Water is a primary driver of the physical, geochemical and biological evolution of the Earth. The near-surface hydrosphere (exosphere) includes the atmosphere, cryosphere (glacial and polar ice), the biosphere, surface water, groundwater, and the oceans. The amounts of water in these various reservoirs of the hydrologic cycle have likely varied significantly over the past 700 Ma, with the cryosphere and continental biosphere reservoirs likely showing the most dramatic variations relative to the modern. For example, 700 Ma, during snowball-Earth conditions, the planet may have been almost entirely enveloped in ice, whereas throughout much of the Phanerozoic, greenhouse conditions predominately prevailed and the Earth had a much smaller cryosphere. Similarly, before about 444 Ma and the proliferation of land plants, the continental biosphere reservoir would have effectively non-existent. However, today, plants play a critical role in storage and transfer of water within the hydrologic cycle. Because the amount of water in the exosphere is thought to have remained relatively constant during the past 700 Ma, variations in the amounts of water held by the in the various exogenic reservoirs exert concomitant effects on other reservoirs in the exosphere. We present a conceptual and numerical model that examines variations in the amount of water in the various reservoirs of the near-surface hydrologic cycle (exosphere) during the past 700 Ma and quantify variations in the rates of exchange of water between these reservoirs in deep time. Variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the movement of water between the atmosphere, surface water, and ocean reservoirs varies in concert with the waxing and waning of the cryosphere. We find that variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the flux of water between the atmosphere, surface water, and ocean reservoirs varies in concert with the waxing and waning of the cryosphere, with some fluxes decreasing to 0.0 kg/yr during snowball-Earth conditions. We find that the amount of water precipitated from the atmosphere to the cryosphere increases from greenhouse conditions to -10.5°C and decreases from -10.5°C to snowball-earth conditions, highlighting "tipping-point" behavior due to changes in temperature and cryosphere surface area. The amount of surface runoff to the oceans varies in proportion to the amount of water removed from the surface water reservoir and transferred into the continental biosphere. Variations in the movement of water between near-surface reservoirs that are driven by the waxing and waning of the cryosphere and emergence and growth of plant life thus have significant implications for the transfer of weathering products to the oceans and could contribute to short-term (<1 Ma) variations in seawater composition and isotopic signatures. / Ph. D.

