777 resultados para trophic resource
Resumo:
In marine benthic communities, herbivores consume a considerable proportion of primary producer biomass and, thus, generate selection for the evolution of resistance traits. According to the theory of plant defenses, resistance traits are costly to produce and, consequently, inducible resistance traits are adaptive in conditions of variable herbivory, while in conditions of constant/strong herbivory constitutive resistance traits are selected for. The evolution of resistance plasticity may be constrained by the costs of resistance or lack of genetic variation in resistance. Furthermore, resource allocation to induced resistance may be affected by higher trophic levels preying on herbivores. I studied the resistance to herbivory of a foundation species, the brown alga Fucus vesiculosus. By using factorial field experiments, I explored the effects of herbivores and fish predators on growth and resistance of the alga in two seasons. I explored genetic variation in and allocation costs of resistance traits as well as their chemical basis and their effects on herbivore performance. Using a field experiment I tested if induced resistance spreads via water-borne cues from one individual to another in relevant ecological conditions. I found that in the northern Baltic Sea F. vesiculosus communities, strength of three trophic interactions strongly vary among seasons. The highly synchronized summer reproduction of herbivores promoted their escape from the top-down control of fish predators in autumn. This resulted into large grazing losses in algal stands. In spring, herbivore densities were low and regulated by fish, which, thus,enhanced algal growth. The resistance of algae to herbivory increased with an increase in constitutive phlorotannin content. Furthermore, individuals adopted induced resistance when grazed and when exposed to water-borne cues originating from grazing of conspecific algae both in the laboratory and in field conditions. Induced resistance was adopted to a lesser extent in the presence of fish predators. The results in this thesis indicate that inducible resistance in F. vesiculosus is an adaptation to varying herbivory in the northern Baltic Sea. The costs of resistance and strong seasonality of herbivory have likely contributed to the evolution of this defense strategy. My findings also show that fish predators have positive cascading effects on F. vesiculosus which arise via reduced herbivory but possibly also through reduced resource allocation to resistance. I further found evidence that the spread of resistance via water-borne cues also occurs in ecologically realistic conditions in natural marine sublittoral. Thus, water-borne induction may enable macroalgae to cope with the strong grazing pressure characteristic of marine benthic communities. The results presented here show that seasonality can have pronounced effects on the biotic interactions in marine benthic communities and thereafter influence the evolution of resistance traits in primary producers.
Resumo:
Over the past several decades, many theories have been advanced as to why efforts to reform the public service have met with only limited success. Clearly, the role of leadership with respect to reform must be examined, since successful organizational leaders should be extremely accomplished in the promotion and protection of the values that underlie decision-making. The issue of effective leadership is particularly significant for the future of the public service of Canada. Large numbers of public servants in the executive ranks are due to retire within the next five years. Given their central role, it is vital that there be enough dedicated and committed public servants to staff future vacancies. It is also essential that future public service leaders possess the competencies and values associated with a world-class public service and, a new type of public organization. Related to this point is the importance of people-management skills. People management in the public service is an issue that has historically faced - and will continue to face - major challenges with respect to recruiting and retaining the leaders it requires for its continued success. It is imperative that the public service not only be revitalized and be seen as an employer of choice, but also that the process by which it accomplishes this goal - the practice of human resource management - be modernized. To achieve the flexibility needed to remain effective, the public service requires the kind ofleadership that supports new public service values such as innovation and which emphasizes a "people- first" approach. This thesis examines the kind of public service leadership needed to modernize the human resource management regime in the federal public service. A historical examination of public service values is presented to help determine the values that are important for public service leaders with respect to modernizing human resource management. Since replenishing the 2 ranks of public service leaders is crucial to ensure the quality of service to Canadians, leadership that supports career planning will be a major focus of this paper. In addition, this thesis demonstrates that while traditional public service values continue to endure, innovative leaders must effectively reconcile new public service values with traditional values in order to increase the possibilities for successful reform as well as achieve business objectives. Much of the thesis is devoted to explaining the crucial role of post-bureaucratic leadership to successful reform. One of the major findings of the thesis is that leaders who demonstrate a blending of new public service values and traditional values are critical to creating effective employment relationships, which are key to modernizing human resource management in the federal public service. It will be apparent that public service leaders must ensure that an appropriate accountability framework is in place before embarking on reform. However, leaders who support new public service values such as innovation and empowerment and who emphasize the importance of people are essential to successful reform.
