6.3 演变的证据
章节大纲
-
A Horse Is a Horse, of Course, of Course
::马是马,是马,是马,是马,是马,是马,是马,是马This drawing was created in 1848, but it's likely that you recognize the it depicts as a horse. Although horses haven't changed that much since this drawing was made, they have a long evolutionary history during which they did change significantly. How do we know? The answer lies in the .
::这幅绘画是1848年创建的,但很可能你认得它描绘成一匹马。虽然自绘画以来,马没有发生多少变化,但马有很长的进化历史,在此期间,他们确实发生了显著变化。我们怎么知道呢?答案就在于它。Evidence from Fossils
::来自化石的证据are a window into the past. They provide clear evidence that evolution has occurred. Scientists who find and study fossils are called paleontologists . How do they use fossils to understand the past? Consider the example of the horse, outlined in the figure . Fossils spanning a period of more than 50 million years show how the horse evolved.
::它们是过去的一个窗口。 它们提供了已经发生了进化的明显证据。 发现和研究化石的科学家被称为古生物学家。 他们如何使用化石来理解过去? 想想图中描述的马的例子。 横跨五千万年的化石展示了马是如何进化的。Evolution of the Horse. The fossil record reveals how horses evolved.
::马的进化 化石记录揭示了马的进化过程The oldest horse fossils show what the earliest horses were like. They were only 0.4 m tall — about the size of a fox — and they had four long toes. Other evidence shows they lived in wooded marshlands, where they probably ate soft leaves. Through time, the climate became drier, and grasslands slowly replaced the marshes. Later fossils show that horses changed, as well.
::最古老的马化石显示了最早的马匹是什么样子。它们只有0.4米高,大约相当于一只狐狸的大小,它们有四只长脚趾。其他证据表明,它们居住在木质沼泽地,可能吃软叶。随着时间的推移,气候变得干燥,草地慢慢取代了沼泽地。 后来的化石显示,马匹也变了。-
They became taller, which would help them see
predators
while they fed in tall grasses. Eventually, they reached a height of about 1.6 m.
::他们越高越好,在用高草喂食时,就能看见捕食者,最终达到约1.6米高。 -
They evolved a single large toe that eventually became a hoof. This would help them run swiftly and escape predators.
::他们进化了一只大脚趾,最终变成了蹄子。这将有助于他们迅速逃跑并逃离掠食者。 -
Their molars (back teeth) became longer and covered with hard cement. This would allow them to grind tough grasses and grass
seeds
without wearing out their teeth.
::他们的齿轮(后牙)变长了,并被硬水泥覆盖。 这样可以让他们在不磨牙的情况下研磨坚硬的草和草籽。
Evidence from Living Species
::活物种的证据Scientists can learn a great deal about evolution by studying living . They can compare the anatomy, embryos , and of modern organisms to help understand how they evolved.
::科学家可以通过研究生命来学习关于进化的丰富知识。他们可以比较解剖学、胚胎和现代生物,帮助了解它们是如何进化的。Comparative Anatomy
::比较解剖学is the study of the similarities and differences in the structures of different species. Similar body parts may be homologous structures or analogous structures . Both provide evidence for evolution.
::研究不同物种结构的异同。类似身体部分可以是同族结构或类似结构。两者都为进化提供了证据。Homologous structures are structures that are similar between related organisms because they were inherited from a common ancestor . These structures may or may not have the same function in the multiple descendants. The figure shows the upper appendages of several different mammals . They all have the same basic pattern of , although they now have different functions. All of these mammals inherited this basic bone pattern from a common ancestor.
::同族结构是相关生物之间相似的结构,因为它们是从共同祖先继承下来的。这些结构在多个后代中可能具有或可能不具有相同的功能。图中显示了几个不同的哺乳动物的上部附着物。它们都有相同的基本模式,尽管它们现在有不同的功能。所有这些哺乳动物都从共同祖先继承了这一基本骨骼模式。Hands of Different Mammals. The forelimbs of all mammals have the same basic bone structure.
::不同哺乳动物的手 所有哺乳动物的前额骨结构都是一样的Analogous structures are structures that are similar between unrelated organisms. The structures are similar because they evolved to do the same job, not because they were inherited from a common ancestor. For example, the wings of bats and , shown in the figure , look similar on the outside and have the same function. However, wings evolved independently in the two groups of animals, which is apparent when you compare the pattern of bones inside the wings.
