An explosion of new animal forms took place about 530 million years ago, and from that era onward, oxygen built up rapidly in the atmosphere. As oxygen levels climbed, the new ecosystems grew in stature and complexity until lush, swampy forests had developed. Thus began the Carboniferous period (roughly 360 to 300 million years ago), named for the deep beds of coal—a form of carbon—that formed from the remains of trees and other organic matter during this time. We know a lot about life in the Carboniferous world because of the many fossils found in coal seams (layers). In 1979, miners working in the town of Bolsover, England, stumbled upon the fossil of an enormous dragonfly, with a wingspan of more than half a meter. Carboniferous scorpions were a meter long, and mayflies had 40-centimeter wingspans. Plants were huge too. The lycopods, which we know today as tiny club mosses, reached heights of 50 meters. All these life forms were giants by today’s standards, so what was going on? A hint at the answer comes from the way the animals breathed. Insects do not have lungs. Instead, their bodies are riddled with tiny tubes called trachea that let air diffuse in and out passively. This puts a size constraint on insects because the passive breathing system cannot deliver oxygen quickly to deep tissues. In today’s atmosphere, a dragonfly the size of the Bolsover specimen would not be able to beat its wings fast enough to fly because its flight muscles would be deprived of oxygen. To get airborne, it must have flown through air much richer in oxygen than ours.
Calculations suggest the Carboniferous air was 30 to 35 percent oxygen, as compared to 21 percent today. The explanation for this high level of oxygen lies in the coal itself. Coal forms when dead plant material doesn’t fully decompose, instead becoming buried and then compressed over vast spans of time. By 375 million years ago, the swampy forests of the Carboniferous were already laying down the first coal seams at a prodigious rate, and they continued doing so for millions of years. In fact, about 90 percent of the world’s coal stems from this time. The Carboniferous plants must have been piling up in the ground when they died, perhaps because the standing water of the swamps protected them from decay—still (unmoving) water lacks oxygen that is needed in order for decomposition to occur. Or perhaps bacteria had not yet evolved the ability to digest the tough fibrous material (lignin) in wood. And because the dead plants weren’t being fully recycled, there was an imbalance in the carbon and oxygen cycles. The trees were taking in carbon dioxide and giving off oxygen through the process of photosynthesis, but the reverse process wasn’t happening—the carbon was staying trapped in the plants, and the oxygen wasn’t being used up by the process of decay. So as forests flourished, producing more and more oxygen, the atmosphere’s oxygen level rose. Life had created an atmosphere in which it could make a leap of evolution.
The Carboniferous was a green world of mosses, vines, horsetails, and ferns, and vast areas of equatorial land were given over to forest swamps. But the oxygen-rich atmosphere brought something else. This is the time when charcoal first appears in the fossil record, and charcoal results from organic matter exposed to high temperatures, which tells us that the atmosphere now had sufficient oxygen to support fire. From around 365 million years ago, ferocious wildfires swept across the land and they were fires like no other, for in air that was 30 percent oxygen, even the damp swamps would have burned. Today, studies of Carboniferous charcoal reveal not only the great intensity of the fires but the nature of the plants that were consumed by them. This, along with fossil evidence, reveals that the plants had adapted to become resistant to fire, with thick bark, high crowns, and long tubers that were protected deep in the soil. Destructive as the wildfires that swept the planet must have been, they were also part of the mechanism that kept the atmosphere in balance, because they would have consumed oxygen and prevented levels from rising too high while also, by burning the forests, injecting carbon dioxide back into the air.
题目：
1
An explosion of new animal forms took place about 530 million years ago, and from that era onward, oxygen built up rapidly in the atmosphere. As oxygen levels climbed, the new ecosystems grew in stature and complexity until lush, swampy forests had developed. Thus began the Carboniferous period (roughly 360 to 300 million years ago), named for the deep beds of coal—a form of carbon—that formed from the remains of trees and other organic matter during this time. We know a lot about life in the Carboniferous world because of the many fossils found in coal seams (layers). In 1979, miners working in the town of Bolsover, England, stumbled upon the fossil of an enormous dragonfly, with a wingspan of more than half a meter. Carboniferous scorpions were a meter long, and mayflies had 40-centimeter wingspans. Plants were huge too. The lycopods, which we know today as tiny club mosses, reached heights of 50 meters. All these life forms were giants by today’s standards, so what was going on? A hint at the answer comes from the way the animals breathed. Insects do not have lungs. Instead, their bodies are riddled with tiny tubes called trachea that let air diffuse in and out passively. This puts a size constraint on insects because the passive breathing system cannot deliver oxygen quickly to deep tissues. In today’s atmosphere, a dragonfly the size of the Bolsover specimen would not be able to beat its wings fast enough to fly because its flight muscles would be deprived of oxygen. To get airborne, it must have flown through air much richer in oxygen than ours.
