浅谈初中生物实验教学有效设计策略

生物学是一门以实验为基础的学科,课程倡导探究性学习方式,而探究性学习的主要内容之一是生物实验。生物实验的有效开展,有助于培养学生的各种能力,提高学生的科学素养。     

新课程标准下的高中生物实验教学

生物学是一门以实验为基础的自然科学,通过实验探究生物的规律,是学习生物学的重要途径,并且近几年来,江西高考生物卷加大了对课本中的常规实验的考查,体现了对生物实验的重视,因此实验在生物教学中占有越来越重要的地位。     

利用无土栽培实验培养学生学习生物学的兴趣

利用无土栽培实验培养学生学习生物学的兴趣苗琦（北京西城区外语学校１０００４４）初一年级学生开始学习一门新的课程——植物学。为了使学生在课堂所学的知识能在实际中得到验证,培养学生的学习兴趣和实验操作能力,从而提高学生学习生物的积极性,我组织初一生物课外...     

浅谈高中生物学实验的拓展教学

高中生物课程教学是高中教学工作的一个重要组成部分,高中生物实验拓展教学,是指在原有的书本实验知识的基础上研究一些新的研究问题,教师带领学生在实验课程学习的基础上有新的实验研究。在高中生物教学中开展实验拓展教学,对于学生的生物知识能力的全面学习和认识有着重要的帮助,此外,这种生物实验的拓展教学也能够培养学生的科学探索能力和创新能力。     

设计课外实验促进生物教学

实验教学在生物教学中占有很重要的地位,在认真完成大纲、教材所规定实验的同时,精心设计生物课外实验,对生物教学具有重要促进作用。因为它不仅能够巩固和深化课堂知识教学,还可以激发学生学习兴趣,培养学生的观察能力,实验技能,思维能力,同时能调动后进生对生物...     

聚焦“导”和“度”,促进生物实验教学

生物是一门实验学科。生物教学中,适当适度增加一些实验,可以激发学生的学习兴趣,把外在的信息转化为内驱力,并实现理论和实践相结合,体现学中用、用中学。     

生物实验教学的层次与思维能力的培养

生物学是以实验为基础的科学,加强实验教学是提高生物教学质量的基本环节。在生物实验教学中,如何做到目的明确,要求具体,计划周密,循序渐进,通过实验课有计划分阶段地使学生既掌握实验技能,又培养以思维能力为核心的各种能力,是一个值得探讨的课题。我们认为:生物实验教学和思维能力的培养是一个多层次、阶梯式向上发展的过程。在生物实验教学中存在着由低级到高级的三个层次:验证性模仿实验、获得性独立实验和启发性探索实验。与之相应的思维能力的发展层次是:模仿性思维、程序性思维和创造性思维。 (一)验证性模仿实验与模仿性思维模仿是学习的手段,也是学习的结果。初     

生物实验教学应注重学生实验能力的培养

生物实验在整个中学阶段的生物教学中都占有非常重要的地位,它既是对学生进行基本技能训练的重要手段,也是激发学生的学习兴趣,提高教学质量的重要环节,教师在生物实验教学过程中应重视实验能力的培养。实验能力包括学生的观察能力、实验操作能力、绘图能力、思维和分析能力、创造能力等,如何利用实验教学,全方位培养学生的上述能力,     

探究水污染对生物的影响及生物的净化作用

本实验是初中生物学"探究环境污染对生物的影响"关于水污染的拓展创新实验,学生积极参与共创最优实验方案,深刻理解生物与环境的关系。从发现问题、选取实验材料,设计实验思路,再到数据统计和作图分析等,在科学探究过程中运用理性思维,实现在教材基础上的深度学习。     

