江西的保护植物

地球上物种资源灭绝很快,据美国的环境保护组织——自然资源保护委员会,委托专家进行的调查研究结果,估计生物种类到本世纪末,有可能从现有的五百万种至一千万种减少到近一百万种。所以近年来,对于自然资源,特别是生物资源的保护,已引起了世界各国的高度重视,相继建立较大规模的自然保护区,以恢复生态平衡,并保护濒危生物种类。     

江西的保护植物（摘要）

地球上物种资源灭绝很快,据美国的环境保护组织——自然资源保护委员会,委托专家进行的调查研究结果,估计生物种类到本世纪末,有可能从现有的五百万种至一千万种减少到近一百万种。所以近年来,对于自然资源,特别是生物资源的保护,已引起了世界各国的高度重视,相继建立较大规模的自然保护区,以恢复生态平衡,并保护濒危生物种类。本文仅就江西省应加以保护的植物种类综述如下五个方面:     

动物灭绝的原因及恶果

地球上自从３５亿年前出现生命以来,已有５亿种生物生存过,如今绝大多数早已消逝。物种灭绝作为地球上生命进化史的一种自然现象,本是正常事件,如２．５亿年前的三叶虫、６５００万年前的恐龙均已灰飞烟灭。但自从人类进入工业社会,目空一切地参与大自然的事务以后,使这个绝灭时间表大大提前。地质时代物种灭绝的速度极为缓慢,鸟类平均３００年灭绝１种,兽类平均８０００年灭绝１种;到１６００年至１７００年,每１０年灭绝１种动物;１８５０年至１９５０年,鸟兽的平均灭绝速度为每年１种,即有１００多种动物灭绝,而且这种灭绝…     

生命的历程系列讲座(十三)生物大灭绝启示录

正当今地球鸟语花香、万紫千红,人类社会迈入了信息化的现代社会生活,很难想象过去漫长的地球历史上曾发生过多次惊天动地、凄惨无比的生物大灭绝。据有关方面统计,地球上曾存活过10亿至40亿种动、植物和菌类,而现在的物种观察估计仅有2000万种,所以绝大多数物种在地质历史长河中灭绝了,它们除部分是自然灭绝外,绝大部分是在生物大灭绝中消失的。那么,是什么原因导致了生物大灭绝事件?它们对我们有什么启示呢?灭绝是自然现象     

我国植物园与野生植物多样性保护及研究

在近代,人口迅速增长、人类对自然资源滥用和环境变化已使生物绝灭迅速比历史上自然绝灭率高一千倍,而一种植物的绝灭常导致另外10—30种生物的生存危机。据世界自然和自然资源保护联盟(IUCN)估计,世界上已知的约25万种高等植物中已有2.0—2.5万种,即占区系成分的1/10处在受严重的威胁状态,按此趋势发展,至公元2050年,受威胁的植物将达六万种,即占区系成分的1/5—1/4。所以IUCN和世界野生生物基金会(WWF)在80年代初期制订了“世界植物保护计划”,并提出了“抢救植物就是拯救人类”的行动纲领。世界     

昆虫进化与植物的关系

<正> 地球在大约35亿年前开始出现生物。到目前,在地球上生存的生物约在200万种以上。它们都是过去绝灭种类的后代,渊源于共同的祖先,经历了从无到有、从少到多、从低级到高级的发展演变过程。不同种类之间常存在着相互适应,关联进化的现象,当今地球上最为繁盛的昆虫种群就与植物存在着互适进化的关系。     

全苏《合理利用和保护有用植物原理和方法》研讨会概况

在苏联近年来由于在国民经济中大量利用野生有用植物,导致对野生有用植物的大量开发,从而使一些植物原料的蕴藏量大量减少,有些已濒临绝灭,而被收入苏联红皮书,做为保护种类。为了更合理利用和保护野生有用植物、以保证苏联各个经济部门对植物原料的不断需求和保存野生植物不致绝灭,并能永续利用。1988年由苏联科学院《合理利用和保护植     

人类生态学(七):野生动物管理(1)

地球上的生物已有大约40亿年的进化史,而人类的起源和进化大约只经历了400万年,约占整个生物进化史的1‰。人类是地球上最晚出现的一种智慧生物,人类起源于生物界,而又离不开生物界。在人类进化历史的绝大部分时期内,人类几乎完全依赖野生生物为生(靠狩猎和采集野生植物),只是在1万多年以前,当农业和畜牧业产生以后,人类才逐渐减少了对野生生物的依赖性(目前仍有许多国     

我国境内曾灭绝的三种哺乳动物

若把化石兽类一并考虑在内,中国历史上已绝灭的兽类种类不少。如北京房山县周口店中国猿人遗址距今约69万年更新世中期,即发现诸如三趾马、剑齿虎和梅氏犀等兽类化石。然而,这些化石种类本文不作论述。现要介绍的是目前在动物园或其它园林中人上条件之下尚驯养,但在中国野生自然环境下已绝灭的种类。据确切的报道,中国已绝灭的兽类有麇鹿(四不     

被撞击的地球

大约在6500万年前的中生代白垩纪晚期,曾经在整个中生代(距今2亿2千5百万年—6千5百万年)都一直兴旺发达,称霸于世的恐龙家族几乎一下子消失了。在白垩纪以后的地层中,再也找不到恐龙的化石。这样一个曾在地球上做了长达1亿数千万年霸主的庞大家族为什么会突然绝灭呢?与此同时,绝灭的还有菊石类、双壳纲中的固着蛤类和叠瓦蛤类、六射珊瑚大型底栖有孔虫和超微浮游生物。从白垩纪末到第三纪,生物属数由原来的2868属一下子锐减为1502属,仅为先前的52％。灭绝的生物种数竟为绝灭前生物     

Natural history of the maldescended testis

In a series of 545 boys with undescended testis, 91 had bilateral spontaneous descent after the age of 10. Forty-five accepted to take part in an investigation of their fertility based on history, clinical examination, sperm analysis and estimation of serum FSH levels. In the majority, the volume of the testis was below normal and the sperm concentration was below the lower limit of the normal range. It is concluded that late spontaneous bilateral descent of the testis carries a serious risk of later impaired spermatogenesis.     

