Sökning: "sharks"

Visar resultat 1 - 5 av 12 avhandlingar innehållade ordet sharks.

  1. 1. 100 million years of shark macroevolution : A morphometric dive into tooth shape diversity

    Författare :Mohamad Bazzi; Per Ahlberg; Matt Friedman; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sharks; Macroevolution; Extinction recovery dynamics; Geometric Morphometrics; Morphospace-Disparity Framework; Teeth; Biology with specialization in Evolutionary Organismal Biology; Biologi med inriktning mot evolutionär organismbiologi;

    Sammanfattning : Few vertebrate clades exhibit the evolutionary longevity and versatility of sharks, which constitute nearly half of all current chondrichthyan biodiversity and represent an ecological diversity of mid-to-apex trophic-level predators in both marine and freshwater environments. The rich fossil record of shark teeth from Mesozoic and Cenozoic rocks also makes the group amenable to large-scale quantitative analyses. LÄS MER

  3. 2. Jurassic and Early Cretaceous selachians - focus on southern Scandinavia

    Författare :Jan Rees; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Geology; Paleontologi; Palaeontology; Lissodus; palaeoecology; England; Denmark; Sweden; sharks; selachians; Jurassic; Early Cretaceous; physical geography; Geologi; fysisk geografi;

    Sammanfattning : The Jurassic and Early Cretaceous selachian faunas of Scania (Skåne), southern Sweden and the island of Bornholm (Denmark) have been investigated. Three Early Jurassic shark tooth assemblages have been recorded and investigated, one from Hettangian strata and the other two from Pliensbachian sediments. LÄS MER

  4. 3. Organohalogen contaminants in Greenland shark (Somniosus microcephalus)

    Författare :Anna Strid; Åke Bergman; Maria Athanasiadou; Shinsuke Tanabe; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; persistent organic pollutants; sub-Arctic; Iceland; shark; Environmental chemistry; Miljökemi; miljökemi; Environmental Chemistry;

    Sammanfattning : The remote sub-Arctic/Arctic environment has due to human activities become a sink for organohalogen contaminants (OHCs). These OHC include traditional contaminants such as polychlorinated biphenyls (PCBs), DDTs and technical mixtures of polybrominated diphenyl ethers (PBDEs), all included in the Stockholm Convention list of persistent organic pollutants (POPs). LÄS MER

  5. 4. Evolution of Vertebrate Eyes: a study on lens suspension and optical proterties

    Författare :Ola Gustafsson; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; evolution; eye; fish; crystalline lens; lens suspension; multifocal optical systems; Agnatha; Actinopterygii; Chondrichthyes; Vertebrate; Sarcopterygii;

    Sammanfattning : Many fishes have well-developed visual systems with color vision capabilities. The crystalline lens is the major refractive element in a fish eye since the cornea is optically inactive underwater. A typical fish eye has a large pupil and a lens of short focal length, features that increase light gathering ability. LÄS MER

  7. 5. Endocranial Morphology and Phylogeny of Palaeozoic Gnathostomes (Jawed Vertebrates)

    Författare :Martin D. Brazeau; Per Ahlberg; Graham Budd; Henning Blom; Michael Coates; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; systematics; palaeontology; anatomy; evolution; Organism biology; Organismbiologi;

    Sammanfattning : Gnathostomes, or jawed vertebrates, make up the overwhelming majority of modern vertebrate diversity. Among living vertebrates, they comprise the chondrichthyans (“cartilaginous fishes” such as sharks, skates, rays, chimaeras) and the osteichthyans (“bony fishes” or bony vertebrates, inclusive of tetrapods). LÄS MER