"模拟自然选择"课堂活动的改进

北师大版《生物学》教材8年级下册“生物的进化”一节中,教材安排了建议活动“模拟自然选择”,这个活动能将抽象的生物进化理论生动地展现在学生面前,解决了教学中生存竞争这个难点。在教学实践中,发现只要对活动做一些改进,就不仅能让学生理解生存竞争,还能让学生理解生物个体差异是普遍存在的及生物多样性产生的原因。下面介绍改进后的活动     

高中生物学新课程标准教学研讨"细胞的增殖、分化、衰老和凋亡"的教学构思

在普通高中《生物课程标准》的内容标准中,“分子与细胞”模块的第4学习单元是“细胞的增殖”,第5学习单元是“细胞的分化、衰老和凋亡”。同细胞代谢一样,细胞的增殖、分化、衰老和凋亡,也是细胞生命活动的具体表现。笔者根据这两个学习单元的具体内容标准和活动建议,对其教学内容、教学目标、教学策略的构思如下:     

北京八中生物技术中心开展"研究性学习"初探

研究性学习是国家教育部2001年1月颁布的《全日制普通高级中学课程计划(试验修订稿)》中综合实践活动板块的一项内容。通过“研究性学习”课程的实施．提高每一个学生的综合素质,使每一个学生的探究精神和实践能力都得到培养．让每一个学生都有所得。如何充分利用生物技术中心的设备与人力资源优势,从学生的中学时代培养符合未来时代要求的高精尖人才,本中心经过一轮学生的科学实践活动,取得了一点成绩．在如何开展“生物技术”领域的研究性学习方面做了一些尝试。     

"细胞膜的结构与功能"一节课堂教学设计

学生在课堂上进行的科学探究包括一系列的活动 ,其中有些活动是为观察事物、收集数据、提出见解和对观察到的现象进行分析打基础。有些活动则是鼓励学生对课本、参考书、期刊杂志等各种媒体提供的辅助性信息源进行严格的分析。北京四中的高一年级试用美国 BSCS《生物科学》教材 ,陈月艳老师编写的“细胞膜的结构和功能”一节课堂教学设计 ,较好地体现出探究型教学模式的基本要求 ,我们推荐给广大读者参考。     

对生物学"研究性学习"的探索

为贯彻新的高中课程改革精神 ,重视学生创新精神和实践能力的培养 ,新的高中《生物》(必修 )教材增设了6个专题性研究课题 ,这些课题涉及人类社会、生活、生产和现代科技。专题性研究是进行“研究性学习”的载体 ,如何开展生物学的“研究性学习”,这是广大中学生物学教师共同面临的新课题 ,笔者现就此问题进行初探。1　开展生物学研究性学习的意义所谓研究性学习 ,是学生在教师的指导下 ,从学习生活和社会生活中选择和确定研究专题 ,以类似于科学研究的方式 ,通过一系列自主的探索活动去发现问题、解决问题 ,以获取知识和应用知识的学习活动…     

高中生物学新课程标准教学研讨"植物的激素调节"教学构思

在普通高中《生物课程标准》的内容标准中,“植物的激素调节”是必修部分中“稳态与环境”模块的第1学习单元。该单元的教学内容主要阐述植物激素对其生命活动的调节作用,以及植物生长调节剂在生产上的应用。本文从单元知识内容、学习目标、教学策略等方面,谈谈对本单元的教学构思。     

"测量不同植被环境的空气温度和湿度"活动改进与实施建议

北师大版《生物学》7年级上册第1章第2节“生物与环境的相互影响”一节有一个“测量不同植被环境的空气温度和湿度”探究活动,安排这个活动的目的是要求学生学会用干湿计测量裸地、草坪和灌木丛的空气温度和湿度,通过分析实验数据,说明不同植被对环境     

冬闯科考"禁区"

2007年1月,在《华夏地理》杂志、《人与生物圈》杂志、云南大河流域传播与推广中心、四川恒鼎实业和奥索克体育用品公司等的支持下,加上他们夏季考察所获得的稿费,共计不到20万元,在众人的不可思议的目光中,杨勇开始了绝对是挑战极限式的考察。     

"蚍蜉"非"匹夫"

你们好,我是《化石》这本书的小读,叫张野青,家住牛庄高中家属楼,在牛庄镇南关小学六年级一班读书,我觉得这本书很好。但我在2004年第一期上发现了错误,在《曾霸世界的巨鬣狗》这篇章中有一句话：‘与大象相争如匹夫撼树’中的‘匹夫’两字写错了,应该是‘蚍蜉’两字,这两字是当大蚂蚁讲的,意思是比喻力量很小而想动摇强大的事物,自不量力。这些也是我从字典中得到的,我想是原错了,应该改正。     

