenetic variation being associated with phenotypic iv plasticity or bet-hedging, respectively; and (iii) the role of phenotypic plasticity in niches diversification was highlighted by comparing individuals’ trophic morphology in natural and controlled conditions. On the other hand, the second part of this thesis has allowed to associate a cost (developmental instability) to phenotypic plasticity and to propose a hypothesis about the existence of a demographic handicap necessary to explain the paradox regarding the coexistence of sexual and asexual sperm-dependent organisms. Understanding these different mechanisms underlying the ecological success of organisms in face of environmental heterogeneity allows us to better establish their evolutionary potential and provides additional tools to protect them against changing environments.

As female adolescents go through the transition phase of adolescence, they respond to a variety of factors influencing their sexual development, for instance, cultural practices, socioeconomic status, media exposure, internet access, increased autonomy to explore their sexuality, as well as quality of care, guidance and supervision by primary caregivers. If they do not get enough guidance from caregivers, teachers or medical clinics, adolescents often fall pregnant. The consequences of unexpected pregnancies prove to be negative on intrapersonal as well as interpersonal levels. There is a need to reduce such pregnancies to give adolescents a better chance in life and to enhance optimal development on individual, social, emotional and moral levels. This study explored female adolescents’ experiences and perceptions of teenage pregnancy in Belfast, Mpumalanga, in South Africa. The researcher tried to make a positive contribution towards reducing the incidence of teenage pregnancy in South Africa, especially in rural, farm and semi-urban settings, through an inductive study of African female adolescents in selected secondary schools. Data were collected through individual in-depth audio-recorded semi-structured interviews with 20 African adolescent girls who were purposefully selected for the study. The researcher used Tesch’s method of analysis to analyse the data collected and to deduce themes and categories. Adolescents mostly fell pregnant, because of changes in sexual interest, emotional experiences, social development dynamics, adolescent thinking patterns and failure to use contraceptives. Teenage pregnancy affected the life-world of adolescents by influencing negatively on their physical health, psycho-emotional wellbeing, moral behaviour, social and school lives. The researcher established that the adolescents, their families, communities and society would continue to face the adverse outcomes of teenage pregnancy if the rates of teenage pregnancy remained unabated. The study therefore recommended collaborative efforts of adults in various governmental and private spheres for prevention of teenage pregnancy and for support of adolescent mothers and their babies during and after early-unexpected pregnancies. Some of the recommendations were: national awareness campaigns to curb teenage pregnancies; the review of the Life Orientation curriculum by the Department of Basic Education; the re-orientation of health delivery services; the positive inputs of teachers and schools; and a re-orientation of the responsibilities of primary caregivers and other adults
Psychology of Education
D. Ed. (Psychology of Education)