章节大纲

  • Fossilized crinoid displaying intricate details, illustrating marine life from Earth's history.

    What's on this rock?
    ::这块石头上是什么?

    This rock contains a fossilized marine animal known as a crinoid . Scientists study fossils of plants, animals, and other organisms in order to better understand what life was like on Earth many years ago and how it has changed over time. Fossils are important evidence for the theory of evolution.
    ::科学家研究植物、动物和其他生物的化石,以便更好地了解多年前地球上的生命是什么样子,以及它如何随时间变化。 化石是进化理论的重要证据。

    The Fossil Record
    ::化石记录

    Fossils are the preserved remains of animals, plants, and other organisms from the distant past. Examples of fossils include bones , teeth, and impressions. By studying fossils, evidence for evolution is revealed. Paleontologists are scientists who study fossils to learn about life in the past. Fossils allow these scientists to determine the features of extinct species . Paleontologists compare the features of species from different periods in history. With this information, they try to understand how species have evolved over millions of years ( Figure ).
    ::化石是远古动物、植物和其他生物的残骸。 化石的例子包括骨头、牙齿和印象。 通过研究化石,可以揭示进化的证据。 古生物学家是研究化石以了解过去生活的科学家。 化石允许这些科学家确定灭绝物种的特征。 古生物学家比较了历史上不同时期的物种特征。 有了这些信息,他们试图了解物种是如何在数百万年中演变的( 图表 ) 。

    Comparison of horse evolution, depicting teeth and leg bone changes over time.

    Evolution of the horse. Fossil evidence, depicted by the skeletal fragments, demonstrates evolutionary milestones in this process. Notice the 57 million year evolution of the horse leg bones and teeth. Especially obvious is the transformation of the leg bones from having four distinct digits to that of today's horse.
    ::马的进化。骨骼碎片所描述的化石证据证明了这一过程的进化里程碑。注意马腿骨和牙齿的5 700万年进化。特别明显的是腿骨从四位不同的数字转换为今天的马。

    Until recently, fossils were the main source of evidence for evolution ( Figure ). Through studying fossils, we now know that today's organisms look much different in many cases than those that were alive in the past. Scientists have also shown that organisms were spread out differently across the planet. Earthquakes, volcanoes, shifting seas, and other movements of the continents have all affected where organisms live and how they adapted to their changing environments.
    ::直到最近,化石是进化的主要证据来源(图 ) 。 通过研究化石,我们现在知道,在很多情况下,今天的有机体看起来都与过去的生物体大不相同。 科学家们还表明,生物体分布在地球各地的情况也不同。 地震、火山、变化的海洋和其他大陆运动都影响到生物体生活的地方以及它们如何适应不断变化的环境。

    Fossilized fly in amber, illustrating preservation of organisms from the Eocene epoch.

    A fly trapped in a gooey substance, called resin, that comes from trees. The fossils in the movie Jurassic Park were trapped in resin.
    ::一只被困在一种叫树脂的谷类物质的苍蝇,它来自树木。电影《侏罗纪公园》中的化石被困在树脂中。

    Rock Layers and the Age of Fossils
    ::岩层和化石时代

    There are many layers of rock in the Earth's surface. Newer layers form on top of the older layers; the deepest rock layers are the oldest. Therefore, you can tell how old a is by observing in which layer of rock it was found. The fossils and the order in which fossils appear is called the fossil record . The fossil record provides evidence for when organisms lived on Earth, how species evolved, and how some species have gone extinct. Geologists use a method called radiometric dating to determine the exact age of rocks and fossils in each layer of rock. This technique, which is possible because radioactive materials decay at a known rate, measures how much of the radioactive materials in each rock layer have broken down ( Figure ).
    ::地球表面有许多层的岩石。 新的层层在老层的顶部形成; 最深层的岩层是最古老的。 因此, 您可以通过观察发现岩层的哪一层来判断岩层的年代。 化石和化石出现的顺序被称为化石记录。 化石记录为生物在地球上生存的时间、 物种如何演变以及某些物种如何灭绝提供了证据。 地质学家使用一种叫作辐射测定日期的方法来确定岩石和矿物在每一层岩石中的确切年代。 这种技术是可能的, 因为放射性物质以已知的速度腐烂, 测量每个岩石层中多少放射性物质已经破裂( 图 ) 。

    A laboratory spectrophotometer used for measuring radioactive decay in rock and fossil samples.