Natural expansion of the genetic code

At the time of its discovery four decades ago, the genetic code was viewed as the result of a "frozen accident." Our current knowledge of the translation process and of the detailed structure of its components highlights the roles of RNA structure (in mRNA and tRNA), RNA modification (in tRNA), and aminoacyl-tRNA synthetase diversity in the evolution of the genetic code. The diverse assortment of codon reassignments present in subcellular organelles and organisms of distinct lineages has 'thawed' the concept of a universal immutable code; it may not be accidental that out of more than 140 amino acids found in natural proteins, only two (selenocysteine and pyrrolysine) are known to have been added to the standard 20-member amino acid alphabet. The existence of phosphoseryl-tRNA (in the form of tRNACys and tRNASec) may presage the discovery of other cotranslationally inserted modified amino acids.     

Synthesis of the Stereoisomers of Natural Rotenone

The reaction of rotenone, which has the 5′β-isopropenyl grouping, with boron tribromide in dichloromethane gives the 1′,5′-seco-5′-bromo compound having the opened E-ring. When treated with sodium bicarbonate in aqueous acetone, the compound closes the E-ring to form two products having the 5′-isopropenyl grouping in the α- and β-configurations. By this cycle, rotenone (5′β-rotenone) gives 5′α-epirotenone as well as rotenone, while d-epirotenone (5′β-epirotenone) gives 5′α-rotenone (the antipode of natural rotenone) as well as d-epirotenone.     

Natural Selection or the Non-survival of the Non-fit

The effects of natural selection as a process in natural populations differs from 'survival of the fittest' as it was formulated by Darwin in his 'Origin of Species'. The environment of a population exists of continuous changing conditions, which are heterogeneous in space. During its life each individual successively meets with differing conditions. During these confrontations the individual may appear to be 'unfit' or 'unlucky' and may die. If it survives it will meet the following conditions to which it is 'tested' anew, a.s.o. Hence, many individuals being less fit under certain conditions will survive and reproduce, because they did not meet a deadly moment. Therefore, being 'fit' only refers to special prevalent conditions. In each generation the individuals thus being 'unfit' will be eliminated together with the 'unlucky' ones. All other individuals will survive and reproduce, notwithstanding their properties.Hence, natural selection results in the 'non-survival of the non-fit' rather than in 'survival of the fittest', because being 'fit' simply means 'having survived and reproduced', whereas being 'unfit' can be connected with many kinds of properties and environmental conditions, e.g. being killed by a predator. Only after many generations (hundreds or even thousands) the effect of eventually dominating properties of the survivors may result in a set of properties suggesting an overall 'survival of the fittest'. This was what Darwin wanted to explain as he was mainly interested in evolutionary processes.As natural selection, as an ecological process, cannot be considered in each generation to be 'survival of the fittest', many ecological concepts supposed to be connected with selection resulting in 'survival of the fittest' within a few generations, such as the dominant role of competition, the critical level of the costs of reproduction, the need of optimization and of optimal life-history traits have to be reconsidered more critically in a less deterministic context. Moreover, these aspects of natural selection, which usually lead to impoverishment of the genepool, contradict the need of a high level of genetic heterogeneity as a base for an effective natural selection.The author gives examples of cases to which these concepts do not apply. On the other hand, natural selection resulting in 'non-survival of the non-fit' allows a continuous reshuffling of all kinds of genes and gene combinations over all kinds of genomes, also many genes with temporarily or even permanently unfavourable effects can be kept in the genepool of the population during a long series of generations. Therefore, natural selection resulting in 'non-survival of the non-fit' leads to spreading of the risk of extinction of the population over genotypes and to the gradual development and accumulation of highly sophisticated adaptations. Only in an environment that has been stationary or even almost constant and homogeneous for a long time may natural selection ultimately lead to 'survival of the fittest'.     

Natural Signs and the Origin of Language

This article considers natural signs and their role in the origin of language. Natural signs, sometimes called primary signs, are connected with their signified by causal relationships, concomitance, or likeliness. And their acquisition is directed by both objective reality and past experience (memory). The discovery and use of natural signs is a required prerequisite of existence for any living systems because they are indispensable to movement, the search for food, regulation, communication, and many other information-related activities. It is argued that the birth of conventional signs, sometimes called secondary signs, was determined by a connotative use of natural signs and that, regulated and maintained by them, human language developed. At the same time, the origin and development of human language presupposes a ‘rational turn’ from the given and external reality of natural signs to the rationally constructed reality of artificial signs and rules that are internally maintained by the subjects’ deliberate activities, and actual and inherited social tradition (social memory). In view of this, language is defined as a dynamic system that must both be natural and artificial, empirical and a priori, inductive and deductive. This bilateral origin and regulation of language is the dual-inference of language.