How Fossils Map the Past
Only a tiny fraction of the organisms that have lived during the geologic past have been preserved as fossils.Normally the remains of an animal or plant are destroyed.When an organism perishes,its soft parts usually are quickly eaten by scavengers or decomposed by bacteria.Occasionally,however,the remains are buried by sediment. When this occurs,they are protected from the environment where destructive processes operate.Rapid burial therefore is an important condition favoring preservation.In addition,animals and plants have a much better chance of being preserved as part of the fossil record if they have hard parts.Although traces and imprints of soft-bodied animals such as jellyfish,worms,and insects exist,they are not common.Flesh usually decays so rapidly that preservation is exceedingly unlikely.Hard parts such as shells,bones,and teeth predominate in the record of past life.
The existence of fossils had been known for centuries,yet it was not until the late 1700s and early 1800s that their significance as geologic tools was made evident.During this period an English engineer and canal builder,William Smith,discovered that each rock formation in the canals he worked on contained fossils unlike those in the beds either above or below.Further,he noted that sedimentary strata in widely separated areas could be identified-and correlated -by their distinctive fossil content.
Based on Smith’s classic observations and the findings of many geologists who followed,one of the most important and basic principles in historical geology was formulated:Fossil organisms succeed one another in a definite and determinable order,and therefore any time period can be recognized by its fossil content. This has come to be known as the principle of fossil succession.In other words,when fossils are arranged according to their age by applying the law of superposition to the rocks in which they are found, they do not present a random or haphazard picture.To the contrary, fossils document the evolution of life through time.
For example,an age of trilobites is recognized as being quite early in the fossil record.Then,in succession,paleontologists recognize an age of fishes,an age of coal swamps,an age of reptiles,and an age of mammals.These“ages”pertain to groups that were especially plentiful and characteristic during particular time periods.Within each of the ages,there are many subdivisions based, for example,on certain species of trilobites,and certain types of fish, reptiles,and so on.This same succession of dominant organisms, never out of order,is found on every major landmass.
Once fossils were recognized as time indicators,they became the most useful means of associating rocks of similar age in different regions.Geologists pay particular attention to certain fossils called index fossils.These fossils are widespread geographically and are limited to a short span of geologic time,so their presence provides an important method of matching rocks of the same age.Rock formations,however,do not always contain a specific index fossil.In such situations,groups of fossils,called fossil assemblages,are used to establish the age of the bed.
In addition to being important and often essential tools for association,fossils are important environmental indicators.Although much can be deduced about past environments by studying the nature and characteristics of sedimentary rocks,a close examination of the fossils present can usually provide a great deal more information.For example,when the remains of certain clam shells are found in limestone,the geologist can assume that the region was once covered by a shallow sea,because that is where clams live today.Also,by using what we know of living organisms,we can conclude that fossil animals with thick shells capable of withstanding pounding and surging waves must have inhabited shorelines.On the other hand,animals with thin,delicate shells probably indicate deep, calm offshore waters.Hence,by looking closely at the types of fossils,the approximate position of an ancient shoreline may be identified.Further,fossils can indicate the former temperature of the water.Certain present-day corals require warm and shallow tropical seas like those around Florida and the Bahamas.When similar corals are found in ancient limestones,they indicate that a Florida-like marine environment must have existed when they were alive.
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Only a tiny fraction of the organisms that have lived during the geologic past have been preserved as fossils.Normally the remains of an animal or plant are destroyed.When an organism perishes,its soft parts usually are quickly eaten by scavengers or decomposed by bacteria.Occasionally,however,the remains are buried by sediment. When this occurs,they are protected from the environment where destructive processes operate.Rapid burial therefore is an important condition favoring preservation.In addition,animals and plants have a much better chance of being preserved as part of the fossil record if they have hard parts.Although traces and imprints of soft-bodied animals such as jellyfish,worms,and insects exist,they are not common.Flesh usually decays so rapidly that preservation is exceedingly unlikely.Hard parts such as shells,bones,and teeth predominate in the record of past life.
According to paragraph 1,all of the following statements about fossil formation are true EXCEPT:
Negative Factual Information Questions否定事实信息题
AMost plants and animals decompose without leaving any fossil remains.
