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991.
E. Maltby 《Plant and Soil》1984,76(1-3):183-193
Summary Major changes in the microbial populations, estimated by the dilution plate technique, of stagnohumic gley and thin pan stagnopodzol profiles occur as a result of moorland reclamation. There is an immediate surge in bacteria as numbers increase by two orders of magnitude compared with unreclaimed soils. Bacteria dominated recently reclaimed soils and make up 97–99% of total counts more than one year after initial ploughing. Actinomycetes assume much increased importance in profiles reclaimed nearly 130 years and it is thought they adjust much more slowly to a new soil environment which leads to development of a brown earth topsoil. Evidence is presented which underlines the value of numerical estimates of microorganisms as indicators of soil ecological conditions and pathways of soil development. 相似文献
992.
Glenn C. Conroy 《American journal of physical anthropology》1982,57(1):7-12
A discriminant analysis was performed on 226 ceboid skulls using data on emissary foramina size and shape. The purposes of the study are to 1) measure the success with which these discriminating variables can distinguish among platyrrhine genera and 2) derive a set of classification functions which will permit the classification of new cases with unknown group membership (i.e., fossil skulls). This technique is able to correctly classify 80% of the 226 ceboid skulls. Support is given to the allocation of Chiropotes, Cacajao, and Pithecia into one morphologically unified subfamily, Pitheciinae. Alouatta, Ateles, and Lagothrix also share many similarities in emissary foramina size and shape and their inclusion into one subfamily, Atelinae, is probably warranted. The distinctiveness of Cebus in these same morphological features is apparent. Possibilities for extending this procedure to study fossil lineages in platyrrhines are discussed. 相似文献
993.
The dual importance of competition and predation as regulatory forces in terrestrial ecosystems: evidence from decomposer food-webs 总被引:9,自引:0,他引:9
The relative importance of predation and competition (resource limitation) in influencing the components of a below-ground food-web consisting of three trophic levels (bacteria and fungi; bacterial-feeding and fungal-feeding nematodes; and top predatory nematodes) was estimated using microbial biomass and nematode frequency data collected throughout a 1-year period in two agro-ecosystems. The study suggested that bacterial and fungal biomass were likely to be regulated by grazing and competition respectively, and that these differences were likely to be attributed to the biological (probably morphological) differences between bacteria and fungi, in contrast to the predictions of the hypothesis of Hairston et al. (1960). Top predatory nematodes were sometimes strongly related to the microbial but not microbial-feeding trophic levels, indicating that microbial biomass may directly influence top predator numbers, and that the intermediate level may simply serve as a conduit by which resources pass from the bottom to top trophic levels. This study also suggests that the detritus food-web acts as two distinct (bacterial-and fungal-based) compartments. 相似文献
994.
Biomass and activity of planktonic bacteria were investigated during a one year study in a shallow sandpit lake. The shallowness of the lake helped keep the water column homogeneous regarding bacterioplankton. Small free-living bacteria (0.03 µm3 cell–1) dominated the populations throughout the period studied. Bacterial abundances varied from 1 to 11 × 106 cells ml–1. Kinetic parameters (V
max, K + S and T) were determined with 14C labelled compounds (glucose and amino acids mixture). V
max values were high and averaged 0.056 and 0.050 µgCl–1 h–1 for glucose and amino acids respectively. Maximal V
max values were observed in summer at the highest temperatures, but also in early spring. T values were much greater in winter. K + S values were significantly higher for amino acids (3 µg Cl–1) than for glucose (1 µg Cl–1). A low percentage of mineralization (about 25% for both tracers) could be the expression of the high growth efficiency expected when bacteria are growing at the expense of low molecular weight compounds as phytoplankton exudates. 相似文献
995.
K Yamashita A Hitoi N Tateishi T Higashi Y Sakamoto A Kobata 《Archives of biochemistry and biophysics》1983,225(2):993-996
Sugar chains of gamma-glutamyltranspeptidase purified from neonatal mouse liver and adult mouse kidney were quantitatively released as oligosaccharides from the polypeptide backbone by hydrazinolysis. A comparative study of the structures of the oligosaccharides has revealed that the GlcNAc beta 1 leads to 4Man beta 1 leads to group is found in the sugar chains of kidney enzyme but not in those of liver enzyme. This is considered as an organ-specific difference common to mammals because the same phenomenon was found in bovine and rat enzymes. 相似文献
996.
997.
《Journal of biological education》2012,46(3):130-132
There is some evidence to suggest that undergraduate biology students need to be given more opportunities for reflection in their education. Some argue that computer-based learning packages may be able to offer such opportunities. This paper presents four different approaches to defining what reflection is and how it can be promoted. These approaches are then used to discuss and review the different ways in which computer-based tutorials can be used to promote lateral thinking. An example of a web-based biology tutorial called ‘How Now Mad Cow’ is described and preliminary evaluation results are presented, in order to illustrate how students may be encouraged to reflect and what factors may influence that. Finally, the role of the tutor in enspiring students to reflect while using computer-based tutorials is discussed. This distinguishes between the role of the tutor in designing a computer-based tutorial, and the role of the tutor in determining and facilitating how a student uses a tutorial once it has been designed. 相似文献
998.
Testing diversification models of endemic Philippine forest mice (Apomys) with nuclear phylogenies across elevational gradients reveals repeated colonization of isolated mountain ranges 下载免费PDF全文
999.
A. López-López M. Richter A. Peña J. Tamames R. Rosselló-Móra 《Systematic and applied microbiology》2013
A metagenomic approach was carried out in order to study the genetic pool of a hypersaline microbial mat, paying more attention to the archaeal community and, specifically, to the putatively methanogenic members. The main aim of the work was to expand the knowledge of a likely ecologically important archaeal lineage, candidate division MSBL1, which is probably involved in methanogenesis at very high salinities. 相似文献
1000.
Jeferson Carneiro Iracilda Sampaio Thaynara Lima José de S. Silva-Júnior Izeni Farias Tomas Hrbek João Valsecchi Jean Boubli Horacio Schneider 《American journal of primatology》2020,82(9):e23167
Cheracebus is a new genus of New World primate of the family Pitheciidae, subfamily Callicebinae. Until recently, Cheracebus was classified as the torquatus species group of the genus Callicebus. The genus Cheracebus has six species: C. lucifer, C. lugens, C. regulus, C. medemi, C. torquatus, and C. purinus, which are all endemic to the Amazon biome. Before the present study, there had been no conclusive interpretation of the phylogenetic relationships among most of the Cheracebus species. The present study tests the monophyly of the genus and investigates the relationships among the different Cheracebus species, based on DNA sequencing of 16 mitochondrial and nuclear markers. The phylogenetic analyses were based on Maximum Likelihood, Bayesian Inference, and multispecies coalescent approaches. The divergence times and genetic distances between the Cheracebus taxa were also estimated. The analyses confirmed the monophyly of the genus and a well-supported topology, with the following arrangement: ((C. torquatus, C. lugens), (C. lucifer (C. purinus, C. regulus))). A well-differentiated clade was also identified within part of the geographic range of C. lugens, which warrants further investigation to confirm its taxonomic status. 相似文献