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91.
PATTY JO WATSON 《American anthropologist》1995,97(4):683-694
The culture concept has been central to anthropology since the formational period of the discipline. Yet for much of the discipline's history it was used without explicit definition. Recent attempts to define it have yielded a range of varied formulations in the subdisciplines of archaeology and sociocultural anthropology. Does this mean that the center of anthropology—shared belief in a unified culture concept—has been destroyed? Quite the opposite, the author concludes—the debate has yielded benefits. 相似文献
92.
SUNG MIN BOO HAN SOON KIM WOONGGHI SHIN GA HUN BOO SUNG MI CHO BOK YEON JO JEE‐HWAN KIM JIN HEE KIM EUN CHAN YANG PETER A. SIVER ALEXANDER P. WOLFE DEBASHISH BHATTACHARYA ROBERT A. ANDERSEN HWAN SU YOON 《Molecular ecology》2010,19(19):4328-4338
The global distribution, abundance, and diversity of microscopic freshwater algae demonstrate an ability to overcome significant barriers such as dry land and oceans by exploiting a range of biotic and abiotic colonization vectors. If these vectors are considered unlimited and colonization occurs in proportion to population size, then globally ubiquitous distributions are predicted to arise. This model contrasts with observations that many freshwater microalgal taxa possess true biogeographies. Here, using a concatenated multigene data set, we study the phylogeography of the freshwater heterokont alga Synura petersenii sensu lato. Our results suggest that this Synura morphotaxon contains both cosmopolitan and regionally endemic cryptic species, co‐occurring in some cases, and masked by a common ultrastructural morphology. Phylogenies based on both proteins (seven protein‐coding plastid and mitochondrial genes) and DNA (nine genes including ITS and 18S rDNA) reveal pronounced biogeographic delineations within phylotypes of this cryptic species complex while retaining one clade that is globally distributed. Relaxed molecular clock calculations, constrained by fossil records, suggest that the genus Synura is considerably older than currently proposed. The availability of tectonically relevant geological time (107–108 years) has enabled the development of the observed, complex biogeographic patterns. Our comprehensive analysis of freshwater algal biogeography suggests that neither ubiquity nor endemism wholly explains global patterns of microbial eukaryote distribution and that processes of dispersal remain poorly understood. 相似文献
93.
CLAUDIA M. D'AVILA-LEVY ALINE C. C. VOLOTÃO FERNANDA M. ARAÚJO JOSÉ B. DE JESUS MARIA CRISTINA M. MOTTA ALANE B. VERMELHO RÉ L. S. SANTOS MARTA H. BRANQUINHA 《The Journal of eukaryotic microbiology》2009,56(5):454-458
ABSTRACT. We report the characterization of cell-associated and extracellular peptidases of Bodo sp., a free-living flagellate of the Bodonidae family, order Kinetoplastida, which is considered ancestral to the trypanosomatids. This bodonid isolate is phylogenetically related to Bodo caudatus and Bodo curvifilus . The proteolytic activity profiles of Bodo sp. were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis containing co-polymerized gelatin, casein, hemoglobin, or bovine serum albumin as substrates. The enzymatic complex degraded gelatin better in acidic pH, and under these conditions four proteolytic bands (120, 100, 90, and 75 kDa) were detected in the cellular or extracellular extracts. Two peptidases (250 and 200 kDa) were exclusively detected with the substrate casein. All these enzymes belong to the serine peptidase class, based on inhibition by aprotinin and phenylmethylsulfonyl fluoride. This is the first biochemical characterization of peptidases in a free-living Bodo sp., potentially providing insight into the physiology of these protozoa and the evolutionary importance of peptidases to the order Kinetoplastida as some of these enzymes are important virulence factors in pathogenic trypanosomatids. 相似文献
94.
Plating efficiency of cultured protoplasts of Solanum brevidensincreased to c. 10% after the addition of 50 mol m3glutamine to the culture medium. Growth of protoplast-derivedcolonies at densities of 20 colonies cm3 was obtainedby lowering the auxin content alter 46 d. A sample of50 protoplast-derived plants was examined for chromosomal variation.Twelve plants were diploid (2n=24), 26 were tetraploid (2n=48)and 12 were aneuploid at the tetraploid level (2n=48?). Tetraploidand aneuploid plants had broader leaves and set fewer or noseeds compared to the diploid regenerants which were similarin gross morphology and seed set to control plants. Key words: Solanum brevidens, protoplasts, plant regeneration, variation 相似文献
95.
96.
97.