BOrganisms are more likely to be preserved if they are quickly covered with sediment.
CThere is no fossil record of soft-bodied animals such as jellyfish, worms,and insects.
DThe most common fossils are shells,bones,teeth,and other hard parts.
2
Only a tiny fraction of the organisms that have lived during the geologic past have been preserved as fossils.Normally the remains of an animal or plant are destroyed.When an organism perishes,its soft parts usually are quickly eaten by scavengers or decomposed by bacteria.Occasionally,however,the remains are buried by sediment. When this occurs,they are protected from the environment where destructive processes operate.Rapid burial therefore is an important condition favoring preservation.In addition,animals and plants have a much better chance of being preserved as part of the fossil record if they have hard parts.Although traces and imprints of soft-bodied animals such as jellyfish,worms,and insects exist,they are not common.Flesh usually decays so rapidly that preservation is exceedingly unlikely.Hard parts such as shells,bones,and teeth predominate in the record of past life.
Which of the following can be inferred from paragraph 1 about the content of the fossil record?
Inference Questions推理题
AIt contains a larger percentage of plants than of animals.
BIt provides more information about how organisms died than about how they lived.
CIt includes more scavengers than any other type of organism.
DIt represents some forms of life but leaves no indication of others.
3
The existence of fossils had been known for centuries,yet it was not until the late 1700s and early 1800s that their significance as geologic tools was made evident.During this period an English engineer and canal builder,William Smith,discovered that each rock formation in the canals he worked on contained fossils unlike those in the beds either above or below.Further,he noted that sedimentary strata in widely separated areas could be identified-and correlated -by their distinctive fossil content.
The word“evident'”in the passage is closest in meaning to
Vocabulary Questions词汇题
Ausable
Bwidespread
Cclear
Dacceptable
4
The existence of fossils had been known for centuries,yet it was not until the late 1700s and early 1800s that their significance as geologic tools was made evident.During this period an English engineer and canal builder,William Smith,discovered that each rock formation in the canals he worked on contained fossils unlike those in the beds either above or below.Further,he noted that sedimentary strata in widely separated areas could be identified-and correlated -by their distinctive fossil content.
Based on Smith’s classic observations and the findings of many geologists who followed,one of the most important and basic principles in historical geology was formulated:Fossil organisms succeed one another in a definite and determinable order,and therefore any time period can be recognized by its fossil content. This has come to be known as the principle of fossil succession.In other words,when fossils are arranged according to their age by applying the law of superposition to the rocks in which they are found, they do not present a random or haphazard picture.To the contrary, fossils document the evolution of life through time.
According to paragraphs 2 and 3,which of the following best describes William Smith’s discovery about fossils?
Factual Information Questions事实信息题
AThe order in which fossils succeed each other is partly determine by measuring the distance separating sedimentary layers.
BThe fossils of organisms from different geological periods sometimes occupy the same sedimentary layer.
CFossils reveal what kinds of organisms were most successful at any given period of time.
DAny time period can be recognized by its fossils,since fossil organisms follow one another in a specific,knowable order.
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For example,an age of trilobites is recognized as being quite early in the fossil record.Then,in succession,paleontologists recognize an age of fishes,an age of coal swamps,an age of reptiles,and an age of mammals.These“ages”pertain to groups that were especially plentiful and characteristic during particular time periods.Within each of the ages,there are many subdivisions based, for example,on certain species of trilobites,and certain types of fish, reptiles,and so on.This same succession of dominant organisms, never out of order,is found on every major landmass.
Which of the following is NOT true of the ages and organisms discussed in paragraph 4
Negative Factual Information Questions否定事实信息题
AAlthough the organisms all occur early in the fossil record,they were found by paleontologists relatively late.
BEach age has been named after a characteristic group of organisms.
CEach age is divided into periods on the basis of the dominance of certain organism species.
DOrganisms are present in the same order on every continent.
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Select the TWO answer choices that according to paragraph 5 are characteristics determining an organism’s usefulness as an index fossil. To receive credit,you must select TWO answer choices.
Factual Information Questions事实信息题
Select 2 answers
AThe organism must be found in many different places.
BThe organism must be restricted to a brief geological period.
CThe organism must be associated with a particular type of rock formation of known age.
