演化

演化definition

进化的定义

演化definition

演化(evo‧lu‧tion,ɛvəluːʃ(ə)n)被定义为在一个人口超过连续世代的基因组成的变化。Natural selection近亲交配杂交, 要么突变可能带来的演变。它也可能涉及到sequence描绘了事件developmentspecies或一组相关的organismsSynonym:phylogeny

When we hear “evolution”, we often think of a progressive change. In the general sense, evolution refers to some sort of development. In a biological context, evolution can be construed as the sequence of events depicting the gradual progression of changes in the genetic composition of a biological population over successive generations. Or, it may also pertain to the genetic change itself over time. Evolution may also pertain to the change in the genetic composition of biological populations over successive generations.

Key players

进化来进行,也有重要的关键球员:突变natural selection,and遗传漂变

Mutation

基因是在进化过程中是至关重要的。他们表达舱单成遗传特征。通过heritable,这意味着该特性能够从父母传递给后代。这些遗传特征是表型性状的一部分,或者干脆“traits”, of an organism. Hence, mutation in these genes will likely affect the manifestation, as well as the passing, of heritable traits from one organism to the next. For instance, the eye color is a character of varying traits, such as brown, green, blue, hazel,etc。在人类中,眼睛的颜色变化从褐色至黑色,这取决于在虹膜黑色素含量和基质的细胞密度。与黑色素生成有关的基因是OCA2基因。所有的人原本棕色眼睛。1然而,人类进化到有其他眼睛的颜色。该蓝色在人类眼睛的颜色不会被蓝颜料所致。科学家们找到了性状,发现内的特定突变HERC2基因部分责任。它改变的功能OCA2基因,导致生产减少黑色素。1,2Further studies suggested that all humans with blue eyes may have come from a single欧洲祖先谁生活在大约6,000 to 10,000 years ago和谁曾负责蓝眼睛的颜色,这在现代人口最终成为广泛的突变。2除了突变,基因重组是遗传变异的另一来源。在性生物体,过程中发生的基因重组减数分裂。染色体的一对具有相同基因■在同一座位但也可能不同等位基因s的叫homologous chromosomes。这些同源染色体配对和交换遗传物质在prophase Iof减数分裂。除了同源重组,同源染色体独立地朝合群减数分裂的端部。产生新的等位基因组合这些减数分裂事件增加的遗传变异。有性繁殖,因此,升级进化。

Natural selection

通过natural selection,有利于个人特征s为更容易复制用更大的成功。因此,这些人可以通过自己的特征s to the next。进化是由驱动natural selection叫做适应性进化

遗传漂变

另一种机制驱动进化遗传漂变。它产生随机changes in the频率of特征s in a人口。进化,从出现遗传漂变叫做neutral evolution
演变时出现的自然选择和遗传变异的遗传漂变行为。其他关键球员也在起作用。例如,基因flow,which refers to the flow of genes between populations as well as between species, can change the course of evolution. When two organisms of different species mate, they could produce an offspring, which could become a new species.

进化的重要性

Biologically, evolution is important because it drivesbiodiversity。Some traits will become predominant while others will become rare over the course of time. Without evolution, life may not be the way as we know it. It will not be as diverse as it is now.
该Earth itself goes through a series of changes. At one point, the Earth was an inhabitable planet. The primitive condition of the Earth was hostile to life. It was presumed that only after about one billion years from the time that the Earth first came into being that life began. RNA-based, self-replicating entities are held as the descendants of all living things. Over a significant period of time, these life forms evolved into single-celled organisms. Multicellular forms came next. They first appeared about 600 million years ago.

Tracking the history of life at various geologic eras, one would find several mass extinctions occurring in between the连发的生活。例如,在二叠纪of the古生代,地球曾经被称为一个超级大陆Pangaea被...围绕泛大洋海洋。这引起了内地很干燥和干旱。因为这,reptiles flourished as they were able to thrive even in such habitats. A reptile group异齿龙evolved and gave rise totherapsids。该therapsids,反过来,发展并产生了cynodonts,这是早期祖先动物秒。During this period, the early dinosaur ancestors,祖龙,也出现了。显然,一个大灭绝称为“大灭绝”发生擦了擦关于地球上90%的生活。下一个时代(Mesozoic era) is called “the Age of the dinosaurs”. These animals dominated the land, the seas, and the air of the Earth. However, a mass extinction occurred and caused the death of the dinosaurs as well as other large animals. Nevertheless,哺乳动物小号代为开龛和扩大。

进化是至关重要的生命在地球不断变化的坚持。生物体需要有适应能力基因and表型。与其他生物共生关系参与也有助于提高生存的倾向和茁壮成长。随着进化,物种蒸腾。物种发散成两个或更多的派生类在整个进化过程。但不幸的是,大多数生活在地球上的物种已经达到了他们的灭亡。地球上的物种的99%已经灭绝。这些微生物消灭和它们的物种完全消失。因此,它似乎是物种灭绝是不可避免的。

生命的进化史

LUCA

图,称为进化树,显示了生物的进化关系。分组是基于相似性和在遗传和物理特性的差异。分支的模式代表物种或实体如何从一个特定的共同祖先进化而来的。追查所有活的东西,生活在地球上进化的过程将完全导致共同的祖先,LUCA(last universal common ancestor)。LUCA是所有生物的祖先的假设和推测出现一些3.5至3.8十亿年前
有作为生命起源如何在地球上没有达成共识尚未。然而,许多人认为,基于RNA的,自我复制的实体很可能所有的生物的后代。这些实体演变成含有细胞质结构但缺少内部条块的单细胞生物。缺乏膜结合的细胞器的单细胞生物被称为原核生物

