• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 117
  • 74
  • 35
  • 21
  • 20
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 363
  • 181
  • 71
  • 49
  • 48
  • 40
  • 34
  • 32
  • 27
  • 27
  • 26
  • 24
  • 24
  • 23
  • 23
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Patterns of Morphological Integration in Modern Human Crania: Evaluating Hypotheses of Modularity using Geometric Morphometrics

Kolatorowicz, Adam 21 May 2015 (has links)
No description available.
102

Central Asian economies and ecologies in the Late Bronze Age : geometric morphometrics of the caprid Astragalus and zooarchaeological investigations of pastoralism

Haruda, Ashleigh Francis January 2014 (has links)
Sheep and goat formed the foundation of pastoral activity across the Central Asian steppe through the Bronze Age. Theories of pastoral activity have assumed that flocks were uniform in association with ethnic groups that crossed the steppe with new ceramic forms and technologies. This study investigated differences between flocks of sheep and goat across the eastern Kazakh steppe in the Late and Final Bronze Age to elucidate the potential for animal exchange and mobility. Geometric morphometric techniques were applied to archaeological astragali from Ovis aries and Capra hircus. The methods for measurement and analysis were carefully developed to control only for inherited characteristics that relate to environmentally driven adaptations in the movement of the hind limb. Efficiency of movement in this limb is tied to survival and reproductive success of animals. Specimens were selected from three archaeological sites located in different ecozones across the steppe to maximize ecological variability. Geometric morphometric results revealed that flocks of sheep exhibited unique astragalus morphology, indicating that crossbreeding and exchange did not occur between sites. These sites were also subjected to full zooarchaeological analyses to investigate variability of economic subsistence patterns. The total number of species as well as investigations into survival and skeletal body part representation revealed that each site had unique subsistence patterns that were related to local ecological resource availability, despite material culture links. This variability in subsistence patterns and flock uniformity indicate that animal trade was not a feature of steppe networks. Local lifeways were specific to small patches of the steppe, despite overarching shared material cultures.
103

The role of the human nasal cavity in patterns of craniofacial covariation and integration

Lindal, Joshua 18 January 2016 (has links)
Climate has a selective influence on nasal cavity morphology. Due to the constraints of cranial integration, naturally selected changes in one structure necessitate changes in others in order to maintain structural and functional cohesion. The relationships between climate and skull/nasal cavity morphology have been explored, but the integrative role of nasal variability within the skull as a whole has not. This thesis presents two hypotheses: 1) patterns of craniofacial integration observed in 2D can be reproduced using 3D geometric morphometric techniques; 2) the nasal cavity exhibits a higher level of covariation with the lateral cranial base than with other parts of the skull, since differences in nasal morphology and basicranial breadth have both been linked to climatic variables. The results support the former hypothesis, but not the latter; covariation observed between the nasal cavity and other cranial modules may suggest that these relationships are characterized by a unique integrative relationship. / February 2016
104

Cisco (Coregonus spp.) diversity in Great Bear Lake Northwest Territories, Canada

Leclaire, Michel 20 January 2017 (has links)
The study characterized the morphological differences among Cisco between geographic arms and depth strata, and determined the trophic positioning of various morphs, based on twelve years of capture data and specimens using morphological measurements, meristic counts, stomach contents, stable isotopes and fatty acids. Two main Cisco morpho-types were identified, a shallow water form and a deep water form that mainly differed in traits associated with swimming and feeding. These results were reinforced by the results on trophic ecology of morphs that demonstrated that each morph occupied a distinct niche. Results showed that shallow water groups had a more varied diet with a high percentage of copepods being ingested whereas deep-water groups showed preferences towards mysids. Although a consistent pattern in differences among shallow and deep morphs was observed, there was some degree of variation among arms of the lake suggesting a degree of isolation and adaptation to local conditions in each area of the lake. For example, in Smith Arm, morphological and dietary differences were found such as narrower body depth and a dietary preference towards daphnia. / February 2017
105

