15.49 无脊椎生物无脊椎动物的 冷战演变 -- -- 先进
章节大纲
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. Why?
::为什么?Why would this organism evolve? Tunicates are filter feeders with a sac-like body structure. Though they may seem to be very simple , they were an important evolutionary stepping stone.
::为什么这个生物体会演变? 肿瘤是过滤器的支线,其身体结构与sac相似。尽管它们似乎非常简单,但它们是一个重要的进化垫脚石。Evolution of Nonvertebrate Chordates
::非脊椎和弦进化Although the vast majority of are represented by the vertebrate , the invertebrate subphyla Urochordata and Cephalochordata provide important clues to the early evolution of the chordate phylum. Traditionally, urochordates have been considered to be the earliest group of chordates despite their limited , which dates back only as far as the Jurassic period. Cephalochordates were considered to be more closely related to vertebrates. This is based on shared features between cephalochordates and vertebrates, including the presence of myomeres, and the fact that, unlike urochordates, they retain most of their chordate-specific characteristics in ( notochord and tail). The fact that urochordates lack most chordate features as adults also lends support to the notion that they represent an earlier chordate group. Molecular phylogenetic studies have recently challenged this view. In the last several years, the complete genomes of several urochordate species, including Ciona intestinalis in the class Ascidiacea and Oikopleura dioica in the class Larvacea, have been sequenced.
::虽然绝大多数是脊椎动物,但无脊椎亚phyla Urochordata 和 Cephalochordata 等无脊椎动物是脊椎动物的早期进化的重要线索。传统上,尽管环十二类动物数量有限,但它们被认为是最早的染色体群,尽管这些染色体仅可追溯到侏罗纪时期。青色动物被认为与脊椎动物的关系更为密切。分子血清学研究最近对这一观点提出了质疑。在过去几年中,若干亚异种物种的完整基因组,包括亚麻洛氏菌、亚麻风类、亚麻风类、亚麻风类、亚麻风类、亚麻风类、亚麻风类、亚氏蛋白质、亚氏菌类、亚氏菌类。By comparing these sequences with the , scientists have been able to gain a much better understanding of the evolutionary relationship between urochordates and vertebrates. These studies help us learn about the evolutionary changes in the genome that contribute to the differences we see in the organism’s physical traits. For example, 80% of the genes in the C. intestinalis genome have counterparts in the human genome, reflecting a very close evolutionary relationship. One major difference between the two genomes is their size. The total number of genes in the genome of C. intestinalis is about half the number found in the human genome. What scientists have discovered in studying the two genomes is that a big part of this size difference is due to the duplication of many genes that are only present as one copy in the urochordate genome. How does that relate to evolutionary differences or changes that have taken place between the two organisms?
::这些研究有助于我们了解基因组的进化变化,这些变化导致我们发现生物体物理特征的差异。例如,C. 肠子基因组的80%的基因组在人类基因组中有相似的基因组,反映了一种非常密切的进化关系。两种基因组之间的一个重大区别是它们的大小。C. 肠子基因组中的基因总数大约是人类基因组中发现的数目的一半。科学家在研究这两种基因组时发现,这种规模差异的一大部分是由于许多基因的重复,这些基因只存在于泌尿基因组中。这与两种生物的进化差异或变化有何关系?Having multiple copies of a gene allows the organism to accommodate adaptive in some copies of the gene, which can lead to new with new functions, without losing the essential function of the original gene. Comparing genes between the two species can help scientists learn which copy of a duplicated gene is most like the ancestral copy. They can then look at the differences in the other copies to understand some of the evolutionary changes that have been selected for in the more recent species. One major finding of these analyses is that, at the molecular level, the subphylum Urochordata is actually more closely related to Vertebrata than the cephalochordates are. This represents a major shift in thinking about the phylogenetic relationships of chordate subphyla and may indicate that cephalochordates were the earliest chordates.
