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  • 1
    Call number: AWI Bio-21-94352
    Type of Medium: Monograph available for loan
    Pages: 795 Seiten
    ISBN: 3904144731
    Series Statement: Diatom monographs 1
    Language: English
    Location: AWI Reading room
    Branch Library: AWI Library
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] DESPITE never having examined our Ross Ice Shelf Project (RISP) slides or photomicrographs, Brady cites 11 specific instances in which he alleges that we either misidentified common Plio-Pleistocene indicator species, or misrepresented their stratigraphical ranges1. Each allegation is vital to ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 293 (1981), S. 130-133 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Previous studies of Ross Sea cores conducted in our laboratory defined two sedimentary units separated by a transition zone of well sorted sandy material1'3. The upper unit, called unit A, consisted of soft-to-soupy, diatom-rich, silty mud of Holocene age. Five radiocarbon dates supported this age ...
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  • 4
    ISSN: 1572-8404
    Keywords: Punctuated equilibria theory ; hierarchy ; synthetic theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
    Notes: Abstract Weak links, in the form of inadequacies in both reasoning and supporting evidence, exist at several critical steps in the derivation of an hierarchical concept of evolution from punctuated equilibria. Punctuation itself is predicated on a distorted reading of phyletic change as phyletic gradualism, and of allopatric speciation as the instantaneous formation of unchanging typological taxa. The concept of punctuation is further confounded by the indescriminate employment of the same term to denote both a causal explanation for evolutionary change and an outcome of substantiated evolutionary processes. Even when the intended usage for the term is specified, each denotation of punctuation entails respective drawbacks. As a causal explanation, punctuation clearly belongs to the class of quantum theories with all their attendant impedimenta, including special salsatory non-adaptive mechanisms of evolutionary change. Redefinition of punctuation as a pattern of morphologic change reduces it to one possible outcome of known microevolutioanry processes, thus obviating any need for an hierarchical explanation of macroevolution. While vacillation between usages has preserved the term in the literature, the end result of this obfuscation has been a circle of faulty reasoning in which the pattern of punctuation is invoked as its own proof. Widespread confusion concerning what constitutes an adequate test of punctuation is directly attributable to imprecision in both the original and revised formulations of the concept. The argument for species-level selection is based on the typological and philosphically flawed premise of species as individuals, and further requires the hypothesis of heritable emergent properties, for which empirical evidence is lacking. Extrapolation of hierarchy to higher taxonomic levels depends on the unproven assumption that mass extinction constitutes a causal mechanism for macroevolution which is qualitatively distinct from, and not reducible to, the causes of microevolution. Because key elements of hierarchical theory depend upon misrepresentations of the synthetic theory, semantic circumvention, and questionable reasoning, and because its central assertions remain unsubstantiated by empirical evidence, the derivation of an hierarchical theory of evolution from punctuation constitutes an exercise an futility and should be abandoned.
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  • 5
    Publication Date: 1988-01-01
    Print ISSN: 0169-3867
    Electronic ISSN: 1572-8404
    Topics: Biology , Philosophy
    Published by Springer
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  • 6
    Publication Date: 1996-01-01
    Description: We present new interpretations of deglaciation in McMurdo Sound and the western Ross Sea, with observationally based reconstructions of interactions between East and West Antarctic ice at the last glacial maximum (LGM), 16000, 12000, 8000 and 4000 BP. At the LGM, East Antarctic ice from Mulock Glacier split; one branch turned westward south of Ross Island but the other branch rounded Ross Island before flowing southwest into McMurdo Sound. This flow regime, constrained by an ice saddle north of Ross Island, is consistent with the reconstruction of Stuiver and others (1981a). After the LGM, grounding-line retreat was most rapid in areas with greatest water depth, especially along the Victoria Land coast. By 12000 BP, the ice-now regime in McMurdo Sound changed to through-flowing Mulock Glacier ice, with lesser contributions from Koettlitz, Blue and Ferrar Glaciers, because the former ice saddle north of Ross Island was replaced by a dome. The modern flew regime was established ∼4000 BP. Ice derived from high elevations on the Polar Plateau but now stranded on the McMurdo Ice Shelf, and the pattern of the Transantarctic Mountains erratics support our reconstructions of Mulock Glacier ice rounding Minna Bluff but with all ice from Skelton Glacier ablating south of the bluff. They are inconsistent with Drewry’s (1979) LGM reconstruction that includes Skelton Glacier ice in the McMurdo-Sound through-flow. Drewry’s (1979) model closely approximates our results for 12000-4000 BP. Ice-sheet modeling holds promise for determining whether deglaciation proceeded by grounding-line retreat of an ice sheet that was largely stagnant, because it never approached equilibrium flowline profiles after the Ross Ice Shelf grounded, or of a dynamic ice sheet with flowline profiles kept low by active ice streams that extended northward from present-day outlet glaciers after the Ross Ice Shelf grounded.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