试论"描述"与"概述"的区别

在本市举办的一次初中生物学教师新教材培训会上,一位教师提出了这样一个问题：“《全日制义务教育生物课程标准(实验稿)》(以下简称《课程标准》)中的两个知识性目标动词——‘描述’与‘概述’的区别是什么?”《课程标准》中的知识性目标动词共计37个,“描述”与“概述”只是其中的两个。但在《课程标     

A histochemical study about the involvement of rat liver cells in the uptake of heterologous immune complexes from the circulation

Intravenously injected immune complexes (ICx) composed of bovine serum albumin (BSA) and rabbit anti-BSA were taken up by the liver. Insoluble complexes, made in antibody excess, were rapidly taken up by Kupffer cells and were metabolized within 24 h. Soluble complexes, made in antigen excess, were only partly taken up by Kupffer cells. In addition these complexes were bound, taken up and metabolized by endothelial cells. Until 2 h after injection soluble complexes could also be observed along the microvilli of hepatocytes. No signs of endocytosis in hepatocytes could be observed. It is concluded, that ICx can be taken up by Kupffer cells as well as by endothelial cells. The physical state of the complexes, soluble or insoluble, determines the cell type in which uptake occurs.     

A histochemical study about the involvement of rat liver cells in the uptake of heterologous immune comples from the circulation

Summary Intravenously injected immune complexes (ICx) composed of bovine serum albumin (BSA) and rabbit anti-BSA were taken up by the liver. Insoluble complexes, made in antibody excess, were rapidly taken up by Kupffer cells and were metabolized within 24 h. Soluble complexes, made in antigen excess, were only partly taken up by Kupffer cells. In addition these complexes were found, taken up and metabolized by endothelial cells. Until 2 h after injection soluble complexes could also be observed along the microvilli of hepatocytes. No signs of endocytosis in hepatocytes could be observed. It is concluded, that ICx can be taken up by Kupffer cells as well as by endothelial cells. The physical state of the complexes, soluble or insoluble, determines the cell type in which uptake occurs. To Prof. Dr. H.G. Goslar on the occasion of his 65th birthday     

The chemical composition of some aquatic macrophyte species and implications for the metabolism of a tropical lacustrine ecosystem — Lobo Reservoir,São Paulo,Brazil

The changes in the concentrations of short-chain carboxylic acids in decomposing snails (Planorbis planorbis L.), incubated under different conditions (10 °C, 20 °C, aerated, non-aerated) were monitored at intervals for up to 14 days. High concentrations of acetate (up to 35 mM), propanoate (up to 2.1 mM), butanoate (up to 5.8 mM), isobutanoate (up to 2.5 mM), and isopentanoate (up to 3.9 mM) were recorded. Pentanoate was only found, at low concentrations, on one occasion. None of these acids could be detected in living snails tissues. The rate of accumulation of the acids was shown to be influenced by temperature but not by aeration. Higher concentrations of all five acids were found at the high temperature treatment (20 °C) than in the low temperature treatment (10 °C) on the ninth day but by the 14th day the converse was the case. The implications of the results to the nutritional and behavioural ecology of pulmonate snails and other freshwater aquatic invertebrates are discussed.     

Inaccuracies in Measurement of Dried Milk Powders

Infant feeds made up from dried milk are known to be hazardous if the mixture is too concentrated. Tests with five commercial brands of dried milk showed that nurses, midwives, and mothers often made up feeds incorrectly; in most cases the amount of powder used was excessive.Fewer mistakes would be made if scoops were standardized or, better, if the milk was made up in small, accurately weighed packets.     

Phytochemical diversity of Origanum vulgare L. subsp. vulgare (Lamiaceae) from Austria

This investigation was aiming at the phytochemical characterisation of Origanum vulgare subsp. vulgare from Austria. To study the qualitative and quantitative composition of essential oil compounds 374 individual plants were analysed via GC. The volatiles of Austrian O. vulgare subsp. vulgare were found to be complex mixtures of 53 mono- and sesquiterpenes. Among the sesquiterpenes β-caryophyllene, germacrene D, E-E-α-farnesene, germacrene D-4-ol and caryophyllene oxide were frequently present in higher amounts. The monoterpenes were mainly made up of sabinyl-compounds [mainly sabinene (up to 48.4%) and cis-sabinene hydrate (up to 57.8%)] and/or cymyl-compounds [mainly p-cymene (up to 49.7%), γ-terpinene (up to 21.5%) and carvacrol (up to 32.9%)] that were accompanied by usually smaller amounts of bornyl-compounds and acyclic compounds. Some exceptional (in O. vulgare rare) chemotypes were detected. The essential oil content of Austrian O. vulgare subsp. vulgare ranged between 0.1 and 1.8%. The content of rosmarinic acid was analysed by HPLC and ranged from 0.6 mg/g dry mass up to 37.2 mg/g dry mass. No arbutin could be detected in the analysed populations.     

