起源与进化

缅甸琥珀研究为蜘蛛起源和演化提供关键证据中国科学院南京地质古生物研究所王博研究员和黄迪颖研究员分别领衔的两个国际科研团队,独立研究了保存于1亿年前缅甸琥珀中的＂怪物蜘蛛＂——应氏奇美拉蛛（Chimerarachne yingi）,为了解蜘蛛的起源和演化提供了关键证据,相关成果以背靠背两篇论文的形式同时发表于《自然—生态学与进化》。     

化学进化与生命起源

生命起源是现代科学三个前沿问题（天体演化．生命起源．基本粒子理论）之一．生命起源是研究地球和地外星球由非生命物质变为原始生命的过程．以及研究利用人为方法模拟原始条件重现这一历程．它能帮助人类更好地认识生命发生和发展的规律．控制生物遗传．具有重大的理论意义和现实意义．     

氧气起源与生命进化

加拿大阿尔伯塔大学的库尔特·康豪瑟尔研究小组最近发表研究结果称,在27亿年前地球上出现单细胞生物的时候,大气里的氧气突然增多。由此形成了地球环境中的“大氧化事件”,并促进了地表环境的改变和高级生命诞生。这是地球生命进化的一个重要转折点。     

性的起源和进化

“易有太极,是生两仪”(《周易》)。两仪者阴阳两性也。从未分化的“太极”状态,到阴阳两性的分化是一个进化过程。古希腊和古代中国的文化中都有阴阳两性的概念,万物都有两性之分;月亮属阴,太阳属阳;水是阴,火是阳。非生命之物的两性区分只是一种观念,生命的两性区分却是真实的。     

狗的起源和进化

狗来自何处?过去这是一个难以回答的问题,如今,美国国家人类基因组研究所的研究人员通过破译狗的基因组图谱获得了较为准确的答案,所有犬类的祖先都是灰狼,人类在过去1.5万年里,根据自己的意愿和犬的特点对犬进行了一系列的选育,培育出400多个犬种。其中各犬种都具备不同特征和不同的遗传密码。2003年美国西雅图的弗雷德·赫奇逊癌症研究中心的研究人员在美国《科学》杂志上报告说,他们分析了85个品种414只纯种狗的基因,将它们相互比较并与狼的基因比较,得出了一些结果。在某个特定品种的狗之间,基因的相似度很高,而不同品种的狗基因存在一…     

生物的进化

地球上的生命是多种多样、形形色色的。陆地有陆地的生物,水中有水中的生物。温热地带有生物,寒冷地带也有生物。所有这些生物是怎么形成的呢?近代生物科学的研究告诉我们,生物是由无生物发展而来的,生命是物质运动的特殊形式。而现代的植物、动物和人,是由那些最简单、最原始的生物逐步发展而来的。自从生命在地球上产生以后,它们就从简单到复杂、从低级到高级不断地“世界上究竟先有鸡,还是先有蛋?”在我国,这是一个常常有人提到的问题,许多人都回答不出来。但是,从生物进化的观点来看,它就很容易回答。家鸡的祖先可能     

狗的起源和进化之谜

<正>人们普通认同一个结论:狗是从狼进化而来,而且是由人驯化的。但是,凶残和嗜血的狼是如何被驯化成温顺和忠诚的狗却一直存在争论。关于谁把狼驯化成狗,一直存在亚洲人、欧洲人,甚至非洲人以及世界各地的人之争;关于何时狼被驯化为狗,则有1万多年前到3万多年前的不同时间跨度之说。     

