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151.
A new approach is described to identify the dominant process (physical
versus biological) in a pelagic marine ecosystem, from simple biological
oceanographic field variables. The approach is based on quantification of
the matching (M) between phytoplankton production
(P) and losses, from field estimates of chlorophyll
a(Chl) and P. Coefficient
M is estimated for a wide range of oceanic and coastal
environments and of trophic characteristics, using dat from the literature.
Results show that M characterizes the dominance of
physical versus biological processes in pelagic systems. The coefficient
may be especially useful as a means for extracting process information on
pelagic marine ecosystems from large data sets of Chl and
P, e.g. recorded by moored instruments or provided by
satellite images of ocean colour.
相似文献
152.
153.
Evolution of Polypyrimidines in Drosophila 总被引:3,自引:0,他引:3
Y. M. T. Cseko N. A. Dower P. Minoo L. Lowenstein G. R. Smith J. Stone R. Sederoff 《Genetics》1979,92(2):459-484
We surveyed 101 different Drosophila species for the presence of a particular highly repetitive DNA sequence containing long tracts of polypyrimidine/polypurine DNA, first found in D. melanogaster. Out of 55 tested species in the melanogaster group, only the sibling species D. simulans and D. mauritiana, as well as one distant relative in the ananassae subgroup, D. varians, contained the same sequence. All four of these species have long pyrimidine tracts as shown by acid hydrolysis of labelled DNA. All four species have the same sequence, bu the amount of this polypyrimidine/polypurine DNA varies greatly. Four other species in the hydei subgroup were found to contain a polypyrimidine/polpurine sequence, with an oligonucleotide composition different from that of D. melanogaster. This polypyrimidine DNA varies from as much as 10% of the total DNA in D. nigrohydei, to as little as 0.4% in D. neohydei. The long pyrimidine tracts in the hydei subgroup are often more than a thousand nucleotides in length, representing exceedingly homogeneous repetitious sequences.--These results show a rapid but discontinuous pattern of evolution for polypyrimidine/polypurine DNA . These sequences are not species specific, yet closely related species have greatly different amounts of polypyrimidines. Drastic changes occur in the amounts of these satellite type DNA sequences, as if the sequence had no continuous selective advantage in evolution. The implications of these results with regard to the general function and evolution of satellite DNA are discussed. 相似文献
154.
Taheri Serpil Karaca Zuleyha Rassoulzadegan Minoo Mehmetbeyoglu Ecmel Zararsiz Gokmen Sener Elif Funda Bayram Kezban Korkmaz Tufan Esra Sahin Mustafa Caglar Marasli Mert Kahraman Memis Mehmet Canatan Halit Ozturk Figen Tanriverdi Fatih Unluhizarci Kursad Kelestimur Fahrettin 《Cellular and molecular neurobiology》2022,42(5):1523-1542