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  • 生命多样性

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    So Many Species!
    ::如此多的物种!

    The collage above shows a single in each of the six kingdoms into which all of Earth's living things are commonly classified. How many species are there in each ? In a word: millions . A total of almost two million living species have already been identified, and new species are being discovered all the time. Scientists estimate that there may be as many as 30 million unique  species alive on Earth today! Clearly, there is a tremendous variety of life on Earth.
    ::上面的拼图显示了六个王国中每一个王国的单一。 地球上所有生物都是被分类的。 每个王国中有多少物种? 一句话: 百万个。 总共已经确定了近200万个生物物种, 并且一直在发现新的物种。 科学家估计,今天地球上可能有多达3000万个独特的物种存在! 显然, 地球上有各种各样的生命。

    What Is Biodiversity?
    ::什么是生物多样性?

    Biological diversity, or , refers to all of the variety of life that exists on Earth. Biodiversity can be described and measured at three different levels: species diversity , genetic diversity , and ecosystem diversity .
    ::生物多样性是指地球上存在的各种生命,生物多样性可分为三个不同层次加以描述和衡量:物种多样性、遗传多样性和生态系统多样性。

    • Species diversity refers to the number of different species in an or on Earth as a whole. This is the most common  way to measure biodiversity. Current estimates for Earth's total number of living species range from 5 to 30 million species.
      ::物种多样性是指一个或整个地球上不同物种的数量,这是衡量生物多样性的最常见方法,目前对地球生物物种总数的估计从500万到3 000万种不等。
    • Genetic diversity refers to the variation in genes within all of these species.
      ::遗传多样性是指所有这些物种中基因的变异。
    • Ecosystem diversity refers to the variety of ecosystems on Earth. An ecosystem is a system formed by of many different species interacting with each other and their environment.
      ::生态系统多样性是指地球上生态系统的多样性,生态系统是由许多不同物种相互互动及其环境组成的系统。

    Defining a  Species
    ::界定物种

    Biodiversity is most often measured by counting species, but what is a species? The answer to that question is not as straightforward as you might think. Formally, a   species is defined as a group of actually or potentially interbreeding organisms . This means that members of the same species are similar enough to each other to produce fertile offspring together. By this definition of species, all human beings alive today belong to one species, Homo sapiens . All humans can potentially interbreed with each other, but not with members of any other species.
    ::生物多样性最经常用数数物种来衡量,但什么是物种?这个问题的答案没有你们想象的那么直截了当。形式上,一个物种被定义为由实际或潜在相互干扰的有机体组成的群体。这意味着同一物种的成员彼此相似,足以共同产生肥沃的后代。根据对物种的这一定义,今天所有活着的人都属于一个物种,即人猿。所有人类都有可能相互交织,但不能与其他任何物种的成员交织。

    In the real world, it isn't always possible to make the observations necessary  to determine whether or not different organisms can interbreed. For one thing, many species reproduce asexually, so individuals never interbreed — even with members of their own species. When studying extinct species represented by , it is usually impossible to know if  different organisms could interbreed.  Keep in mind that 99 percent of all species that have ever existed are now extinct! I n practice, many biologists and virtually all paleontologists generally define species on the basis of morphology, rather than breeding behavior.   Morphology refers to the form and structure of organisms. For classification purposes, it generally refers to relatively obvious physical traits. Typically, the more similar to one another different organisms appear , the greater the chance that they will be classified in the same species.
    ::在现实世界中,我们并不总是能够做必要的观察以确定不同的生物能否相互繁殖。 一方面, 许多物种是性繁殖的, 所以个人从不相互繁殖, 即使与自己物种的成员发生性关系。 当研究由...代表的灭绝物种时, 通常不可能知道不同的生物能否互相繁殖。 记住, 曾经存在的所有物种中, 99%现在已经灭绝了 。 实际上, 许多生物学家和几乎所有的古生物学家一般都是根据形态学而不是繁殖行为来定义物种的。 生理学是指生物的形态和结构。 为了分类的目的, 它一般是指相对明显的物理特征。 一般来说, 与其他不同的生物体相比, 更相似的是, 它们被分类在同一个物种中的可能性越大 。