Popularity of less frequent follow up for breast cancer in randomised study: initial findings from the hotline study.

OBJECTIVE: To compare the experiences of patients with breast cancer who were conventionally monitored with those in whom routine follow up was restricted to the time of mammography. DESIGN: Randomisation to conventional schedule of clinic visits or to visits only after mammography. Both cohorts received identical mammography and were invited to telephone for immediate appointments if they detected symptoms. SETTING: Combined breast clinic, Chelsea and Westminster Hospital. SUBJECTS: 211 eligible outpatients with a history of breast cancer. MAIN OUTCOME MEASURES: Acceptability of randomisation, interim use of telephone and general practitioner, satisfaction with allocation to follow up. RESULTS: Of 211 eligible patients, 196 (93%) opted for randomisation in the study. Of these, 55 were under 50 years, 78 were diagnosed fewer than five years before, 90 had stage T2-4 tumours, and 71 had involved axillary nodes. Patients who did not participate were more likely to be under 50 years, to be two to five years after diagnosis, and to have had aggressive primary disease. Twice as many patients in both groups expressed a preference for reducing rather than increasing follow up. No increased use of local practitioner services or telephone triage was apparent in the cohort randomised to less frequent follow up by specialists. CONCLUSIONS: Reducing the frequency of routine follow up has so far proved popular among patients with breast cancer at standard risk in this cohort. A multicentre study is needed to determine the effectiveness and cost-effectiveness of routine follow up with respect to disease outcomes.     

Mycotoxins in laboratory rodent feed

Twenty-one batches of fixed-formula rodent diets from three feed manufacturers were tested for the presence of five mycotoxins: deoxynivalenol (DON), nivalenol (NIV), HT-2 toxin, T-2 toxin and ochratoxin A (OTA). Five batches were also tested for the presence of zearalenone (ZEN) and six batches for aflatoxins. Detectable levels of DON (up to 298 microg/kg), NIV (up to 118 microg/kg), OTA (up to 3.1 microg/kg) or ZEN (up to 26.7 microg/kg) were found in samples from all manufacturers. Three batches contained two (DON or NIV and OTA or ZEN) and one batch contained three (DON, OTA and ZEN) different mycotoxins. Aflatoxins, T-2 and HT-2 were not detected in any of the batches. The concentrations of mycotoxins detected in the feed were low, but indicated that feed ingredients, probably the cereal ingredients, were contaminated by mycotoxins. Since mycotoxins are known to have toxic and/or immunosuppressive effects, non-contaminated ingredients should be used for production of laboratory animal feed. The results imply that an improved quality control of ingredients used for laboratory rodent feed should be implemented.     

Growth of ornamental plants in two composts prepared from agroindustrial wastes

Two composts prepared from agroindustrial wastes were assayed as substrates: C1 from brewing waste (yeast and malt) plus lemon tree prunings; and C2 from the solid fraction of olive mill wastewater plus olive leaves. Sixteen substrates were prepared by combining each compost with Sphagnum peat or a commercial substrate (CS) in different proportions. The nutrients (N and K) provided by the composts, which acted as slow-release fertilisers, influenced especially the development of calendula, although the physical and physico-chemical properties such as total pore space and electrical conductivity (EC) were also relevant. On the other hand, in the salt-sensitive calceolaria hybrid, EC and chloride concentration were the main factors influencing growth. Adequate substrates for the development of calendula can be prepared by mixing C1 at up to 75% with peat or at up to 50% with CS, and C2 at up to 50% with peat or CS. For calceolaria, the substrate should have a lower proportion of compost, C1 at up to 50% and C2 at up to 25%, both mixed with peat or CS. Therefore, composts of agroindustrial origin such as these can be used as an alternative to peat and CSs for growing ornamental plants. provided the mixture contains at least 25% peat or CS.     

Ion-exchange purification of proteins using magnetic nanoclusters

Polymer-coated magnetic nanoclusters were used for recovery and purification of proteins from both model systems and cell-free Pichia pastoris fermentation broth. The nanoclusters exhibited extremely high capacity for proteins, up to 900 mg/mL adsorbent, and were recovered by high gradient magnetic separation (HGMS) at flow rates of up to 3,600 cm(3)/cm(2) h (flow rates up to 15,000 cm(3)/cm(2) h are possible). The nanoclusters were coated with a primary coating of poly(acrylic acid-co-styrenesulfonic acid-co-vinylsulfonic acid), which allowed both electrostatic and hydrophobic interactions with the protein to be used to enhance specificity for targeted products. With this dual mode separation, nearly pure protein could be recovered from complex mixtures, such as fermentation broth, in a few quick steps.