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  • Springer  (310)
  • American Association of Petroleum Geologists  (14)
  • American Association for the Advancement of Science (AAAS)
  • 2015-2019  (283)
  • 1995-1999  (13)
  • 1980-1984  (16)
  • 1975-1979  (6)
  • 1970-1974  (6)
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  • 1
    Digitale Medien
    Digitale Medien
    Population dynamics and harvesting of semelparous species with phenotypic and genotypic variability in reproductive age (1995)
    Springer
    Journal of mathematical biology 33 (1995), S. 521-556 
    Details
    ISSN: 1432-1416
    Schlagwort(e): Population dynamics modeling ; Evolutionarily stable strategies ; Polymorphic life histories ; Age-at-maturity ; Harvesting
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract We study the evolution of polymorphic life histories in anadromous semelparous salmon and the effects of harvesting. We derive dynamic phenotypic and genetic ESS models for describing the evolutionary dynamics. We show in our deterministic analysis that polymorphisms are not possible in a panmictic random mating population. Instead, genetic or behavioral polymorphisms may be observed in populations with assortative mating systems. Positive assortative mating may be supported and generated by behavioral and phenotypic traits like male mate choice, spawning ground selection by phenotype, or within-river homing-migration-distance by size. In the case of an evolutionarily stable dimorphism, the ESS is characterized by a reproductive ideal free distribution such that at an equilibrium the individuals are indifferent from the fitness point of view between the two life histories of early and late reproduction. Different strategy models - that is, phenotypic and genetic ESS models - yield identical behavioral predictions and, consequently, genetics does not seem to play an important role in the present model. An evolutionary response to increased fishing mortality is obvious and may have resource management implications. High sea fishing mortalities drive the populations toward early spawning. Thus it is possible that unselective harvesting at sea may eliminate, depending on the biological system, behavioral polymorphisms or genetic heterozygozity and drive the population to a monomorphic one. If within-river homing migration distances depend on the size of fish, unselective harvesting at sea, or selective harvesting of spawning runs in rivers, may reduce local population sizes on spawning grounds high up rivers. Finally, harvesting in a population may cause a switch in a dominant life-history strategy in a population so that anticipated sustainable yields cannot be realized in practice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00163041
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    The occurrence of microbodies and peroxisomal enzymes in achlorophyllous leaves (1972)
    Springer
    Planta 105 (1972), S. 114-138 
    Details
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Several types of leaves of leaf parts lacking chlorophyll were fixed and embedded according to conventional procedures and examined electron-microscopically for microbodies. Comparisons of relative abundance of microbodies, plastids and mitochondria were made by computing the average numbers of organelle profiles per cell section. Similar leaves were homogenized and assayed for three enzymes characteristic of leaf peroxisomes. The localization of these enzymes in microbodies was indicated for the achlorophyllous tissues by the positive result obtained when 3,3′-diaminobenzidine was used as an electron cytochemical stain for catalase activity. Microbodies were present in all non-photosynthetic leaves or leaf parts examined, including yellowish-white segments of variegated leaves, albino leaves, and etiolated leaves of two species. In several cases, the numbers of microbody profiles per cell section were as great in the achlorophyllous leaves as in the chlorophyllous. The levels of peroxisomal enzyme activity in the yellowish-white leaves were substantial, although often not as high as in the green leaves. It was concluded that enzymatically these microbodies are probably similar to the peroxisomes characterized from chlorophyllous leaves. In the absence of the photosynthetic product, glycolate, however, it seems unlikely that the organelle is performing the same functions as in green leaves. It is also apparent that the initial formation of peroxisomes in leaves can occur when neither light nor a photosynthate such as glycolate is present as an inducer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00385572
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Response of American cockroach (Periplaneta americana) olfactory receptors to selected alcohol odorants and their binary combinations (1997)
    Springer
    Journal of comparative physiology 180 (1997), S. 701-709 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Key words Olfaction  ;  Odor discrimination  ; Mixture perception