    Classifying Living Things
    ::将生活事物分类

    People have been trying to classify the tremendous diversity of life on Earth for more than two thousand years. The science of classifying organisms is called taxonomy . Classification is an important step in understanding the present diversity and past evolutionary on Earth. It helps us make sense of the overwhelming diversity of living things.
    ::两千年多来,人们一直试图将地球上生命的巨大多样性分类,生物分类科学被称为分类学。分类是了解地球当前多样性和过去进化的重要一步。它帮助我们理解生命的绝大多数多样性。

    Linnaean Classification
    ::林内人分类

    All modern classification systems have their in the Linnaean classification system, which was developed by Swedish botanist Carolus Linnaeus in the 1700s. He tried to classify all living things known in his time by grouping together organisms that shared obvious morphological traits, such as number of legs or shape of leaves. For his contribution, Linnaeus is known as the “father of taxonomy.”
    ::所有现代分类系统都包含在Linnaean分类系统中,该系统由瑞典植物学家Carolus Linnaeus于1700年代开发。 他试图通过将具有明显形态特征的生物(如腿数或叶形)集中在一起,将他时代已知的所有生物分类。 林瑙斯的贡献是被称为“分类之父 ” 。

    The Linnaean system of classification consists of a hierarchy of groupings, called taxa (singular, taxon). The figure shows an expanded version of Linnaeus's original classification system. In the original system, taxa ranged from the kingdom to the species. The kingdom  (ex. plant kingdom, kingdom) is the largest and most inclusive grouping. It consists of organisms that share just a few basic similarities. The species is the smallest and most exclusive grouping. Ideally, it consists of organisms that are similar enough to interbreed, as discussed above. Similar species are classified together in the same genus (plural, genera), then similar genera are classified together in the same family, and so on, all the way up to the kingdom.
    ::Linnaean分类制度由分类分类的等级结构组成,称为分类( singula, cason),图中显示了Linnaeus原有分类制度的扩大版。在原始制度中,分类从王国到物种不等。王国(如植物王国、王国)是最大和最包容的分类组。它由只有几个基本相似点的有机体组成。物种是最小和最排他性的分类组。理想的情况是,它由足以与相互交织的有机体组成,如上文所述。相似的物种被分类在同一基因组中(多元、基因组),然后类似的基因组被分类在同一个家族中,等等,一直到王国。

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    The hierarchy of taxa in the original Linnaean system of taxonomy included taxa from the species to the kingdom. The domain was added later.
    ::最初的林奈人分类学制度中的分类学等级包括从物种到王国的分类学,后来又增加了域。

    Binomial Nomenclature
    ::二进制名词

    Perhaps the single greatest contribution Linnaeus made to science was his method of naming species. This method, called binomial nomenclature , gives each species a unique, two-word Latin name consisting of the genus name followed by  a specific species identifier. An example is Homo sapiens, the two-word Latin name for humans. It literally means “wise human.” This is a reference to our big brains.
    ::也许林内乌斯对科学的最大贡献 是他命名物种的方法。这个方法叫做二元论术语,给每个物种一个独特的、两字的拉丁名,由基因名称和特定物种识别符组成。一个例子是人的两个拉丁名“智人 ” 。 它的字面意思是“智人 ” 。 这是对我们大大脑的提法。

    Why is having two names so important? It is similar to people having a first and a last name. You may know several people with the first name Michael, but adding Michael’s last name usually pins down exactly which Michael you mean. In the same way, having two names for a species helps to uniquely identify it.
    ::为什么有两个名字如此重要? 它与拥有第一个和一个姓氏的人相似。 你可能认识几个名字叫迈克尔的人,但加上迈克尔的姓通常会确定你指的是迈克尔的姓。 同样,一个物种有两个名字有助于独特识别它。

    Revisions in the Linnaean Classification
    ::林内人分类的修订

    Linnaeus published his classification system in the 1700s. Since then, many new species have been discovered. Scientists can also now classify organisms on the basis of their biochemical and genetic similarities and differences, and not just their outward morphology. These changes have led to revisions in the original Linnaean system of classification.
    ::林内乌斯在1700年代公布了他的分类制度。 自那时以来,发现了许多新的物种。 科学家现在也可以根据生物的生化和遗传相似和差异,而不仅仅是外向形态,对生物进行分类。 这些变化导致了最初的林内亚分类制度的修改。