::类比结构是非关联生物之间的类似结构。结构相似,因为它们进化为同一工作,不是因为它们是从共同祖先继承下来的。例如,蝙蝠的翅膀和图中显示的蝙蝠的翅膀在外表上看起来相似,并且具有相同的功能。然而,翅膀在两组动物中独立演变,这在比较翅膀内骨头的形态时是显而易见的。Wings of Bats and Birds. Wings of bats and birds serve the same function. Look closely at the bones inside the wings. The differences show they developed from different ancestors.
::蝙蝠和鸟的翅膀,蝙蝠和鸟的翅膀发挥同样的功能。仔细看看翅膀里的骨头。这些差异表明它们是由不同的祖先形成的。Comparative Embryology
::比较内脏学Comparative embryology is the study of the similarities and differences in the embryos of different species. Similarities between embryos are likely evidence of common ancestry. All vertebrate embryos, for example, have gill slits and tails. All of the embryos in the figure , except for , lose their gill slits by , and some of them also lose their tail. In humans, the tail is reduced to the tail bone. Thus, similarities that organisms share as embryos may no longer be present by adulthood. This is why it is valuable to compare organisms in the embryonic stage.
::比较胚胎学是对不同物种胚胎的相似性和差异的研究。胚胎之间的相似性可能是常见的祖先的证明。例如,所有脊椎胚胎都有刺片和尾巴。除(......)外,图中的所有胚胎都因(......)而丧失了刺片,其中一些胚胎也失去了尾巴。在人类中,尾巴被减为尾骨。因此,生物作为胚胎共享的相似性在成年时可能不再存在。这就是为什么在胚胎阶段比较生物是有价值的。Embryos of different vertebrates look much more similar than the animals do at later stages of life. Rows A through C illustrate the development of each embryo, from earliest to latest stages.
::不同脊椎动物的胚胎与生命后期动物的胚胎看起来要相似得多。 A至C行说明了每个胚胎的发育,从最早的阶段到最新的阶段。Vestigial Structures
::立体结构Structures like the human tail bone are called vestigial structures . Evolution has reduced their size because the structures are no longer used. The human appendix is an example of a vestigial structure. It is a tiny remnant of a once-larger organ . In a distant ancestor, it was needed to digest food , but it serves no purpose in the today. Why do you think structures that are no longer used shrink in size? Why might a full-sized, unused structure reduce an organism’s fitness ?
::人类尾骨等结构被称为残余结构。 进化已经缩小了体积,因为结构不再使用。 人类附录是残余结构的一个例子。 它是一个一度大器官的微小残余物。 在一个遥远的祖先,它需要消化食物,但在今天却毫无用处。 为什么你认为不再使用体积结构会缩小? 为什么一个完整、未使用的结构会降低一个生物体的体质?Comparing DNA
::比较DNAcould compare only the anatomy and embryos of living things. Today, scientists can compare their DNA, as well. Similar DNA sequences are the strongest evidence for evolution from a common ancestor. Look at the diagram in the figure . The diagram is a cladogram , a branching diagram showing related organisms. Each branch represents the emergence of new traits that separate one group of organisms from the rest. The cladogram in the figure shows how humans and apes are related based on their DNA sequences.
::只能比较生物的解剖和胚胎。 如今, 科学家也可以比较他们的DNA。 类似的DNA序列是从共同祖先进化的最有力的证据。 看看图中的图表。 图表是一个单形图, 一个显示相关生物的分支图。 每个分支代表着新特征的出现, 将一组生物与其他生物分开。 图中的单形图显示了人类和猿的DNA序列关系。Cladogram of Humans and Apes. This cladogram is based on DNA comparisons. It shows how humans are related to apes by descent from common ancestors.
::人类和人猿的光谱图。 光谱图基于DNA比较。 它显示人类如何通过从共同祖先的血统而与猿类相关。Evidence from Biogeography
::来自生物地球学的证据is the study of how and why organisms live where they do. It provides more evidence for evolution. Let’s consider the camel family as an example.
::这是研究生物体如何和为什么生活在它们所生活的地方。 它为进化提供了更多的证据。 让我们把骆驼家庭当做一个例子。Biogeography of Camels: An Example
::Cames生物地理学:实例Today, the camel family includes different types of camels. They are shown in the figure . All of today’s camels are descended from the same camel ancestors. These ancestors lived in North America about a million years ago.