::拥有多个基因副本可使生物体适应某些基因副本的适应性,这可以带来具有新功能的新基因,同时又不丧失原始基因的基本功能。 比较这两个物种之间的基因可以帮助科学家了解哪个复制基因副本最像祖传基因副本。 然后他们可以查看其他基因副本的差异,以了解最近物种中选择的一些进化变化。 这些分析的一个主要发现是,在分子层面,亚硫代乌罗乔尔数据实际上与Vertebrata有更紧密的联系,而不是阴道切片日期。这代表了对chorate 亚phyla 的植物遗传关系的思考发生重大转变,并可能表明,青喉日期是最早的染色日期。Studies of have also shed light on the origins of some vertebrate traits that are essential to our health and survival. A fascinating example is the beginning of the adaptive immune system . In the Immune System concepts, you will learn about the human adaptive immune system. This system is shared with many other vertebrates, allowing them to identify foreign, infectious organisms within the body and respond by generating protein molecules, called antibodies , that are specifically designed to attack the particular offending invaders. Researchers examining lancelets have found that they have a very primitive form of adaptive immune proteins with similarities to antibodies. Lancelets are the earliest group in the animal to show the beginning of an adaptive immune system. This finding will now help us understand how the immune system evolved over time from its rudimentary beginnings to its current, highly complex state.
::研究还揭示了一些对健康和生存至关重要的脊椎动物特征的起源。一个引人入胜的例子是适应性免疫系统的开端。在免疫系统的概念中,你将了解人类适应性免疫系统。这个系统与其他许多脊椎动物共享,使他们能够识别体内的外来传染性有机体,并通过生成蛋白分子(称为抗体)作出反应,这些分子是专门设计用来攻击特定侵犯者的。研究者们检查肺部发现,它们有一种非常原始的适应性免疫蛋白形式,与抗体相似。兰刀是动物中最早显示适应性免疫系统的开始的一组。这个发现现在将帮助我们了解免疫系统如何从原始的开始到目前非常复杂的状态,经过一段时间后演变。These examples highlight the importance of studying organisms at the level of their molecules, particularly their and proteins, for making accurate assessments about their evolutionary histories. The revolution in molecular biology that has made DNA sequencing efficient and inexpensive has made a major contribution to phylogenetic studies. These studies are likely to continue and rapidly expand our understanding of the evolutionary changes that led to the many species of chordates and other organisms living on Earth today.
::分子生物学革命使DNA测序效率高,价格低廉,为植物基因研究作出了重大贡献,这些研究有可能继续并迅速扩大我们对导致当今地球上许多物种的变异变化和其他生物体的认知。Summary
::摘要-
Traditionally, urochordates have been considered to be the earliest group of chordates despite their limited fossil record, which dates back only as far as the Jurassic period. Cephalochordates were considered to be more closely related to vertebrates.
::传统上,尽管化石记录有限,但极地合唱团被认为是最早的染色体群。 化石记录仅可追溯到侏罗纪时期。 切帕罗氏舞团被认为与脊椎动物的关系更为密切。 -
One major finding of these analyses is that, at the molecular level, the subphylum Urochordata is actually more closely related to Vertebrata than the cephalochordates are.
::这些分析的一项主要结论是,在分子一级,亚植物类Urochordata实际上与Vertebrata比切喉日期更密切相关。 -
Researchers examining lancelets have found that they have a very primitive form of adaptive immune proteins with similarities to antibodies.
::研究气囊的研究人员发现,它们有一种非常原始的适应性免疫蛋白质形式,与抗体相似。
Review
::回顾-
Which group of chordates were traditionally regarded as the earliest group?
::哪些染色体传统上被视为最早的组? -
Scientists discovered that urochordates have many genes in common with humans, but urochordates usually only have one copy of each gene. Why does having multiple copies of the same gene benefit an organism?
::科学家发现,极地合唱团有许多与人类相同的基因,但极地合唱团通常只有每个基因的复制件。 为什么同一基因的多个复制件对有机体有利? -
How is the lancelet immune system similar to that of vertebrates?
::长子免疫系统如何与脊椎动物的免疫系统相似?
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Traditionally, urochordates have been considered to be the earliest group of chordates despite their limited fossil record, which dates back only as far as the Jurassic period. Cephalochordates were considered to be more closely related to vertebrates.