DThe organism must be commonly found with certain other fossils, as part of an assemblage.
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In addition to being important and often essential tools for association,fossils are important environmental indicators.Although much can be deduced about past environments by studying the nature and characteristics of sedimentary rocks,a close examination of the fossils present can usually provide a great deal more information.For example,when the remains of certain clam shells are found in limestone,the geologist can assume that the region was once covered by a shallow sea,because that is where clams live today.Also,by using what we know of living organisms,we can conclude that fossil animals with thick shells capable of withstanding pounding and surging waves must have inhabited shorelines.On the other hand,animals with thin,delicate shells probably indicate deep, calm offshore waters.Hence,by looking closely at the types of fossils,the approximate position of an ancient shoreline may be identified.Further,fossils can indicate the former temperature of the water.Certain present-day corals require warm and shallow tropical seas like those around Florida and the Bahamas.When similar corals are found in ancient limestones,they indicate that a Florida-like marine environment must have existed when they were alive.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.
Sentence Simplification Questions句子简化题
AThe nature and characteristics of sedimentary rocks provide a great deal of information about the past.
BThe more closely fossils are examined,the more information they provide about past environments.
CFossils can provide even more information about past environments than sedimentary rocks can.
DAlthough much has been learned about past environments from rocks and fossils,a great deal remains unknown.
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In addition to being important and often essential tools for association,fossils are important environmental indicators.Although much can be deduced about past environments by studying the nature and characteristics of sedimentary rocks,a close examination of the fossils present can usually provide a great deal more information.For example,when the remains of certain clam shells are found in limestone,the geologist can assume that the region was once covered by a shallow sea,because that is where clams live today.Also,by using what we know of living organisms,we can conclude that fossil animals with thick shells capable of withstanding pounding and surging waves must have inhabited shorelines.On the other hand,animals with thin,delicate shells probably indicate deep, calm offshore waters.Hence,by looking closely at the types of fossils,the approximate position of an ancient shoreline may be identified.Further,fossils can indicate the former temperature of the water.Certain present-day corals require warm and shallow tropical seas like those around Florida and the Bahamas.When similar corals are found in ancient limestones,they indicate that a Florida-like marine environment must have existed when they were alive.
The author discusses corals in paragraph 6 in order to
Organization Questions组织结构题
Aargue that the shallow tropical seas around Florida and the Bahamas have changed little over the centuries
Billustrate that fossils can reveal how hot or cold a body of water once was
Csupport the claim that fossils can help determine the approximate position of an ancient shoreline
Dexplain what fossils can tell us about the evolutionary history of marine life
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Only a tiny fraction of the organisms that have lived during the geologic past have been preserved as fossils.Normally the remains of an animal or plant are destroyed.When an organism perishes,its soft parts usually are quickly eaten by scavengers or decomposed by bacteria.Occasionally,however,the remains are buried by sediment. ⬛When this occurs,they are protected from the environment where destructive processes operate.⬛Rapid burial therefore is an important condition favoring preservation.⬛In addition,animals and plants have a much better chance of being preserved as part of the fossil record if they have hard parts.⬛Although traces and imprints of soft-bodied animals such as jellyfish,worms,and insects exist,they are not common.Flesh usually decays so rapidly that preservation is exceedingly unlikely.Hard parts such as shells,bones,and teeth predominate in the record of past life.
Look at the four squaresthat indicate where the following sentence could be added to the passage
Most fossils consist only of shells,skeletal remains, or teeth.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
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The study of fossils has revealed a range of important information about the geologic past of organisms.
Prose Summary Questions概要小结题
Select 3 answers
AThe fossil record is most complete for periods of sudden geologic change,when conditions favored preservation of animals with hard parts.
BBecause the evolution of organisms has followed a consistent order, rock layers can be linked to particular time periods by their fossil content.
CAs well as being time indicators,fossils provide information about water conditions,location of shorelines,and other aspects of past environments.
DWilliam Smith was the first to discover that fossil beds were found not only in water but also on land in widely separated sedimentary strata.
EAncient history is divided into a series of ages named for characteristic fossil types,from an age of trilobites to an age of mammals.
FCertain present-day organisms,such as some corals,can indicate the presence of ancient limestone and other fossil-rich environments.