::如今,骆驼家族包括不同类型的骆驼。 数字中显示了这些骆驼。 今天所有的骆驼都是来自同一批骆驼祖先的后裔。 这些祖先大约在一百万年前就生活在北美。Camel Migrations and Present-Day Variation. Members of the camel family now live in different parts of the world. They differ from one another in a number of traits, but they share basic similarities. This is because they all evolved from a common ancestor. What differences and similarities do you see?
::骆驼迁徙和当今变异:骆驼家庭成员现在生活在世界不同地区,他们在许多特征上彼此不同,但有着基本相似之处。这是因为他们都是从共同祖先演变而来的。你看到了什么不同和相似之处?Early North American camels migrated to other places. Some went to East Asia via a land bridge during the last ice age. A few of them made it all the way to Africa. Others went to South America by crossing the Isthmus of Panama. Once camels reached these different places, they evolved independently. They evolved adaptations that suited them for the particular environment where they lived. Through , descendants of the original camel ancestors evolved the diversity they have today.
::北美早期骆驼迁移到其他地方,有些在上一个冰河时代通过陆桥前往东亚,有些则通过陆桥前往非洲,有些则通过穿越巴拿马地峡前往南美洲,另一些则通过穿越巴拿马地峡前往南美洲,骆驼一旦到达这些不同的地方,它们就独立地演变,它们演变成适合它们所居住特定环境的适应措施。通过这些办法,原始骆驼祖先的后代发展了今天的多样性。Island Biogeography
::岛屿生物地理学The biogeography of islands yields some of the best evidence for evolution. Consider the birds called finches that Darwin studied on the Galápagos Islands (see the figure ). All of the finches probably descended from one bird that arrived on the islands from South America. Until the first bird arrived, there had never been birds on the islands. The first bird was a seed eater. It evolved into many finch species, each adapted for a different type of food. This is an example of adaptive radiation , a process in which a single species evolves into many new species to fill available ecological niches.
::岛屿生物地理学为进化提供了一些最佳证据。 想象一下达尔文在加拉帕戈斯群岛上研究的叫芬奇的鸟类( 见图 ) 。 所有雀巢可能都来自从南美抵达群岛的鸟类。 在第一批鸟类抵达之前,岛上从未出现过鸟类。 第一只鸟是种子食用器。 它演变成许多大小的物种,每个物种都适合不同种类的食物。 这是一个适应性辐射的例子,在这个过程中,一个单一物种演变成许多新的物种,以填补现有的生态位置。Galápagos finches differ in beak size and shape, depending on the type of food they eat.
::加拉帕戈斯的鱼翅在嘴唇大小和形状上各不相同,取决于它们所食食物的类型。Eyewitnesses to Evolution
::向进进进的目击证人In the 1970s, biologists Peter and Rosemary Grant went to the Galápagos Islands to re-study Darwin’s finches. They spent more than 30 years on the project, but their efforts paid off. They were able to observe evolution by natural selection actually taking place.
::1970年代,生物学家彼得(Peter)和罗斯玛丽·格兰特(Rosemary Grant)前往加拉帕戈斯群岛重新研究达尔文的雀巢。 他们花了30多年的时间在这个项目上,但他们的努力取得了成效。 他们通过自然选择观察了实际的演变。While the Grants were on the Galápagos, a drought occurred, so fewer seeds were available for finches to eat. Birds with smaller beaks could crack open and eat only the smaller seeds. Birds with bigger beaks could crack open and eat seeds of all sizes. As a result, many of the smaller-beaked birds died in the drought, whereas birds with bigger beaks survived and reproduced. As shown in the figure , within two years, the average beak size in the finch increased. Evolution by natural selection had occurred.
::当赠款在加拉帕戈斯岛时,发生了干旱,因此,可供鹰翅食用的种子减少了。小嘴鸟可以裂开,只吃小的种子。大嘴鸟可以裂开,吃各种大小的种子。结果,许多小嘴鸟在干旱中死亡,而大嘴鸟则存活和繁殖。如图所示,在两年内,小嘴鸟的平均小嘴尺寸会增加。自然选择的演化已经发生。Evolution of Beak Size in Galápagos Finches. The top graph shows the beak sizes of the entire finch population studied by the Grants in 1976. The bottom graph shows the beak sizes of the survivors in 1978. In just two years, beak size increased.
::Galápagos Finches 的嘴大小演变。 上图显示了1976年补助金所研究的全部finch人口的嘴大小。 下图显示了1978年幸存者的嘴大小。 在短短两年内, 嘴大小增加了 。Summary
::摘要-
Fossils provide a window into the past because they are evidence for evolution. Scientists who find and study fossils are called paleontologists.