蔷薇科植物的起源和进化

Rosaceae. consisting of about 126 genera and 3200 species,  is widely distribu- ted in warm temperate and subtropical regions of the Northern Hemisphere,  while more than half of the genera are Asiatic and more then 80% of the total number of Asiatic occur in China (Table 1). In this paper,  the origin and evolution of Chinese genera is discussed mainly.  The principal tendency of the whole family is also described from the point of view of evolution.      First of all,  the systematic position of Rosaceae in Angiospermae is reviewed. Ac- cording to the records of paleobotany,  rosaceous plants occurred first in the Tertiary, from the early period of Eocene (genera such as Spiraea and Prunus) to the late period of Miocene (e.g. Crataegus,  Malus amd Rosa).  They have quite a long history in geolo- gical data. Where has this big and old family originated and what steps does it stand in the long course of evolution of flowering plants?  There are several opinions and ex- planations by different authors.  In this paper,  a general survey of the six prevailing classical systems (Table 2) is made to give a brief idea of the position of this family in the Angiospermae and of the relationships between the subfamilies and also the rela- tionships between different genera in each subfamily. At the end of this paper,  an at- tempt is made to analyse and sum up the major evolutionary tendency of the whole fa- mily.       As generally condidered,  Rosaceae originated from Magnoliales,  and woody plants of the family still hold a dominant position. For instance,  subfamily Spiraeoideae con- sists of only one herbaceous genus (i.e.,  Aruncus) and subfamily Rosoideae only a few herbaceous genera.  All of these herbaceous genera are derived from the closely related woody genera of the same subfamily.       In the course of evolution of Angiospermae,  Rosaceae stands at the initial to the middle stages of development.  All parts of plant body in this family are at the chang-  ing and developing stages,  with carpels,  fruits and inflorescences being the most active.       The primitive types in this family,  such as the members of subfamily Spiraeoideae,  usually have 5 and free carpels,  the number of which are either reduced to 2-1 or in- creased to 10-numerous. They have different levels of union and are either completely  free from each other or coherent at base. The carpels usually occur on the upper part of the receptacle,  because the shapes of receptacle are variable,  sometimes disk-shaped,  cup- shaped,  tube-shaped or even bottle-shaped. In the last case carpels grow inside the rece- ptacle.  Thus the position of carpels has changed from superior to inferior through half- superior.       In accordance with the development of the carpels,  various kinds of fruits are produ- ced.  The primitive types of fruit are follicles,  with dry,  dehiscent carpels opened along different sutures.  The next step,  the carpels have developed into an indehiscent,  I-celled and l-seeded fruit,  the so-caned achene. In different genera,  the achenes have different coat types and appendages to facilitate dispersing the seeds. Some of the achenes grow upon the fleshy receptacle (like strawberry) and some of them inside the fleshy rece- ptacle (like rose).  Sometimes a few carpels are united with the receptacle and develop into a pome (like apple and pear). Another direction of the fruit development is the single carpel with fleshy exocarp and mesocarp,  and a bony endocarp,  then becoming a drupe (like peach and plum).       In addition to fleshy receptacle of thickened fruit coats,  they usually have showy colour,  fragrant smell and also plenty of sugars,  acids,  vitamins,  etc.  which are edible and attract animals and human beings to assist the dispersion of seeds.      In this family,  there are various types of flower arrangements,  both indefinite inflo- rescences including raceme,  umbel,  corymb and panicle,  and the definite inflorescence, such as solitary flower,  cyme and compound cyme.  In the evolution course,  they tend to change mostly from multiflowered compound inflorescence towards few-flowered sim- ple inflorescence,  and finally becoming a solitary flower: simultaneously with the decre- asing of number of flowers on the inflorescence,  the increasing of size of petals,  which become very showy for attraction of insects so as to guarantee pollination and fertiliza- tion of the plants concerned. Another tendency,  if the bisexual flowers change to uni- sexual,  either monoecious- or dioecious-polygamous,  then they form a dense spike which is beneficial to cross pollination. The abundance,  diversity,  and wide range of distribu- tion of the species and genera of Rosaceae are considered mainly resulted  from their highly developed reproductive organs.     

耐辐射奇球菌的起源与进化的“主动进化说”

1956年美国科学家Arthur Anderson博士注目于辐射灭菌后的肉罐头而创造了一个惊人的发现。当用可杀死其周围的其它微生物的强烈的射线照射这种生长在肉上的细菌时．其外部形态不受任何影响．这种后来被取名为耐辐射奇球菌Deinococcus radiodurans微生物在10000戈瑞(Gy)也就是1000倍于广岛和长崎原子弹爆炸的辐射剂量下，这个     

线粒体起源和蛋白含量进化

线粒体是真核生物重要的细胞器,为细胞提供大部分能量,同时也是活性氧(ROS)产生场所及细胞凋亡控制中心。线粒体来自与宿主共生的α-变形菌(α-Protobacteria),在形成细胞器的过程中α-变形菌蛋白组逐渐变小,将大部分遗传物质转移到核的同时与宿主建立了稳定的内共生关系。大多数现存真核生物的线粒体仍保留有少量来自α-变形菌的基因,其功能非常保守,仅编码线粒体蛋白合成相关的t RNA、r RNA、核糖体蛋白和氧化磷酸化复合物亚基蛋白。本文将从线粒体起源及蛋白含量进化进行综述。     

探索宇宙的起源

我们所在的世界从何而来?这也许是人类最古老的问题。无论是宗教、哲学还是科学,都试图回答这个问题。在知识蒙昧的时代,人们把世界的创生归结为神的创造。而今天,科学已成为主流文化,人们摆脱了超自然的思维方式,转而以科学的方法探索宇宙     

地球生物的进化历程

46亿年前，火热的地球形成了。大约在38亿年前，地球的陆地上还是一片荒芜时，在汹涌澎湃的海洋中开始由无机物合成有机小分子(氯基酸、核苷酸)，在闪电轰击、岩浆喷发的激发下，再由有机小分子合成有机大分子(蛋白质、核酸、类脂、多糖)，生物大分子之间的相互作用最终演化出原始生命。这种原始生命是一种非细胞生物，躯体仅以一层“界膜”与海     

植物LEAFY基因的起源和进化分析

植物LEAFY(LFY)基因编码植物特有的一类转录因子,在显花植物营养生长向生殖生长的转变中起了重要作用。本研究采用同源性检索、系统进化分析和正选择作用检测等方法对植物LEAFY基因进行了系统的进化分析,结果发现植物LEAFY基因最早起源于轮藻,并在陆生植物基因组中稳定遗传下来;不同陆生植物基因组的LEAFY基因具有相似的基因结构;单子叶植物的LEAFY基因经历了明显的正选择作用,而玉米和油棕中分别具有2个LEAFY基因,且其中的一个经历了正选择作用,可能与新功能的形成及功能分化有关。     

数字进化成生物?

它们是数字也是生物,它们繁殖的速度比细菌还快。有人说它们是没有DNA的生命,是动物、植物和微生物之外的第四种生命体。进化论有关生物进化过程的关键环节,它们一个也不少。是进化遵循一样的规则,还是它们先行一步,走在了所有进化的前列?