共查询到20条相似文献，搜索用时 15 毫秒
1.
Streptomycetes In 2016, the VAAM selected streptomycetes as the microbe of the year. These bacteria exhibit a highly differentiated life‐cycle and a huge genetic diversity. They dominate in many soil‐types in which they act as experts to recycle biopolymers ultimately leading to the formation of precious humus. Their master‐performances provoke the synthesis of nearly exhaustless repertoires of small molecules. From these, an impressive number is in therapeutic use to cure infectious diseases and to treat tumors. 相似文献
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Prof. Dr. Dieter Uhl 《当今生物学》2013,43(4):228-236
Fires in the Earth history Fire is a naturally occurring factor in the biosphere ever since the first appearance of land plants in the Late Silurian about 425 million years ago. Charcoal and characteristic polyaromatic hydrocarbons can be used as evidence for such palaeo‐wildfires. Besides the presence of fuel (=plant biomass) and sources of ignition (i.e. lightning strikes) the most important factors influencing the occurrence of fires throughout the Earth history are varying atmospheric oxygen concentrations and climatic changes. Although our knowledge about palaeo‐wildfires remains incomplete for several periods of the Earths history it is possible to use the existing knowledge to gain a better understanding of the possible impacts of current and future climate change on the fire‐ecology of modern ecosystems. 相似文献
3.
Henner Hollert Markus Brinkmann Sebastian Hudjetz Catrina Cofalla Holger Schüttrumpf 《当今生物学》2014,44(1):44-51
Flood events – an underestimated danger Floods events are a constant threat to life, health and property of the population as well as for industry, agriculture and infrastructure in flood‐prone areas. But of concern are not only the direct effects: historical contamination – ticking ”time bombs\" – in the sediment can re‐enter the water column through erosion. Once present, they can have negative impact on water quality and endanger health of aquatic organisms and humans. This article features several studies on the hazardous potential of flood events and especially the findings of a combined hydrological and ecotoxicological investigation strategy. 相似文献
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In order to test against contingency in a 3-way table, simplified X2-formulas are given for (1) the general r xcxl-table, (2) for the rxcx2-table, (3) for the 2x2xl-table, and (4) for the 2×2×2-table. The tests are valid only if a sample of N individuals is observed as to 3 discrete or discretisized (dichotomized) variables which are, under H0, assumed to be totally independent. 相似文献
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Prof. Dr. Helmut Segner 《当今生物学》2014,44(4):232-241
Environmental estrogens Endocrine disrupters are environmental substances which interfere with the hormone system of organisms and thereby induce adverse effects. They exert their biological activity either by disrupting hormone metabolism or by imitating the biological action of the endogenous hormones. In the aquatic environment, an important group of endocrine disrupters is represented by the estrogen‐active compounds, which mimic the female sex hormone, 17β‐estradiol. Both laboratory experiments and field studies on fishes have demonstrated that already very low concentrations of environmental estrogens are able to induce disturbances in the hormone system and hormone‐regulated processes of fishes. 相似文献
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Prof. Dr. Susanne Bickel 《当今生物学》2012,42(4):222-231
Oil plants in Middle Europe Renewable resources have an increasing impact on industry and technology. Oil plants supply vegetable oil, which is important for our nutrition but can also be used as an industrial resource. Plant oils have many non‐food uses. They are not only used as Biofuels, but can also be found in many technical products including industrial lubricants, hydraulic oils, washing agents, paints and varnishes, and much else. In Europe rapeseed, sunflower, and olive are the primary oil plants. Rapeseed oil is newly recommended for infant nutrition, as it contains a high concentration of α‐linolenic acid, which is an important building block in brain development. 相似文献
7.
Effects of invasive crayfish in Europe Native crayfish in Europe are threatened by the rapid spread of non‐indigenous crayfish species. An especially potent invader is the North‐American signal crayfish (Pacifastacus leniusculus) due to its tolerance to low temperatures and its high reproduction rate. A three year study aims to detect ecological effects of rising signal crayfish densities as well as their behavioral effects on fish. Results show that high crayfish densities lead to severely decreasing numbers in benthic invertebrate communities as well as in fish densities. Signal crayfish also ousted Brown Trout from shelters permanently, which will lead to higher predation risks for the fish. 相似文献
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Biofuels from developing countries The pressure for reducing greenhouse gas emissions, rising oil prices, but also the lobbying by the agricultural sector and the automotive industry have induced the recent boom on biofuels. Due to limited land availability, competition with food production and high overall environmental impacts, the sustainability market potential for biofuels is assumed to be significantly smaller than 10% of global fuel consumption. Nevertheless, niches for the sustainable production and use of biofuels exist especially in developing countries. It is often more sustainable to use biomass feedstock for local supply of electricity and heat than producing biofuels for export. 相似文献
10.