内共生理论

原核生物出现了真核生物以前那样。他们能够承受了地球原始的敌对状态。后来,单细胞真核生物周围出现1。6 to 2.7 billion years ago。该endosymbiotic theoryproposes that larger cells took in smaller cells, such asbacteriaandcyanobacteria,对于合作协会(endosymbiosis)。他们一起经历了进化。在适当的时候,较小的原核生物演变成半自主细胞器。细菌演化成mitochondriawhereas the cyanobacteria, intochloroplast秒。膜结合细胞器导致的出现在细胞内的存在真核生物秒。

多细胞

Neoproterozoic era,particularly in the埃迪卡拉期(周围600 million years ago)the first multicellular form emerged. How multicellularity came about is still a matter of debate until now. The most popular theory in this regard is that of Haeckel’s. According to hisGastraea理论,发生多细胞时逐渐,某些细胞在集落后行细胞分化在囊胚样集落的相同物种基团一起的细胞,和。也是在这一时期,海绵状生物进化而来基于恢复的化石埃迪卡拉生物群。他们被认为是第一个动物。

寒武纪生命大爆发

该next era, thePaleozoic,由来自寒武纪到二叠的地质时期的,每个突出显示由主要进化事件。在Cambrian period(周围5.41亿年前),生活突然发生了爆裂。这种地质活动被称为寒武纪生命大爆发。不同的植物和动物应运而生。植物和真菌蔓延至土地。不久,动物如节肢动物上岸冒险,可能交配和产卵。

Rise of invertebrates

奥陶纪485 to 440 million years ago)theinvertebrate小号是占主导地位的动物。原始鱼类继续发展,在未来的地质时期,志留纪,发生鱼的质量演变。此外,在志留纪440 to 415 million years agoarachnidS和arthropod开始吧殖民的土地,而不是冒险了。内部气体交换系统,防水外层,骨骼系统(内或外骨骼),并再现不涉及水的形式来了解,并帮助在陆地上生活似是而非。

“鱼的时代”

Devonian period415至360万年前)被称为鱼的年龄。该fish became the dominant marine vertebrate species. On land, plants evolved and primitive plants, trees, and shrub-like forests served as new habitats. With the evolution of land plants, the animals, too, evolved and diversified. Amphibians were the first四足动物s到出现。他们身边出现3.64亿年前

Emergence of the amniotes

在石炭纪(360至300万年前),一个主要的进化事件发生。奠定羊膜卵四足动物出现。羊膜卵在干燥的环境中铺设允许的四足动物羊膜to move father away from the waterside and thereby dominate farther inland. Because of this, these early amniotes diversified greatly towards the end of this period.

Permian reptiles

二叠期间(300 to 250 million years agoreptiles和synapsids蓬勃发展。不久,一个主要的进化事件发生,而导致猛兽面临therapsids的出现。这些therapsids后来引起了cynodonts(哺乳动物的早期祖先)。第一祖龙(恐龙的早期祖先)也出现在二叠纪时期。

“Age of the Dinosaurs”

继古生代是中生代(252 to 66 million years ago),其被称为“恐龙的时代”。该恐龙s roamed and dominated the Earth. However, a mass extinction event occurred. They perished together with the other large animals (>25 kg in weight) by the end of this era.

“New Life”

在未来的时代,新生代(6600万年以前到现在) era is called the “New Life”.Mammals expanded and diversified. The great apes evolved and led to the evolution of hominids, which was the evolutionary line that led to the Homo species. The only extant species of the genus智人is the智人(anatomically modern humans).

研究进化

演化ary biology是一种生物学子字段主要侧重于发展。在进化生物学专家称为进化生物学家。Some of the major topics arenatural selection遗传漂变biodiversity,and形态
Charles Darwin1809-1882被许多人认为是进化生物学为他的科学贡献的“父亲”考虑,如他通过自然选择进化理论。1858年,他的理论被刊登在了联合出版Alfred Russel Wallace1823–1913, a naturalist who independently formulated a similar theory. This prompted Darwin to publishOn the Origin of Speciesin 1859 where he explicated his ideas in details. In brief, the theory posited that natural selection (‘survival of the fittest’) caused the branching pattern of evolution. Darwin believed in the common ancestors from where species descended from.
查尔斯·达尔文可能是最具代表性的人在这个领域,但他不是一个人在塑造进化思想。卡尔·林奈1707至1778年,例如,通过他在1735年他归类到生物体基于物理相似点和不同层次群体的生物生物学分类帮助。让 - 巴蒂斯特·拉马克1744年至1829年提出的“嬗变论”,他推测物种的嬗变。因此,生物开始通过自发生成简单的生命形式,然后成为随着时间的推移越来越复杂。此外,他认为,植物或动物的器官可能改变基于使用或废弃,而这种变化是可遗传的。拉马克的理论被视为发展的第一完全成形的理论。但是,与达尔文谁在共同祖先认为,拉马克没有。
在进化生物学incorpora当前的研究tes the methods of mathematical and theoretical biology and of molecular genetics. The modern synthesis makes use of a mathematical framework that reconciles Darwin’s theory of evolution and Gregor Mendel’s laws of heredity to come up with a unified theory of evolution.

Etymology

  • 拉丁进化论(“an unrolling, unfolding”), ex- (“from, out of”) + volere (“to roll”)

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References

  1. Bryner,J.(2008年31月)。“遗传突变使那些棕色眼睛蓝色”。MSNBC.从...获得链接
  2. “All Blue-Eyed People Have This One Thing In Common”.IFLScience。从...获得链接

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