National Repository of Grey Literature 177 records found  previous11 - 20nextend  jump to record: Search took 0.00 seconds. 
A neural network for reconstruction of extinct animals
Pešek, David ; Bilík, Šimon (referee) ; Jirsík, Václav (advisor)
This work was focused on designing, learning and evaluating an artificial neural network for reconstructing extinct species. First, the main element of the proposed artificial neural network, i.e., the generative model, was selected. Given their excellent performance in the field of image generation, the class of diffusion models reasonably seemed to be the right choice. Specifically, the Stable diffusion model was chosen. One of the initial steps of the work was to create a training set for the proposed model. The animal images needed to be paired with some labels that could be used to identify the animal. For this purpose, the cytochrome c oxidase subunit I genes of the given animals were used. Furthermore, the sequential transformer model GPT-2, which is learned on the training set of human natural language, was used. This model was used to encode the DNA sequences into a vector form in which the semantics and context between the different parts of the DNA sequence were captured. The models would be very difficult to learn from scratch due to the large training set size required and the computational and time requirements. Thus, the GPT-2 model was only learned on the training set of DNA sequences of the passeriformes order, and the diffusion model itself was learned on pairs of images of these animals and DNA sequences encoded by the GPT-2 model. To generate the images, the original DNA sequences that resembled the sequences from the training set were generated using GPT-2. The encoding of these sequences was then passed to the diffusion model, which generated the images itself. The method of generating new DNA sequences using the GPT-2 model is based on the idea that the generated DNA sequence partially resembles the DNA sequences from the training set. Such experimentally generated DNA sequences may resemble DNA sequences of extinct ancestors or relatives of the passeriformes order. The model was in some cases able to generate images that could be considered as animal species , but it should be noted that often the generated images could not be considered as animal reconstructions. The success rate of generating a decent animal image was approximately 10%. The functionality of the model was also tested on a test set of DNA sequences of animals of several orders that fall under the class of birds as well as the order of passeriformes. The success rate of generating a reconstruction that could be compared to a photograph was around 5%.
Species-specific and individual predictors of birds' collisions with glass obstacles in the Czech Republic
Semeráková, Anna ; Sedláček, Ondřej (advisor) ; Viktora, Lukáš (referee)
Recent landscape transformation is associated with the emergence of various artificial obstacles that change the natural form of habitats and biocorridors of free-ranging animals. Glass obstacles represent a particular problem due to their transparency and reflectivity. Collisions with glass represent one of the most significant causes of bird mortality worldwide, accounting for over hundreds of millions bird deaths annually. Many authors consider this source of mortality to be completely non-selective. In that case, total collisions mortality would represent a function of population size. However, here I assume that the relationship between collision mortality and population size is more complex and that certain avian ecological groups may be differently susceptible to glass collisions based on their specific ecological characteristics. Long-term records of bird-glass collisions in the Czech Republic were provided by the Czech faunistic databases. These records were compared with the population size of analysed species and with selected ecological and morphological species characteristics. Consistently with the premise, I found out that the greatest amount of collision mortality is explained by the species' population size. However, other species characteristics, such as higher body weight,...
Synurbanization in wood pigeon (Columba palumbus) and Eurasian magpie (Pica pica)
Tesařík, Jáchym ; Lučan, Radek (advisor) ; Hořák, David (referee)
Both Eurasian magpie and Wood pigeon are typical synanthropic bird species. By studying the available sources, I found that during their synurbanisation, both species have undergone several changes that have facilitated their transition from rural to urban habitats. Due to their adaptability, they have no problems colonizing urban environment and have managed to occupy new and diverse range of nest sites. Thanks to synurbanisation, both Magpie and Wood Pigeon have been able to expand their range and increase their overall abundance. Possibly the biggest threat to urban populations of both species is nest predation, which locally leads to declining population trends and reduced breeding success. Because of predation pressure and the adaptability of both species, I think we can expect not only an increase in abundance and population density in their urban population in the future, but also the occupation of new and more diverse nesting habitats in closer proximity to human settlements.
Host-microbiota, pro-inflammatory immunity and physiological senescence in wild birds
Těšický, Martin
Triggered by microbial ligands, inflammation serves as a "double-edged sword" to fight infections on the one hand, but on the other hand causing tissue damage due to oxidative stress if it is dysregulated. For example, chronic inflammation can contribute to inflammaging, which is now widely regarded as one of the causes of ageing. In my interdisciplinary dissertation, my colleagues and I investigated three interrelated aspects of inflammation, using an evolutionary framework and various free-living birds as models: (1) ecological and evolutionary determinants of gut microbiota (GM) composition and diversity, a driver of wild bird immunity, (2) diversity in immune genes affecting inflammatory responses in wild birds and (3) inflammation-related physiological senescence in a free-living passerine bird, the great tit (Parus major). Firstly, using 16S rRNA gene metabarcoding, we revealed high intra- and interspecific variation in passerine gut microbiota (GM) dominated by the major phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Although in mammals GM depends strongly on host phylogeny and diet, in birds we found only moderate effects of phylogeny and very limited effects of host geography and ecology on GM composition. While microbiota diverged between the upper and lower...