谈中学生物实验中运动技能的培养

教育心理学认为,技能的学习过程包括智力技能的学习和运动技能学习两类。本文从教育心理学的角度,谈谈如何培养学生的生物实验运动技能。     

Échinodermes de l'Ordovicien supérieur (Ashgill) de Sardaigne et d'Algérie

Research on the influence of sea level variations on the benthic faunas have been carried out in the Upper Ordovician of Sardinia. Study of the depositional facies and sequence analysis of the upper part (Lower Ashgill) of the Portixeddu Formation led to the identification of the sedimentary environments. Cystoids and crinoids are associated to bryozoans and brachiopods in most levels. The numerical analysis of associations and megaguilds shows that crinoids and cystoids have a higher frequency in the proximal and median facies of the upper offshore. The columnal association characterized by Conspectocrinus celticus and the coronoid Mespilocystites tregarvanicus has been discovered in the upper part of the formation. This material and complementary samples from Upper Ordovician of Sardinia and Kabylia (Algeria) bring additional data on the systematic and show the wide distribution of this fauna outside of the Ibero-armorican domain. The distribution of this echinoderm association supports a palaeogeographical position of the Ibero-armorican domain and Sardinia within the north gondwanan margin during the Lower Palaeozoic.     

A phylogenetic analysis of basal Anseriformes, the fossil Presbyornis, and the interordinal relationships of waterfowl

A phylogenetic analysis of 123 morphological characters of basal waterfowl (Aves: Anseriformes) and other selected avian orders confirmed that the screamers (Anhimae: Anhitn-idae) are the sister-group of other waterfowl (Anseres), and that the magpie goose (Anseranatidae: Anseranas semipalmata) is the sister group of other modern waterfowl exclusive of screamers (Anatidae sensu stricto). The analysis also supports the traditional hypothesis of the gallinaceous birds (Galliformes) as the sister group of the Anseriformes. Presbyornis, a fossil from the early Eocene of Wyoming and averred by Olson & Feduccia as showing that the Anseriformes were derived from shorebirds (Charadriiformes), was found to represent the sister group of the Anatidae. Associated hypotheses by Olson & Feduccia concerning the implications of Presbyornis for the phylogenetic relationships of flamingos (Phoenicopteriformes), the position of the Anhimidae within the waterfowl, relationships among modern Anatidae, and a plausible evolutionary scenario for waterfowl also are rejected. Analyses revealed that cranial characters were critical to the establishment of the Galliformes as the sister group of the Anseriformes; exclusion of the Anhimidae, especially in combination with Anseranas, also undermined the support for this inference. Placement of Presbyornis as the sister group of the Anatidae casts doubt on the role suggested by Feduccia of ‘transitional shorebirds' in the origin of modern avian orders, and calls into question the concept of ‘fossil mosaics’. The phylogenetic hypothesis is used to reconstruct an evolutionary scenario for selected ecomorphological characters in the galliform-anseriform transition, to predict the most parsimonious states of these characters for Presbyornis, and to propose a phylogenetic classification of the higher-order taxa of waterfowl. This re-examination of Presbyornis also is used to exemplify the fundamental methodological shortcomings of the intuitive approach to the reconstruction of phylogenetic relationships.     

人工合成多样性突变文库研究进展*

突变文库的构建是定向进化研究过程中一个关键步骤,主要利用天然存在的系统或者人工合成的分子技术来产生多样性核酸分子文库,为制备和筛选具有一定特性的蛋白酶、多肽、人工抗体等提供庞大的遗传基因库,也可用于合成生物学中相关基因元件的研究与筛选,为目标生物制品的高效工业化生产提供动力。随着对突变文库构建技术研究的日益深入,各种文库构建策略相继被开发出来,并在生物能源、生物化工、生物医药、生物试剂和食品工业等方面得到了广泛的应用。然而,定向进化中的文库构建策略多有不同,各种突变文库构建技术的核心方法也在不断创新。主要介绍近年来实验室中人工合成多样性文库的前沿技术,并对文库构建技术在自动化和智能化方向的发展进行了展望。     

L’habitat en grotte au Néolithique : vers une estimation de l’intensité des occupations

The archaeological excavation of the cave of the Gardon has brought to light a dilated and nearly continuous stratigraphy for the Neolithic era. The analysis of lithic industry has showed the existence of variations between those neolithic layers, which are independents of the technological processes of tools productions. Four criteria allow us to characterize the occupation’s type of each layer. Compared to the excavations data and to sedimentological analysis, these results allow us to display the evolution of the intensity of occupations of the cave throughout the whole Neolithic.     

