Biology Commons^™

Evolution Of Hybrid Incompatibilities In Gene Regulatory Networks, Alexander Y. Tulchinsky

Open Access Dissertations

Under the Dobzhansky-Muller model, postzygotic isolation results from incompatibility between interacting genes. Evidence points to regulatory networks as a rich source of incompatibilities that impact hybrid fitness. Pleiotropy is a natural feature of regulatory networks because regulatory elements generally have multiple targets. Both pleiotropy and hybrid incompatibility arise due to genetic interactions; therefore we can expect an intimate association between them. In the following chapters, I investigate the relationship between pleiotropy and hybrid incompatibility in the context of regulatory networks.

In chapter one, I extend a general network-based study of hybrid incompatibility by incorporating a sequence-based thermodynamic model of transcriptional …

The Ecology And Conservation Of The Eastern Spadefoot (Scaphiopus Holbrookii) In The Province Lands Of Cape Cod National Seashore, U.S.A., Brad Timm

Open Access Dissertations

The eastern spadefoot (Scaphiopus holbrookii) is an ephemeral wetland breeding amphibian that ranges from southern Florida north and westward to southeastern Missouri and northward along the Atlantic coastal plain to Massachusetts. This species is listed as either "threatened" or "endangered" in the four states (Connecticut, Massachusetts, New York, and Rhode Island) in the northeastern United States where it is known to exist. Population declines and extirpations throughout the region over the past century have been documented and are largely believed to be the result of habitat loss and/or alteration.

Very limited empirical results exist on many life history attributes of …

Target Recognition And Competitive Synaptogenesis In The Drosophila Giant Fiber System, Jason Joseph Hill

Open Access Dissertations

The development of complex neural networks relies on a careful balance of environmental cues to guide and shape both ends of the eventual connection. However, the correct wiring of circuits whose components share molecular profiles depends on a more elaborate phenomenon, competition. Despite being highly studied, there is still a lack of understanding as to the mechanism that allows molecularly identical cells to form exclusive connections with their targets. To address this complex question, we turned to a simple circuit within the genetically tractable fly. Responsible for the escape reflex, the Giant Fiber System is comprised of bilaterally symmetrical axons …

The Conservation Value Of Residential Landscapes For Native Bird Communities: Patterns, Processes, And Management Implications, Susannah Beth Lerman

Open Access Dissertations

Urbanization, as it transforms natural biotic systems into human-dominated landscapes, is recognized as one of the greatest threats to biodiversity throughout the world. Furthermore, urban dwellers are becoming increasingly disconnected with the natural world. Here I investigate whether residential landscape designs that mimic the natural environment can provide habitat for native birds. First I uncover some of the patterns of bird distribution in residential yards by incorporating habitat features, urbanization measurements and socioeconomic factors with bird monitoring data into a multivariate analysis. The results indicate that native birds associate with neighborhoods with native plants and shrubs, neighborhoods closer to desert …

New Genomic Approaches Reveal The Process Of Genome Reduction In Prochlorococcus, Zhiyi Sun

Open Access Dissertations

Small bacterial genomes are believed to be evolutionarily derived from larger genomes through massive loss of genes and are usually associated with symbiotic or pathogenic lifestyles. It is therefore intriguing that a similar phenomenon of genome reduction has been reported within a group of free-living phototrophic marine cyanobacteria Prochlorococcus. Here I have investigated the roles of natural selection and mutation rate in the process of Prochlorococcus genome size reduction. Using a data set of complete cyanobacterial genomes including 12 Prochlorococcus and a sister group of 5 marine Synechococcus, I first reconstructed the steps leading to Prochlorococcus genome reduction …

The Role Of Dawn Song In Tree Swallows And Its Place In The Diversity Of Oscine Song Learning, Benjamin Nichols Taft

Open Access Dissertations

Aspects of the behavioral ecology of bird song learning are examined in three parts. First, an approach from image analysis is extended to allow rapid, quantitative description of animal sounds. In this approach, sounds are summarized as sets of time-frequency-amplitude landmarks. Second, the role of dawn song in tree swallow (Tachycineta bicolor) breeding biology is examined. Song syllable sharing among tree swallows was found to be high among birds nesting at the same site, but sharing was lower between birds nesting at different sites. When birds nested at different sites, the distance between those sites was not related …

Piping Plover (Charadrius Melodius) Conservation On The Barrier Islands Of New York: Habitat Quality And Implications In A Changing Climate, Jennifer Ruth Seavey

Open Access Dissertations

Habitat loss is the leading cause of species extinction. Protecting and managing habitat quality is vital to an organism's persistence, and essential to endangered species recovery. We conducted an investigation of habitat quality and potential impacts from climate change to piping plovers (Charadrius melodius) breeding on the barrier island ecosystem of New York, during 2003-2005. Our first step in this analysis was to examined the relationship between two common measures of habitat quality: density and productivity (Chapter 1). We used both central and limiting tendency data analysis to find that density significantly limited productivity across many spatial scales, especially broader …

The Activity Of Eg5 And Dynein During Mammalian Mitosis, Nicholas P. Ferenz

Open Access Dissertations

The development and maintenance of multicellular organisms depends fundamentally on cell division, a series of events largely mediated by the mitotic spindle. Errors in spindle formation and/or function are often associated with severe consequences, most notably cancer. In order to elucidate the cause of such errors and the potential for therapeutic intervention, it is imperative to attain a clear understanding of how cell division normally operates. In this regard, this dissertation focuses on the activity of two microtubule-based motor proteins, Eg5 and dynein, prior to and immediately following nuclear envelope breakdown during mitosis. I show that prophase microtubules are remarkably …

Determinants For Stop-Transfer And Post-Import Pathways For Protein Targeting To The Chloroplast Inner Envelope Membrane, Antonio Americo Barbosa Viana

Open Access Dissertations

Chloroplast biogenesis relies on the import of thousands of nuclear encoded proteins into the organelle and proper sorting to their sub-organellar compartment. The majority of nucleus-encoded chloroplast proteins are synthesized in the cytoplasm and imported into the organelle via the Toc-Tic translocation systems of the chloroplast envelope. In many cases, these proteins are further targeted to subcompartments of the organelle (e.g. the thylakoid membrane and lumen or inner envelope membrane) by additional targeting systems that function downstream of the import apparatus. The inner envelope membrane (IEM) plays key roles in controlling metabolite transport between the organelle and cytoplasm, and is …