Biotic Assemblages and Ecological Controls on Reefs and Banks of the Northwest Gulf of Mexico 总被引:3,自引:0,他引:3
REZAK RICHARD; GITTINGS STEPHEN R.; BRIGHT THOMAS J. 《Integrative and comparative biology》1990,30(1):23-35
This paper summarizes the results of investigations of the ecologyof reefs and banks in the northwestern Gulf of Mexico. Nearshoresurface waters are turbid out to approximately the 10 m isobath.A turbid nepheloid layer up to 20 m in thickness exists beyondthis depth. Seasonal temperature and salinity variability ishigh in nearshore waters. At the shelf edge, the temperatureto 50 m depth remains above 19°C. Topographic prominencesare common in the region. Most are surface expressions of thediapirism of underlying salt domes derived from deeply buriedJurassic salt deposits. Biotic zonation on the banks is primarilydepth related. Zones of major reef-building include the Diploria-Montastrea-Porites Zone (1536 m), the Madracis Zone (2846m), the Stephanocoenia-Millepora Zone (3652 m), and theAlgal-Sponge Zone (4598 m). A zone of minor reefbuildingon some banks is the Millepora Zone (1852 m). An AntipatharianTransitional Zone exists from 56 to over 100 m on some banks.The Nepheloid Zone near the base of the banks is a zone of noreef-building. Not all zones are present on all banks. The communitystructure and depths of these zones depend on and are modifiedby the regional current regime, depth of the bank crests, substratecharacteristics, winter temperature minima, river influences,and the relative depth and thickness of the nepheloid layer.Nearshore communities are warm temperate in nature, though tropicalorganisms are occasionally abundant. Progressing offshore, thebenthos becomes increasingly tropical. The northerly locationand isolated nature of the Flower Gardens have lead to reducedcommunity diversity (e.g., only 18 of the 55 Western Atlantichermatypic coral species exist), but not reduced abundancesor growth rates of the species present. Assemblages on otherbanks exist below the tolerance limits of thriving tropicalreefs due to their frequent immersion in turbid water, excessivecrest depths, or lower minimum winter temperatures. 相似文献
98.
JOÃO A. M. FERREIRA DALYSON F. S. CUNHA ANGELO PALLINI MAURICE W. SABELIS ARNE JANSSEN 《Ecological Entomology》2011,36(4):435-441
1. Although theory suggests that intraguild predation destabilises food webs and may result in exclusion of species, empirical observations of food webs reveal that it is a common interaction. It has been proposed that habitat structure reduces the interaction strength of intraguild predation, thus facilitating the coexistence of species. 2. This was tested using acarodomatia, tiny structures on plant leaves, and predatory mites, which usually reside in these domatia. Sweet pepper plants (Capsicum annuum L.) were used, which possess domatia consisting of tufts of hair, and coffee plants (Coffea arabica L.) with pit‐shaped domatia. 3. On sweet pepper, the predatory mites Neoseiulus cucumeris Oudemans and Iphiseius degenerans Berl. feed on each other's juveniles. Larvae of each of the species were therefore used as intraguild prey with adult females of the other species as intraguild predators. On coffee, a similar set‐up was used, with larvae and adult females of Amblyseius herbicolus Chant and Iphiseiodes zuluagai Denmark & Muma as intraguild prey and intraguild predators, respectively. 4. Domatia on detached, isolated sweet pepper and coffee leaves were either closed with glue or left open, after which larvae and adult predators were released. As a control, larvae were released on leaves with open or closed domatia without an adult predator. 5. Survival of larvae was high in the absence of the adult (intraguild) predator. In the presence of the intraguild predator, survival was significantly higher on leaves with open domatia than on leaves with closed domatia. 6. This shows that even such tiny structures as plant domatia may significantly affect the interaction strength of intraguild predation. 相似文献
99.
SÓNIA VIEIRA HELENA COELHO RITA NOLASCO JOÃO SERÔDIO RICHARD BARNES HENRIQUE QUEIROGA 《Biological journal of the Linnean Society. Linnean Society of London》2010,100(2):439-450
Intertidal animals display a suite of cyclic behaviours that evolved as adaptations to the predictable cycle of inundation and exposure. In estuarine habitats, mud snails from the genus Hydrobia are among the most abundant grazers, and have received considerable attention with respect to the behavioural mechanisms mediating locomotion, dispersal, and feeding, although the nature of the control of these processes has remained elusive. In particular, it is not clear whether endogenous activity patterns are related to periodic changes of microphytobenthos biomass at the sediment surface, or whether they are timed to the tidal cycle at all. In the present study, we address the crawling activity of Hydrobia ulvae under constant conditions, as well as the effects of individual size and previous short‐term exposure to tides of different range, by recording immersed individual snails under constant dark conditions. We show that the species displays an overt circatidal pattern of crawling, with activity peaks around high water, and that the start of inundation may act as an entrainment agent of the rhythm. Moreover, the results obtained indicate that smaller snails display higher levels of activity, although neither the size nor previous in situ influence of tidal range has an effect on the period and on the amplitude of the rhythm. These findings suggest that fluctuations of microphytobenthos biomass are not a sufficiently strong selective pressure to have shaped locomotor activity in H. ulvae. Moreover, feeding of H. ulvae should take place mostly during high water and be independent of periodic fluctuations of microphytobenthos biomass at the surface of the sediment. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 439–450. 相似文献
100.
JO TURNER LYNNE M DRUMMOND SUMAN MUKHOPADHYAY HAMID GHODSE SARAH WHITE ANUSHA PILLAY NAOMI A FINEBERG 《World psychiatry》2007,6(2):108-111
There have been relatively few studies examining sleep in patients with
obsessive-compulsive disorder (OCD) and these have produced contradictory
findings. A recent retrospective study identified a possible association between
OCD and a circadian rhythm sleep disorder known as delayed sleep phase syndrome
(DSPS). Patients with this pattern of sleeping go to bed and get up much later
than normal. They are unable to shift their sleep to an earlier time and,
as a result, suffer considerable disruption to social and occupational functioning.
In this study, we examined the sleep of patients with OCD prospectively. We
aimed to establish the frequency of DSPS in this population and any associated
clinical or demographic factors which might be implicated in its aetiology. 相似文献