岛屿生物地理学理论：模型与应用

前言岛屿有许多显著特征,如地理隔离,生物类群简单。这些特点为重复性研究和统计学分析奠定了基础,从而有利于许多深入而细致的生物学研究。因此,岛屿为发展和检验自然选择、物种形成及演化,以及生物地理学和生态学诸领域的理论和假设,提供了重要的自然实验室。岛屿生物地理学理论(MacArthurwilson学说)即为岛屿生物学研究中所产生的著名理论之一。该理论发展之     

大鼠海马—小脑皮层—小脑深部核团投射的电生理学和HRP研究

本文用电生理学和HRP示踪法,研究了大鼠海马-小脑皮层投射的空间分布,小脑皮层的海马投射区与其深部核团间的纤维联系。 电生理学的实验结果表明,刺激背侧海马CA_1/CA_3区,均可使小脑皮层第Ⅵ小叶的浦肯野细胞产生顺行多突触的诱发简单锋电位和复杂锋电位反应。提示背侧海马CA_1/CA_3区与小脑皮层之间有经苔状纤维和攀缘纤维的多突触投射。实验证明,大鼠的这一投射的终止区域,集中在小脑皮层第Ⅵ小叶中线外侧0.8—1.4mm的范围内;并且来自CA_1区的投射以对侧性为主,CA_3区的投射以同侧性为主。HRP示踪的实验表明,背侧海马CA_1/CA_3区在小脑皮层第Ⅵ小叶的投射区是小脑纵区组构的间位区,该区皮层与间位核之间存在着交互投射关系。     

对渤海藻类的新认识

本文阐述了对渤海藻类的新认识。主要指明其为由顶和前间系组成的( 3Ia 或 3I)联合古口的性质,腰凸的数量(2—4个)和分布(2个位腹面,0—2个位背面)及腰褶的次生性质。据此,讨论了该类在多甲藻亚目中的系统位置。除修订本亚科所属的老属、种外,本文还描述了该亚科的2个新种和3个新形态型。并在回顾世界上非海相沟鞭藻的历史、阐述渤海藻亚科在地层中的产出及共生分子的基础上,结合其他地质、古生物证据,探讨了本亚科的古生态及它为多甲藻亚目中一支向淡水环境迁侈的先祖的可能性。     

Simulated and measured nitrogen conditions in a manured and fertilised soil

The governing factors for soil nitrogen dynamics were identified with a simulation model. In addition, the model was used to interpret measurements from a plot fertilisation experiment in southwest Sweden.Simulated moisture and temperature conditions were the driving variables for the simulation of soil nitrogen dynamics and leaching during a 6-year period. The results of the simulation were compared with monthly observations on two plots with grain crops, one with liquid manure and commercial fertilisers applied and one with commercial fertilisers only.Simulated temporal variations of the nitrate and ammonium storages generally agreed with observations. The dominant role of the crops as a determinant of soil nitrogen conditions was demonstrated. A higher leaching loss from the plot with application of commerical fertilisers only occurred both in simulations and measurements compared to the plot with application of both commercial fertilisers and manure. The main reason was the higher N-application in the former treatment.The effect of water flows in macropores was interpreted as a delay of simulated leaching compared to observed leaching on some occasions in summer and early autumn. No direct effect of the macropores on the yearly rates of leaching could be seen.     

Anion exchange reactions in bacteria

Bacterial anion exchange now includes both carboxylate-linked reactions, in which there is an antiport of mono- and dicarboxylic acids, and Pi-linked reactions that build on phosphate (Pi) and organic phosphates. To illustrate the general features of this expanding class, this article discussed the biochemistry, physiology, and molecular biology of Pi-linked antiporters that accept glucose 6-phosphate (G6P) as their primary substrate. Kinetic and biochemical analysis suggsts that Pi-linked exchangers have a bifunctional active site that accepts a pair of negative charges. For this reason, exchange stoichiometry moves between the limits of 2:1 and 2:2 to reflect the ratio of mono- and divalent substrates at either membrane surface. This results in a particularly interesting reaction sequencein vivo, where, because cytosolic pH is relatively alkaline, one can expect the asymmetric exchange of two monovalent G6P anions against a single divalent G6P. In this way, an otherwise futile self-exchange of G6P gives a net flux driven (indirectly) by the pH gradient. Despite this biochemical and physiological complexity, Pi-linked carriers resemble all other secondary carriers at a molecular level. Indeed, sequence analysis leads one to infer a common (albeit low resolution) structural theme in which each functional unit has two sets of six trans-membrane helices separated by a central hydrophilic loop. Present examples show that this topology can derive from either a single protein, as is typical in bacteria, or from pairs of identical subunits, as found in mitochondria and chloroplasts. The finding of this common structure should make it possible to build detailed structural models that have implications for all membrane carrier proteins.     