    This device, called a spectrophotometer, can be used to measure the level of radioactive decay of certain elements in rocks and fossils to determine their age.
    ::这个称为光谱光谱仪的装置可用于测量岩石和化石中某些元素的放射性衰变程度,以确定其年龄。

    Radiometric dating has been used to determine that the oldest known rocks on Earth are between 4 and 5 billion years old. The oldest fossils are between 3 and 4 billion years old. Remember that during Darwin's time, people believed the Earth was just about 6,000 years old. The fossil record proves that Earth is much older than people once thought.
    ::辐射测定日期被用来确定地球上最古老的已知岩石在40亿到50亿之间。最古老的化石在30亿到40亿之间。记住达尔文时代人们相信地球只有6000岁。化石记录证明地球比人们想象的要老得多。

    Summary
    ::摘要

    • Fossils, or preserved parts of organisms from the distant past, have shown that species change over time.
      ::古老的原生生物或保存的生物部分表明,物种随时间而变化。
    • Radiometric dating can be used to determine the age of fossils by measuring the how much of the radioactive materials in each rock layer have broken down.
      ::通过测量每个岩石层的放射性材料的碎裂程度,可以使用辐射测量日期来确定化石的年代。

    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

    • James Hagadorn, Paleontologist: Traces of Early Animal Life
      ::James Hagadorn, 帕莱翁学家:早期动物生命的踪迹

     

     

    1. Why is it believed the first animals left no fossilized bones?
      ::为什么相信第一批动物 没有留下化石化的骨头?
    2. What do paleontologists look for when they search for evidence of early organisms?
      ::古生物学家在寻找早期生物的证据时 寻找什么?
    3. How old are the geologic deposits Dr. Hagadorn is searching? How old is the evidence he has found for the first mobile organisms?
      ::哈加多恩博士正在搜寻的地质矿床几岁了?他为第一批移动生物找到的证据几岁了?
    4. What does the ability to hunt others do to the fossil record? Why?
      ::猎杀他人的能力对化石记录有什么作用?

    Explore More II
    ::探索更多情况二

    • Jenny Clack, Paleontologist: The First Vertebrate Walks on Land
      ::Jenny Clack,Paleontlogist:第一次静脉步行在陆地上

     

     

    1. What is a "tetrapod"? What question do paleontologists hope they can answer by studying them?
      ::古生物学家希望通过研究他们能回答什么问题?
    2. What is special about "Boris"?
      ::"Boris"有什么特别的?

    Explore More III
    ::探索更多三

    • Why This Whale Ancestor is an Evolutionary Surprise at  (2:54)

      ::为什么这个鲸鱼祖先 是一个进化惊喜 在(2: 54)
    1. What is the ancestor of modern whales?
      ::现代鲸鱼的祖先是什么?
    2. Was the ancestor terrestrial, aquatic, or live on both land and in water?
      ::祖先是陆生、水生、还是既生活在陆地上,又生活在水中?
    3. What physical transformations occurred to allow for the fully aquatic life modern whales have today?
      ::现代鲸鱼今天为了让水生生物 完全存活而发生的物理变异是什么?

    Review
    ::回顾

    1. What is a fossil? Give three examples.
      ::化石是什么?请举三个例子。
    2. What has the fossil record revealed about life on Earth?
      ::化石记录揭示了地球上的生命吗?
    3. How does radioactive dating work?
      ::放射性约会如何运作?
    4. What is radioactive dating used for?
      ::放射性日期是用来做什么的?