Scanning motion,ocellar morphology and orientation mechanisms in the phototaxis of the nematode Mermis nigrescens

Summary The putative ocellus of Mermis females consists of a hollow cylinder of dense hemoglobin pigmentation located in the anterior tip. The exact location of the photoreceptive nerve endings, however, is unknown. During phototaxis a continual bending or scanning motion of the head (anterior 2 mm) causes the orientation of the tip to swing about the direction of the source. By turning off (shuttering) the light source whenever the tip orientation was to one side of the source direction, the average orientation of the base of the head, and eventually the body orientation, was caused to be biased about 28° to the opposite side. Because the shuttering was synchronized with the scanning motion, the scanning motion must be involved in the maintenance of orientation to light. The direction of the bias rules out a two-signal comparison mechanism of orientation and demonstrates that a deviation of the tip from the source direction must decrease, rather than increase, the illumination of the photoreceptors. These findings, and the ocellar morphology, require that the photoreceptors be located inside the hollow tube of pigmentation where they can be shadowed by the pigment during deviations of the tip. Focusing by the curved anterior end should cause a similar modulation of the illumination at this location. The occasional episodes of transverse phototaxis can be explained by the leakiness of the pigment walls to transverse illumination. Analysis of the motion of the anterior in the presence and absence of shuttering indicates that the orientation of the base of the head, due to the motion of the neck, is controlled by the signals generated during one or more cycles of the scanning motion of the head. The orientation may be regulated by the phase relationship between the photoreceptor signal and putative proprioceptive signals that indicate the bending in the head.     

An NMR Study of the Spatial Structure and Intramolecular Dynamics of Modified Analogues of Steroid Hormones

Special features of the use of homo- and heteronuclear correlation methods of NMR in one and two dimensions for studying the spatial structure and intramolecular dynamics of modified analogues of steroid hormones (MASH) are considered. The application of these methods to the assignment of resonances in the high-field ¹H NMR region and to the determination of the most stereospecifically important parameters, such as the vicinal constants of spin–spin coupling (³ J _H–H) and nuclear Overhauser effects (NOE), are discussed using the example of NMR studies of some estrogens and androgens at 300 MHz and on the basis of literature data. The most efficient combination of the methods and the necessary modification of each of them may be chosen considering the spectral and relaxation parameters of MASH in liquid medium, including the anisotropy of the overall diffusive motion. The characteristics of MASH are the wide use of correlations through long-range couplings (COSY-45 and DQF-COSY), the application of the ^4,5 J _H–H constants for the determination of spatial structure, and the advantage of heteronuclear HSQC methods with and without ¹³C decoupling over the corresponding HMQC methods in both resolution and sensitivity. In the conformationally rigid MASH molecules, the anisotropy of the MASH diffusive motion in liquid adversely affects the determination of interproton distances by the calibrating processing method for the NOE difference and NOESY spectra: it results in both overestimated and underestimated distance values depending on the polar angle ratios of the reference and the determined distances. Under certain conditions, conformationally mobile MASH demonstrate the additional contribution of the scalar relaxation mechanism between the indirectly (scalarly) bound protons. This mechanism is responsible for the underestimated values of NOE and the corresponding errors in the distance determination.     

Ultrastructural aspects of storage lipid mobilization in the tapetum of Lilium hybrida var. enchantment

Stages in the formation and degradation of pollenkitt in the anther of Lilium have been investigated using the electron microscope. This material, which appears to be a complex of lipid and carotenoids, is formed during the autolysis of the tapetal cells by the fusion of lipidic inclusions with globules derived from plastids. Autolysis of the tapetal cells is progressive for it commences with the disintegration of many cytoplasmic components, followed by the breakdown of storage lipids. The plasma membrane maintains its integrity during these events apparently, by proliferation, aiding in the transfer of the products of hydrolysis into the loculus. During the course of lipid breakdown, a striking vacuolar system is formed in the tapetal cytoplasm, presumably containing the products of this hydrolysis. The source of membranes for this system is clearly the lipid globules themselves. The generation of the membrane apparently involves the participation of electronopaque material, possibly enzymic, contained within the lipid globules.     