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The cockroach is known to possess several morphologically distinct types of sensilla on its antenna, each of which contain a couple or a few receptor cells that respond to an array of compounds. We recorded the response of cells exclusively from one type of sensillum to evaluate the variation in the response of the cells in these sensilla to three closely related alcohols and their binary mixtures. Our results indicate that cells within the class of those responsive to aliphatic alcohols are otherwise variable in their response to particular aliphatic alcohols and not easily classifiable into subclasses. They also indicate that patterns of responses among cells are not robust with respect to concentration. Finally, a considerable level of inhibition is indicated in the response of the receptor cells to binary mixtures compared with the response to pure odorants. The data suggest that discrimination of alcohols (and other odorants of general but not special significance) by the cockroach cannot be understood simply in terms of labeled lines or linear filters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003590050084
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    A correlative ultrastructural and enzymatic study of cotyledonary microbodies following germination of fat-storing seeds (1970)
    Springer
    Planta 93 (1970), S. 269-288 
    Details
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Sunflower, cucumber, and tomato cotyledons, which contain microbodies in both the early lipid-degrading and the later photosynthetic stages of post-germinative growth, were processed for electron microscopy according to conventional procedures and examined 1, 4 and 7 days after germination. Homogenates of sunflower cotyledons were assayed for enzymes characteristic of glyoxysomes and leaf peroxisomes (both of which are defined morphologically as microbodies) at stages corresponding to the fixations for electron microscopy. The particulate nature of these enzymes was demonstrated by differential and equilibrium density centrifugation, making it possible to relate them to the microbodies seen in situ. One day after germination, the microbodies are present as small organelles among large numbers of protein and lipid storage bodies; the cell homogenate contains catalase but no detectable isocitrate lyase (characteristic of glyoxysomes) or glycolic acid oxidase (characteristic of leaf peroxisomes). 4 days after germination, numerous microbodies (glyoxysomes) are in extensive and frequent contact with lipid bodies. The microbodies often have cytoplasmic invaginations. At this stage the cells are rapidly converting lipids to carbohydrates, and the homogenate has high isocitrate lyase activity. 7 days after germination, microbodies (peroxisomes) are appressed to chloroplasts and frequently squeezed between them in the green photosynthetic cells. The homogenate at this stage has substantial glycolic acid oxidase activity but a reduced level of isocitrate lyase. It is yet to be determined whether the peroxisomes present at day 7 are derived from preexisting glyoxysomes or arise as a separate population of organelles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00384101
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Effects of seed size on seedling size in Virola surinamensis; a within and between tree analysis (1982)
    Springer
    Oecologia 53 (1982), S. 347-351 
    Details
    ISSN: 1432-1939
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We conducted a greenhouse study of the effects of initial seed mass on seedling characteristics in a Panamanian population of Virola surinamensis, a canopy tree in which mean seed mass of different individuals ranges from 1.34 to 4.04g. The system is of particular interest because birds preferentially eat fruits of small-seeded plants, leaving seedlings of large-seeded individuals under conditions of potentially severe sibling competition (Howe and Vande Kerckhove 1980). Effects of differences of mean seed mass between trees are explored using an analysis of variance, while effects of seed-mass variation within crops are demonstrated with a regression analysis. A two-way analysis of variance decisively shows effects of parental source and light condition on seedling height, leaf length, and dry shoot mass (all P〈0.0001). A posteriori tests show that differences in seedling characteristics reflect differences in initial seed mass, with especially strong differences apparent in shoot mass. Regression of seedling characteristics on initial seed mass shows that variation of seed size within a crop is sufficient to influence shoot mass at 15 weeks (P〈0.0001). Effects of size differences of seeds that land adjacent to each other, either under the parent or in monkey droppings, are documented with growth of pairs of seedlings in pots. Differences in shoot height and mass at 15 weeks are evident when seeds of average size differ by only 0.2 g, and dramatic differences are evident when paired seeds differ by an average of 1.5 g. Seedlings grow more when isolated than when planted with conspecifics. These experimental results offer indirect support for the hypothesis that small-seeded Virola parents secure an advantage in reproduction through differential dispersal, while large-seeded plants produce more competitive seedlings under their own crowns — an advantage most likely to be of importance when frugivores are scarce.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00389011
