The marine environment is the only uninterrupted, internally moving, three-dimensional environment. Uninterrupted means that, in principle, each organism can reach all places in this environment; internally moving means that inactive organisms are constantly subjected to transport; three-dimensional implies that populations and migratory movements are also three-dimensional. With regard to dispersal these three factors are unique. The marine environment, sea-water throughout, is uniform, relatively stable and isolated from other biotopes. Thus, the selective pressure is rather unvariable in Space; and stable means that it is not very variable in time either, while the isolated Position means that influences, biotic as well as abiotic, from other surrounding biotopes, do not affect the marine fauna. The dominant ecological features which nevertheless shape the distributions in the oceans, are the currents, the temperature, the food web and the interaction of species, and it is also these features which give shape to the communities.
KeywordsBiomass Migration Phytoplankton Assimilation Cretaceous
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