On the influence of fishes on the evolution of benthic crustaceans

Though the interweavement of trophic chains in marine ecosystems of the past cannot be reconstructed, as the abundance, nutrition, reproductive rates and other aspects of the biology of fossil species are not known, it is possible to correlate trends in the evolution of single groups of animals, in the presented case the Crustacea, with the influence of other evolving organisms. The evolution of carnivorous, buoyant, well swimming modern fishes probably induced profound changes in marine ecosystems and influenced the evolution of crustaceans. Indications for these interactions are a. the absence or rare occurrence of defenseless archaic crustaceans in habitats, which are populated by teleostean fishes and the survival of some of these forms in refuges like caves and subterranean waters, and b. the reduction of the pleon in the course of the mesozoic evolution of the Decapoda, which occurs parallel to the radiation of the Teleostei, namely in the period between the early Jurassic and the Tertiary. The shortening of the pleon is interreted as a consequence of the stepwise change from a hyperbenthic to a more benthic Iife-stJe and the abandonment of the caridoid escape reaction. Other adaptations are also construed as results from the selective pressure produced by predators. Extant crustaceans which are able to coexist with fishes, among the macrozoobenthos especially the Decapoda and Peracarida, have a variety of protective adaptations, which help to reduce predation.     

Seasonal distribution and abundance of tsetse flies (Glossina spp.) in the Faro and Deo Division of the Adamaoua Plateau in Cameroon

Ten years after the large-scale tsetse control campaigns in the important cattle rearing areas of the Faro and Deo Division of the Adamaoua Plateau in Cameroon, the seasonal distribution and abundance of tsetse flies (Glossina spp.) were determined. During a period of 12 consecutive months (January-December 2005), the tsetse population was monitored along four trap transects consisting of a total of 32 traps and two flyround transects traversing the study area, which comprised the tsetse-infested valley, a buffer zone and the supposedly tsetse-free plateau. Throughout the study period, a total of 2195 Glossina morsitans submorsitans and 23 Glossina tachinoides were captured in the traps and 1007 G. m. submorsitans (78.8% male flies) were captured along the flyround transects. All G. tachinoides and almost all G. m. submorsitans were captured in the valley. Five G. m. submorsitans were captured in traps located in the buffer zone, whereas no flies were captured in traps located on the plateau. The index of apparent abundance (IAA) of G. m. submorsitans was substantially higher in the areas close to game reserves. In the remaining part of the valley, where wildlife is scarce and cattle are present during transhumance (dry season), the IAA of tsetse was substantially lower. In this part of the valley, the abundance of tsetse seemed to be associated with the presence of cattle, with the highest IAA during transhumance when cattle are present and the lowest apparent abundance during the rainy season when cattle have moved to the plateau. It is concluded that the distribution of tsetse in a large part of the valley undergoes substantial seasonal changes depending on the presence or absence of cattle. The repercussions of those findings for the control of tsetse in the valley and the probability of reinvasion of the plateau are discussed.     

果实膨大期喷布磷酸二氢钾对三月红荔枝果实贮藏性的影响

在三月红荔枝(Litchi chinensis cv.Sanyuehong)果实膨大期对树冠喷施0.2%磷酸二氢钾(KP)水溶液,以探讨磷酸二氢钾对荔枝果实贮藏性的影响。结果表明:(1) KP处理的果实在贮藏期前17d,失重率及果肉可溶性固形物、酸、VitC、花色素苷等指标的变化趋势与对照基本相似;(2) KP处理的果肉可溶性蛋白质含量变化与对照有明显差异,而果皮的可溶性蛋白质含量在贮藏期前10d变化动态与对照一致,此后呈相反的变化趋势;(3)果皮POD活性显著高于果肉,KP处理和对照的果肉POD活性在贮藏第3d后、果皮POD活性在第17d前分别具有相似变化趋势;(4)果肉中CAT活性在贮藏第3~17d期间都显著或极显著高于果皮,KP处理和对照果肉、果皮CAT活性动态变化均为单峰曲线。