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    An Evolutionary "Arms" Race
    ::进化“武装”种族

    This garter snake preys on a variety of small , including small called rough-skinned newts.  The newts produce a powerful toxin that is concentrated in their skin. Garter snakes have evolved resistance to this toxin through a series of random genetic , allowing them to safely prey upon the newts. The predator-prey relationship between these animals has created an evolutionary "arms" race. It has resulted in extremely high toxin levels in the newts and ever greater resistance to the toxin in the snakes. This is an example of the of two . Coevolution is a type of .
    ::这种装饰蛇在各种小小的猎物上捕食,包括小的、叫粗皮的牛头。这些牛头产生一种强大的毒素,集中在它们的皮肤上。 袋头蛇通过一系列随机遗传学发展了对这种毒素的抵抗力, 允许它们安全地捕食牛头。 这些动物之间的食肉动物和猎物关系造成了进化“武器”的种族。 它在牛头中造成了极高的毒素水平,对蛇头毒素的抵抗力也越来越大。 这是两种病毒的例子。 革命是一种。

    What Is Macroevolution?
    ::什么是“宏观革命”?

    Macroevolution  is evolution that occurs at or above the level of the species. It  is the result of microevolution taking place over many generations.  Macroevolution may involve evolutionary changes in two interacting species — as in coevolution — or it may involve the emergence of one or more brand new species.
    ::宏观演变是在物种水平上或以上发生的演进,是几代人发生的微演的结果,宏观演进可能涉及两种相互作用的物种的演进变化——如共变——或者可能涉及一种或多种品牌的新物种的出现。

    Origin of Species
    ::物种起源

    One of the main topics in macroevolution is how new species arise. The process by which a new species evolves is called . How does speciation occur? How does one species evolve into two or more new species? 
    ::宏观进化的主要议题之一是新物种是如何出现的。新物种的演变过程被称为 。 物种特征是如何发生的? 一个物种是如何演变成两个或两个以上新物种的?

    To understand how a new species forms, it is important to review what a species is. A species is a group of organisms that can breed and produce fertile offspring together in nature. For a new species to arise, some members of a species must become reproductively isolated from the rest of the species. This means they can no longer interbreed with other members of the species. How does this happen? Usually, they become geographically isolated first.
    ::要了解新物种的形成方式,必须审查物种是什么。一个物种是能够共同繁殖和产生繁殖后代的生物群体。要产生一个新的物种,一个物种的某些成员必须从生殖上与物种的其余部分隔离开来。这意味着他们不能再与物种的其他成员接触。这种情况是如何发生的?通常,它们首先在地理上孤立开来。

    Allopatric Speciation
    ::国与国间团结

    Assume that some members of a species become geographically separated from the rest of the species. If they remain separated long enough, they may evolve genetic differences. If the differences prevent them from interbreeding with members of the original species, they have evolved into a new species. Speciation that occurs in this way is called allopatric speciation . An example of allopatric speciation involves Kaibab squirrels that live on the rim of the Grand Canyon, as described in the figure .
    ::假设某一物种的某些成员在地理上与该物种的其他物种分离,如果保持足够长的时间分离,它们可能会演变出遗传差异。如果这些差异阻止它们与原始物种成员进行血缘接触,它们已经演变成一个新的物种。 以这种方式出现的特征被称为异族恋种。 一如图中描述的那样,异族恋父关系分割的例子涉及生活在大峡谷边缘的凯巴巴松鼠。

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    Allopatric Speciation in the Kaibab Squirrel. The Kaibab squirrel is in the process of becoming a new species.
    ::Kaibab Squirrel的Alolatric Speciation。 Kaibab松鼠正在成为一个新的物种。

    Sympatric Speciation
    ::血后血后血后血后血 血后血后血后 血后血后血后血后血后

    Less often, a new species arises without geographic separation. This is called  sympatric speciation . The following example — featuring hawthorn flies — shows one way that this can occur.
    ::较不常见的情况是,一种新物种在没有地理分离的情况下出现,这称为同父异母的物种特征,下面的例子——以霍霍恩苍蝇为特色——表明了一种可能发生这种情况的方式。