    A major change to the Linnaean system is the addition of a new taxon called the . The  domain is a taxon that is larger and more inclusive than the kingdom, as shown in the figure . Most biologists agree that there are three domains of life on Earth: , , and Eukarya (shown in the diagram ). Both the Bacteria and the Archaea d omains consist of single-celled organisms that lack a . This means that their genetic material is not enclosed within a membrane inside the . The Eukarya  d omain, in contrast, consists of all organisms whose cells do  have a nucleus, so that their genetic material is enclosed within a membrane inside the cell. The Eukarya d omain is made up of both single-celled and . This domain includes several kingdoms, including the animal, plant, , and kingdoms.
    ::Linnaean 系统的一项重大改变是增加了一个新的分类,称为 。 如图所示, 域是一个比王国更大和更具包容性的分类, 如图所示。 多数生物学家都认为地球上有三种生命领域: , 和 Eukarya (图中显示)。 细菌和Archaea 域由缺乏单细胞生物组成。 这意味着它们的遗传物质没有被嵌入内膜内。 相比之下, Eukarya 域由细胞内细胞有核的所有生物组成, 因此它们的遗传物质被嵌入细胞内的膜内。 Eukarya 域由单细胞和细胞组成。 这个域包括几个王国, 包括动物、植物和王国。

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    The three domains of life, as well as how they are related to each other and to a common ancestor
    ::生活的三个领域,以及它们彼此的关系和与共同祖先的关系

    Phylogenetic Classification
    ::生代遗传学分类

    Linnaeus classified organisms based on morphology. Basically, organisms were grouped together if they looked alike. After published his theory of evolution in the 1800s, scientists looked for a way to classify organisms that accounted for  phylogeny . Phylogeny is the evolutionary history of a group of related organisms. It is represented by a phylogenetic tree , or some other tree-like diagram, like the one shown   to illustrate the three domains. A phylogenetic tree shows how closely related different groups of organisms are to one another.  Each branching point represents a common ancestor of the branching groups. The diagram , for example, shows that the Eukarya shared a more recent common ancestor with the Archaea than they did with the Bacteria. This is based on important similarities and differences among the three domains.
    ::Linnaeus基于形态学的分类生物。 基本上, 生物如果看起来相似, 就会被组合在一起。 在发表了他在1800年代的进化理论之后, 科学家们寻找了一种方法, 将具有植物遗传性的生物分类。 Phylgeny 是一组相关生物的进化史。 它由植物基因树或其他类似树形图来代表, 就像用来说明这三个领域的图一样。 植物基因树显示, 不同的生物组彼此之间有多么密切的联系。 每个分支点代表着分支组的共同祖先。 例如, 图表显示, Eukarya 与Archaea 相比, 与Archaea 有着更近的共性祖先。 这是基于三个领域之间的重要相似性和差异。

    Summary
    ::摘要

    • Biodiversity refers to the variety of life that exists on Earth. It includes species diversity, genetic diversity (within species), and ecosystem diversity.
      ::生物多样性是指地球上存在的各种生命,包括物种多样性、遗传多样性(物种内部)和生态系统多样性。
    • The formal biological definition of species is a group of actually or potentially interbreeding organisms. Our own species, Homo sapiens, is an example. In reality, organisms are often classified into species on the basis of morphology.
      ::物种的正式生物定义是由实际或潜在相互交织的生物构成的一组生物,我们自己的物种,即人猿同族,就是一个例子,在现实中,生物往往根据形态被归类为物种。
    • A system for classifying living things was introduced by Linnaeus in the 1700s. It includes taxa from the species (least inclusive) to the kingdom (most inclusive). Linnaeus also introduced a system of naming species, which is called binomial nomenclature.
      ::Linnaeus在1700年代引入了生物分类系统,其中包括从物种(最小包容)到王国(最包容)的分类群。 Linnaeus还引入了命名物种系统,称为二元命名。
    • The domain — a taxon higher than the kingdom — was later added to the Linnaean system. Living things are generally grouped into three domains: Bacteria, Archaea, and Eukarya. The human species and other animal species are placed in the Eukarya d omain.
      ::这个领域——比王国高的税种——后来被添加到林纳纳体系中,生活的东西一般分为三个领域:细菌、Archaea和Eukarya,人类和其他动物物种被置于尤卡里亚领域。
    • Modern systems of classification take into account  phylogenies, or evolutionary histories of related organisms, rather than just morphological similarities and differences. These relationships are often represented by phylogenetic trees or other tree-like diagrams.
      ::现代分类系统考虑到相关生物的植物基因或进化史,而不仅仅是形态上的相似和差异,这些关系往往由植物基因树或其他树形图所体现。

