The history of an actively star-forming region, containing the young, open cluster NGC 2264, is examined in this thesis using UBVRIHα photographic plate material. After digitization and removal of the variable background from these plates, automatic detection and photometry algorithms yield magnitudes for a set of candidate low-mass cluster members. Using the photographic plates and a supplementary video camera Hα survey, these candidates are selected on the basis of their exhibiting significant Hα emission, large amplitude variability, or anomalously blue colors. To study the age spread in NGC 2264, a theoretical H-R diagram is constructed. Infrared photometry of 33 candidate members permits an evaluation of the bolometric luminosities of these stars; the unreddened (V - R) and (V - I) colors yield effective temperatures. The theoretical mass tracks and isochrones of Cohen and Kuhi (1979) are adopted and extrapolated to lower luminosities and temperatures. The effects of circumstellar dust and gas shells on the location of the NGC 2264 stars in the H-R diagram are examined. No systematic biases in the derived bolometric luminosities and temperatures are found. The optical and infrared excesses of these stars are found to be uncorrelated, requiring separate mechanisms for their generation. A gaseous envelope is most likely the source of the optical excess; thermal emission from hot dust most probably leads to the observed infrared excesses. An age spread for the low-mass NGC 2264 stars of ≳10⁷ years is indicated. Star formation in NGC 2264 is found to have proceeded sequentially as a function of mass and time. Low-mass star formation began ∼2-3 x 10⁷ years ago, peaked ∼4-5 x 10⁶ years ago, and declined thereafter. Star formation at successively higher masses has started, peaked, and then declined at successively younger ages. No significant differences are seen between the field and NGC 2264 luminosity functions to the faintest levels observed (Mᵥ ≈ +11). There is no evidence for a low-mass turnover in NGC 2264.

No description available.

No description available.

Sex-differences in phenotype, development, and life-history can alter the strength of selection experienced by males and females. In particular, theoretical models have demonstrated that differences in the strength of selection between the sexes can influence the deleterious mutation load of populations. Stronger selection acting on males, via the action of sexual selection, could lower the mutation load for females if deleterious mutations tend to be harmful for both sexes. The necessary data to evaluate these models have been lacking, however, as most empirical studies of mutations have overlooked the fundamental differences between the sexes. Using the IV laboratory-adapted population of Drosophila melanogaster, I have measured the sex-specific impact of mutations in both sexes. This was done both for mutations naturally segregating in IV and for new mutations occurring on the X-chromosome. For both classes of mutations, males suffered a greater selective cost than females, and the mutations responsible were deleterious in both sexes. Further characterization of the male fitness phenotype revealed widespread decline in sexually selected characters combined with an increase in the correlation between sexually selected traits and viability, indicative of pleiotropy between new mutations. My work establishes the necessary conditions for sexual selection to reduce the mutation load of females, and helps fill a crucial gap in our understanding of the consequences of deleterious mutations. / Thesis (Ph.D, Biology) -- Queen's University, 2012-01-25 19:27:08.17

An organism’s entire life history - the timing of development, reproduction, senescence and death - can depend on the nature of selection for reproductive age. The outcome of selection will depend both on the particular features of the selective environment and on the genetic architecture of life history in the population. The genetic architecture is highly complex and itself variable in response to selection. Various features of the architecture, including available genetic variation, pleiotropy, epistasis, intersexual genetic correlation, mitochondrial genomes and mito-nuclear interactions all play a role in determining the trajectory of life history evolution, and to interact with one another in doing so. Using eleven laboratory-adapted populations of Drosophila melanogaster that have been subject to controlled long-term selection for differing ages of reproduction, I undertook several experiments that help characterize how these aspects of genetic architecture have contributed to the life history of each population. These experiments combined assays of life history trait values in the standing genetic variation with manipulations of mutation accumulation rate and hybridization, to better understand the nature of selection shaping each life history. I found surprisingly strong positive pleiotropy between early reproduction and longevity, sufficient to maintain a stable ‘surplus’ life span lasting several weeks post-selection. Selection for extremely early reproduction, on the other hand, induced pleiotropic costs to reproductive traits in each sex in a trade-off with development time. Characterization of the intersexual genetic architecture for life span revealed it was largely sex-limited in nature, consistent with a history of intralocus sexual conflict affecting the trait. There was also evidence, however, that mutations affecting life span might interact to reinforce their effects, and that the resulting costs were manifested in both sexes. Selection on mitochondrial genomes in isolation did not contribute to evolution of age-specific reproduction, but mito-nuclear coadaptation was clearly important to its evolution for males in particular. Together, these results expand our understanding of how age-specific selection shapes life history in a popular model organism. They can be used to guide future research in this system and allow us to pose important questions to be tested in other species as well. / Thesis (Ph.D, Biology) -- Queen's University, 2014-05-06 16:01:58.175