    1. Hawthorn flies lay eggs in hawthorn trees. The eggs hatch into larvae that feed on hawthorn fruits . Both the flies and trees are native to the U.S.
      ::Hawthorn苍蝇在Hawthorn树上产卵。这些蛋孵化成以Hawthorn水果为食的幼虫。这些苍蝇和树都是美国本土的。
    2. Apple trees were introduced to the U.S. by European settlers in the 1600s. A pple trees often grow near hawthorn trees, so some hawthorn flies started to lay eggs in nearby apple trees. When the eggs hatched, the larvae fed on apples.
      ::欧洲定居者在1600年代将苹果树引入美国。 苹果树往往在哈霍恩树附近生长,因此一些哈霍恩苍蝇开始在附近的苹果树上产卵。 当卵子孵化时,幼虫靠苹果喂养。
    3. Over time, the two fly — those that feed on hawthorn fruits and those that feed on apples — evolved reproductive isolation because they breed at different times. Their breeding season matches the season when apples or hawthorn fruits mature.
      ::随着时间的推移,这两只苍蝇——那些靠黄蜂水果为生的苍蝇和那些靠苹果为生的苍蝇——因为在不同的时间繁殖而演变成生殖隔离,它们的繁殖季节与苹果或黄蜂水果成熟的季节相吻合。
    4. Because they rarely interbreed, the two populations of flies are evolving other genetic differences. They appear to be in the process of becoming separate species.
      ::这两组苍蝇很少相互交织,因此正在演变其他基因差异。 它们似乎正在成为独立的物种。

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    Sympatric Speciation in Hawthorn Flies. Hawthorn flies are diverging from one species into two. As this example shows, behaviors and physical traits may evolve and lead to speciation.
    ::Hawthorn Flies的Sympouric Speciation。 Hawthorn的苍蝇从一个物种分为两个物种。正如这个例子所显示的,行为和身体特征可能会演变并导致分化。

    Coevolution
    ::革命

    Evolution generally occurs in response to changes in the environment. Environmental change often involves other species. In fact, many species evolve along with other species with which they interact. This is called coevolution . As one species changes, the other species must also change in order to adapt. The coevolution of rough-skinned newts and garter snakes is described above. Many other cases of coevolution occur in flowering plants and the species that pollinate them. See the picture of the  flowering plant and hummingbird  . The two species  have evolved matching structures. The tubular flowers of the plant are matched by the long, narrow beak of the hummingbird.
    ::环境变化通常会因环境变化而演变,环境变化往往涉及其他物种。事实上,许多物种会与其他物种一起演变。这称为“演化”。随着一种物种的变化,其他物种也必须改变以适应变化。上文说明了粗皮嫩树和吊带蛇的演化。许多其他的演化案例发生在开花植物和授花植物的物种中。见花卉植物和蜂鸟的景象。两种物种都有进化的匹配结构。植物的管状花朵与蜂鸟长的、狭窄的角形相匹配。

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    Results of Coevolution in a Flower and Its Pollinator. The very long mouth part of this hummingbird has coevolved with the tubular flower it pollinates. Only this species of bird can reach the nectar deep in the flower. What might happen to the flower if the bird species went extinct?
    ::这只蜂鸟的长嘴部分与它授粉的管状花朵相融合。只有这种鸟类种类才能到达花朵深处的花蜜。 如果鸟种灭绝,花朵会怎样呢?

     Timing of Macroevolution
    ::宏观演变的时间安排

    Is evolution slow and steady— or does it occur in fits and starts? It may depend on what else is going on, such as changes in climate or geologic conditions.
    ::进化是缓慢而稳定的吗? 进化是恰如其分还是开始呢? 它可能取决于其他正在发生的情况,例如气候或地质条件的变化。

    • When climate and geologic conditions are stable, evolution may occur steadily and gradually. This is how thought evolution occurred. This model of the timing of evolution is called gradualism .
      ::当气候和地质条件稳定时,进化可能会稳定而渐进地发生。这就是进化思想是如何发生的。进化时间的模型被称为渐进式。
    • When climate or geologic conditions are changing, evolution may occur more quickly. Long periods of little change may be interrupted by bursts of relatively rapid change. This model of the timing of evolution is called punctuated equilibrium . It is generally better supported by the than is gradualism.
      ::当气候或地质条件发生变化时,进化可能更快。 长期的微小变化可能会因相对快速的变化而中断。 进化时间的模型被称为“标点平衡 ” 。 一般说来,它比渐进主义得到更好的支持。