    Review
    ::回顾

    1. What is biodiversity? Identify three ways that biodiversity may be measured.
    ::1. 什么是生物多样性?确定可以衡量生物多样性的三种方式。

    2. Define biological species. Why is this definition often difficult to apply?
    ::2. 界定生物物种:为什么这一定义往往难以适用?

    3. Explain why it is important to classify living things, and outline the Linnaean system of classification.
    ::3. 解释为什么必须对生物进行分类,并概述林内亚分类制度。

    4. What is binomial nomenclature? Give an example.
    ::4. 二元性术语是什么?举一个例子。

    5. Contrast the Linnaean and phylogenetic systems of classification.
    ::5. 比较林内亚和植物遗传分类系统。

    6. Describe the taxon called the domain, and compare the three widely recognized domains of living things.
    ::6. 描述称为域名的分类,比较三个广泛公认的生物领域。

    7. True or False:  Humans have identified all of the species on Earth.
    ::7. 真实或假:人类已查明地球上的所有物种。

    8. True or False:  In the binomial nomenclature for humans, Homo is the genus and sapiens  refers to the specific species.
    ::8. 真实或假:在人类的二义论术语中,同性人是指特定物种的基因和人种。

    9. A kingdom is a:
    ::9. 王国是:

    a. domain
    ::a. 域域域

    b. taxon
    ::b. 计分法

    c. genera
    ::c.

    d. phylogeny
    ::d. 血源化

     

    10. In Linnaean classification, similar classes together make up a ___________ .
    ::10. 在林内人分类中,类似班级合在一起组成了___________________________________________________________________________________________________________________________________________________________________________________________________________________________

     

    11. Based on the phylogenetic tree for the three domains of life above, explain whether you think Bacteria are more closely related to Archaea or Eukarya.
    ::11. 根据上述三个生活领域的植物基因树,解释你认为细菌与Archaea或Eukarya的关系更密切。

     

    12. A scientist discovers a new single-celled organism. Answer the following questions about this discovery.
    ::12. 科学家发现了一种新的单细胞生物,回答关于这一发现的问题。

    a. If this is all you know, can you place the organism into a particular domain? If so, what is the domain? If not, why not?
    ::a. 如果这是你所知道的,你能将生物体放入特定的领域吗?如果是这样,那这个领域是什么?如果没有,为什么不呢?

    b. What is one type of information that could help the scientist classify the organism?
    ::b. 何种类型的信息可以帮助科学家对生物进行分类?

    13. Define morphology. Give an example of a morphological trait in humans.
    ::13. 界定形态学,举人类形态特征的例子。

     

    14. Which type of biodiversity is represented in the differences between humans?
    ::14. 人类之间的差异代表了哪种生物多样性?

     

    15. Why do you think it is important to the definition of a species that members of a species can produce fertile offspring?
    ::15. 为什么你认为一个物种的成员能够产生肥沃的后代对于界定一个物种很重要?

    Explore More
    ::探索更多

    Watch the video below to learn more about Carolus Linnaeus' life and work. 
    ::观看下面的视频, 以了解更多关于卡罗尔斯·林瑙斯的生活和工作。

     Watch the video below to see what one cardiologist learned from expanding her research from one species only (humans) to many species. 
    ::看看一位心脏病学家在将研究范围从一个物种(人类)扩大到许多物种的过程中学到了什么。