Resumo:
Relationships between surface sediment diatom assemblages and lake trophic status were studied in 50 Canadian Precambrian Shield lakes in the Muskoka-Haliburton and southern Ontario regions. The purpose of this study was to develop mathematical regression models to infer lake trophic status from diatom assemblage data. To achieve this goal, however, additional investigations dealing with the evaluation of lake trophic status and the autecological features of key diatom species were carried out. Because a unifying index and classification for lake trophic status was not available, a new multiple index was developed in this study, by the computation of the physical, chemical and biological data from 85 south Ontario lakes. By using the new trophic parameter, the lake trophic level (TL) was determined: TL = 1.37 In[1 +(TP x Chl-a / SD)], where, TP=total phosphorus, Chl-a=chlorophyll-a and SD=Secchi depth. The boundaries between 7 lake trophic categories (Ultra-oligotrophic lakes: 0-0.24; Oligotrophic lakes: 0.241-1.8; Oligomesotrophic lakes: 1.813.0; Mesotrophic lakes: 3.01-4.20; Mesoeutrophic lakes: 4.21-5.4; Eutrophic lakes: 5.41-10 and Hyper-eutrophic lakes: above 10) were established. The new trophic parameter was more convenient for management of water quality, communication to the public and comparison with other lake trophic status indices than many of the previously published indices because the TL index attempts to Increase understanding of the characteristics of lakes and their comprehensive trophic states. It is more reasonable and clear for a unifying determination of true trophic states of lakes. Diatom specIes autecology analysis was central to this thesis. However, the autecological relationship of diatom species and lake trophic status had not previously been well documented. Based on the investigation of the diatom composition and variety of species abundance in 30 study lakes, the distribution optima of diatom species were determined. These determinations were based on a quantitative method called "weighted average" (Charles 1985). On this basis, the diatom species were classified into five trophic categories (oligotrophic, oligomesotrophic, mesotrophic, mesoeutrophic and eutrophic species groups). The resulting diatom trophic status autecological features were used in the regressIon analysis between diatom assemblages and lake trophic status. When the TL trophic level values of the 30 lakes were regressed against their fi ve corresponding diatom trophic groups, the two mathematical equations for expressing the assumed linear relationship between the diatom assemblages composition were determined by (1) uSIng a single regression technique: Trophic level of lake (TL) = 2.643 - 7.575 log (Index D) (r = 0.88 r2 = 0.77 P = 0.0001; n = 30) Where, Index D = (0% + OM% + M%)/(E% + ME% + M%); 4 (2) uSIng a' multiple regressIon technique: TL=4.285-0.076 0%- 0.055 OM% - 0.026 M% + 0.033 ME% + 0.065 E% (r=0.89, r2=0.792, P=O.OOOl, n=30) There was a significant correlation between measured and diatom inferred trophic levels both by single and multiple regressIon methods (P < 0.0001, n=20), when both models were applied to another 20 test lakes. Their correlation coefficients (r2 ) were also statistically significant (r2 >0.68, n=20). As such, the two transfer function models between diatoms and lake trophic status were validated. The two models obtained as noted above were developed using one group of lakes and then tested using an entirely different group of lakes. This study indicated that diatom assemblages are sensitive to lake trophic status. As indicators of lake trophic status, diatoms are especially useful in situations where no local trophic information is available and in studies of the paleotrophic history of lakes. Diatom autecological information was used to develop a theory assessing water quality and lake trophic status.