Host-microbiota, pro-inflammatory immunity and physiological senescence in wild birds
Těšický, Martin ; Vinkler, Michal (advisor) ; Tschirren, Barbara (referee) ; Štěpánek, Ondřej (referee)
Triggered by microbial ligands, inflammation serves as a "double-edged sword" to fight infections on the one hand, but on the other hand causing tissue damage due to oxidative stress if it is dysregulated. For example, chronic inflammation can contribute to inflammaging, which is now widely regarded as one of the causes of ageing. In my interdisciplinary dissertation, my colleagues and I investigated three interrelated aspects of inflammation, using an evolutionary framework and various free-living birds as models: (1) ecological and evolutionary determinants of gut microbiota (GM) composition and diversity, a driver of wild bird immunity, (2) diversity in immune genes affecting inflammatory responses in wild birds and (3) inflammation-related physiological senescence in a free-living passerine bird, the great tit (Parus major). Firstly, using 16S rRNA gene metabarcoding, we revealed high intra- and interspecific variation in passerine gut microbiota (GM) dominated by the major phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Although in mammals GM depends strongly on host phylogeny and diet, in birds we found only moderate effects of phylogeny and very limited effects of host geography and ecology on GM composition. While microbiota diverged between the upper and lower...
Mechanisms of reproductive isolation between two hybridizing passerine species, the common nightingale and the thrush nightingale
Poignet, Manon ; Reifová, Radka (advisor) ; Choleva, Lukáš (referee) ; Kratochvíl, Lukáš (referee)
iv - ABSTRACT (in English) - A key step in the origin of new species is the evolution of the reproductive isolation mechanisms separating the gene pools of newly emerging species. Despite a growing number of studies, we still know very little about the molecular, physiological and genetic mechanisms underlying reproductive isolation. Hybrid zones represent useful examples of ongoing species differentiation and can provide information about the nature of reproductive isolation separating the species and mechanisms facilitating or limiting the hybridization. Using two naturally hybridizing passerine species, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia), we evaluated several mechanisms of reproductive isolation at the chromosomal, phenotypic, and genetic levels, with a focus on postmating prezygotic (PMPZ) and postzygotic isolation mechanisms. These nightingale species diverged ~1.8 Mya and currently hybridize in a secondary contact zone running across Central and Eastern Europe. First, we analysed the genetic composition of the secondary contact zone, demonstrating that parental forms are predominant in the hybrid zone, with few F1 hybrids (3.4%), early backcross hybrids (3.1%) and the absence of F2 hybrids. This suggests strong but incomplete reproductive isolation....
Diversity and abundance of birds in 3D space of Žofínský prales primary forest
Kučerová, Eliška ; Hořák, David (advisor) ; Korňan, Martin (referee)
Bird species are specialized in diverse types of environments. Considering for example forest species, this does not mean that all species inhabit the same ecological niches. Some species occupy undergrowth while others prefer treetops. Some birds are bound to clearings and other gaps in forest cover, and other species require old trees with cavities. Primary Central European mixed forest is not a homogenous environment. But, on small spatial scales, the environment is very heterogeneous. We get an unprecedented variety of habitats especially when including the forest vertical dimension, which birds use much more than it is usually considered in studies. This diploma thesis describes in detail the bird assemblage in the Czech oldest nature reserve NPR Žofínský prales in which vegetation research is currently in progress. However, research dealing with bird mapping in forests still rarely consider the vertical dimension of the environment. Most bird censuses focus on the diversity of species at a site but usually do not include abundance of individual species. I, therefore, focused on a detailed mapping of the bird community on a 50-hectare area in NPR Žofínský prales. During the census, each bird and each bird's exact position in the 3D space of the forest were recorded. Special attention is paid...
Technická řešení zabraňující střetu ptactva s transparentními a reflektivními plochami
NOSEK, Michal
The presented bachelor thesis is focused on measures against loss of contact with transparent and reflective surfaces. The main task is to list and describe the impact of technical solutions in the natural landscape, where it is necessary to influence. It focuses mainly on noise walls, bus stops, glazed vehicles and glazed parts of buildings.
Kokcidie ptáků Galapág
KORDÍKOVÁ, Lucie
This study investigates coccidian parasites of the genera Eimeria and Isospora in faecal samples of birds from the Galapagos Islands. The study determines prevalence of coccidia on individual islands and bird species. Description of recorded coccidian parasites is based on morphological features of their oocysts as well as on phylogenetic relationships.
Střevní paraziti ptáků na Svalbardu
ŽÁNOVÁ, Veronika
The study aimed to obtain essential knowledge about the distribution of intestinal parasites of birds occurring in Svalbard. Noninvasive coprological techniques were used to detect coccidian, cryptosporidian and microspordian parasites. The research included field collection of faecal samples and laboratory examination by microscopic and molecular methods.

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