::化石是历史的窗口,因为它们是进化的证据。 发现和研究化石的科学家被称为古生物学家。 -
Scientists compare the anatomy, embryos, and DNA of living things to understand how they evolved. Evidence for evolution is provided by homologous structures, which are structures shared by related organisms
and
inherited from a common ancestor. Other evidence is provided by analogous structures. These are structures that unrelated organisms share because they evolved for the same function.
::科学家比较了生物的解剖学、胚胎和DNA,以了解它们是如何演化的。 进化的证据由同质结构提供,这些结构是相关生物共有的结构,是从共同祖先继承下来的。 其它证据则由类似结构提供。 这些结构是互不相干的生物共有的,因为它们是为同一功能而进化的。 -
Biogeography is the study of how and why plants and animals live where they do. It also provides evidence for evolution. On island chains, such as the Galápagos, one species may evolve into many new species to fill available niches. This is called adaptive radiation.
::生物地理学是研究植物和动物如何和为什么生活在那里,它也为进化提供了证据。 在加拉帕戈斯岛等岛屿链条上,一种物种可能演变成许多新物种,以填补现有的位置。 这被称为适应性辐射。 -
Peter and Rosemary Grant re-studied Galápagos finches. During a drought in the 1970s, they were able to directly observe evolution.
::彼得和罗斯玛丽·格兰特重新研究了加拉帕戈斯角。 在1970年代的干旱期间,他们能够直接观察进化。
Review
::回顾1. How do paleontologists learn about evolution?
::1. 古生物学家如何了解进化?2. Describe what fossils reveal about the evolution of the horse.
::2. 描述化石揭示的马的进化过程。3. What are vestigial structures? Give an example.
::3. 什么是遗迹结构?举一个例子。4. Define biogeography.
::4. 界定生物地理学。5. Describe an example of island biogeography that provides evidence for evolution.
::5. 描述一个岛屿生物地理学的例子,为演变提供证据。6. Humans and apes have five fingers they can use to grasp objects. Are these analogous or homologous structures? Explain.
::6. 人类和猿类有五根手指可以用来捕捉物体,它们是相似的还是同质的结构?7. Compare and contrast homologous and analogous structures. What do they reveal about evolution?
::7. 比较和对比同系和类似结构,它们揭示进化情况如何?8. Why does comparative embryology demonstrate similarities between organisms that do not appear to be similar when the organisms are adults?
::8. 为什么比较胚胎学显示生物体之间的相似性,而当生物体是成年人时,这些生物体似乎并不相似?9. What does a cladogram show?
::9. 单片显示什么?10. Explain how DNA is useful in the study of evolution.
::10. 解释脱氧核糖核酸在研究演变过程中如何有用。11. A bat wing is more similar in anatomical structure to a cat forelimb than to a bird wing. Answer the following questions about these structures.
::11. 蝙蝠翼在解剖结构上比鸟翼更类似于猫前额,回答以下关于这些结构的问题。a. Which pairs are homologous structures?
::a. 哪对是同族结构?b. Which pairs are analogous structures?
::b. 哪些对类比结构?c. Based on this, do you think a bat is more closely related to a cat or to a bird? Explain your answer.
::c. 基于这一点,你认为蝙蝠与猫或鸟的关系更密切吗?解释你的答复。d. If you wanted to test the answer you gave to part C, what is a different type of evidence you could obtain that might help answer the question?
::d. 如果你想测试你对C部分的回答,你可以得到哪些不同类型的证据来帮助回答问题?12. True or False: Fossils are the only type of evidence that supports the theory of evolution.
::12. 真实或假:化石是支持进化理论的唯一证据。13. True or False: Adaptive radiation is a type of evolution that produces new species.
::13. 真实或虚假:适应性辐射是产生新物种的一种进化。Explore More
::探索更多The Galapagos finches remain one of our world's greatest examples of adaptive radiation. Watch as these evolutionary biologists detail their 40-year project to document the evolution of these famous finches:
::加拉帕戈斯雀巢仍然是我们世界上适应性辐射的最大例子之一。 当这些进化生物学家详细描述他们的40年项目来记录这些著名的雀巢的演变:Did you know you have useless body parts? Check these out:
::你知道你身上有没用的零件吗? -
They became taller, which would help them see
predators
while they fed in tall grasses. Eventually, they reached a height of about 1.6 m.
