• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 16
  • 5
  • Tagged with
  • 21
  • 21
  • 21
  • 21
  • 7
  • 7
  • 5
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 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.
11

Taxonomy of the Lesser Whitethroat Curruca curruca evaluated by song

Berg Jöesaar, Märta January 2022 (has links)
No description available.
12

The effects of a new gall midge in the Panamanian fig/fig wasp mutualism

Hedberg, Roberta January 2022 (has links)
The mutualism between the fig tree and the fig wasp pollinator is an important keystone interaction for tropical forests. However, many antagonistic and parasitic species take advantage of the fig/fig wasp mutualism. One such parasite is the gall midge that develops inside fig syconia. Gall midges in fig syconia have sporadically been seen around the world, but until now they have never been observed in Panama. In this study a new Panamanian gall midge in fig syconia is described, together with a supposed parasitoid of the gall midge. The study furthermore investigates the gall midge effect on reproductive success for the fig/fig wasp mutualism. The gall midge is thought to be a new species belonging to the Ficiomyia family. The parasitoid share morphological similarities with the Physothorax family. However, both species need further investigation for proper identification. The gall midge had a significant negative effect on the fig/fig wasp mutualism’s reproductive success. Figs with gall midges inside had less flowers and a lower number of fig wasp offspring. Although, the effect on the reproductive success is small with low gall midge infestation rates.
13

Analys av bipollensorter i Västerbotten : Betydelse och för- och nackdelar med klassiska morfologiska metoder / Pollen grain analysis in Västerbotten, Umeå : Pros and cons using classic morphological methods

Persson, Jesper January 2021 (has links)
Composition of pollen pellets foraged by honeybees, sampled in Degernäs and Tavelsjö, Västerbotten County, during early summer 2020, is used to explore if honeybees are monofloral or polyfloral. Samples from different days and different colours were evaluated by light microscopy. Each unique pollen species in each pellet was morphologically identified with help of an international pollen database (PalDat) and a common bee plant document, using light microscopy and scanning electron microscope photographs. A selection of pollen species were identified down to species level and were used to explore which wild pollinators can also pollinate these plant species, to speculate around possible competition scenarios between them and honeybees. SEM and DNA extraction were performed with a selection of the pollen pellets and with the extracted DNA, different PCR primers targeting different plant gene markers were tested to see which ones worked with pollen from northern Sweden. More detailed pictures of the pollen grains were seen in SEM which helped ease the species identification of some of them. The results showed that only a few of the pollen pellets had only one detected plant species while the rest had 2 or more plant species in them. Thus, these data indicate that the honeybees in Degernäs and Tavelsjö are polyfloral, at least for the samples studied in this bachelor thesis. Methods are evaluated and the findings were that a combination of morphological and molecular biology studies are both needed to be able to establish a new updated pollen database for northern Sweden.
14

Tree diversity and edge effects in Nhamacoa miombo forest, Mozambique

Gårdman, Anton January 2020 (has links)
Mozambique is to fifty percent covered by forest, most of which belongs to the biodiverse miombo woodlands. The last decades, Mozambique has been suffering from rapid deforestation. The once continuous forest cover has turned into a mosaic of forest patches, farmland, settlements etc. The remaining forest patches are in many cases very isolated. These forests have distinct edges towards the neighbouring land, which means that the edge zones have different environmental conditions (more light, higher temperatures etc.) and tree species composition than the interior. In order to examine how the forests of Mozambique are affected by edge effects, the highly isolated Nhamacoa forest was studied. An additional aim of the project was to make a floristic inventory of the forest in order to further assess its conservation status. Specimens were collected, pressed and photographed for identification. Edge effects were studied in plots at the edge and in the interior of the forest in a paired design. Trees inside the plots were identified, counted and measured (dbh (diameter at breast height) and height) to search for differences in species richness, diversity, biomass and height-to-dbh ratios. Environmental parameters (air temp., soil temp., light and slope) were also measured. In total, 76 species of trees were sampled and 44 (35 in the interior and 32 at the edge) of these were found inside the plots. The interior plots harboured significantly more individuals and species of trees than their paired edge plots. Additionally, biomass and height-to-dbh ratios were higher in the interior plots than in the edge plots. These differences strongly suggest that the Nhamacoa forest is affected by edge effects, although none of the measured environmental parameters could explain why. That the Nhamacoa forest is affected by edge effects goes in line with the research hypothesis and shows that it is important to maintain large and intact pieces of forest in order to preserve the Mozambican miombo forests. For future studies, additional environmental parameters (wind speed, humidity etc.) could be examined in order to better explain the presence of edge effects in the Nhamacoa forest.
15

