章节大纲

  • 常规

    全部折叠 展开全部

  • 物种起源

    A variety of colorful seashells displayed together, showcasing marine biodiversity.

    Where did this diversity of life come from?
    ::生命的多样性来自何方?

    If you have ever been to the beach, then you realize there is not just one species of marine life. The wide variety of shells that wash up on the beach indicate that there are many forms of life in the ocean. This wide diversity of life requires that many new species have appeared over time. But how does a new species come into being?
    ::如果你去过海滩,那么你就会意识到,不仅有海洋生物的物种。在海滩上洗涤的种类繁多的炮弹表明,海洋中存在着多种生命形式。这种广泛的生命多样性要求许多新的物种会随着时间的流逝而出现。但是,一个新的物种是如何形成的呢?

    The Origin of Species
    ::物种起源

    The creation of a new species is called speciation . Most new species develop naturally. But humans have also artificially created new breeds and species for thousands of years.
    ::新物种的创造被称为物种特征。 多数新物种自然地发展。 但人类在数千年的时间里还人为地创造了新物种和新物种。

    New species develop naturally through the process of . Due to natural selection, organisms with traits that better enable them to adapt to their environment will tend to survive and reproduce in greater numbers. Natural selection causes beneficial heritable traits to become more common in a and unfavorable heritable traits to become less common. For example, a giraffe’s neck is beneficial because it allows the giraffe to reach leaves high in trees. Natural selection caused this beneficial trait to become more common than short necks.
    ::新物种通过自然选择过程自然地发展。由于自然选择,具有更好地适应其环境的特性的生物往往会存活并大量繁殖。 自然选择导致有益的遗传特征在不受欢迎的遗传特征中变得更为常见。 比如,长颈鹿的颈部是有用的,因为它允许长颈鹿接触到树中的高叶。 自然选择使得这种有益的特征比短颈更为常见。

    As new changes in the sequence are constantly being generated in a population's gene pool (changing the population's allele frequencies), some of these changes will be beneficial and result in traits that allow adaptation and survival. Natural selection causes evolution of a species as these beneficial traits become more common within a population. Evolution can occur within a species without completely resulting in a new species. Therefore, evolution and speciation are not the same.
    ::随着人口基因库中不断产生新的基因序列变化(改变人口同源频率),其中一些变化将是有益的,并产生能够适应和生存的特性。自然选择导致物种的进化,因为这些有益的特性在人群中越来越常见。进化可能在物种中发生,而不会完全导致新的物种。因此,进化和分化是不一样的。

    Artificial Selection
    ::人工选择

    Artificial selection occurs when humans select which plants or animals to breed in order to pass on specific traits to the next generation. For example, a farmer may choose to breed only cows that produce the best milk. Farmers would also avoid breeding cows that produce less milk. In this way, selective breeding of the cows would increase milk quality and quantity.
    ::人工选择发生在人类选择哪些植物或动物繁殖以将特定特性传给下一代时。 比如,农民可能选择只饲养生产最佳牛奶的奶牛。 农民也会避免饲养奶量较少的奶牛。 这样,选择性饲养牛可以提高奶的质量和数量。

    Humans have also artificially bred dogs to create new breeds ( Figure ).
    ::人类还用人工培育的狗来创造新的品种(图)。

    Two different dog breeds illustrate artificial selection in breeding practices.

    Artificial Selection: Humans used artificial selection to create these different breeds. Both dog breeds are descended from the same wolves, and their genes are almost identical.
    ::人造选择:人类利用人工选择来创造这些不同的品种。 这两种狗种都是同一种狼种的后裔,它们的基因几乎完全相同。

    Reproductive Isolation
    ::隔离生殖

    There are two main ways that speciation happens naturally. Both processes create new species by reproductively isolating populations of the same species from each other. Organisms can be geographically isolated or isolated by a behavior. Either way, they will no longer be able to mate. Over a long period of time, usually thousands of years, each of the isolated populations evolves in a different direction, forming distinct species.
    ::物种分化自然有两种主要方式。 这两种过程通过在生殖上将同一物种的种群相互隔离来创造新的物种。 生物可以在地理上孤立, 或由某种行为隔离。 不论哪种方式, 它们都不再能够交配。 在很长的一段时间里, 通常是几千年, 每个孤立的种群都朝着不同的方向发展, 形成不同的物种 。

    How do you think scientists test whether two populations are separate species? They bring species from two populations back together again. If the two populations do not mate and produce fertile offspring , they are separate species.
    ::你认为科学家如何测试两个种群是否是不同的物种?它们将两个种群的物种重新凝聚在一起。如果这两个种群不交配并产生肥沃的后代,那么它们是不同的物种。

    Geographic Isolation
    ::地理隔离

    Allopatric speciation occurs when groups from the same species are geographically isolated for long periods. Imagine all the ways that plants or animals could be isolated from each other:
    ::当同一物种的组群在地理上被长期隔绝时,就会出现异族物种。想象一下植物或动物可以相互隔离的所有方式:

    • Emergence of a mountain range.
      ::山地山脉的出现。
    • Formation of a canyon.
      ::峡谷的形成
    • New rivers or streams.
      ::新的河流或溪流。

    Here are two examples of allopatric speciation:
    ::以下是两个同父异母的分化的例子:

