Search results for "EVOLUTION"

Phosphorus limitation enhances parasite impact: feedback effects at the population level

2014

Background Nutrient deficiency affects the growth and population dynamics of consumers. Endoparasites can be seen as consumers that drain carbon (C) or energy from their host while simultaneously competing for limiting resources such as phosphorus (P). Depending on the relative demands of the host and the parasite for the limiting nutrient, intensified resource competition under nutrient limitation can either reduce the parasite’s effect on the host or further reduce the fitness of the nutrient-limited host. So far, knowledge of how nutrient limitation affects parasite performance at the host population level and how this affects the host populations is limited. Results We followed the popu…

Oxidative stress biomarkers in the copepod Limnocalanus macrurus from the northern Baltic Sea : effects of hydrographic factors and chemical contamin…

2015

The importance of phytoplankton production for carbon budgets in a semiarid floodplain wetland

2011

Phytoplankton production (PP) in wetlands is not measured as often as that of macrophytes. A three year-study during a period of sustained high flooding was undertaken in a central Spanish floodplain wetland (Las Tablas de Daimiel National Park) to determine net PP, its spatial heterogeneity and controlling factors, and compare it with primary production in macrophyte communities. This enabled us to estimate carbon budgets for each community. All PP variables showed high spatial and temporal variability among sites, resulting in low coherence even when flooding connected all sites. Net PP corresponded to 25- 36% of submerged plant production and 3-10% of helophyte production. Net PP was con…

Browning-induced changes in trophic functioning of planktonic food webs in temperate and boreal lakes: insights from fatty acids

2022

AbstractThe effects of lake browning on trophic functioning of planktonic food webs are not fully understood. We studied the effects of browning on the response patterns of polyunsaturated fatty acids and n−3/n−6 ratio in seston and compared them between boreal and temperate lakes. We also compared the regional differences and the effects of lake browning on the reliance of zooplankton on heterotrophic microbial pathways and the mass fractions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in zooplankton. Lake browning was associated with increasing phytoplankton biomass and concentrations of EPA and DHA in both temperate and boreal lakes, but the seston n−3/n−6 ratio was low…

An experimental model for mimicking biological systems: the Belousov-Zhabotinsky reaction in Lipid membranes

2006

Modeling multipartite virus evolution: the genome formula facilitates rapid adaptation to heterogeneous environments

2020

Multipartite viruses have two or more genome segments, and package different segments into different particle types. Although multipartition is thought to have a cost for virus transmission, its benefits are not clear. Recent experimental work has shown that the equilibrium frequency of viral genome segments, the setpoint genome formula (SGF), can be unbalanced and host-species dependent. These observations have reinvigorated the hypothesis that changes in genome-segment frequencies can lead to changes in virus-gene expression that might be adaptive. Here we explore this hypothesis by developing models of bipartite virus infection, leading to a threefold contribution. First, we show that th…

Die Ästhetik und das Lebendige: Biologischer Akt, Bürde und Verantwortung

2020

Wenn es wahr ist, dass dem Projekt der Morphologie im Laufe des 20. Jahrhunderts eine wirkliche Verfinsterung zuteil wird, die seine heuristische Fähigkeit sowohl im Bereich der Lebenswissenschaften als auch in der ästhetischen und historisch-künstlerischen Reflexion zu verdunkeln scheint, dann wird nur in dieser neuen Situation der produktiven Marginalität Raum geboten, um einige Konzepte zu diskutieren, die heute in der Lage sein können, eine Brücke zwischen den Wissensbereichen zu schlagen und eine neue disziplinäre Synthese zutage zu fördern. Dazu gehören das Konzept des „Biologischen Aktes“, das die Einheit von Handlung und Leiden des Lebewesens postulieren soll, und die gegensätzliche…

Développement et caractérisation d’électrodes pour l’électrolyse alcaline de l’eau

2020

Splitting water into hydrogen and oxygen by electrolysis using electricity from intermittent ocean current, wind, or solar energies is one of the easiest and cleanest routes for high-purity hydrogen production and an effective way to store the excess electrical power without leaving any carbon footprints. The key dilemma for efficient large-scale production of hydrogen by splitting of water via the hydrogen and oxygen evolution reactions is the high overpotential required, especially for the oxygen evolution reaction. Hence, engineering highly active and stable earth-abundant oxygen evolution electrocatalysts with three-dimensional hierarchical porous architecture via facile, effective and …

Etude de l'évolution du potentiel génétique de populations bactériennes dégradant l'atrazine

2011

Atrazine, one of the most used herbicide to control the development of weeds in crop, has led to the contamination of the environment. Repeated exposure to this herbicide resulted in the emergence of microbial populations able to degrade atrazine and to use it as a nitrogen source for its growth. These microbial populations are responsible for accelerated biodegradation of atrazine (BDA), a key ecosystemic service diminishing the persistence of this herbicide in the environment. The aim of this PhD work was to study genetic and physiological mechanisms responsible for functioning and improving of this ecosystemic service. We applied an experimental approach starting from genes to communitie…

Chemical composition and biological activity of the essential oil of Ballota hispanica (L.) Benth. growing wild in Sicily

2015

Ballota L. comprises several relevant species largely used for their excellent therapeutic properties. Ballota hispanica (L.) Benth. is widely used in herbal medicine, and it is sold in herbalist shops for its sedative and antispasmodic properties. Considering its traditional medicinal use and the lack of scientific studies on the volatile components of this species as well as on its biological activities, in this study the chemical composition of the essential oil from aerial parts of B. hispanica, collected in Sicily, was evaluated by gas chromatography and gas chromatography–mass spectrometry. α-Elemol was the most abundant component of the oil (10.9%), followed by α-ylangene (8.5%),…