The word“standards”in the passage is closest in meaning to
Acomparisons
Bcriteria
Crecords
DSpecies
2
An explosion of new animal forms took place about 530 million years ago, and from that era onward, oxygen built up rapidly in the atmosphere. As oxygen levels climbed, the new ecosystems grew in stature and complexity until lush, swampy forests had developed. Thus began the Carboniferous period (roughly 360 to 300 million years ago), named for the deep beds of coal—a form of carbon—that formed from the remains of trees and other organic matter during this time. We know a lot about life in the Carboniferous world because of the many fossils found in coal seams (layers). In 1979, miners working in the town of Bolsover, England, stumbled upon the fossil of an enormous dragonfly, with a wingspan of more than half a meter. Carboniferous scorpions were a meter long, and mayflies had 40-centimeter wingspans. Plants were huge too. The lycopods, which we know today as tiny club mosses, reached heights of 50 meters. All these life forms were giants by today’s standards, so what was going on? A hint at the answer comes from the way the animals breathed. Insects do not have lungs. Instead, their bodies are riddled with tiny tubes called trachea that let air diffuse in and out passively. This puts a size constraint on insects because the passive breathing system cannot deliver oxygen quickly to deep tissues. In today’s atmosphere, a dragonfly the size of the Bolsover specimen would not be able to beat its wings fast enough to fly because its flight muscles would be deprived of oxygen. To get airborne, it must have flown through air much richer in oxygen than ours.
Select the TWo characteristics of the Carboniferous period that are mentioned in paragraph 1 from the answer choices below.To receive credit,you must select TWO answers.
AThere were swampy forests with dense vegetation.
BLarge amounts of coal were produced.
CThere was a wider variety of insects than in previous eras.
DPlants such as lycopods became smaller as an adaptation to the oxygen-rich atmosphere.
3
In paragraph 1,why does the author explain how insects breathe?
ATo argue that the Bolsover dragonfly must have had a different breathing system than dragonflies today
BTo support the claim that there was an explosion of new animal forms 530 million years ago
CTo provide evidence that trachea are more efficient than lungs
DTo explain why today’s insects are not as large as those in the Carboniferous
An explosion of new animal forms took place about 530 million years ago, and from that era onward, oxygen built up rapidly in the atmosphere. As oxygen levels climbed, the new ecosystems grew in stature and complexity until lush, swampy forests had developed. Thus began the Carboniferous period (roughly 360 to 300 million years ago), named for the deep beds of coal—a form of carbon—that formed from the remains of trees and other organic matter during this time. We know a lot about life in the Carboniferous world because of the many fossils found in coal seams (layers). In 1979, miners working in the town of Bolsover, England, stumbled upon the fossil of an enormous dragonfly, with a wingspan of more than half a meter. Carboniferous scorpions were a meter long, and mayflies had 40-centimeter wingspans. Plants were huge too. The lycopods, which we know today as tiny club mosses, reached heights of 50 meters. All these life forms were giants by today’s standards, so what was going on? A hint at the answer comes from the way the animals breathed. Insects do not have lungs. Instead, their bodies are riddled with tiny tubes called trachea that let air diffuse in and out passively. This puts a size constraint on insects because the passive breathing system cannot deliver oxygen quickly to deep tissues. In today’s atmosphere, a dragonfly the size of the Bolsover specimen would not be able to beat its wings fast enough to fly because its flight muscles would be deprived of oxygen. To get airborne, it must have flown through air much richer in oxygen than ours.
4
Calculations suggest the Carboniferous air was 30 to 35 percent oxygen, as compared to 21 percent today. The explanation for this high level of oxygen lies in the coal itself. Coal forms when dead plant material doesn’t fully decompose, instead becoming buried and then compressed over vast spans of time. By 375 million years ago, the swampy forests of the Carboniferous were already laying down the first coal seams at a prodigious rate, and they continued doing so for millions of years. In fact, about 90 percent of the world’s coal stems from this time. The Carboniferous plants must have been piling up in the ground when they died, perhaps because the standing water of the swamps protected them from decay—still (unmoving) water lacks oxygen that is needed in order for decomposition to occur. Or perhaps bacteria had not yet evolved the ability to digest the tough fibrous material (lignin) in wood. And because the dead plants weren’t being fully recycled, there was an imbalance in the carbon and oxygen cycles. The trees were taking in carbon dioxide and giving off oxygen through the process of photosynthesis, but the reverse process wasn’t happening—the carbon was staying trapped in the plants, and the oxygen wasn’t being used up by the process of decay. So as forests flourished, producing more and more oxygen, the atmosphere’s oxygen level rose. Life had created an atmosphere in which it could make a leap of evolution.