Sur la Plate-forme Est Européenne (PEE), des sédiments silicoclastiques néoprotérozoïques ont livré une faune animale édiacarienne type dans le bassin de Podolya. Sa géologie montre un domaine marin littoral et indiquent que cette faune vivait dans la zone euphotique. Situé en bordure du Bouclier Ukrainien, le bassin est resté à l'abri des événements tectoniques et sa subsidence a été faible, ce qui explique l’absence de métamorphisme et de processus liés à la diagenèse d’enfouissement. Ces conditions ont permis la préservation des fossiles d’animaux et des minéraux argileux. Ainsi, quatre couches riches minéraux interstratifiés (IS) ont permis d’identifier des bentonites i.e. des produits pyroclastiques altérés. Les zircons de la bentonite la plus récente, qui coiffe les niveaux fossilifères, ont été datés (238U/206Pb) à 557-555 Ma ; le macrobiota édiacarien de Podolya est donc plus âgé. De plus, les variations de teneurs en kaolinite dans la pile sédimentaire indiquent que le continent Baltica voisin (actuelle PEE), source du détritisme, a connu une succession de climats tempéré-chaud-tempéré. En accord avec les données paléomagnétiques, Baltica a donc migré depuis les hautes vers les basses latitudes avant d’amorcer un mouvement rétrograde. Les strates fossiles pauvres en kaolinite peuvent être corrélées avec une position de Baltica en latitude élevée, près de la bordure nord de Rodinia et du continent Avalon.Nos résultats permettent de situer les fossiles édiacariens de l'Ukraine sur l'échelle biochronostratigraphique mondiale, et de mieux comprendre les relations spatio-temporelles du biote de Podolya par rapport aux autres macrofaunes situées à proximité de Baltica à cette époque. Les nouvelles données et les morphologies primitives des fossiles de Podolya – d’ordinaire uniquement comparées à celles de la Mer Blanche (Russie) pourraient expliquer la ressemblance phylogénique entre le biote édiacarien d’Ukraine et certains macrofossiles d'Avalon. / On the East European Platform (EEP), Neoproterozoic siliciclastic sediments have revealed a typical animal fauna of Ediacaran in the Podolya basin. The geological data are typical of marine tidal domain and suggest that this fauna lived under a water depth that did not exceed the euphotic zone. After this period, the basin, located on the edge of the Ukrainian Shield, has remained safe from tectonic events and its subsidence was low, which explain that these deposits are unmetamorphosed and unaffected by processes of burial diagenesis. These conditions allowed both the preservation of animal fossils and argillaceous minerals. Thus, four levels rich in IS mixed-layers could be identified as bentonites, altered pyroclastic products. Zircons of the youngest bentonite, which caps the fossiliferous levels, have been dated (238U/206Pb ratio) to 556±1 Ma, so Podolya's ediacaran macrobiota is of older age. Moreover, the variations of the kaolinite content in sedimentary pile indicates the neighboring mainland of the Baltica micro-continent (current EEP), source of the detritism, has been subjected to temperate-warm-temperate climate cycle. According to the paleomagnetic data, this shows that Baltica migrated from high to low latitudes and followed a retrograde motion. The kaolinite-poor fossil stratas can be correlated with high latitude position of Baltica, close to the northern border of Rodinia and of Avalon micro-continent. Our results make it possible to better situate the Ediacarian fossils of Ukraine in relation to the global biochronostratigraphic scale, but also to better understand the spatial and temporal relationships of Podolya’s ediacaran biota compared to other faunas located in the vicinity of Baltica at this time. The new data and primitive morphologies of Podolya's fossils – usually compared to the only fossils of White Sea (Russia) might explain why Ediacaran biota from Podolya Basin has more phylogenic resemblance to some Avalon’s macrofossils.

The history of research on the Late Paleozoic amphibians at Faculty of science of Charles University in Prague coincides with the 50th of the last century, when it was acquired rich collection material from field collection prof. Špinar. This is connected with the necessity of cataloging and processing of this material. The catalog alone contains large amounts of material, 3,237 pieces of items that will be the basis for subsequent research directions in the fields of morphology, anatomy, taxonomy, biomechanic and more. The most numerous species in collections is discosauriscus austriacus.

<p>The Geologic <i>TimeScale Creator </i>(TSCreator) project has compiled a range of paleo-environmental and bio-diversity data which provides the opportunity to explore origination, speciation and extinction events. My PhD research has four major interconnected themes which include the visualization methods of evolutionary tree and the impacts of climate change on the evolution of life in longer and shorter timeframes: <b>(1) </b>Evolutionary range data of planktonic foraminifera and nannofossils over the Cenozoic era have been updated with our latest geological timescale. These evolutionary ranges can be visualized in the form of interactive, extensible evolutionary trees and can be compared with other geologic data columns. <b>(2) </b>A novel approach of integrating morphospecies and lineage trees is proposed to expand the scope of exploration of the evolutionary history of microfossils. It is now possible to visualize morphological changes and ancestor-descendant lineage relationships on TSCreator charts which helps mutual learning of these species based on genetic and bio-stratigraphic studies. <b>(3) </b>These evolutionary datasets have been used to analyze semi-periodic cycles in the past bio-diversity and characteristic rates of turnover. Well-known Milankovitch cycles have been found as the drivers of fluctuations in the speciation and extinction processes. <b>(4) </b>Within a shorter 2000-year time period, global cooling events might have been a factor of human civilization turnover. Using our regional and global cultural turnover time series data, the effect of climate change on human culture has been proposed. The enhancement of the evolutionary visualization system accomplished by this research will hopefully allow academic and non-academic users across the world to research and easily explore Earth history data through publicly available TSCreator program and websites. </p>