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1.
广西金钟山鸟类保护区鸟类多样性初步研究   总被引:7,自引:0,他引:7  
本文共记录到金钟山鸟类274种,分别隶属于18目57科,其中陆生鸟类251种,水鸟23种;以留鸟为主,共157种;候鸟、旅鸟分别为104种、13种;东洋种为优势类群,共有171种,古北种和广布种分别为4种、27种。这些鸟类中有国家重点保护鸟类39种,中国特有种鸟类3种,列入世界自然保护联盟红皮书名录中的鸟类5种,列入中国濒危动物红皮书名录中的鸟类20种,列入CITES附录中的鸟类34种。本文还对金钟山鸟类保护区的5种不同生境类型的鸟类种类组成作了比较,结果表明灌丛+农田的鸟种多样性指数最高,为3.04;水域的鸟种多样性指数最低,为2.14。  相似文献   

2.
Mode of Operation of Ampullae of Lorenzini of the Skate, Raja   总被引:5,自引:4,他引:1       下载免费PDF全文
Ampullae of Lorenzini are sensitive electroreceptors. Applied potentials affect receptor cells which transmit synaptically to afferent fibers. Cathodal stimuli in the ampullary lumen sometimes evoke all-or-none "receptor spikes," which are negative-going recorded in the lumen, but more frequently they evoke graded damped oscillations. Cathodal stimuli evoke nerve discharge, usually at stimulus strengths subthreshold for obvious receptor oscillations or spikes. Anodal stimuli decrease any ongoing spontaneous nerve activity. Cathodal stimuli evoke long-lasting depolarizations (generator or postsynaptic potentials) in afferent fibers. Superimposed antidromic spikes are reduced in amplitude, suggesting that the postsynaptic potentials are generated similarly to other excitatory postsynaptic potentials. Anodal stimuli evoke hyperpolarizations of nerves in preparations with tonic activity and in occasional silent preparations; presumably tonic release of excitatory transmitter is decreased. These data are explicable as follows: lumenal faces of receptor cells are tonically (but asynchronously) active generating depolarizing responses. Cathodal stimuli increase this activity, thereby leading to increased depolarization of and increased release of transmitter from serosal faces, which are inexcitable. Anodal stimuli act oppositely. Receptor spikes result from synchronized receptor cell activity. Since cathodal stimuli act directly to hyperpolarize serosal faces, strong cathodal stimuli overcome depolarizing effects of lumenal face activity and are inhibitory. Conversely, strong anodal stimuli depolarize serosal faces, thereby causing release of transmitter, and are excitatory. These properties explain several anomalous features of responses of ampullae of Lorenzini.  相似文献   

3.
SUMMARY. Two centrioles, an old one and a new one, are always present in the resting cell. From prophase onward two new ones and two old ones are present. Beginning with the resting stage, five types of centriole life cycles are described and compared with one another: In type 1, both centrioles are elongate; in type 2, the old one is long and the new one, which is short, elongates in prophase; in type 3, both are short, both elongate in prophase, and both, except for their anterior tips, degenerate in late telophase; in type 4, both are long but in prophase their distal ends become free of the rest of the centrioles, these ends migrate to center or posterior end of cell, where, after they produce the achromatic figure and it completes its function in nuclear division, they degenerate; in type 5, both are short and neither elongates at any stage of its life cycle.
New centrioles are produced by the anterior ends of old ones. In their first generation, centrioles produce only extranuclear organelles (flagella, parabasals, axostyles, etc.); in their second and later generations, they produce only the achromatic figure (gametogenesis in Trichonympha and reorganization in Barbulanympha and Rhynchonympha are exceptions to this rule).
The distal ends of centrioles in some types of cycles are surrounded by centrosomes; in others they are not. In one type of centriole life cycle a small central spindle is present in the resting cell in two genera; in the other types this is not the case.  相似文献   

4.
截至2010年12月,为期2年的河南大学校园鸟类调查共记录到鸟类44种,隶属11目、25科;其中雀形目鸟类28种,留鸟20种,夏候鸟18种,冬候鸟和旅鸟各3种,分别占总数的63.6%、45.5%、40.9%、6.8%和6.8%;区系分析表明东洋种9种,古北种16种,广布种19种,分别占总数的20.5%、36.4%和43.2%。整体表现出南北混杂,古北种鸟类较东洋种比例大,广布种鸟类较多的特点。在调查基础上,提出了一些校园鸟类保护的建议。  相似文献   