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Host-parasite dynamics and the evolution of host immunity and parasite fecundity strategies (1997)
    Springer
    Bulletin of mathematical biology 59 (1997), S. 427-450 
    Details
    ISSN: 1522-9602
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract We explore evolutionarily stable co-evolution of host-macroparasite interactions in a discrete-time two-species population dynamics model, in which the dynamics may be stable, cyclic or chaotic. The macroparasites are assumed to harm host individuals through decreased reproductive output. Hosts may develop costly immune responses to defend themselves against parasites. Parasites compete with conspecifics by adjusting their fecundities. Overall, the presence of both parasites and the immune response in hosts produces more stable dynamics and lower host population sizes than that observed in the absence of the parasites. In our evolutionary analyses, we show that maximum parasite fecundity is always an evolutionarily stable strategy (ESS), irrespective of the type of population interaction, and that maximum parasite fecundity generally induces a minimum parasite population size through over-exploitation of the host. Phenotypic polymorphisms with respect to immunity in the host species are common and expected in ESS host strategies: the benefits of immunication depend on the frequency of the immune hosts in the population. In particular, the steady-state proportions of immune hosts depend, in addition to all the parameters of the parasite dynamics only on the cost of immunity and on the virulence of parasites in susceptible hosts. The implicit ecological dynamics of the host-parasite interaction affect the proportion of immune host individuals in the population. Furthermore, when changes in certain population parameters cause the dynamics of the host-parasite interaction to move from stability to cyclicity and then to chaos, the proportion of immune hosts tends to decrease; however, we also detected counter-examples to this result. As a whole, incorporating immunological and genetic aspects, as well as life-history trade-offs, into host-macroparasite dynamics produces a rich extension to the patterns observed in the models of ecological interactions and epidemics, and deserves more attention than is currently the case.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02459459
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Development of intra-natural killer complex (NKC) recombinant and congenic mouse strains for mapping and functional analysis of NK cell regulatory loci (1999)
    Springer
    Immunogenetics 49 (1999), S. 238-241 
    Details
    ISSN: 1432-1211
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002510050486
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    BOOK REVIEW: Classical Electrodynamics, by John David Jackson (1999)
    Springer
    Foundations of physics 29 (1999), S. 133-135 
    Details
    ISSN: 1572-9516
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018821305089
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    G. R. Carmichael, G. E. Folk and J. L. Schnoor (eds.): 1995, Preparing for Global Change: A Midwestern Perspective (1997)
    Springer
    Climatic change 37 (1997), S. 569-573 
    Details
    ISSN: 1573-1480
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005330330263
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Composition and abundance of phytoplankton in tributaries of the lower Colorado river, Grand Canyon region (1979)
    Springer
    Hydrobiologia 66 (1979), S. 81-93 
    Details
    ISSN: 1573-5117
    Schlagwort(e): algae ; phytoplankton ; Colorado River ; Grand Canyon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phytoplankton distribution and abundance in eleven tributaries of the Colorado River within the Grand Canyon were investigated from April, 1975 to June, 1976. During this period a total of 56 genera and 156 species of phytoplankton was identified. Phytoplankton species of the individual tributaries were quite distinct, with only four diatom species, Diatoma vulgare, Navicula tripunctata, Nitzschia linearis and Synedra ulna, common to all the tributaries. Bright Angel Creek, Shinumo Creek and Elves Chasm were the tributaries with the most diverse algal flora, whereas Vaseys Paradise, Tapeats Creek, Deer Creek and Havasu Creek showed the lowest species richness. Elves Chasm and Diamond Creek had the highest phytoplankton numbers. Phytoplankton abundance and species richness appeared to be influenced by high turbidity, current velocity, fluctuating water levels and age of the water. Some of the dominant algal species, Biddulphia laevis, Cocconeis pediculus, Cymbella ventricosa, Epithemia sorex, Gomphonema parvulum and Synedra ulna, showed significant correlations with specific physico-chemical characteristics of the tributaries.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019143
    Standort Signatur Erwartet Verfügbarkeit
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