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  • Electronic Resource  (22)
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  • Electronic Resource  (22)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 27 (1974), S. 51-57 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A population of the cosmopolitan deep-sea ophiuran Ophiomusium lymani was studied by gel electrophoresis, and proved to be highly variable genetically; about 53% of the 15 loci studied are polymorphic, and the average individual is heterozygous at about 17% of the loci. This is approximately the same genetic variability displayed by other species, belonging to other phyla or classes, from the same deep-sea trawl. A similarly high level of genetic variation occurs in deep-sea organisms in general, and in a shallow-water tropical species. Both the deep-sea and the tropics are trophically stable environments. On the other hand, low genetic variabilities have been found in marine species from trophically unstable environments. These data suggest that any phylogenetic effects on genetic variability are secondary, and that the trophic regime may be of major importance in determining genetic strategies of adaptation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 33 (1975), S. 341-345 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A population of the bivalve mollusk Tridacna maxima (Röding) from Hron Island, Great Barrier Reef, Australia, was studied by gel electrophoresis, and proved to be highly variable genetically, with an average heterozygosity of about 22%. This compares closely with a population of T. maxima from Enewetak (Eniwetok) Atoll, with an average heterozygosity of about 20%, very high for marine organisms. Enewetak Atoll was the site of a series of nuclear tests. The Heron Island study verifies that the high variability is natural, and supports the hypothesis that species from trophically stable environments tend to be highly variable genetically.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 257 (1975), S. 514-515 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] VAN VALENI has proposed an evolutionary law that has attracted considerable attention2"6. He showed that plots of survivorship of taxa as a function of age are commonly log-linear (see Fig. 1 of ref. 1). This he interpreted to mean that the probability of extinction of a taxon is independent of its ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genetics 10 (1976), S. 1-7 
    ISSN: 0066-4197
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 5 (1974), S. 115-138 
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 35 (1988), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . We have studied linkage disequilibrium in natural populations of Trypanosoma cruzi, the agent of Chagas’ disease, by analyzing (i) a set of 524 stocks from the whole geographical range of the parasite, characterized at four gene loci coding for enzymes; (ii) a subsample of 121 stocks characterized at 12 enzyme loci; and (iii) a subset of 386 stocks from six locations in Bolivia, characterized by four enzyme loci. Our results show that the linkage disequilibrium reaches the maximum possible value, given the observed allelic frequencies, for almost all the locus pairs. This result is most consistent with the hypothesis that genetic recombination is absent or very rare in T. cruzi natural populations. Partition of the linkage disequilibrium variance for the six Bolivian populations shows that both inter- and intrapopulation components are substantial and that the relationships among the components are DIS2 〈 DST2, and D'IS2 〈 D'ST2. These inequalities are interpreted as the result of an interplay between genetic drift, rare or absent mating, and clonal selection in generating linkage disequilibrium in T. cruzi populations.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 227 (1970), S. 89-90 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the competition between species of Paramecium, P. aurelia lived predominantly in the upper layer of the liquid medium and fed mostly on bacteria, while P. bursaria lived preferentially in the bottom layer and fed on yeast. There was therefore only a slight mutual depression between the species. ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 27 (1971), S. 343-343 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Resumen El resultado de la competencia entreDrosophila willistoni yD. pseudoobscura depende de la constitución genética de las estirpes que compiten y de la temperatura. A 20 °C las dos especies coexisten, lo cual indica que el principio de exclusión competitiva no es universalmente válido.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 36 (1980), S. 837-839 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Satellite DNAs of theDrosophila willistoni group have been analyzed by Hae III endonuclease digestion. Differences were observed between the 2 speciesD. willistoni andD. paulistorum and also between semispecies ofD. paulistorum and, to a lesser extent, between subspecies ofD. willistoni. Differences did not appear to be consistently greater between strains producing sterile hybrid males than between those producing fertile hybrids.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 26 (1970), S. 208-208 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Resumen Seis poblaciones deDrosophila pseudoobscura han evolucionado, debido a la selección natural, hacia una mayor adaptación al ambiente. Durante 20 o 25 generaciones el número de individuos nacidos por unidad de comida y el tamano de la poblacion han aumentado gradualmente entre un dos y un cuatro por ciento por generaciön.
    Type of Medium: Electronic Resource
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