5.
Populations oscillations in isolated populations of flies are considered. Qualitative methods of analysis are applied to the functional differential equation representing the system and conditions for the occurrence of oscillations are derived. These conditions are readily visualized in terms of parameters which are easily measured and have a straightforward biological interpretation.  相似文献   

6.
Flocks of birds are highly variable in shape in all contexts (while travelling, avoiding predation, wheeling above the roost). Particularly amazing in this respect are the aerial displays of huge flocks of starlings (Sturnus vulgaris) above the sleeping site at dawn. The causes of this variability are hardly known, however. Here we hypothesise that variability of shape increases when there are larger local differences in movement behaviour in the flock. We investigate this hypothesis with the help of a model of the self-organisation of travelling groups, called StarDisplay, since such a model has also increased our understanding of what causes the oblong shape of schools of fish. The flocking patterns in the model prove to resemble those of real birds, in particular of starlings and rock doves. As to shape, we measure the relative proportions of the flock in several ways, which either depend on the direction of movement or do not. We confirm that flock shape is usually more variable when local differences in movement in the flock are larger. This happens when a) flock size is larger, b) interacting partners are fewer, c) the flock turnings are stronger, and d) individuals roll into the turn. In contrast to our expectations, when variability of speed in the flock is higher, flock shape and the positions of members in the flock are more static. We explain this and indicate the adaptive value of low variability of speed and spatial restriction of interaction and develop testable hypotheses.  相似文献   

7.
By means of the electron scanning microscope, structure of the olfactory rosella has been investigated in 5 species of marine Teleostei. Among the species investigated variability in number and arrangement is observed in the olfactory rosella folds. Arrangement order of the receptor and indifferent epithelia of the fold is presented by four types. Interspecies differences in organization of the sensory epithelium is revealed in ratio of various types of receptor and secretory cells. In Teleostei flagellar olfactory cells are the most numerous. In the Limanda yokohamae sensory epithelium certain flagella are described, that essentially differ by their size from usual receptor flagella and, evidently, are their complexes. The secretory cells are found in indifferent and sometimes in sensory epithelium as dark ostia; they are most numerous in mediosmatics. Some of the ostia are like wide craters and are, evidently, ostia of ducts of multicellular olfactory glands.  相似文献   

8.
Topographo-anatomical position of the jugular trunks has been investigated in 30 human corpses. Certain differences in structure of the left and right jugular trunks are revealed, their peculiarities in persons with different habitus type are noted. The peculiarities mentioned are expedient to take into account in surgical practice, when pathways of lymphatic drenage are cut with prophylactic aims in patients suffering from inflammatory processes in the maxillofacial area.  相似文献   

9.
The crystal structures of chymotrypsinogen-A and α-chymotrypsin are compared and the parts of the main chain which differ in the two structures are identified. Changes in main-chain torsion angles and hydrogen bonds are tabulated. The residues Asp(102), His(57) and Ser(195) are compared in detail. Possible relationships among those parts of the molecules which change upon activation are discussed.  相似文献   

10.
Ultrastructure of the proximal part of the axon in the neurons, identified according to a number of morphological signs as pyramidal, has been studied in the layer III of the cat cerebral hemisphere sensomotor cortex. In sections, tangential to the cortical surface, in the initial axonal segment, a submembranous osmophilic layer and fasciculi of microtubules are revealed. On the initial segment spines are found, they contain cysterns resembling by their structure the spine system of the dendritic spines. Axonal terminals revealed along the axonal distribution are in contact both with the axonal trunk and with the spines. Regarding the initial segment, they are presynaptic, contain oval synaptic vesicles and form symmetric axo-axonal synapses only. In transversal sections axonal terminals are detected, arranging on the surface of the initial segment mostly as single ones, in longitudinal sections they are seen as clusters. Analysing the author's data and those from the literature, a conclusion is made that in intact animals the synaptic contacts at the initial segment of the axon are the only form of axo-axonal synapses in the neocortex.  相似文献   