Functional Integration of the Hominin Forelimb

Macias, Marisa Elena January 2015 (has links)
<p>During the last six million years, humans shifted from a primarily arboreal lifestyle to a habitually bipedal, terrestrial lifestyle. Australopithecus had a significant bipedal component to its locomotion; whether suspensory and climbing behavior were also important has remained unclear. Morphological features of the forelimb have been linked to locomotor differences among primates, but the interpretation of human fossils has remained problematic.</p><p>This dissertation examined the total morphological pattern of the forelimb, specifically the functional integration of the musculature and joint systems. This approach employed both geometric morphometrics and a biomechanical modeling approach to studying how and how well the forelimb morphology of living suspensory and quadrupedal primates, as well as humans and fossil hominins, accommodate climbing and suspensory locomotion. Data collected with a microscribe 3-D digitizer on the scapula, humerus, radius, and ulna of Australopithecus sediba, Australopithecus afarensis, and Homo erectus were compared to a sample of Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus, Hylobates lar, and Macaca fuscicularis.</p><p>The hominin upper limb is a rich mosaic of primitive and derived traits. The blade of Australopithecus sediba, although appearing most similar to extant orangutans, is in fact functionally most similar to chimpanzees. The overall morphology of the australopith elbow joint appears most similar to Pan, as does the elbow joint of Homo erectus, suggesting that the modern human configuration happened more recently than 1.5 million years ago. </p><p>Au. afarensis and Au. sediba share important similarities, but are clearly distinct species. While their overall elbow joint shape is strikingly similar, the articular surface is not identical. Au. afarensis is more similar in this respect to Pan and Homo, while Au. sediba is more similar to extant taxa that spend substantially more time engaging in vertical climbing and suspensory behavior.</p><p>The results from this study support previous interpretations that not all australopiths across time were employing the same locomotor repertoire. While this study does not present unambiguous conclusions regarding early hominin arboreal locomotion, this study suggests that the morphology of the upper limb is varied, and caution must be taken when interpreting single skeletal elements in the hominin fossil record.</p> / Dissertation
106

Impacts of Habitat Fragmentation on the Cranial Morphology of a Threatened Desert Fish (Cyprinodon Pecosensis)

Gilbert, Michael Chaise 01 July 2016 (has links)
Drastic alterations to the North American Southwest’s hydrology have highly influenced resident fish communities. In New Mexico and Texas, the Pecos River has been severely altered as a result of water manipulation, isolating backwaters and various habitats that were once connected to the main river. Cyprinodon pecosensis (Pecos pupfish) has been highly impacted due to the effects of anthropogenic water manipulation, as well as species introductions. Cyprinodon pecosensis populations have become isolated and scattered, residing in sinkholes, remnant lakes, and static backwaters, thus creating numerous micropopulations. The purpose of this study was to assess the morphological variation in cranial features that occur in response to varied habitats, especially in terms of environmental factors and species co-occurrence. Landmark-based geometric morphometrics was used to assess shape variation across the aforementioned micropopulations comprising four general habitat types and 27 different localities, each with varied community structure and salinity. Results from this study suggest that head and mandible morphology vary temporally, with year to year variation, as well as among different localities. The head morphology of C. pecosensis was most heavily influenced by habitat type and localities within habitat types, but was largely canalized with the exception of localities classified as deep sinkholes. Year to year variation and localities among habitat types were the most influential factors associated with mandible morphology, but there was strong overlap among the convex hulls that defined regions of morphospace for habitat types. As C. pecosensis is a threatened species, this research has important implications for future conservation and management. Additionally, these results could further aid in the understanding of preserving species in fragmented landscapes.
107

An investigation into bilateral asymmetry of the appendicular skeleton of the adult human and its use in physical and forensic anthropology

Garrido Varas, Claudia E. January 2013 (has links)
The aim of this study was to establish whether the asymmetry of bilateral elements of the skeleton is useful for the reassociation of paired elements in the analysis of commingled skeletal remains; particularly addressing the forensic scenario of Chilean Human Rights cases. The asymmetry of the appendicular skeleton of the modern adult Chilean population was investigated in its morphological aspect, using both traditional anthropometry and geometric morphometrics. The sample was selected from the Colección Subactual de Santiago, housed in the University of Chile, Santiago, Chile, with N= 131 (69 males and 62 females). The traditional metric analysis of size and the geometric morphometric analysis of shape showed that there was a significant difference between sides in both sexes with a strong component of directional asymmetry. Mean metrics and ranges of asymmetry were established, contributing to the characterization of this population. A method to pair match elements from commingled settings, which is a combination of metric ranges of asymmetry and principal component analysis of shape variables, was created resulting in 95% accuracy when pair matching the humerus, radius, femur and tibia. This constitutes an important contribution to the analysis of shape in forensic contexts due to its strong mathematical component, objectivity and repeatability.
108

The evolutionary ecology and population systematics of day geckos (Phelsuma) in the Seychelles

