2.4化石
章节大纲
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Lesson Objectives
::经验教训目标- Explain what fossils are.
::解释化石是什么
- Describe how fossils form.
::描述化石的形态
- State what scientists can learn from fossils.
::科学家们能从化石中学到什么
Lesson Vocabulary
::词汇表课程- fossilization
::化化
- index fossil
::指数化化石
Introduction
::导言For thousands of years, people have found fossils. The fossils caused curiosity about Earth's past. How did these organisms live? What type of world did they live in? Fossils can tell us a lot about Earth's history.
::数千年来,人们都发现了化石。化石引起了人们对地球过去好奇。这些生物是如何生存的?他们生活在什么样的世界中?化石可以告诉我们很多关于地球历史的事情。In ancient times, fossils inspired myths and stories. These stories included tales of monsters and other incredible creatures. What type of creature do you know that could inspire such stories? Of course, dinosaur fossils were once mistaken for dragon's bones.
::在古代,化石激发了神话和故事。这些故事包括怪物和其他神奇生物的故事。你知道哪种生物可以激发这样的故事?当然,恐龙化石曾经被误认为龙骨。Two thousand years ago, people discovered fossils in China. At the time, they were thought to be dragon bones. We know now that these were not bones, but fossils. So what is the difference?
::两千年前,人们在中国发现了化石。当时,他们被认为是龙骨。我们现在知道这些不是骨头,而是化石。有什么区别呢?What Are Fossils?
::什么是化石?Fossils are preserved in two ways. They can be the remains of organisms or traces of them. These organisms lived in Earth's past.
::化石有两种保存方式。它们可以是生物的残骸,也可以是它们的痕迹。这些生物生活在地球的过去。Most fossils that are found are hard parts from ancient organisms. These hard parts are remains such as teeth, bones, and shells. Examples of these kinds of fossils are pictured in Figure .
::大部分发现的化石都是古代生物的硬化石,这些硬化石是牙齿、骨头和贝壳等硬化石。图中可图出这类化石的例子。Preserved traces can include footprints, burrows, or even wastes. Examples of trace fossils are also shown in Figure .
::保存的痕迹可能包括脚印、洞穴,甚至废物。 图中还显示了痕迹化石的例子。A variety of fossil types are pictured here. Preserved Remains: (A) teeth of a cow, (B) nearly complete dinosaur skeleton embedded in rock, (C) sea shell preserved in a rock. Preserved Traces: (D) dinosaur tracks in mud, (E) fossil animal burrow in rock, (F) fossil feces from a meat-eating dinosaur in Canada.
::这里描绘了各种各样的化石类型。 保存的遗迹是A) 牛的牙齿,(B) 几乎完整的恐龙骨骼嵌入岩石,(C) 保存在岩石中的海壳。(D) 泥土中的恐龙足迹,(E) 岩石中的化石动物洞穴,(F) 加拿大食肉恐龙的化石粪便。
How Fossils Form
::化石如何形成The process by which fossils form is called fossilization . Most fossils form in sedimentary rocks.
::化石形成的过程被称为化石化化,大多数化石形成沉积岩石。Fossils in Sedimentary Rock
::沉积岩中的化石Most fossils form from a dead organism. These organisms are then buried in sediment. Layers of sediment slowly build up. The sediment is buried by even more sediment. Over time, the sediment turns into sedimentary rock. The remains of the organisms also turn to rock. The remains are replaced by minerals. The remains of the old plants and animals literally turn to stone. This process is shown in Figure .
::大多数化石来自死亡生物体,这些生物随后被埋在沉积物中;沉积物层慢慢积聚;沉积物被更多的沉积物掩埋;随着时间的推移,沉积物变成沉积岩;生物的残骸也变成岩石;遗骸被矿物质所取代;旧植物和动物的残骸实际上变成了石头。这个过程在图中显示。Fossilization. This flowchart shows how most fossils form.
::化石化。这个流程图显示了大多数化石是如何形成的。Other Ways Fossils Form
::其他方式 化石形式Fossils may form in other ways. Sometimes fossils are preserved almost completely. In this process, the organism doesn't change much. As seen below, tree sap may cover an organism. With time, the sap turns into amber. The original organism is preserved. This is very exciting for scientists. They are able to study the DNA of the fossilized organism. Organisms can also be completely preserved in tar or ice.