11.
Wood, bark and stem anatomy of New World species of Gnetum   总被引:1,自引:0,他引:1  
Quantitative and qualitative data are presented for 11 collections of six species. The wide range of character states for the species is presented in the form of a key to emphasize their potential systematic correlations. Distinctive among these are phcllem characteristics. Fibre-tracheids are newly reported for lianoid Gnetum species. Cells previously thought to be like companion cells in secondary phloem are shown to be uniseriate rays, counterparts to uniseriate xylem rays. Laticifers are abundant in most of the species, and are newly described for secondary tissues of Gnetum. Presence of tyloses in laticifers of two species is apparently a new report for vascular plants. Tori are present in two New World Gnetum species, adding to the report in African species. Perforation plates are simple except near or in primary xylem, where they are simple or foraminate. Torus presence and foraminate perforation plate presence are features more reminiscent of Ephedra and other gymnosperms than of angiosperms. The bark of Gnetum is also very similar to that of Ephedra.  相似文献   

12.
Intracellular sites of lipid synthesis and the biogenesis of mitochondria   总被引:21,自引:0,他引:21  
Experimental data are presented on the intracellular localization in rat liver of three enzymes which are involved in the biosynthesis of phosphatidylethanolamine and diphosphatidylglycerol. These enzymes are phosphatidylserine decarboxylase, CDP-diglyceride-l-alpha-glycerophosphate phosphatidyl transferase, and phosphatidylethanolamine-l-serine phosphatidyl transferase. It was found that the first two enzymes are primarily mitochondrial while the latter enzyme is primarily microsomal. The intracellular sites for the biosynthesis of phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol are discussed, and the implications of their sites of biosynthesis on the assembly processes involved in the biogenesis of mitochondria are considered.  相似文献   

13.
Heat transfer processes proceeding in the living organisms are described by the different mathematical models. In particular, the typical continuous model of bioheat transfer bases on the most popular Pennes equation, but the Cattaneo-Vernotte equation and the dual phase lag equation are also used. It should be pointed out that in parallel are also examined the vascular models, and then for the large blood vessels and tissue domain the energy equations are formulated separately. In the paper the different variants of the boundary element method as a tool of numerical solution of bioheat transfer problems are discussed. For the steady state problems and the vascular models the classical BEM algorithm and also the multiple reciprocity BEM are presented. For the transient problems connected with the heating of tissue, the various tissue models are considered for which the 1st scheme of the BEM, the BEM using discretization in time and the general BEM are applied. Examples of computations illustrate the possibilities of practical applications of boundary element method in the scope of bioheat transfer problems.  相似文献   

14.
The main stages and ways of development of insect biogeography in Russia are discussed. Three general research programs (studies of ranges, zones, and regions) are described. The role of the regional approach in biogeography is characterized. Some problems related to studies of insect ranges are evaluated, and the need for creating practical range maps is emphasized. The relationships between the insect distribution patterns and the life zones are discussed. The specific features of zonation in insect biogeography are noted. Special attention is paid to establishing the zones with unified population distribution patterns within a species range. The role of geozoological investigations and opportunities of modern information technologies are characterized relative to evaluation of general patterns of insect assemblage distribution. The problems of regionalization in insect biogeography are discussed. Three main approaches (intuitive, a priori, and a posteriori) are determined. Some advantages of using population and assemblage distribution patterns in regionalization are emphasized. The role and possibilities of insect biogeography studies for in the field of reconstruction of past and long-term forecasting are characterized.  相似文献   

15.
中国兜兰属植物生态地理分布   总被引:15,自引:0,他引:15  
王英强   《广西植物》2000,20(4):289-294
分析了国产兜兰属植物的生态地理分布特点和发展趋势及兜兰属植物的系统演化趋势与生态地理环境的关系。国产兜兰野生种共有 18种 ,主要分布于热带过渡地区 (南亚热带 ) ,主产西南各省区 ;大多数种类生长于石灰岩山地 ,多为半附生兰 ,呈丛生生长 ,另一部分生长于酸性砂岩面的腐叶土上 ,多为地生兰 ,呈单株生长或分蘖状散生 ;大部分兜兰分布于较高海拔地区 ;国产兜兰属中最原始的短瓣亚属绝大部分种类仅分布在滇东南地区与贵州、广西连成一片的岩溶地貌的石灰岩地区 ,而兜兰属中较进化的兜兰亚属大部分种类在本区皆有分布。以上说明滇东南的石灰岩地区可能是兜兰属的起源中心和演化中心 ,中国的南亚热带地区是兜兰属植物的生态多样性中心  相似文献   

16.
Although conformationally heterogeneous states of proteins are involved in a range of important biological processes, including protein folding and misfolding, and signal transduction, detailed knowledge of their structure and dynamics is still largely missing. Proteins in many of these states are constantly changing shape, such that they are better described as ensembles of conformations rather than in terms of well-defined structures, as is normally the case for native states. Methods in which molecular simulations are combined with experimental measurements are emerging as a powerful route to the accurate determination of the conformational properties of these states of proteins.  相似文献   

17.
A numerical analysis of the probability of fixation of a chromosomal mutation with partial sterility of the heterozygote in a single population is performed. Three different genetic models are considered: the first model entails constant selection against the heterozygote and is the model almost universally used in previous works; in the other two models selection against the heterozygote depends on its frequency. The exact values of the fixation probability are found by iterating transition matrices with genotype specification. Differences in results among models are small. The exact values found in the first model are compared to estimates obtained from approximations. Solutions based on diffusion models give good approximations when selection against the heterozygote is low, especially if the population is very small. For the higher values of the selection coefficient against the heterozygote, the estimates are rather imprecise, especially when the populations are not very small.  相似文献   

18.
Two placoderms of different orders from a concretion of the Zyabrevo locality (Evlanovo Regional Stage, Frasnian) in central Russia are described. Five plates of the ventral and lateral sides of the trunk armor are assigned to a plourdosteid arthrodire. Three bones located in the region of its stomach are determined as a juvenile ptyctodontid, Ctenurella sp. Records providing actual evidence of predation in Devonian vertebrates are extremely scarce. Finds of this kind are listed for the first time.  相似文献   

19.
The soluble proteins of the nucleoplasm are synthesized on cytoplasmic ribosomes. Proteins larger than about 40 kDa are post-translationally targeted to the nucleus via energy-dependent processes, passing through the nuclear pore complex into the nucleoplasm. Targeting involves nuclear localization signals (NLSs) found within the primary sequences of the imported proteins. In higher plants, information has come primarily from study of proteins carrying 'classical' NLSs, comprising stretches of basic amino acids, and has required assays to measure nuclear uptake both in vitro and in vivo . In general, these assays are not entirely satisfactory; they are either technically demanding, are of limited accuracy and statistical rigor, or are unsuitable for in vivo applications.  相似文献   

20.
Nine of 10 genera and 119 of approximately 240 species of the Pinaceae occur in China, including 67 endemic species and two endemic genera. In this paper, the distributional maps of all the genera of the Pinaceae are presented (fig. 1-8). The horizontal and vertical distributions of species in each genus are discussed. The analysis of the distribution patterns of the genera indicates that some genera, such as Keteleeria, Tsuga, Pseudotsuga, Cathaya and Pseudolarix, are restricted to the area south of the Qinling Mountains and the Huaihe River, and the others, i. e. Picea, Abies, Larix and Pinus, extend northward to northeastern China. However, all of the genera except Keteleeria and Pinus are not found in very dry areas and tropical mountainous regions of China. The monotypic genera, Cathaya and Pseudolarix, are distributed in eastern and central China. The genus Keteleeria consists of 10 species, 7 of which are concentrated in southern Guizhou, northern Guangxi, southwestern Hunan and easternmost Yunnan. The distribution of the remaining 6 genera shows the maximum concentration in western Sichuan and northwestern Yunnan. (Figs. 2-8). Furthermore, more than third of species of the Pinaceae (37.8%) are also concentrated in western Sichuan and northwestern Yunnan. where a great variety of habitats and different topographic features occur. It is apparent that to conduct our systematic and evolutionary studies on this family in these region is especially needed. The relations between the areal size and the tolerance of species are discussed. The distributions of macrofossils and microfossils of the genera of the Pinaceae ia China are given, and it has been proved that areas of most genera of the family were considerably larger in the past. than at present.  相似文献   

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