Sökning: "naturvetenskap biologi"
Visar resultat 21 - 25 av 5964 avhandlingar innehållade orden naturvetenskap biologi.
21. Biodiversity and Species Extinctions in Model Food Webs
Sammanfattning : Many of the earth’s ecosystems are experiencing large species losses due to human impacts such as habitat destruction and fragmentation, climate change, species invasions, pollution, and overfishing. Due to the complex interactions between species in food webs the extinction of one species could lead to a cascade of further extinctions and hence cause dramatic changes in species composition and ecosystem processes. LÄS MER
22. Comparative Seed Morphology and Phylogenetics : Case Studies in Basal Angiosperms (ANITA) and Asterids (Lysimachia, Ericales)
Sammanfattning : The first half of the thesis deals with the seed morphology of members of the ANITA grade at the base of the angiosperm phylogeny (Amborella, Nymphaeales, Illiciales, Trimeniaceae, and Austrobaileyaceae), especially Illiciaceae and Schisandraceae. Seed characters support a major division between the New World and Old World species of Illicium. LÄS MER
23. The decline of great Arctic charr in Lake Vättern : empirical and theoretical analyses of suggested causes
Sammanfattning : Human activity is affecting species and ecosystems all over the world. In aquatic systems negative trends can be seen for many fish stocks and potential consequences of this, for ecosystem structure and functions, are of particular concern. LÄS MER
24. Physiological adaptations in two ecotypes of Fucus vesiculosus and in Fucus radicans with focus on salinity
Sammanfattning : The in origin intertidal marine brown alga Fucus vesiculosus L. grow permanently sublittoral in the brackish Bothnian Sea, side by side with the recently discovered F. radicans L. Bergström et L. LÄS MER
25. Cyanobacterial Hydrogen Metabolism : Regulation and Maturation of Hydrogenases
Sammanfattning : In times with elevated CO2 levels and global warming there is a need of finding alternatives to carbon based energy carriers. One such environmental friendly solution could be H2 produced by living organisms. LÄS MER