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  • 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

Evoluční strategie v biomineralizaci schránek zástupců kmene Mollusca: Mikromechanické vlastnosti schránek a jejich vztah k prostředí / Evolutionary strategy in biomineralization of mollusc shells: Micromechanical properties of shells and their relationship with the environment

Hrabánková, Iva January 2015 (has links)
This thesis deals with the micromechanical properties (microhardness and elastic modulus) of selected molluscan shell microstructures and their relationship to crystallographic textures and environment. Results of the study suggest that extremely high hydrostatic pressure has a relatively weak influence on the mechanical properties of calcitic as well as aragonitic shell layers. No statistically significant difference was found in microhardness and elastic modulus of nacre between bivalvian species living in marine and freshwater environments. On the other hand, the study reveals a statistically significant positive correlation between the micromechanical properties and thickness of aragonitic platelets forming the nacre. Unexpected result is a negative correlation of the degree of ordering of aragonitic platelets with both elastic modulus as well as microhardness. Thus the degree of ordering explains about 80% of the variability of these micromechanical properties. Statistically significant but weaker correlation was also found between micromechanical properties and textural type of bivalvian nacre. The nacre with uniaxial texture is harder and more elastic than the nacre with quasimonocrystallic texture. The data suggests that higher hardness and elasticity corresponds to a primitive state of nacre and that during the subsequent evolution values of these micromechanical properties were decreasing. This trend contradicts with generally accepted hypothesis of increassing predation pressure in the marine ecosystem during the Paleozoic and Mesozoic.
12

Species diversity and speciation mechanisms in Crenicichla (Neotropical cichlids) / Species diversity and speciation mechanisms in Crenicichla (Neotropical cichlids)

PIÁLEK, Lubomír January 2013 (has links)
This thesis contributes to the knowledge of the species diversity of the Crenicichla lacustris sp. group in the La Plata River basin with description of three new species. Speciation mechanisms within two different species flocks from the middle Paraná/Iguazu and Uruguay Rivers were studied with a phylogenomic approach applying a novel genotyping method based on a Double-Digest Restriction site Adjacent DNA (ddRAD) sequencing. Our results support a repeated origin of morphological species being evolved several times sympatrically and independently in different drainages. A considerable role of hybridization/introgression as an evolutionary force was also proposed. The thesis further uncovers biogeographic aspects of the southern part of Brazilian shield and adjacent coastal rivers.
13

Phylogeny of Brimstone butterflies (genus \kur{Gonepteryx}): The evolution of colour pattern in UV spectrum and geographical area

HANZALOVÁ, Dana January 2018 (has links)
Phylogeny, phylogeography and evolution of UV reflecting patterns were studied in 12 species of the genus Gonepteryx. Sequences of one mitochondrial (COI) and one nuclear gene (Wingless) were used for phylogenetic analyses and reconstruction of the biogeographical events. The results were later compared with the extent of UV reflecting pattern to construct the ancestral situation and evolution of the UV pattern within the genus.
14

Vztah recentní systematiky žab (Anura) a výzkumného úsilí / Relationship of recent systematics of frogs (Anura) and research efforts

MRÁZKOVÁ, Nikola January 2018 (has links)
Over the last few decades there has been a confusion in the classification system of organisms with the development of molecular and genetic methods. Life is currently perceived from a different perspective than in the past due to different methods, and old, standard systems have significantly changed as a result of such alteration. As a consequence, it is harder and harder to distinguish which taxonomic changes are caused by objectively better recognition of biodiversity and which seem to be only subjective opinions of particular taxonomists. Results show a significant growth in the number of genuses in observed families of frogs (Anura) in the aforementioned period (2000-2017) while the research efforts of taxonoms were proved to be the most relevant factors causing such increase in diversity with respect to genuses.
15

Rekonstrukce morfologické evoluce a fylogenetických vztahů šupinatých chrysomonád rodu Mallomonas / Reconstructing the evolution and fylogenetic relationships of silica-scaled chrysophyte genus Mallomonas

Čertnerová, Dora January 2015 (has links)
The taxonomic concept of the algal genus Mallomonas (Synurales, Synurophyceae) was based on an extraordinary morphological diversity of their siliceous scales. The main aims of this study were elucidation of phylogenetic relationships among its representatives and reconstruction of shape evolution of particular siliceous structures of their scales. Molecular data for six species were acquired for the first time, enabling a successful assessment of their phylogenetic relationships with the other representatives of the genus. On the basis of molecular data, the genus Mallomonas can be divided in two evolutionary lineages and this division is also reflected morphologically (with only a few exceptions) through presence or absence of a V-rib structure. Fine ornamentation of siliceous scales is species-specific and interestingly, the overall differences in morphology of siliceous scales are mostly reflecting phylogenetic relationships among representatives of the genus. In this context, morphological species concept of Mallomonas seems to be justified. Morphologically-based sections of the genus are often paraphyletic, because small sections (frequently containing only single species) tend to be nested within particular larger sections. The main reason for this discrepancy is accelerated morphological...
16