::化石可能以其他方式形成。 有时化石几乎被完全保存。 在此过程中, 有机体不会发生多大变化 。 如下文所示, 树苗可能覆盖有机体。 随着时间的推移, 树苗会变成琥珀。 原始生物会受到保护。 这对科学家来说是非常令人兴奋的。 他们可以研究化石生物的DNA。 生物体也可以被完全保存在焦油或冰中 。Have you ever walked in soft mud and left footprints? In just the right situation, these types of traces of organisms can be preserved. In this case, nothing is left of the organism. Molds and casts are another way organisms can be fossilized. A mold is an imprint of an organism that is preserved in rock. The organism's remains break down completely. The impression left behind by the organism forms a mold, or impression. This mold is then filled with other rock. The fossil that forms in the mold is called a cast. Molds and casts usually form in sedimentary rock. You can read about them in Figure .
::你曾经走过软泥和左脚足迹吗? 在正确的情况下,这些生物的痕迹是可以保存的。 在这种情况下,没有生物留下任何痕迹。 模具和石膏是生物被化化的另一种方式。 模具是保存在岩石中的有机体的印记。 有机体的残骸完全碎裂。 有机体留下的印象形成一个模具或印象。 这个模具随后被填满了其他岩石。 模具中的化石被称为石膏。 石膏和石膏通常以沉积岩的形式形成。 您可以在图中读取它们 。Ways Fossils Form. (A) Complete Preservation. This spider looks the same as it did the day it died millions of years ago! (B) Molds and Casts. A mold is a hole left in rock after an organism's remains break. A cast forms from the minerals that fill that hole and solidify. (C) Compression. A dark stain is left on a rock that was compressed. These ferns were fossilized by compression.
:Why Fossilization Is Rare
::为什么化石化是稀有的For fossils to form, conditions must be just right. It’s very unlikely organisms will become a fossil. Why don't many dead organisms get turned into fossils?
::化石形成的条件必须是正确的。 它极不可能成为化石。 为什么许多死生物不变成化石呢?The soft remains of many organisms are eaten by other animals. Insects may break down remains. Others may be broken down by the elements. Insects too may break down remains.
::许多生物体的软残骸被其他动物吃掉,昆虫可能会把残骸碎裂,其他则可能按元素细分,昆虫也可能把残骸碎裂。Hard parts are much more likely to become fossils than soft parts. Even an animal's hard parts are unlikely to become a fossil. Fossils of soft organisms, from bacteria to jellyfish, are very rare.
::硬部分比软部分更有可能成为化石。 即使是动物硬部分也不太可能成为化石。 从细菌到水母,软有机体的化石非常罕见。Learning From Fossils
::从化石中学习There have been many organisms that have lived in Earth's past. Only a tiny number of them became fossils. Still, scientists learn a lot from fossils. Fossils are our best clues about the history of life on Earth.
::许多生物都生活在地球的过去,其中只有一小部分成为化石。不过,科学家还是从化石中学到了很多东西。化石是我们了解地球生命史的最佳线索。Fossils provide evidence about life on Earth. They tell us that life on Earth has changed over time. Fossils in younger rocks look like animals and plants that are living today. Fossils in older rocks are less like living organisms.
::化石提供了地球上生命的证据。它们告诉我们,地球生命随着时间的变化而变化。在较年轻的岩石中,化石看起来像今天生活的动物和植物。老岩石中的化石不像活生物体。Fossils can tell us about where the organism lived. Was it land or marine? Fossils can even tell us if the water was shallow or deep. Fossils can even provide clues to ancient climates.
::化石可以告诉我们有机体住在哪里。它是陆地还是海洋?化石甚至可以告诉我们水是浅水还是深水。 化石甚至可以提供古代气候的线索。Fossil Clues
::化石结壳Fossils give clues about major geological events. Fossils can also give clues about past climates.