Resumo:
Within sport, a tremendous amount of effort is committed to the on-the-field performance of athletes and coaches, neglecting the off-the-field performance and development of sport managers. This study examines the impact of human resource training on the performance of five Canadian national sport organizations (NSO) and their managers (N=22). Data were collected on three outcome variables (learning, individual performance, organizational performance) and three mediating variables (motivation to transfer, training design, organizational climate) at three time measures (pre-training, post-training1, post-training2). Results indicate that training improves the learning and individual performance of sport managers, as well as the organizational performance of NSOs. Varying relationships were found at each of the three time measures, demonstrating that a progression to training-related performance change exists, while providing support for three levels of analysis (individual, organizational, systemic). Implications and future research directions are discussed and highlight the need for on-going training opportunities for Canadian sport managers.
Resumo:
This project focuses on the bullying found in the 21st century elementary classrooms, more specifically in grades 4-8. These grades were found to have high levels of bullying because of major shifts in a student’s life that may place a student of this age at risk for problems with their peer relationships (Totura et al., 2009). Supporting the findings in the literature review, this handbook was created for Ontario grade 4-8 classroom teachers. The resource educates teachers on current knowledge of classroom bullying, and provides them with information and resources to share with their students so that they can create a culture of upstanders. Upstanders are students who stand up for the victims of bullying, and have the self-esteem and strategies to stand up to classroom bullies. These upstanders, with the support of their classroom teachers and their peers, will be a force strong enough to build the government-mandated Safe School environment.
Resumo:
This project focuses on the bullying found in the 21st century elementary classrooms, more specifically in grades 4-8. These grades were found to have high levels of bullying because of major shifts in a student’s life that may place a student of this age at risk for problems with their peer relationships (Totura et al., 2009). Supporting the findings in the literature review, this handbook was created for an Ontario grade 4-8 classroom teachers. The resource educates teachers on current knowledge of classroom bullying, and provides them with information and resources to share with their students so that they can create a culture of upstanders. Upstanders are students who stand up for the victims of bullying, and have the self-esteem and strategies to stand up to classroom bullies. These upstanders, with the support of their classroom teachers and their peers, will be a force strong enough to build the government-mandated Safe School environment.
Resumo:
This project is aligned with examining the role of the education system and the foster care context on the learning experiences of young children in the classroom. This project is a study of the literature and research conducted on the life experiences, adverse effects of these experiences (such as attachment disorder), socioemotional development, and resiliency of foster care children. Furthermore, the project explores the literature on how the experiences of these foster children traverse contexts and impact the education setting. This study also outlines specific strategies and practices for teachers and school staff in order to promote students’ resiliency, competency, behaviour management, and overall educational success and positive academic experience. These strategies resulted from a critical review of the literature and translated into the development of an informative handbook intended for teachers. The handbook developed in this study focuses on the understanding of the lives of foster care children, their histories, adverse experiences, socioemotional development, strategies to manage behaviour, unique needs, and encouraging their resiliency and success in school. To ensure the soundness of the handbook, 2 education liaisons at a Family and Child Services agency within Ontario and a former child and service social worker from Manitoba reviewed the first draft and provided comments on the validity of the content and the potential usability of the handbook for educators. Suggestions and comments provided by these experts were used to enhance the final product of the handbook.
Resumo:
This study surveyed practicing classroom teacher’s perceptions of a proposed educational resource “Avatar Academy” designed to enhance students’, particularly young boys, motivation and general attitude towards learning. The Avatar Academy resource is an instructional guide for implementing a classroom reward system based on common game mechanics. The resource emphasizes the modification of current pedagogies to exploit the use of game design to engage boys. A survey of recent literature indicated an opportunity to study teachers’ perceptions of the possible applications of game design mechanics to support the enhancement of student motivation and learning in the classroom. As a result the Avatar Academy handbook and blog resource were developed to assist teachers with the integration and administration of a program designed to enhance student motivation, especially boys, using avatars and a point based reward system. The resources were initially distributed to several practicing teachers for their review, and their feedback formed the basis for revisions of the Avatar Academy resource. After implementing changes to the resource based on initial teacher feedback, an updated Avatar Academy was redistributed and teacher opinions and perceptions of the tool’s possible impacts on classroom learning were collected.
Resumo:
This study sought to create a curriculum resource for Ontario secondary school educators that addresses the inadequate preparation of students prior to their involvement in community service. Specifically, Helping Youth Venture Into Volunteerism: A Resource for Ontario Secondary School Educators was designed to help grade 10 Civics and Citizenship teachers prepare students for the 40 hours of community service that are a prerequisite for the Ontario Secondary School Diploma. The resource discusses problems with the current unstructured program, outlines researchers’ recommendations to address such problems, and provides comprehensive unit and lesson plans to help educators meet curriculum expectations for grade 10 Civics and Citizenship. In addition, the study examined the rationale and development of the community service program and reviewed related literature corresponding both to Ontario’s community service program as well as service-learning programs in schools. Study results and the accompanying resource will help improve the community service program’s effectiveness by integrating it into school practices and curriculum and making it more relevant, structured, and meaningful to students. By improving the community service program, students will be more engaged in community service and more likely will become lifelong volunteers and active members of their community.
Resumo:
Dans Cet Article, Nous Etudions les Distorsions Que Cause L'impot Sur le Revenu des Societes Dans le Profil de Production des Firmes Extractives et Dans L'allocation des Ressources Entre les Secteurs D'extraction et les Autres Secteurs Soumis a L'impot Sur les Societes. Nous Etudions En Particulier L'allocation D'epuisement, Dont Nous Montrons Qu'elle Peut Trouver Sa Justification, Non Pas a Assurer la Neutralite de L'impot, Mais En Permettant L'etablissement de Taux Effectifs D'imposition Identiques Dans les Secteurs D'extraction et Dans les Autres Secteurs.
Resumo:
This paper proposes a model of natural-resource exploitation when private ownership requires costly enforcement activities. For a given wage rate, it is shown how enforcement costs can increase with labor's average productivity on a resource site. As a result, it is never optimal for the site owner to produce at the point where marginal productivity equals the wage rate. It may even be optimal to exploit at a point exhibiting negative marginal returns. An important parameter in the analysis is the prevailing wage rate. When wages are low, further decreases in the wage rates can reduce the returns from resource exploitation. At sufficiently low wages, positive returns can be rendered impossible to achieve and the site is abandoned to a free-access exploitation. The analysis provides some clues as to why property rights may be more difficult to delineate in less developed countries. It proposes a different framework from which to address normative issues such as the desirability of free trade with endogenous enforcement costs, the optimality of private decisions to enforce property rights, the effect of income distribution on property rights enforceability, etc.
Resumo:
We study a simple model of assigning indivisible objects (e.g., houses, jobs, offices, etc.) to agents. Each agent receives at most one object and monetary compensations are not possible. We completely describe all rules satisfying efficiency and resource-monotonicity. The characterized rules assign the objects in a sequence of steps such that at each step there is either a dictator or two agents who “trade” objects from their hierarchically specified “endowments.”
Resumo:
We analyze the behavior of a nonrenewable resource cartel that anticipates being forced, at some date in the future, to break-up into an oligopolistic market in which its members will then have to compete as rivals. Under reasonable assumptions about the value function of the individual firms in the oligopolistic equilibrium that follows the break-up, we show that the cartel will then produce more over the same interval of time than it would if there were no threat of dissolution, and that its rate of extraction is a decreasing function of the cartel's life; that there are circumstances under which the cartel will attach a negative marginal value to the resource stocks, in which case the rate of depletion will be increasing over time during the cartel phase; that, for a given date of dissolution, the equilibrium stocks allocated to the post-cartel phase will increase as a function of the total initial stocks, whereas those allocated to the cartel phase will increase at first, but begin decreasing beyond some level of the total initial stocks.