章节大纲

  • 常规

    全部折叠 展开全部

  • 物种起源

    What you will learn
    ::你会学到什么

    • How new evolve through
      ::新的变化如何通过
    • Allopatric and sympatric speciation
      ::异族和同族种族

    A rushing river surrounded by forest, illustrating separation of organisms due to geographical barriers.

    How can a river influence evolution?
    ::河流如何影响进化?

    Imagine a group of small organisms , such as mice, that become separated by a mighty river. This group has now become isolated and formed two separate groups. The groups are obviously no longer able to breed together. Over many generations, each group will evolve separately, eventually forming two completely new species of mice.
    ::想象一小类生物,如小鼠,被一条强大的河流隔开。这一类生物现已变得孤立,形成两个不同的组。这些组显然不再能够共同繁殖。在许多代人中,每个组将分别演变,最终形成两个全新的小鼠物种。

    Origin of Species
    ::物种起源

    is evolution over geologic time above the level of the species. One of the main topics in macroevolution is how new species arise. The process by which a new species evolves is called speciation . How does speciation occur? How does one species evolve into two or more new species?
    ::地质时间的进化高于物种水平。 宏观进化的一个主要议题是新物种是如何产生的。 新物种的进化过程被称为分层。 物种是如何发生的? 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’s 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 the 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.
    ::为了了解新物种的形成方式,重要的是要审查物种是什么。 物种是一组有机体,在自然界中可以共同繁殖和产生繁殖后代。 要产生新物种,某些物种必须从生殖上与其它物种隔离开来。这意味着他们不能再与物种的其他成员发生接触。 通常,它们会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 is described in the Table .
    ::假设某一物种的某些成员在地理上与该物种的其他物种隔开,如果保持足够长的隔开,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发生血缘关系,它们就会演变成一个新的物种。以这种方式出现的特征被称为异族物种特征。一个实例在表格中描述。

    A Kaibab squirrel perched on a tree branch, showcasing its distinctive white tail.

     

    • Kaibab squirrels are found only on the north rim of the Grand Canyon, on the Kaibab plateau.
      ::Kaibab松鼠只在Kaibab高原大峡谷北端发现。
    • Kaibab squirrels became geometrically isolated from Albert's squirrels, which are found on the south rim of the canyon.
      ::Kaibab松鼠从阿尔伯特的松鼠的几何上分离出来 松鼠在峡谷南端被发现
    • In isolation, Kaibab squirrels evolved distinct characteristics, such as a completely white tail.
      ::孤立地说,Kaibab松鼠形成了独特的特征,如完全白色的尾巴。
    • Kaibab squirrels are currently classified as a sub-species of Albert's squirrels.
      ::Kaibab松鼠目前被归类为Albert松鼠的亚种。
    • Kaibab squirrels may eventually become different enough to be classified as a separate species.
      ::Kaibab松鼠最终可能变得与众不同,可被划为单独的物种。
    Albert's squirrel among leaves, showcasing its gray fur and prominent ears.
    • Albert's squirrels occupy a larger area on the south rim of the Grand Canyon.
      ::阿尔伯特的松鼠占据了大峡谷南边更大的区域
    • Albert's squirrels are the original species from which Kaibab squirrels diverged.
      ::阿尔伯特的松鼠是凯巴巴松鼠的原始物种

    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 shows one way this can occur.
    ::较不常见的情况是,新物种在没有地理分离的情况下出现。这被称为同父异母的物种特征。下面的例子说明了一种可能发生的方式。

    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. and often grow near hawthorn trees. Some hawthorn flies started to lay eggs in nearby apple trees. When the eggs hatched, the larvae fed on apples.
      ::苹果树被引入美国,并常常在哈霍恩树附近生长。 一些哈霍恩苍蝇开始在附近的苹果树上产卵。 当蛋孵化时,幼虫靠苹果喂养。
    3. Over time, the two fly populations—those that fed on hawthorn trees and those that preferred apple trees—evolved reproductive isolation. Now they are reproductively isolated because they breed at different times. Their breeding season matches the season when the apple or hawthorn fruits mature.
      ::随着时间推移,两种苍蝇——即那些靠长角树为食的苍蝇和那些偏爱苹果树的苍蝇——在生殖上与世隔绝,现在它们由于在不同的时间繁殖而处于生殖上的孤立状态,它们的繁殖季节与苹果或长角水果成熟的季节相匹配。
    4. Because they rarely interbreed, the two of flies are evolving other genetic differences. They appear to be in the process of becoming separate species.
      ::苍蝇很少相互插手,因此它们正在演变其他基因差异。 它们似乎正在成为独立的物种。
    • Close-up of a fly, likely illustrating hawthorn or apple fly species.
      Hawthorn fly

      ::霍桑飞翔
    • Hawthorn fruits on the tree, related to sympatric speciation in hawthorn flies.
      Hawthorn tree

      ::霍桑树
    • A cluster of red apples hanging from a tree branch against a blue sky background.
      Apple tree

      ::苹果树

    Check your understanding!
    ::检查你的理解!

     

     

     

    Summary
    ::摘要

    • New species arise in the process of speciation.
      ::在物种划分过程中出现了新物种。
    • Allopatric speciation occurs when some members of a species become geographically separated. They then evolve genetic differences. If the differences prevent them from interbreeding with the original species, a new species has evolved.
      ::当某一物种的某些成员在地理上被分离时,就会出现异族异族现象,然后它们演变出遗传差异。如果这些差异阻止它们与原始物种发生血缘关系,新物种就演变了。
    • Sympatric speciation occurs without geographic separation, such as changes in behavior and different breeding seasons.
      ::血缘特征的发生没有地理上的分离,例如行为变化和不同的繁殖季节。

    Review
    ::回顾

    1. Define speciation.
      ::定义物种。
    2. Describe how allopatric speciation occurs.
      ::描述如何发生同父异母的特征。
    3. Why is sympatric speciation less likely to occur than allopatric speciation?
      ::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?