Modeling in the museum: On the role of remnant models in the work of Joseph Grinnell

Accounts of the relation between theories and models in biology concentrate on mathematical models. In this paper I consider the dual role of models as representations of natural systems and as a material basis for theorizing. In order to explicate the dual role, I develop the concept of a remnant model, a material entity made from parts of the natural system(s) under study. I present a case study of an important but neglected naturalist, Joseph Grinnell, to illustrate the extent to which mundane practices in a museum setting constitute theorizing. I speculate that historical and sociological analyses of institutions can play a specific role in the philosophical analysis of model-building strategies.     

Hydration of 3-cyanopyridine to nicotinamide by crude extract nitrile hydratase

Summary The kinetic and stability characteristics of crude extract nitrile hydratase fromBrevibacterium R-312 were studied for the hydration of 3-cyanopyridine to nicotinamide. The enzyme was substrate and product inhibited and had the following kinetic constants:K _m =28 mM;K _p =36 mM;K _s =155 mM;V _m =5.8 mol/min/mg protein (25°C). Itsmaximum temperature and pH (phosphate buffer) were 35°C and 8.0, respectively and it had half-lives of 50 days, 10 days and 1 day at 4°C, 10°C and 25°C, respectively. The crude extract also exhibited amidase activity on nicotinamide, but it became significant only at nicotinamide concentrations greater than 300 mM. Mathematical models for batch and fed-batch hydrations were developed to account for substrate and product inhibitions and for enzyme decay. They predicted to within 10% experimental results for initial substrate and final product concentrations up to 300 mM; the accuracies decreased at higher concentrations primarily because of the relatively rapid hydrolysis of nicotinamide.     

PROBLEMS WITH TESTING INBREEDING AVOIDANCE: THE CASE OF THE COLLARED FLYCATCHER

Four year's data on collared flycatchers, Ficedula albicollis, breeding in a nestbox plot on the island of Gotland, Sweden, was used to investigate whether individuals avoid mating with close kin (i.e., parents or sibs). Only one case of close inbreeding (0.5% of all pairs) was observed during the years of study. The observed frequency of close inbreeding was compared to expected frequencies based on two different null models. Assuming no inbreeding avoidance behaviors (e.g., dispersal or kin recognition), but taking into account the fact that mortality, and different arrival and pairing times of individuals reduce the probability of mating with close kin, the expected frequency of close inbreeding is 10% and 15% for female and male recruits (i.e., born in the study plot), respectively. However, assuming mating to be random within the study plot reduced the expected frequency of close inbreeding to 1% or less for both males and females. Consequently, conclusions drawn concerning inbreeding avoidance depend on the null model used. Contrasting estimated costs of tolerating close inbreeding with those of avoiding it (by dispersal to other plots), however, suggests that the costs of avoiding close inbreeding are substantially greater than those of tolerating it. Therefore, although inbreeding avoidance cannot be rejected as a cause of dispersal of this species, it is not the primary cause, and particularly not for sex-biased dispersal. The general problems of investigating inbreeding avoidance are discussed. It is argued that all previous null models based on random mating in finite populations produce expected frequencies of close inbreeding that in fact include inbreeding avoidance, since they implicitly assume random dispersal within a finite population. Thus, comparisons between observed and expected frequencies of close inbreeding based on random mating are inadequate. The most promising method of investigating inbreeding avoidance is to experimentally study individual movements and mating preferences in the presence and absence of close kin.     

Modeling competition between Laurencia obtusa (Ceramiales,Rhodophyta) and Hypnea spinella (Gigartinales,Rhodophyta) at Cabo Frio Island,Rio de Janeiro,Brazil

The Lotka-Volterra competition model was used to represent the interaction between Laurencia obtusa and Hypnea spinella. A new model that considers effects of competition on algal carrying capacity is suggested. To test the models, data from field experiments conducted in an intertidal region at Cabo Frio Island, Rio de Janeiro, Brazil, were used. Both models showed that Hypnea was a stronger competitor than Laurencia. The model of interaction through the carrying capacity showed a stable coexistence between the algal populations and better represented the experimental data.     

闽北地区四代三化螟发生动态Fuzzy预测模型研究

根据Fuzzy数学原理和三化螟生物学特性,组建了四代三化螟发生动态综合预测模型经对福建省将乐县16年四代三化螟发生期、发生量回报及1995年的预报,拟合率及正确率均达100％。