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1.
The controversial family Adapisoriculidae, a group of shrew-sized Paleocene mammals, had proposed relationships with insectivores, marsupials and more recently to plesiadapiforms. Adapisoriculid remains are numerous in the early Paleocene locality of Hainin, Belgium, and allow us a test of these different phylogenetic hypotheses. Here, we identify the first tarsal bones of adapisoriculid mammals. The highly specialised bones indicate an arboreal mode of life with euarchontan affinity. Moreover, the tarsal bones are morphologically very close to those of the late Cretaceous Deccanolestes from the Deccan intertrappean beds of India, and also share several characters with the Paleocene plesiadapiforms and the extant cynocephalid dermopterans. The adapisoriculid affinities of Deccanolestes are also confirmed by tooth morphology, indicating that Deccanolestes is a primitive member of this family. These phylogenetic affinities suggest a paleobiogeographic scenario for the family with dispersal either via East Africa or across the Tethys area.  相似文献   

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Verrecchia  E. P.  Ribier  J.  Patillon  M.  Rolko  K. E. 《Die Naturwissenschaften》1991,78(11):505-507
The Science of Nature -  相似文献   

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In an attempt to understand the origin of living systems we encounter the following problems: How can we conceive the origin of the first self-reproducing forms, and by means of what stimuli could a constant increase in the complexity of such forms commence? How can a translation apparatus for genetic information develop? One cannot that such an apparatus for the synthesis of enzymes can function alone without the interference of enzymes themselves, which, however, could only become available after the construction of the apparatus itself. What stimulus mechanism is conceivable that leads to the division of the genetic apparatus into a replication system, and an enzyme-synthesis system?The main problem therefore, is not the search for basic theoretical concepts. It is not a question which can be answered by means of specific experiments. One should rather explore the principal possibilities of how molecules combine to produce more and more complicated functional units. We look for the fundamental structural changes in the organizational systems and the driving forces initiating these developments. Questions concerning the detailed chemical realization are of secondary importance. In trying to solve the puzzle of how the genetic apparatus is gradually built up as complex aggregates of molecules, we consider a consistent causal chain of simple and transparent physicochemical model steps.  相似文献   

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Ant-garden (AG) associations are systems of epiphytic plants and arboricolous (i.e., tree-living) ants, in which the ants build fragile carton nests containing organic material. They collect and incorporate seeds or fruits of epiphytes that then germinate and grow on the nest [sensu Corbara et al. (1999) 38:73–89]. The plant roots stabilize the nest carton. AGs have been well-known in the neotropics for more than 100 years. In contrast, reports on similar associations in the paleotropics are scarce so far. After discovering a first common AG system on giant bamboo [Kaufmann et al. (2001) 48:125–133], we started a large-scale survey for AGs in Peninsular Malaysia, Borneo, Java, and southern Thailand. A great variety of AG systems (altogether including 18 ant species and 51 plant species) was discovered and is described in the present paper. The high number of species participating in AG associations was reflected by a great variability in the specific appearances of the nest gardens. Frequently, further groups of organisms (e.g., hemipteran trophobionts, fungi) were also involved. Preference patterns of particular ant and epiphyte species for each other and for particular phorophytes (carrier trees) were detected. We integrate domatia-producing, so-called ant-house epiphytes in our study and compare their phases of establishment, as well as other characteristics, to “classical” AGs, coming to the conclusion that they should be regarded only as a special type of AG epiphyte and not as a separate ecological category.Electronic Supplementary Materials  Supplementary material is available for this article at  相似文献   

6.
Diopsid flies have eyes set on stalks which are in some cases so long that the distance between the eyes exceeds the body length. These conspicuous structures have given rise to much speculation about their adaptive value, but there are very few actual observations by which to judge these hypotheses.Cyrtodiopsis whitei Curran lives in the tropical rainforest of Malaysia. We describe a number of aspects of its morphology and biology, some functional properties of the eye, and the ritualized fights between males, by which harems are acquired. The evolutionary significance of the eyestalks is discussed: they represent structures subjected to a double selection pressure; they are an adaptation by which a sensory system is better matched to the special problems encountered in a densely structured habitat (in that the field of view is extended and the ability to estimate distance and size and to identify objects at a large distance is improved), also they act as key stimulus for species recognition and as releaser for intraspecific behaviour.  相似文献   

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亚洲氮循环案例研究   总被引:30,自引:0,他引:30  
以IPCC(Intergovernmental Panel on Climate Change)方法为基础,用IAP-N-1.0氯循环模型分析1961~2030年时间序列、亚洲各国家和地区的氮收支情况.农作物数据来源于联合国粮农组织(FAO)数据库.各参数及排放因子以亚洲国家检测出的数据为主,缺省值采用IPCC的默认值.本文主要讨论了活性氮产生及其不同的迁移和转化途径,以及环境对氮的富集作用和主要驱动因子.亚洲地区活性氮含量从1961年约14.4 Tg N/a迅速地增加到2000年约67.7 TgN/a,预计到2030年可能达105.3Tg N/a.人类对食物和能源需求的增长,以及缺乏提高氮肥利用率、降低矿物燃料燃烧释放NOx的有效措施,使得由人类活动产生的大部分活性氮在环境中累积.解决这一问题还有待于用先进的生物技术,研制出新型高效氮源来代替目前的合成氮.  相似文献   