Andrew M. Allen Augusta Dorey Jonas Malmsten Lars Edenius Göran Ericsson Navinder J. Singh 《Ecology and evolution》2017,7(1):305-319
The demographic consequences of changes in habitat use driven by human modification of landscape, and/or changes in climate, are important for any species. We investigated habitat–performance relationships in a declining island population of a large mammal, the moose (Alces alces), in an environment that is predator‐free but dominated by humans. We used a combination of demographic data, knowledge of habitat selection, and multiannual movement data of female moose (n = 17) to understand how space use patterns affect fecundity and calf survival. The calving rate was 0.64 and was similar to calving rates reported in other populations. Calf survival was 0.22 (annually) and 0.32 (postsummer), which are particularly low compared to other populations where postsummer survival is typically above 0.7. Home ranges were mainly composed of arable land (>40%), and selection for arable land was higher in winter than in summer, which contrasts with previous studies. Females that spent more time in broadleaf forest in the summer prior to the rut had higher fecundity rates, while more time spent in arable land resulted in lower fecundity rates. Females that spent more time in thicket/scrubland habitats during winter had lower calf survival, while females that had higher use of mixed forests tended to have higher calf survival. The dominance, and subsequent use, of suboptimal foraging habitats may lead to poor body condition of females at parturition, which may lower calf body weights and affect the mother's ability to lactate. In addition, our results indicated that the growing season has advanced significantly in recent decades, which may be causing a mismatch between parturition and optimal resource availability. These effects may exacerbate the female's ability to meet the energetic demands of lactation. Therefore, the observed low calf survival appears to be caused by a combination of factors related to current land use and may also be due to changing vegetation phenology. These results have important implications for the management of species in human‐dominated landscapes in the face of climate change, and for an increased understanding of how species may adapt to future land use and climate change. 相似文献
11.
W. Foissner 《Hydrobiologia》1984,119(3):193-208
The morphology, infraciliature, and ecology of 8 species of the ciliate family Amphileptidae were investigated. A new species, Litonotus trichocystiferus nov. spec., and some new combinations and synonyms are described., Improved diagnoses are given for the genera Litonotus, Amphileptus, and Opisthodon. 相似文献
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Seabirds face a number of challenges in Antarctic and Subantarctic breeding areas, such as variations in food supply and changes in the ecosystem due to climate change, aggregation and competition from the limited number of suitable breeding areas, and inaccessible breeding areas due to changes in precipitation. Adjustments to irregular food supplies, such as flexible incubation and nesting times, and torpor in chicks can help seabirds keep pace with changes occurring due to climate change. Data loggers are used to better understand the responses of adult birds to changes in the ecosystem and the resulting population trends. Various data loggers are used for a variety of applications, from one gram light loggers for long‐term tracking across large scales to high‐resolution GPS loggers with acquisition of acceleration data that can also be used to model energy expenditure. In order to fully understand the movement ecology of seabirds, several approaches need to be considered: ecological segregation in space, time and choice of food, energy landscapes and the non‐lethal effects of predation (landscapes of fear). 相似文献
14.
Abstract. The spatial distribution of seedlings in fertilized and non-fertilized grassland patches (1 m x 2 m) was examined in alvar vegetation on the island of Öland, Sweden. We established whether variation in seedling distribution in grassland patches reflects the distribution of conspecific adults. We also established the significance of microsite turf attributes for prediction of seedling distribution at a small scale (10 cm x 10 cm), and the significance of conspecific adults abundance, assemblage of adult species and cover of lichens, mosses, litter and bare ground. Our results indicate that fertilization reduces the importance of regeneration by seed of perennial species and enhances seedling recruitment of winter annuals and biennials. At the patch scale, enrichment does not affect species richness. Community patchiness contributes to the maintenance of diversity by providing a variety of environments with differential regeneration of the component species. Cover of lichens, mosses, litter and bare ground, accounts, in part, for the spatial variation in seedling numbers of certain species. The strong association of seedlings of some species with conspecific adults indicates that limitations in dispersal and/or the occurrence of a more suitable environment for emergence and/or establishment close to conspecific adult plants are likely to constrain the spatial distribution of new individuals in many cases. For other species, the lack of association of seedling densities with the cover of their conspecific adults, suggests that long-distance dispersal or a long-lived seed bank can play a role in counteracting the effect of short-distance dispersal. 相似文献
15.
Soil – an underestimated biotope The soil is a biotope with high species abundances and richness. It is, furthermore, a location where important ecosystem services are realized. Recent research projects on the origin and development of soil animal communities, on the heterogeneous interactions within the soil nutrient net and the distribution of soil animals show the different ecological traits and adaptabilities of the world beneath our feet. So research contributes to maintain the eco‐resource of soil and its sustainable use. 相似文献
16.