Gardner, Andrew Somerville January 1984 (has links)
The evolutionary ecology and population sytematics of the genus Phelsuma (Gekkonidae) were studied in the Seychelles. The distributions of all 18 Seychelles lizard species are described. These give little evidence for species turnover or the equilibrium model of island biogeography. Aspects of Phelsuma behaviour, social systems and reproduction were investigated. Phelsuma can digest pollen, which, with nectar may constitute a large part of the diet. On Praslin, P.sundbergi and P.astriata breed throughout the year, and partition their macro-habitat, micro-habitat and food resource dimensions such that P.sundbergi mainly occupies nectiferous and polliniferous palms and larger hardwood trees, whilst the smaller P.astriata is found on non-flowering palms and smaller trees. Interspecific competition is demonstrated by population density and habitat shifts between populations on islands in sympatry and allopatry. The biomass of Phelsuma geckos supported by coconut plantations in sympatric and allopatric situations tends to be relatively constant, such that there are either more small geckos or fewer large geckos. It is suggested that large body size is an adaptation to the defence of predictable and defensible food sources, such as palm flowers. Racial differention was investigated by multivariate morphometrics of shape, scalation and colouration, using appropriate techniques to negate ontogenetic effects. In the granitic islands, three phenetic aggregations of island populations were identified in the P.madagascariensis group, and two aggregations in the P.astriata group. Conventional taxonomic methods have failed to illustrate these patterns of phenetic variation, and new classification of island populations is proposed. Primary patterns of racial differentiation appear to have arisen from the sectioning of pre-existing clinal variation by rising Holocene sea levels, while secondary patterns relate to recent ecological selection pressures. P.abbotti populations on Aldabra and Assumption are sub-specifically distinct and not conspecific with granitic island forms. P.laticauda on the Farquhar group are probably not subspecifically distinct from Madagascan populations. All other coralline island populations appear to be recent introductions from the granitic islands.
109

Morphometric and genetic variation among populations of the southern short-tailed shrew, Blarina carolinensis, located along the Coastal Plain of Virginia

Kersten, Devon 01 January 2011 (has links)
The distribution of short-tailed shrews, Blarina carolinensis and B. brevicauda, demonstrates contiguous allopatry in peninsular situations in the Coastal Plain of Virginia, and in other areas. The distribution of these two species is unusual in that they do not exhibit syntopy except within a narrow corridor along the borders of their ranges. Interestingly, along the Coastal Plain of Virginia, B. carolinensis is generally found only at the distal ends of the peninsular areas, existing as local populations that appear to be isolated from each other and from the primary population that exists in south-central Virginia. It is thought that the disjunct distribution of B. carolinensis populations results from the unique physiography of Chesapeake Bay, namely peninsular water barriers, and that the intervening distribution of its congener, B. brevicuada, should promote morphometric and population differentiation due to isolation. Whether populations of B. carolinensis along the Coastal Plain of Virginia are truly isolated (and possibly morphologically and/or genetically dissimilar to the continuous southeastern Unites States distribution) is unknown. I examined cranial morphometrics and molecular genetic characters (mitochondrial DNA control region and exon-primed intron-crossing nuclear DNA, EPIC) from peninsular populations of B. carolinensis and compared them to shrews of the mainland population to address this question. The sources of specimens were shrews ensnared in discarded bottles along roadsides, museum skins, and specimens frozen in alcohol. Principle coordinate analyses did not indicate a correlation between cranial morphology and genetic structuring of the populations. MANOVA analyses correlate distinct geographic regions with variation of four cranial measurements related to length. A 492 base pair region of the mitochondrial control region was obtained for many specimens and found to be polymorphic resulting in 27 unique haplotypes evenly partitioned across populations reflecting low levels of differentiation. Nuclear DNA markers were not found to exhibit repeatable amplification and therefore were not useful. Genetic variance detected among populations ranged from ΦPT = 0.001 to 0.045. The effective number of migrants (Nem), as estimated from the standard relationship with ФPT values, indicated panmixia. Both sets of observations indicated that physiography and B. brevicauda are not as severe factors limiting migration among the Coastal Plain populations of B. carolinensis as was thought.
110

Přestavby dentálního fenotypu hrabošů v průběhu současného glaciálního cyklu / Dental phenotype variation in voles during the present glacial cycle

Putalová, Tereza January 2016 (has links)
The phenotype dynamics of arvicolid rodents during the terminal stages of the Vistualian glacial and the earliest Holocene was investigated with aid of a detailed morphometric analyses of extensive dental material from three sedimentary series of that age. The particular attention was paid to the record from a section in Býčí skála cave, Moravian karst, which demonstrated details of the Pleistocene/Holocene transition (12.4-8.4 ky BP) with extraordinary resolution. It revealed that dramatic rearrangements in community structure were accompanied by significant rearrangements of the phenotype dynamics in all arvicolid species. Despite some trends specific for particular species, some common features were identified as well. One of them was a rapid turnover in phenotype structure by the end of Younger Dryas, at time of the Preboreal event. (11.7-11 ky BP), the other was associated with the extensive shifts in community structure and habitat diversity at terminal stage of the Preboreal (9.7-9.3 ky). The core arvicolid species of Preboreal communities, Clethrionomys glareolus, Microtus arvalis, M.agrestis and Arvicola terrestris, exhibited repeated fluctuations during that stage (ll-9,3 ky BP) both in abundance and phenotype characteristics, supposedly related to serial invasion events during that time....

Page generated in 1.9958 seconds