Integrative Approaches Illuminate Evolutionary Divergence in the Bar-tailed Lark Complex ( Ammomanes cinctura)

Liu, Zongzhuang January 2023 (has links)
Ammomanes cinctura (Bar-tailed Lark) is a lark species with a wide distribution in the Palearctic. One of its subspecies, A. c. arenicolor, has a wide range across northern Africa, within which it shows very minor morphological variation but deep divergence in the mitochondrial cytochrome b locus between two geographically widely separated populations. There are two additional allopatric subspecies, A. c. cinctura (Cape Verde Islands) and A. c. zarudnyi (Iran to Pakistan), which differ slightly more in morphology. The genomic population structure, evolutionary history, and taxonomic status of the different populations within this species remain unclear. I applied an integrative approach, using genomic single nucleotide polymorphisms (SNPs), mtDNA and morphological data, to investigate the evolutionary divergence within Ammomanes cinctura. I acquired whole-genome sequence data from twelve individuals from Morocco (n=2), Saudi Arabia (n=7), and Iran (n=3), and performed phylogenetic and population structure analyses. Mitochondrial genomes were assembled and cytochrome b was extracted for phylogeny. Biometric measurements and quantified plumage analysis were conducted on museum specimens of all three subspecies. According to the mitochondrial data, the samples from Saudi Arabia and Iran form a clade that is deeply diverged (5.94 Mya, 95%HPD 3.15–8.95 Mya) from a clade comprising the samples from Morocco and Cape Verde Islands. In contrast, the nuclear SNPs recovered a very shallow divergence (0.095 Mya, 95%HPD 0.04-0.16 Mya) and weak population structure between the samples from Morocco vs. Saudi Arabia–Iran. Morphological results indicated that zarudnyi is slightly differentiated from the other two subspecies, with a larger body size, and the three subspecies are slightly divergent in plumage. The close similarity between Moroccan and Saudi Arabian birds in morphology was also confirmed, in conflict with the molecular data – highlighting the problem with trinomials in this case. The results suggest that the deep divergence in mitochondrial DNA is due to a complex evolutionary history.
16

Optimization of protein extraction from red algae

Kasparaviciute, Deimante January 2024 (has links)
The plastid is an important organelle that allows eukaryotes to photosynthesize. The endosymbiotic event that led to the development of a primary plastid occurred more than one billion years ago. Since then the organelle has undergone a significant genome reduction, losing a large portion of non-essential genes whose function is covered by the eukaryotic host. The majority of the proteins needed for essential plastid function are transcribed in the nucleus and translated in the cytosol. These proteins are then translocated across the inner and outer plastid membranes. The difference in where proteins are translated and transported can be used to study plastid evolution, this can be done by examining what proteins are present in the red algae plastid and comparing it to proteins found in other algae groups. In this project, the exact placement of the proteins, mainly plastid proteins is of interest. In order to localize and identify proteins in the algal cell, an efficient method of cell lysis, both total and incomplete, where the preservation of organelles is essential needs to be developed. This thesis examines a set of different methods of cell lysis, both complete and incomplete, coupled with organelle fractionation, to achieve the isolation of proteins belonging to the different cellular compartments. I show that complete cell lysis with bead milling using 0.1-0.5 mm silica beads is more efficient than a method using a Dounce homogenizer. For incomplete lysis, I show that nitrogen cavitation at 750 psi for 15 min and 1,000 psi for 30 min provides the same level of cellular lysis, indicating that the nitrogen gas equilibrates within 15 minutes. Organelle fractionation with OptiprepTM gradient showed that the majority of the sample did not travel through the gradient, staying in the first layer, which also prevented revelation of the protein pattern on an SDS-PAGE gel, indicating insufficient centrifugation. A great deal of optimization is still required to make these methods as efficient as possible. The step that requires the most optimization is sample preparation for nitrogen cavitation and the use of an ultracentrifuge.
17