    • Darwin observed thirteen distinct finch species on the Galápagos Islands that had evolved from the same ancestor . Different finch populations lived on separate islands with different environments. They evolved to best adapt to those particular environments. Later, scientists were able to determine which finches had evolved into distinct species by bringing members of each population together. The that could not mate were a separate species.
      ::达尔文观测到加拉帕戈斯群岛上13个不同的芬奇物种,这些物种从同一个祖先演变而来。不同的芬奇种群居住在不同环境的不同岛屿上,它们最能适应这些特定环境。后来,科学家们通过将每个种群的成员聚集在一起,能够确定哪些鳍类已经演变成不同的物种。不能交配的是不同的物种。
    • When the Grand Canyon in Arizona formed, two populations of one squirrel species were separated by the giant canyon. After thousands of years of isolation from each other, the squirrel populations on the northern wall of the canyon looked and behaved differently from those on the southern wall ( Figure ). North rim squirrels have white tails and black bellies. Squirrels on the south rim have white bellies and dark tails. They cannot mate with each other, so they are different species.
      ::当亚利桑那州的大峡谷形成时,一个松鼠物种的两个种群被巨大的峡谷隔开。经过数千年的隔绝之后,峡谷北墙上的松鼠种群与南墙上的松鼠种群(Figure ) 不同, 看上去和行为方式不同。北边松鼠有白色尾巴和黑色贝子。南边的松鼠有白色贝子和黑暗尾巴。它们不能相互交配,因此它们是不同的物种。

    Abert squirrel and Kaibab squirrel compared, showing different colors and traits.

    Abert squirrel ( left ) on the southern rim of the Grand Canyon. Kaibab squirrel ( right ) found on northern rim of the Grand Canyon.
    ::大峡谷南端的松鼠(左侧),在大峡谷北端发现的Kaibab松鼠(右侧)。

    Isolation without Physical Separation
    ::无实际隔离隔离的隔离

    Sympatric speciation occurs when groups from the same species stop mating because of something other than physical or geographic separation. The behavior of two groups that live in the same region is an example of such separation. The separation may be caused by different mating seasons, for example. Sympatric speciation is more difficult to identify.
    ::同一物种的组群因物理或地理分离以外的原因停止交配时,即发生血缘分离。居住在同一区域的两个组群的行为就是这种分离的一个例子。例如,分离可能是不同的交配季节造成的。血缘分离更难识别。

    Here are two examples of sympatric speciation:
    ::以下是两个血缘特征的例子:

    • Some scientists suspect that two groups of orcas (killer whales) live in the same part of the Pacific Ocean part of the year but do not mate. The two groups hunt different prey species, eat different foods, sing different songs, and have different social interactions ( Figure ).
      ::有些科学家怀疑两组虎鲸(杀手鲸)在一年的太平洋同一部分生活,但并不配对。 这两组动物猎食不同的猎物,吃不同的食物,唱不同的歌曲,有不同的社会互动(图 ) 。
    • Two groups of Galápagos Island finch species lived in the same space, but each had his or her own distinct mating signals. Members of each group selected mates according to different beak structures and bird calls. The behavioral differences kept the groups separated until they formed different species.
      ::加拉帕戈斯岛的两组芬奇物种生活在同一个空间,但每个组都有自己的不同的交配信号。每个组的成员根据不同的嘴唇结构和鸟类召唤选择了伴侣。行为差异使得这些组保持了分离,直到它们形成不同的物种。

    Two orca whales swimming side by side in the ocean.

    Scientists suspect that two types of orca whales live in the same part of the Pacific Ocean for part of the year, but they do not mate.
    ::科学家怀疑有两种类的美洲豹鲸在太平洋同一地区生活了一年的一部分时间,但它们并不交配。

    Summary
    ::摘要

    • Speciation, the creation of a new species, can happen through natural selection or artificial selection.
      ::通过自然选择或人为选择,可以创造新的物种。
    • Reproductive isolation is necessary for speciation to occur, and this can happen through a geographic barrier (allopatric speciation) or without a geographic barrier (sympatric speciation).
      ::生殖隔离是出现物种特征的必要条件,这可以通过地理障碍(允许的物种特征)或没有地理障碍(同父异母的物种特征)实现。
    • Different behaviors can result in sympatric speciation.
      ::不同的行为可能导致共产主义的分化。

    Explore More
    ::探索更多

    Use the resources below to answer the questions that follow.
    ::利用以下资源回答以下问题。

    Explore More I
    ::探索更多

    • Allopatric Speciation at .
      ::国与国之间的拼写
    1. What is allopatric speciation?
      ::什么是异父派的特征?
    2. Give two examples of events that can cause physical separation of members of a population?
      ::举两个可以造成人口成员实际分离的事件的例子?
    3. How did scientists determine if the shrimp were two different species?
      ::科学家如何确定虾是两种不同的物种?

    Explore More II
    ::探索更多情况二

    • Richard Dawkins: Diatoms: The Evolution of a New Species at  (2:10)

      ::Richard Dawkins: Diatoms:新物种的演变(2:10)
    1. What is a diatom?
      ::亚原子是什么?
    2. Where is Stephanodiscus yellowstonensis found?
      ::Stephano讨论黄石碑在哪里找到的?
    3. What technique did scientists use to determine what diatoms occurred historically in the lake where Stephanodiscus yellowstonensis now occurs?
      ::科学家用什么技术来决定 亚原子在史蒂芬诺讨论黄石本的湖中 曾经发生过什么?
    4. What were the environmental conditions when Stephanodiscus niagarae lived in the lake?
      ::Stephanodiscuss niagarae在湖中居住时的环境状况如何?
    5. What has happened to the diatoms in the lake as the climate has changed over the last 14,000 years?
      ::过去14000年的气候变化 湖中的二亚原子到底怎么了?

    Review
    ::回顾

    1. Compare and contrast natural selection and artificial selection.
      ::比较和对比自然选择和人工选择。
    2. What is meant by reproductive isolation?
      ::生殖隔离意味着什么?
    3. Compare and contrast allopatric speciation and sympatric speciation.
      ::比较和对比异族血统和异族血统。