The evolution of galaxy populations is dependent upon the environment in which they are located, from low mass galaxy groups to rich galaxy clusters. However, what remains unclear is which physical process(es) dominate this evolution. We investigate this using uniform CFHT Megacam photometry for X-ray selected galaxy clusters from the X-Ray Multi-Mirror (XMM) Large Scale Structure (LSS) survey and the Canadian Cluster Comparison Project (CCCP). These clusters possess X-ray temperatures of 1<kT(keV)<12 and occupy a redshift interval 0.15<z<0.41 to minimise any redshift dependent photometric effects. We investigate the colour bimodality of cluster galaxy populations and compute blue fractions, identifying a trend of increasing blue fraction versus redshift. We also identify an environmental dependence of cluster blue fraction with cool clusters displaying higher values than hotter clusters. Using the local galaxy density parameter, ∑5, we find a greater variation in blue fraction as a function of ∑5 in low mass groups compared to high mass clusters, but all samples show a decrease in blue fraction with increasing local galaxy density, consistent with galaxy-galaxy interactions. Global cluster environment is also playing a role, at similar local galaxy densities, there is a greater decrease in blue fraction as cluster temperature increases. Through simple modelling, we find that our mid and hot samples have had large enough halo masses for sufficient lengths of time for environmental mechanisms to act and observe that the value of fB does not depend strongly on the current state of the X-ray gas. Our dwarf-to-giant ratios add further support to an emerging picture of galaxy-cluster and galaxy-galaxy interactions where we find that the dwarf population is produced via ram-pressure stripping and passive reddening before conversion into giants via the effects of merging. Using the GIM2D modelling package to determine morphological parameters, we observe an increase in the fraction of bulge-dominated galaxies with increasing local galaxy density, however, the morphological mix responds less strongly to variations in global environment than does the colour mix. / Graduate / 0605 / 0606 / sheonaurquhart4@gmail.com

This thesis attempts a positive evaluation of Genesis 1 as a "living cosmology" in our modern age of science and technology. The challenge science poses for traditional religion is identified as functional and philosophical, with the major focus being Neo-Darwinism. Issues raised which are problematic for any doctrine of creation include the explanatory power of Darwinian theory, questions concerning design and morality in relation to natural selection, and the relativisation of the importance and significance of <I>Homo Sapiens</I>. After an examination of the nature of creation faith in the Hebrew Bible and a review of the literary and theological issues in contemporary hermeneutics, Genesis 1 is placed in an exilic context and its original meaning and significance is assessed. In the light of this, and through the appropriation of "reader-criticism", it is argued that Genesis 1 can still be, justifiably, utilised today as a meaningful "literary-theological" response to the question of origins, with many of its features allowing for fruitful correspondence with the details of evolutionary history.

Thesis (M. Div.)--St. Vladimir's Orthodox Theological Seminary, 1988. / Includes bibliographical references (leaves 77-80).

Zugl.: Karlsruhe, Univ., Diss., 2008 / Hergestellt on demand

Zugl.: Karlsruhe, University, Diss., 2008.