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  • 7
    Publication Date: 1983-01-01
    Description: One method of increasing the resolving power of paleontological inquiries is to assess the time distribution, or phenology, of perispeciational change. The rationale for this test is that, while concentration of morphologic change around the time of speciation is consistent with both known microevolutionary mechanisms and punctuated equilibria, punctuated equilibrium theory presupposes that most of the change occurs either before or during initial allopatry to produce morphologically static taxa. Considerable change in the initial phases of speciation could also result from known microevolutionary mechanisms, but if significant change occurs in the neosympatric phase, or at any time after the species have become differentiated, then that change is best explained by known microevolutionary mechanisms.Amount and rate of morphologic change during each phase of the allopatric speciation process were determined for two cognate species of the radiolarian genus Eucyrtidium. In this case, morphologic change accruing to these species during the neosympatric phase was 2-3 times as great as that which occurred during the initial allopatric phase. Morphologic trends in both these species during the allopatric phase differed significantly from a random walk. The size differential that characterized this speciation event was not the product of a single large step early in the process but of a disproportionate number of small steps in one direction during neosympatry. Therefore, the hypothesis of no statistically significant change following the “first stage” of speciation, which is a major tenet of punctuated equilibrium theory, is falsified for this case.
    Print ISSN: 0094-8373
    Electronic ISSN: 0094-8373
    Topics: Geosciences
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  • 8
    Publication Date: 1975-01-01
    Description: In this paper, we present detailed quantitative studies of evolutionary changes over all or part of the stratigraphic ranges of five fossil radiolarian species from Pacific deep-sea sediment cores. Each of these species shows some variation of a distinctive evolutionary pattern: increase in size of measured morphologic characters, preceded and/or followed by an interval during which little or no significant change occurred.One of the species studied (Eucyrtidium matuyamai) was allopatrically differentiated from another (Eucyrtidium calvertense). The others (Calocycletta caepa, Pterocanium prismatium and Pseudocubus vema) underwent phyletic change within a single lineage. Those species undergoing phyletic change towards larger size maintained almost constant variability of shell size over long periods of time, including periods of both rapid and extremely slow evolution. This constancy of variability suggests that diminution of selection against larger size may have acted as a stimulus to size increase. In contrast, E. calvertense decreased in variability during evolution towards smaller shell size. We believe this decrease may be interpreted as the result of two factors: (1) strong selection against larger size apparently exerted on this species by its direct descendant, E. matuyamai, during the neosympatric phase of speciation and (2) continuation of previous selection against very much smaller size.
    Print ISSN: 0094-8373
    Electronic ISSN: 0094-8373
    Topics: Geosciences
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  • 9
    Publication Date: 1975-01-01
    Description: While the importance of allopatric speciation in the fossil record has long been underestimated, phyletic change within single unbranching lineages also occurs. The 50% increase in thoracic width observed in the radiolarian species Pseudocubus vema from an Antarctic deep-sea core is a clear example of a long-term phyletic trend in a continuous fossil sequence. Phyletic change in P. vema occurred at varying rates, but changes in the morphologic rate of evolution do not correspond to any obvious breaks in the fossil record such as would be indicated by missing segments of the core's magnetic stratigraphy. Variation in thoracic width, as measured by the coefficient of variation, does not depend on the morphologic rate of evolution, proportional rate of evolution, nor the amount of time required for the width to change by one standard deviation, so much as it depends on whether change was accomplished by addition or removal of extreme phenotypes to or from the population.
    Print ISSN: 0094-8373
    Electronic ISSN: 0094-8373
    Topics: Geosciences
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  • 10
    Publication Date: 1987-01-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
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