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The endemic South American mammals Meridiolestida, considered previously as dryolestoid cladotherians, are found to be non-cladotherian trechnotherians related to spalacotheriid symmetrodontans based on a parsimony analysis of 137 morphological characters among 44 taxa. Spalacotheriidae is the sister taxon to Meridiolestida, and the latter clade is derived from a primitive spalacolestine that migrated to South America from North America at the beginning of the Late Cretaceous. Meridiolestida survived until the early Paleocene (Peligrotherium) and early Miocene (Necrolestes) in South America, and their extinction is probably linked to the increasing competition with metatherian and eutherian tribosphenic mammals. The clade Meridiolestida plus Spalacotheriidae is the sister taxon to Cladotheria and forms a new clade Alethinotheria. Alethinotheria and its sister taxon Zhangheotheria, new clade (Zhangheotheriidae plus basal taxa), comprise Trechnotheria. Cladotheria is divided into Zatheria (plus stem taxa, including Amphitherium) and Dryolestida, including Dryolestidae and a paraphyletic array of basal dryolestidans (formerly classified as “Paurodontidae”). The South American Vincelestes and Groebertherium are basal dryolestidans.  相似文献   

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广州亚运会对水环境质量保障提出较高的要求,水环境监测是水环境质量保障的重要一环,本文在全面分析了广州亚运会所面临的水环境质量压力和水环境监测所遇到难度,从监测环节和保障环节介绍了广州亚运水环境质量保障监测系统的建立思路、组成和特点,并对其应用效果进行了分析。  相似文献   

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Tropical peat swamp forests, which are predominantly located in Southeast Asia (SEA) and play a prominent role as a global carbon store, are being intensively degraded and converted to agricultural lands and tree plantations. For national inventories, updated estimates of peat emissions of greenhouse gases (GHG) from land use (LU) and land-use change in the tropics are required. In this context, we reviewed the scientific literature and calculated emission factors of peat net emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in seven representative LU categories for SEA i.e. intact peat swamp forest, degraded forest (logged, drained and affected by fire), mixed croplands and shrublands, rice fields, oil palm, Acacia crassicarpa and sago palm plantations. Peat net CO2 uptake from or emissions to the atmosphere were assessed using a mass balance approach. The balance included main peat C inputs through litterfall and root mortality and outputs via organic matter mineralization and dissolved organic carbon. Peat net CO2 loss rate from degraded forest, croplands and shrublands, rice fields, oil palm, A. crassicarpa and sago palm plantations amounted to 19.4?±?9.4, 41.0?±?6.7, 25.6?±?11.5, 29.9?±?10.6, 71.8?±?12.7 and 5.2?±?5.1 Mg CO2 ha?1 y?1, respectively. Total peat GHG losses amounted to 20.9?±?9.4, 43.8?±?6.8, 36.1?±?12.9, 30.4?±?10.6, 72?±?12.8 and 8.6?±?5.3 Mg CO2-equivalent ha?1 y?1 in the same LU categories, respectively. A single land-clearing fire would result in additional emissions of 493.6?±?156.0 Mg CO2-equivalent ha?1.  相似文献   

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By combining information about Biotechnology in Japan manually retrieved from Chemical Abstracts (Biochemical Section) with information obtained from Japanese sources, Japanese scientific meetings and from appropriate magazines such as Nikkei Biotech, a basis was formed for a better understanding of the status and perspectives of this field. Through the development of a "biotechnology abstract analyzer" program, these data were further refined and prepared for continuous up-date. Thus, assessment of changes in institute structures and trends in research goals became possible. It is evident that similar procedures can be applied to any field of science in other geographic areas.  相似文献   

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Two balanced reciprocal translocations were found in an amniotic fluid cell culture undertaken because of maternal age. One translocation had been inherited from each parent. Both translocations were traced through three generations of each family. The importance of banding techniques in diagnostic cytogenetics is stressed.  相似文献   

16.
Eukaryotic nuclei of endosymbiontic origin?   总被引:1,自引:0,他引:1  
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17.
Ferganodon narynensis gen. et sp. nov. is represented by a lower molariform tooth from the Middle Jurassic (Callovian) Balabansai Svita in Kyrgyzstan. The new genus is allied with Klamelia zhaopengi Chow and Rich 1984 from the Middle Jurassic Shishugou Formation in Xinjiang, northwest China to the new family Klameliidae based on parallelogram-shaped lower molariforms, imbricating rather than interlocking of cusps e-d-f, by a peculiar distolabial cingulid cusp, and by vertical folding of the enamel on the labial crown side. The new family Klameliidae fam. nov. is most similar to Gobiconodontidae by the structure of the molariform teeth and represents a previously unrecognized radiation of eutriconodontan mammals possibly endemic to Central Asia.  相似文献   

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《环境》2007,(9):7-7
经过20多年的沉寂,世界核电市场终于迎来了新一轮的发展高峰.其中,亚洲各国的动作最大,竞相推出雄心勃勃的核电发展计划.  相似文献   

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