Finding the Lady of the Lake : A Geospatial Analysis of Bronze Age Lake Deposition Sites / Sökandet efter damen i sjön : En geospatial studie av bronsåldersdepåer vid sjöar

Schulte Koskinen, julia January 2022 (has links)
During the Bronze Age, bronze items were sacrificed to the gods by leaving them in the landscape. When making these sacrifices, known as deposits, the Bronze Age people followed certain landscape rules. These rules, and other similarities between the sites, can be rediscovered by analyzing the attributes of the sites. By understanding which attributes are relevant for the deposition sites, we can find more sites and contribute to the understanding of how Bronze Age depositions took place. This study aims to identify relevant attributes for the siting of Bronze Age Lake deposition sites near the lakes Mälaren and Hjälmaren in Sweden. 13 lake deposition sites were examined in ArcMap with respect to 6 attributes: Elevation, Soil Wetness, Aspect, Soil Type, Shore Distance, and Shore Direction. The attributes were studied independently of one another. The results revealed that a majority of deposits were the closest to a southern shore, there were no deposits in northern slopes, and no deposits were made between certain distances from the Bronze Age shoreline. Therefore, the attributes Shore Direction, Shore Distance, and Aspect appear to be relevant to lake deposition sites. The study briefly discusses how these results are related to archeological theories. As this study had a small sample size, the results cannot be assumed to apply to all lake deposit sites. Future studies should study more attributes, how attributes relate to one another, and examine the relevant attributes in other landscape features.
18

From Mossdjur to Kokemushirui: Comparing Swedish and Japanese Bryozoan Diversity fromFour Cheilostomatid Families in Museum Collections

Pittman, Casey January 2023 (has links)
No description available.
19

Effekten av predatorinducerade morfologiska förändringar hos Rana temporaria / The effect of predatorinduced morphological changes in Rana temporaria

Tjärnlund Norén, Lindy January 2017 (has links)
Phenotypic plasticity is the ability of an organism to express different phenotypes depending on the biotic or abiotic environment. In many cases, the response to the environment is beneficial to the individual and can therefore represent adaptive phenotypic plasticity. An example includes morphological and life-historical response to predators. Because there has been a weak interest in the effect of these morphological changes, and it often assumes, but rarely shown, that predator-induced changes are adaptive. I tested how different variables, such as maximum acceleration and velocity, were related to each other in different Gosner stages. Eggs and tadpoles of the species Rana temporaria were exposed to various predator enclosures, a control, a stalking predator (European Perch, Perca fluviatilis), and an ambush predator (dragonfly larvae). The tadpoles mean weight, maximum acceleration and velocity, mobility, boldness, and morphological changes in various Gosner stages were analyzed. My tests showed a significant difference in tadpole weight and their morphology, however, there were no differences in speed, acceleration, boldness or mobility. The morphometric analysis of the tadpoles showed a significant change of tadpoles in the perch treatment compared to the tadpoles in the control. The tadpoles in the perch treatment showed a higher TH/TL (tail height/tail length) ratio, and were overall heavier, than the tadpoles in the control, but no significant change compared to the tadpoles in the dragonfly treatment. This shows that the kairomones and alarm cues triggered a large morphological change, but the effect of the change requires more research.
20

Taxonomy of the Rufous-naped lark (Mirafra africana) complex based on song analysis

Nymark, Marianne Kristine January 2021 (has links)
The Rufous-naped lark Mirafra africana complex consists of 22 subspecies spread across the African continent. Several of the subspecies have recently been suggested to potentially be treated as separate species. In this study a comparative analysis was done on the song from seven of the subspecies: M. a. africana, M. a. athi, M. a. grisescens, M. a. kabalii, M. a. nyikae, M. a. transvaalensis and M. a. tropicalis. The results showed that M. a. athi, M. a. kabalii and M. a. nyikae are all very divergent from each other as well as from the other four subspecies. In contrast, M. a. tropicalis, M. a. grisescens, M. a. africana and M. a. transvaalensis are not clearly separable from each other. Based on the results, I suggest that M. a. athi, M. a. kabalii and M. a. nyikae can be classified as separate species, with M. a. africana, M. a. tropicalis, M. a grisescens and M. a. transvaalensis forming a fourth species (M. africana sensu stricto). Finally, I conclude that this study shows that more studies need to be done on the subspecies of the Mirafra africana complex.

Page generated in 0.1204 seconds