Diverzita rodu Monocercomonoides / Diversity of the genus Monocercomonoides

Vlasáková, Jitka January 2014 (has links)
Oxymonads (Excavata, Preaxostyla) are a group of anaerobic endobiotic flagellates living primarily in guts of xylophagous insects (cockroaches and termites). Some representatives of the genus Monocercomonoides belonging to the morphologically simplest family Polymastigidae have been described also from the guts of vertebrates. Oxymonads are a group of protist in which mitochondrion has not been proven yet. In this work, we have sequenced gene fo SSU rRNA of two strains of Monocercomonoides and performed phylogenetic analysis of oxymonads. Five selected strains Monocercomonoides isolated from different hosts and distantly related on the phylogenetic tree were studied by using light (DIC and protargol staining) and transmission electron microscopy. The aim was to find differences between these strains. We have focused primarily on the morphology of the nucleus, appearance of the endoplasmic reticulum and structure of the fibre R1. We were able to distinguish the strains by the position of karyosome (central and parietal) and the number of microtubules in the R1 fibre (6-12) and we assume that they represent separate species. The phylogenetic position and appearance of the strains NAU3 were so different that it may represent a new genus. Mitochondria or double-membrane bounded organelles have not been...
17

Fylogenetické postavení rodu Polymastix a jeho prokaryotických symbiontů / Phylogenetic Position of Genus Polymastix and Its Prokaryotic Symbionts

Kubánková, Aneta January 2020 (has links)
Polymastigidae is one of the five families of oxymonads (Metamonada, Preaxostyla). It includes small flagellates inhabiting the digestive tract of insects. Recently obtained molecular phylogenetic data have questioned the monophyly of this group. The type genus of the family Polymastigidae is Polymastix. The phylogenetic position of this genus has not been studied yet, although this information could significantly help to clarify the relationships within this group. This work provides the first sequence data of this genus, which we have obtained using a single- cell genome amplification and subsequent whole genome sequencing on Illumina HiSeq X Ten (Macrogene) from three individuals of P. melolonthae inhabiting the posterior hindgut of crane fly larvae. Phylogenetic analysis based on the gene for 18S rRNA, EF-1α and HSP90 yielded several roughly equally probable hypotheses about the position of this genus within Oxymonadida. The first of them places the genus Polymastix in a close proximity to the genus Streblomastix, according to the second hypothesis, Polymastix is sister to Termitimonas travisae. A characteristic feature of this protist is ectosymbiotic bacteria attached to its surface. These were necessarily amplified and sequenced together with their hosts, which allowed us to obtain sequence...
18

Fylogeneze a evoluční trendy v subtribu Hieraciinae (Asteraceae) / Phylogeny and evolutionary trends in subtribe Hieraciinae (Asteraceae)

Zahradníček, Jaroslav January 2017 (has links)
No description available.
19

Intraindividuální komparace vybraných koordinačních ukazatelů bruslařského kroku na ledě a při in-line / Intraindividual comparison of selected indicators of coordinating steps on the skating step and on the in-line step

Hospůdka, Jakub January 2010 (has links)
4 Summary: Title: Intraindividual comparison of selected indicators of coordinating steps on the ice skating and in-line. Objective: Assessment of coordination relationship rate of the skating forward during ice hockey and inline skating. Methods: Surface electromyography combinated with kinematography analysis used synchronized video recording. Results: Kinesiological content of movement during ice skating and inline skating is not the same. The general stereotype of the skating step is significantly different from the walking stereotype. Key words: human locomotion, sport locomotion, phylogeny, ontogeny, surface electromyography, ice hockey skating, inline skating.
20

Diverzita a diverzifikace ptáků: Vedou různé procesy ke stejné patrnosti? / Bird diversity and diversification: Different processes converging to the same pattern?

Černá, Vladimíra January 2015 (has links)
Latitudinal diversity gradient is one of the oldest known trends in the distribution of life on the Earth. Scientists have been trying to find causes of its formation for more than two hundred years. There are several hypotheses suggested to explain this gradient. Recently, it is one of the main themes of discussion among ecologists and evolutionary biologists. By this Thesis, I will try to contribute to understanding of processes that generate the latitudinal diversity gradient. Particularly, I study if there is a relationship between ambient temperature and diversification rate. Is this relationship different for individual groups of animals? I choose birds as a model group. Specifically, these six families of birds: Accipitridae, Columbidae, Furnariidae, Picidae, Psittacidae and Strigidae. These groups include more than 1500 species. Each of them has the same universal gradient of diversity, with the highest diversity concentrated in the tropics. My objective was to find out, whether the universal gradients of bird's diversity had been shaped by the same historical processes. Or alternatively, whether different evolutionary trajectories had converged to the same gradients. The main outcome of my work is a discovery that some of the selected families diversified faster in warmer climates...

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