::化石可以提供重大地质事件的线索。 化石也可以提供过去气候的线索。- Fossils of ocean animals on the top of Earth's tallest mountain? It's hard to believe, but it is true. These fossils were found on at the top of Mt. Everest. Mt. Everest is the highest mountain on Earth. These fossils showed that this entire area was once at the bottom of a sea. It can only mean that Mt Everest was uplifted. In fact, the entire Himalaya mountain range was raised. It was forced up from the collision of two continents. An example is shown in Figure .
::地球最高山顶的海洋动物的化石? 很难相信, 但确实如此。 这些化石是在珠穆朗玛峰顶部发现的。 珠穆朗玛峰是地球上最高的山峰。 这些化石表明整个地区曾一度处于海底。 这只能意味着珠穆朗玛峰被提升了。 事实上,整个喜马拉雅山脉被提升了。 从两个大陆的碰撞中,这些化石被迫上升。图中举了一个例子。
- Fossils of plants are found in Antarctica. Now, Antarctica is almost completely covered with ice. Plants do not grow in Antarctica. According to fossils, they once did. This means that Antarctica was once warmer than it is now. These fossils tell us about Antarctica's past climate.
::南极洲有植物的化石。现在,南极洲几乎完全被冰覆盖。南极洲的植物并不生长。根据化石,它们曾经存在过。这意味着南极洲曾经比现在更温暖。这些化石告诉我们南极洲过去的气候。
What can we learn from fossil clues like this fish fossil found in the Wyoming desert?
::我们从在怀俄明沙漠发现的鱼的化石 等化石线索中能学到什么?Lesson Summary
::经验教训摘要- Fossils are preserved remains or traces of organisms. They lived in Earth's past.
::化石保存着残骸或生物的痕迹 它们活在地球的过去
- Most fossils form in sedimentary rock. Fossils can also be preserved in other ways.
::大多数化石形成沉积岩中,化石也可以以其他方式保存。
- Fossils in younger rocks look like animals and plants that are living today. Fossils in older rocks are less like living organisms.
::更年轻的岩石中的化石看起来像今天生活的动植物。 古老岩石中的化石不像活生物体。
- It is rare for any given organism to become a fossil.
::任何生物很少成为化石。
- Fossils are the best form of evidence about the history of life on Earth. Fossils also provide clues about Earth's past. They can tell us about major geological events and past climates.
::化石是地球生命史的最佳证据形式。 化石也为地球的过去提供了线索。 他们可以告诉我们重大地质事件和过去气候。
Lesson Review Questions
::经验回顾问题Recall
::回顾- What are fossils?
::什么是化石?
- Give examples of trace fossils.
::举例说明痕量化石。
- Why are most preserved remains teeth, bones, or shells?
::为什么大部分被保存起来的都是牙齿、骨头或贝壳?
- Describe how fossils form in sedimentary rock.
::描述化石如何在沉积岩中形成。
- Why is fossilization rare?
::为什么化化化稀罕?
Apply Concepts
::应用概念- Create an original diagram to explain the concept of index fossil. Your diagram should include sedimentary rock layers and fossils.
::创建用于解释索引化石概念的原始图表。 您的图表应该包含沉积岩层和化石 。
Think Critically
::仔细仔细思考- Compare and contrast the frog fossil in Figure and the fossil dinosaur tracks in Figure . Infer what you might learn from each type of fossil.
::比较和对比图中的青蛙化石和图中的化石恐龙足迹。
- Earth’s climate became much cooler at different times in the past. Predict what fossil evidence you might find for this type of climate change.
::地球的气候在过去的不同时期变得更冷酷。 预测你可能找到的这类气候变化的化石证据是什么。
Points to Consider
::需要考虑的要点Fossils can help scientists estimate the ages of rocks. Some types of evidence show only that one rock is older or younger than another. Other types of evidence reveal a rock’s actual age in years.
::化石可以帮助科学家估计岩石的年代。 某些类型的证据表明,只有一块岩石比另一块岩石年长或更小。 其他类型的证据表明岩石的实际年代是年长的。- What evidence might show that one rock is older or younger than another?
::哪些证据可以证明一块岩石比另一块岩石年长或更小?
- What evidence might reveal how long ago rocks formed?
::什么证据能揭示岩石形成多久了?
- Explain what fossils are.