    Summary
    ::摘要

    • New species arise in the process of speciation. Allopatric speciation occurs when some members of a species become geographically isolated and evolve genetic differences. If the differences prevent them from interbreeding with the original species, a new species has evolved. Sympatric speciation occurs without geographic isolation first occurring.
      ::在物种划分过程中出现了新物种,当某一物种的某些成员在地理上与世隔绝并演变成遗传差异时,就出现了异族血统的特征,如果差异阻止他们与原始物种发生血缘关系,新物种就会演变。
    • Coevolution occurs when interacting species evolve together. Examples include predator species and their prey, and flowering plants and their pollinators.
      ::当相互作用的物种共同演变时,就会发生演变,例如捕食性物种及其猎物、花卉植物及其授粉者。
    • Darwin thought that evolution occurs steadily and gradually. This model of evolution is called gradualism. The fossil record better supports the model of punctuated equilibrium. In this model, long periods of little change are interrupted by bursts of relatively rapid change.
      ::达尔文认为进化是稳定而渐进的。 这种进化模式被称为渐进。 化石记录更好地支持标点平衡模式。 在这个模式中, 长期的微小变化会因相对快速的变化而中断。

    Review
    ::回顾

    1. Define speciation.
    ::1. 界定范围。

    2. Describe how allopatric speciation occurs.
    ::2. 描述如何发生异父关系特征。

    3. What is gradualism? When is it most likely to apply?
    ::3. 什么是渐进主义?何时最有可能适用?

    4. Describe the timing of evolutionary change according to the punctuated equilibrium model.
    ::4. 按照标出平衡模型描述进化变化的时间。

    5. Why is sympatric speciation less likely to occur than allopatric speciation?
    ::5. 为什么同父异母的物种特征发生的可能性比同父异父的物种特征少?

    6. Why would macroevolution occur more quickly when there are major changes in the environment (such as changing climate or geologic conditions) than when the environment is stable?
    ::6. 当环境发生重大变化(如气候变化或地质条件变化)时,为何宏观革命发生得比环境稳定时更快?

    7. What is reproductive isolation? Why is it necessary for speciation to occur?
    ::7. 什么是生殖隔离?为什么必须进行分化?

    8. Kaibab squirrels are an example of ___________ speciation.
    ::8. Kaibab松鼠是投机的例子。

    9. Imagine there is a large lake that dries up in certain regions, creating several smaller, separate lakes. The original lake had a particular species of fish and some fish got trapped inside each of the smaller lakes as the large lake dried up.
    ::9. 想象一下,在某些地区有一个大湖干涸,形成几个较小的、单独的湖泊,最初的湖泊有特定种类的鱼类,随着大湖干涸,一些鱼类被困在每一个较小的湖泊中。

    a. Is there a greater chance of speciation in the fish in the smaller, separate lakes, or in the original large lake? Explain your answer.
    ::a. 在较小的、分开的湖泊或原大湖中的鱼类中是否有更大的采样机会?解释你的答复。

    b. If new fish species evolve from the original species in the small, separate lakes, would this be sympatric or allopatric speciation? Explain your answer.
    ::b. 如果新的鱼类物种从不同的小湖的原始物种中演变而来,这是共同的还是共同的?解释你的答复。

    c. If speciation occurred in the small lakes as described in part b, and then flooding occurred and the small lakes joined to become one large lake again, do you think the fish are likely to become one species again? Why or why not?
    ::c. 如果如B部分所述在小湖中发生物种划分,然后发生洪水,而小湖又合并成一个大湖,那么你是否认为鱼有可能再次成为单一物种?为什么或为什么不能?

     

    10. True or False:  Speciation due to two populations breeding at different times in the same area is an example of sympatric speciation.
    ::10. 真实或假:同一地区不同时间生育的两群人口造成的血压是血缘分化的一个例子。

     

    11. True or False:  Coevolution always occurs between individuals of the same species.
    ::11. 真实或虚假:同一物种的个人之间总是发生革命。

     

    12. Explain what the “punctuated” and “equilibrium” periods are in the phrase “punctuated equilibrium”.
    ::12. 解释 " 平衡 " 一语中的 " 平衡 " 和 " 平衡 " 期间是什么。

    Explore More
    ::探索更多

    Watch this video about  the coevolutionary relationship between the leaf cutter ant and the fungi on which it feeds: 
    ::观看这段影片, 描述切叶蚂蚁与菌类之间的连动关系:

     

     

     

     

    There is a dizzying diversity of species on our planet. Based on genetic evidence, we know that all of those species evolved from a single ancient ancestor — but how does one species split into many? The answer is: through the evolutionary process of speciation. This video illustrates the speciation process in birds to help you understand the basis of earth's biodiversity: 
    ::我们星球上物种的多样性令人目眩。根据遗传证据,我们知道所有这些物种都从一个古老的祖先演变而来,但一个物种是如何分裂成许多物种的?答案是:通过物种的进化过程。这段视频展示了鸟类的分层过程,帮助你们了解地球生物多样性的基础: