An unusually high level of inter- and intraspecific variability in spermatozoa has been well documented. However, recent evidence indicates that the level of variation within spermatozoa differs markedly across taxa. In particular, it appears that the variability in spermatozoa tends to decrease across species as the risk of sperm competition increases. In this thesis, I present a model that explains how variability in spermatozoa may arise due to errors made during the sperm production process. In doing so, I also provide an explanation for why variability in sperm traits tends to decrease as the level of sperm competition experienced by males of a given species increases. The model presented in this study provides a novel perspective on spermatozoa and their production. While many sperm traits are thought to be selected upon, I suggest that variability in spermatozoa may also be the result of evolutionary forces such as sperm competition. Variability in spermatozoa, then, can be adaptive and can represent an optimal reproductive strategy. / Thesis (Master, Biology) -- Queen's University, 2009-09-25 21:53:23.172

Inadequate demographic data in Lesotho inhibits demographic research. Nonetheless, indirect demographic techniques have proven to be useful tools in the developing world, as their application to census and survey data has greatly expanded knowledge of the demographic situation in data deficient countries (Brass, 1996). The different techniques are based on specific assumptions and robustness of available data, thus deserves caution in application. Failure to adhere to these methodological specifications results in generation of more errors (Feeney, 1996). The impetus of this research was to assess the applicability of the P/F ratio method in estimating recent fertility levels in Lesotho. In particular, the data was evaluated to verify the following P/F ratio assumptions; (1) constant fertility; (2) accurate reporting of fertility by younger women; and (3) correct age pattern of fertility. In order to obtain optimal fertility estimates, the research undertook extensive data assessment, and corrections where possible, of individual variables employed in the P/F ratio method. In line with previous studies, the magnitude and pattern of the P/F ratios represented strong evidence of fertility decline in Lesotho. This evidence rendered the Brass P/F ratio method inappropriate for estimation of recent fertility levels in the country. Therefore, this research presents the Relational Gompertz model faring better in indirectly estimating fertility levels in Lesotho. Not undermining the Bureau of Statistics, the current study challenges the Bureau's estimates, and declares own estimates as more likely precise estimates of recent fertility levels in Lesotho when using the P/F ratio method. This assertion is grounded on the basis that compared to the Bureau, the study undertook and presented detailed data evaluation and adjustments, as well as adhering to the P/F ratio methodological assumptions. Nonetheless, the research also concludes that indirect techniques do not necessarily provide an utopia to demographic estimation in poor data countries. Even when the robust measures were employed, the quality of the 1996 data yielded implausible estimates as the method could not account for the degree of unreported births. This calls for caution during data collection and processing in order to minimise the reporting errors. / Thesis (M.Dev.Studies)-University of KwaZulu-Natal, Durban, 2006.

Zimbabwe is amongst the few countries in Africa with a low fertility rate. The fertility transition began in the 1980s and has continued in recent years. The total fertility rate (TFR) declined from 5.5 births in 1988 to 4.3 births in 1994 and further declined in 1999 and 2005 to 4.0 births and 3.8 births respectively. Fertility declined by 1.7 births from 1988 to 2005. This study examines and evaluates the proximate determinants responsible for fertility decline in Zimbabwe from 1988 to 2005. The study attempts to address two questions: What are the principal proximate determinants responsible for fertility reduction in Zimbabwe? What is the contribution of each of the proximate determinants to fertility decline at different periods of time in Zimbabwe? This study utilizes data from the Zimbabwe Demographic and Health Surveys (ZDHS) conducted in Zimbabwe from 1988 to 2005. The model introduced by Bongaarts (1978, 1982) and later modified by Jolly and Gribble (1993) will be utilized in this study to evaluate the impact of these proximate determinants on fertility. The results from the study confirm that fertility has declined in Zimbabwe from 1988 to 2005. The decline in fertility was influenced by proportion of women married, contraceptive use and postpartum infecundability. Since abortion is illegal in Zimbabwe, there is no reliable data available to examine its impact on fertility. As a result this determinant was not examined in this study. The results show that contraceptive use is the leading inhibitive factor of fertility from 1988 to 2005 in Zimbabwe. The findings also confirm that postpartum infecundability followed by marriage patterns is also responsible for fertility reduction during the same period. The results also showed that there are no variations in proximate determinants of fertility from 1988 to 2005. A review of the literature suggests that Zimbabwe is amongst the few countries in the subSaharan Africa with a high contraceptive rate. The family planning programmes introduced by the government before and after independence which were well organized and administered influenced fertility levels observed in Zimbabwe. It is hoped that this study will assist policy makers in developing countries especially Africa to reduce fertility rates. / Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2008.

The mitochondria are the primary energy providers for most eukaryotic cells. The substrate and products of the mitochondria need to be translocated across the semi-permeable mitochondrial outer membrane (MOM). Mitochondrial porin is an aqueous channel in the MOM thought to provide the primary pathway for metabolite translocation. Porin is a nuclear encoded protein and therefore needs to be transported to the mitochondria, translocated across and assembled within the MOM. Of all the recognition signals required for successful transport, import and assembly, only the β-sorting signal used in assembly is known. In addition, this protein possesses the ability to gate, and in doing so can preferentially allow the passage of anions in the open state and cations in the closed state. However, the precise mechanism by which gating of porin occurs and a complete understanding of porin’s function in vivo remains elusive. The essentiality of porin was examined by constructing a strain of Neurospora crassa deficient for porin. This strain, denoted as WS004, exists as evidence that porin is non-essential for the survival of Neurospora crassa. However, the loss of porin results in a reduction in growth rate due to the dysfunction of the cytochrome mediated respiratory pathway, which was made evident by the reduction of cytochrome b and almost complete lack of cytochrome aa3. WS004 survives by inducing the expression of alternative oxidase, which funnels the electrons from the Q pool directly to oxygen, bypassing the cytochrome b and aa3 containing complexes III and IV respectively. Additional phenotypic differences observed included loss in ability to produce aerial hyphae, reduced amount of conidia produced and strains that were female sterile. It was determined, that additional genetic factors influenced the resulting phenotype due to the loss of porin. LC-MS/MS, in combination with iTRAQ labelling, was utilized to examine changes in the proteome profiles of porin containing and porin lacking mitochondria and showed several different proteins as significantly up- or down-regulated which lend to an explanation to some of the phenotypes observed. Taken together, these results demonstrate the central role of porin in regulating both mitochondrial and cellular processes.

No description available.

Recent literature finds that in OECD countries the cross- country correlation between the total fertility rate and the female labor force participation rate has changed from negative till the mid-1980s to positive afterwards. In sharp contrast, other studies show that this negative relationship continues to exist, however the magnitude of the effect is lower. In this paper I look at a panel of 23 OECD aggregate fertility and labor market data from 1965 – 2013 and account for country as well as year fixed effects. My findings document that there exists a negative relationship between fertility and female employment for the years 1965 – 1985, as there existed a high level of incompatibility between mother and worker roles at that time. After this time period no relationship between fertility and employment exists. The presence of a number of other country and year specific factors affects the level of labor force participation and fertility decisions of a woman. When accounted for, the cross-country time-series association between fertility and female employment seems to fade away and does not exist any longer after the mid-1980s.

This study of Fertility Differentials in Bangladesh is based on a subset of data obtained from the 1983 Bangladesh Contraceptive Prevalence Survey. The focus of the study is to identify the variables that significantly affect the cumulative fertility of women in Bangladesh and to examine differentials in fertility.Path analysis has been used for analyzing the data of this thesis. Differentials in fertility are examined in terms of selected demographic and socio-economic characteristics of the ever married women and their husbands.The study shows that age of women has the highest effect on number of children ever born. Religion has positive and significant direct effects on fertility. Education of women has significant negative effects on fertility. Employment status of women effect fertility negatively in rural Bangladesh. The results of this study also suggest that high fertlity in Bangladesh will persist if immediate action is not taken to halt it. / Department of Mathematical Sciences

The mitochondria are the primary energy providers for most eukaryotic cells. The substrate and products of the mitochondria need to be translocated across the semi-permeable mitochondrial outer membrane (MOM). Mitochondrial porin is an aqueous channel in the MOM thought to provide the primary pathway for metabolite translocation. Porin is a nuclear encoded protein and therefore needs to be transported to the mitochondria, translocated across and assembled within the MOM. Of all the recognition signals required for successful transport, import and assembly, only the β-sorting signal used in assembly is known. In addition, this protein possesses the ability to gate, and in doing so can preferentially allow the passage of anions in the open state and cations in the closed state. However, the precise mechanism by which gating of porin occurs and a complete understanding of porin’s function in vivo remains elusive. The essentiality of porin was examined by constructing a strain of Neurospora crassa deficient for porin. This strain, denoted as WS004, exists as evidence that porin is non-essential for the survival of Neurospora crassa. However, the loss of porin results in a reduction in growth rate due to the dysfunction of the cytochrome mediated respiratory pathway, which was made evident by the reduction of cytochrome b and almost complete lack of cytochrome aa3. WS004 survives by inducing the expression of alternative oxidase, which funnels the electrons from the Q pool directly to oxygen, bypassing the cytochrome b and aa3 containing complexes III and IV respectively. Additional phenotypic differences observed included loss in ability to produce aerial hyphae, reduced amount of conidia produced and strains that were female sterile. It was determined, that additional genetic factors influenced the resulting phenotype due to the loss of porin. LC-MS/MS, in combination with iTRAQ labelling, was utilized to examine changes in the proteome profiles of porin containing and porin lacking mitochondria and showed several different proteins as significantly up- or down-regulated which lend to an explanation to some of the phenotypes observed. Taken together, these results demonstrate the central role of porin in regulating both mitochondrial and cellular processes.

No description available.

No description available.