Lynn Margulis, 1938--2011

Organismic and Evolutionary Biolog

Paleobiological Perspectives on Early Eukaryotic Evolution

Eukaryotic organisms radiated in Proterozoic oceans with oxygenated surface waters, but, commonly, anoxia at depth. Exceptionally preserved fossils of red algae favor crown group emergence more than 1200 million years ago, but older (up to 1600–1800 million years) microfossils could record stem group eukaryotes. Major eukaryotic diversification ∼800 million years ago is documented by the increase in the taxonomic richness of complex, organic-walled microfossils, including simple coenocytic and multicellular forms, as well as widespread tests comparable to those of extant testate amoebae and simple foraminiferans and diverse scales comparable to organic and siliceous scales formed today by protists in several clades. Mid-Neoproterozoic establishment or expansion of eukaryophagy provides a possible mechanism for accelerating eukaryotic diversification long after the origin of the domain. Protists continued to diversify along with animals in the more pervasively oxygenated oceans of the Phanerozoic Eon.Earth and Planetary SciencesOrganismic and Evolutionary Biolog

An Analysis of Communion Hymns in The Lutheran Hymnal and of Certain Communion Hymns Available from Outside Sources

The purpose of this project is to analyze the Communion hymns of the present Lutheran Hymnal in terms of their eucharistic value and to investigate other Communion hymns of the Christian Church as to their usability in our future hymnal, especially their accent on the euchariatic nature of the Sacrament. It is the writer\u27s opinion that hymns 304 to 316 (\u27\u27The Lord\u27s Supper section of TLH) are inadequate both in number and in quality for expressing our reawakened appreciation of the Lord\u27s Supper as an opportunity joyously to receive the grace of God in Christ for the preservation and strengthening of our Christian lives. Since many congregations have increased the frequency of their celebrations, and since our theology is tending toward placing the Sacrament in its historic center of the worship life of the Church, our present repertoire is not representative of this spirit

The Abundance and Distribution of Mallards in the Lower Mississippi Alluvial Valley of Arkansas

The management of wintering waterfowl in North America requires flexibility because of constantly changing landscapes and conditions. Many mallards use the lower Mississippi Alluvial Valley (MAV) for wintering habitat, making this an area of emphasis for improving management strategies. In this study, I used mallard observation data from 2009-2014 aerial surveys collected in the Arkansas portion of the lower MAV to explain the abundance and distribution and of mallards. Using spatial hierarchical models and breaking covariate data to 2x2 km grid cells, I analyzed how covariates relate to the changes of abundance and distributions within and among surveys. Mallard abundance and distributions responded positively to surface water along with the land cover habitat inundated by that water. Rice fields, wetlands, soybean fields, and fallow (uncultivated) fields were used most by mallards. My models also showed a strong spatial pattern of mallard abundance across the MAV suggesting that covariates other than the ones used here may be important in better explaining mallard distribution. Biologists in the lower MAV can use these results to better conserve and manage lands for mallards

Studies Of The Visual Detection Of Bilateral Symmetry

Ernst Mach (1897) first observed that bilateral symmetry was most easily observed when the axis of symmetry was vertical, and proposed this occurred because of symmetric connections across the vertical midline of the visual system. This neuroanatomical account has been reasserted by Julesz (1971) and Braitenberg (1984, 1990). Braitenberg suggested that the corpus callosum could serve as a conduit for connections between cells representing symmetric areas in space around the vertical midline. If vertical symmetry in the visual system mediates the vertical advantage there are a number of predictions that follow. One would expect that the tuning of symmetry detection around vertical should be narrow, eccentric presentation of patterns should reduce the vertical advantage, and the vertical advantage should be absent at fixation in individuals without a corpus callosum. Five experiments were conducted to test these predictions. Subjects were tested using a signal detection paradigm. Symmetric and random patterns composed of 72 dots placed within a circular field were presented for brief durations. Vertical symmetry was found to be more detectable at fixation than symmetry at other orientations (from 5{dollar}\sp\circ{dollar} to 90{dollar}\sp\circ{dollar} off vertical, Experiments 1 & 3). No systematic differences were observed for the detection of non-vertical symmetry when patterns were presented at different positions along the horizontal midline (up to 4.8{dollar}\sp\circ{dollar} from fixation to the left or right, Experiments 2, 3, & 4), and the vertical midline (Experiment 4). Vertical symmetry was best detected when presented at fixation (Experiments 2, 3, & 4), and detectability dropped off when stimuli were presented as little as 0.6{dollar}\sp\circ{dollar} off fixation (Experiment 3). Two individuals born without a corpus callosum did not detect vertical symmetry best at fixation, whereas their age, intelligence, and gender matched controls demonstrated a vertical symmetry preference (Experiment 5). These results are in general agreement with the neuroanatomical proposal, and are interpreted in relation to other proposals for how bilateral symmetry may be detected. It is unclear how non-vertical or non-fixated bilateral symmetry is detected, although arguments for a spatial-frequency decomposition of images are discussed