L. Brzsnyi 《Biometrical journal. Biometrische Zeitschrift》1978,20(6):585-592
From the examination of the properties of symmetry of the correlation functions it appears that the asymmetrical functions contain information capability to be used with advantage for the characterization of causal effects. The paper describes a new interpretation of the K measure of HELLMICH as well as its application in the field of investigation of connections. Computer calculations carried out on plant and human populations justify the use of the introduced measure. Concrete results are presented with respect to two maize diseases “stalk rot” and “ear rot”; further a completely analogous problem to examine the relation between diabetes and high blood pressure is outlined. Finally some remarks are made on further investigation of measuring numbers and application in a broader sense. 相似文献
17.
Monika Hassel 《当今生物学》2016,46(4):228-234
Axis formation in animals The last common ancestor of Cnidaria and Bilateria likely used the WNT/β‐Catenin pathway in a regionalized fashion to establish its primary, anterior‐posterior axis. Unexpectedly, the morphological head of Cnidaria corresponds to the rear end of Bilateria. Moreover, annelids use the WNT/β‐Catenin system for early, local and binary decisions, and insects developed a completely unrelated pathway. They use Bicoid (Drosophila) – or Hunchback/Orthodenticle (Tribolium) – to control axis formation. Nevertheless, WNT functions are essential during the segmentation phase in insects and in ancestral insects as well as in other arthropods during formation of posterior structures. In summary, the WNT/β‐Catenin system is an essential part of the molecular tool kit, which helped to establish the unique features of animals. 相似文献
18.
Andrew P. Dare Sumathi Tomes Midori Jones Tony K. McGhie David E. Stevenson Ross A. Johnson David R. Greenwood Roger P. Hellens 《The Plant journal : for cell and molecular biology》2013,74(3):398-410
We have identified in apple (Malus × domestica) three chalcone synthase (CHS) genes. In order to understand the functional redundancy of this gene family RNA interference knockout lines were generated where all three of these genes were down‐regulated. These lines had no detectable anthocyanins and radically reduced concentrations of dihydrochalcones and flavonoids. Surprisingly, down‐regulation of CHS also led to major changes in plant development, resulting in plants with shortened internode lengths, smaller leaves and a greatly reduced growth rate. Microscopic analysis revealed that these phenotypic changes extended down to the cellular level, with CHS‐silenced lines showing aberrant cellular organisation in the leaves. Fruit collected from one CHS‐silenced line was smaller than the ‘Royal Gala’ controls, lacked flavonoids in the skin and flesh and also had changes in cell morphology. Auxin transport experiments showed increased rates of auxin transport in a CHS‐silenced line compared with the ‘Royal Gala’ control. As flavonoids are well known to be key modulators of auxin transport, we hypothesise that the removal of almost all flavonoids from the plant by CHS silencing creates a vastly altered environment for auxin transport to occur and results in the observed changes in growth and development. 相似文献
19.
Xiaobing Dai 《植被学杂志》2000,11(5):715-724
Abstract. Seed banks in cattle dung, soil under cattle dung and soil under vegetation and growth response of plant species to the changes in soil nitrogen availability were studied in an alvar limestone grassland on Öland, Sweden, in order to analyse the impact of dung deposition and decomposition on the formation of patches of plant species. Results suggest that patches of four plant species could result from cattle dung deposition and decomposition. Impact of dung could proceed in three ways: (1) by changing the relative abundance of species in the soil seed bank under dung, and/or (2) by influencing the deposition of seeds in the dung, and/or (3) by intensifying the growth of some species through nutrient release. Species patches could result from one or more of these aspects. For instance, patches of Arenaria serpyllifolia may be induced by dung deposition because of the dominance of its seeds in dung, while the pattern of Cerastium semidecandrum and Festuca ovina may be due to the abundance of their seeds in the soil seed bank under dung and their positive growth response to increased nitrogen availability. 相似文献
20.
Abstract. In herbaceous plant communities of Stora Alvaret (the Great Alvar), Öland, Sweden, we studied the dependence of species-area relationships on the canopy cover of the colonizing shrubs Juniperus communis and Potentilla fruticosa. A series of plots 0.25 - 256 m2 in area were sampled in communities with varying canopy cover of Juniperus or Potentilla. Species number - log (area) regressions always fitted data better than log (species number) - log (area) regressions. The number of species declines more dramatically with increasing Potentilla cover than with increasing Juniperus cover. The total species number in large Juniperus plots follows a unimodal curve with a peak at about 75% shrub cover. The alvar (limestone grassland) species number in plots of all sizes declines monotonically with Juniperus cover following the regression equation S = 31.09 + 10.75 log A - 0.0025 P2, where A is area and P is percentage Juniperus cover. There is a monotonic decline of species number with increasing shrub cover in Potentilla plots of all sizes. The species richness in plots with Potentilla was fitted by the regression equation S = 16.48+ 14.91 log A-0.131 P-0.00104 P2 log A, where P is% Potentilla cover. A faster initial decline of species number with Potentilla colonization is apparently caused by its preferential establisment in species-rich, elevated microsites. 相似文献