According to paragraph 2,which of following is true of coal?
AThe first 90 percent of the world’s coal formed at a much slower pace than the last 10 percent.
BThe richest seams of coal from the Carboniferous period are typically found in areas outside swampy forests.
CCoal is created when partially decomposed plant material is compressed over time.
DCoal is unlikely to form in places with standing water.
5
The Carboniferous was a green world of mosses, vines, horsetails, and ferns, and vast areas of equatorial land were given over to forest swamps. But the oxygen-rich atmosphere brought something else. This is the time when charcoal first appears in the fossil record, and charcoal results from organic matter exposed to high temperatures, which tells us that the atmosphere now had sufficient oxygen to support fire. From around 365 million years ago, ferocious wildfires swept across the land and they were fires like no other, for in air that was 30 percent oxygen, even the damp swamps would have burned. Today, studies of Carboniferous charcoal reveal not only the great intensity of the fires but the nature of the plants that were consumed by them. This, along with fossil evidence, reveals that the plants had adapted to become resistant to fire, with thick bark, high crowns, and long tubers that were protected deep in the soil. Destructive as the wildfires that swept the planet must have been, they were also part of the mechanism that kept the atmosphere in balance, because they would have consumed oxygen and prevented levels from rising too high while also, by burning the forests, injecting carbon dioxide back into the air.
The word“ferocious”in the passage is closest in meaning to
Adeveloping
Bfrequent
Cfierce
Dsudden
6
The Carboniferous was a green world of mosses, vines, horsetails, and ferns, and vast areas of equatorial land were given over to forest swamps. But the oxygen-rich atmosphere brought something else. This is the time when charcoal first appears in the fossil record, and charcoal results from organic matter exposed to high temperatures, which tells us that the atmosphere now had sufficient oxygen to support fire. From around 365 million years ago, ferocious wildfires swept across the land and they were fires like no other, for in air that was 30 percent oxygen, even the damp swamps would have burned. Today, studies of Carboniferous charcoal reveal not only the great intensity of the fires but the nature of the plants that were consumed by them. This, along with fossil evidence, reveals that the plants had adapted to become resistant to fire, with thick bark, high crowns, and long tubers that were protected deep in the soil. Destructive as the wildfires that swept the planet must have been, they were also part of the mechanism that kept the atmosphere in balance, because they would have consumed oxygen and prevented levels from rising too high while also, by burning the forests, injecting carbon dioxide back into the air.
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.
ALarge wildfires helped keep the atmosphere in balance by consuming oxygen and releasing carbon dioxide.
BThe wildfires must have been very destructive,sweeping over the planet and burning forests.
CTo prevent oxygen levels from rising too high, a mechanism was needed to keep the atmosphere in balance.
DAs they consumed oxygen and injected carbon dioxide into the air,wildfires burned the planet’s forests.
7
The Carboniferous was a green world of mosses, vines, horsetails, and ferns, and vast areas of equatorial land were given over to forest swamps. But the oxygen-rich atmosphere brought something else. This is the time when charcoal first appears in the fossil record, and charcoal results from organic matter exposed to high temperatures, which tells us that the atmosphere now had sufficient oxygen to support fire. From around 365 million years ago, ferocious wildfires swept across the land and they were fires like no other, for in air that was 30 percent oxygen, even the damp swamps would have burned. Today, studies of Carboniferous charcoal reveal not only the great intensity of the fires but the nature of the plants that were consumed by them. This, along with fossil evidence, reveals that the plants had adapted to become resistant to fire, with thick bark, high crowns, and long tubers that were protected deep in the soil. Destructive as the wildfires that swept the planet must have been, they were also part of the mechanism that kept the atmosphere in balance, because they would have consumed oxygen and prevented levels from rising too high while also, by burning the forests, injecting carbon dioxide back into the air.
Which of the following is true of the studies of Carboniferous charcoal and other fossil evidence mentioned in paragraph 3
AThey revealed why around 365 million years ago more and more plants migrated away from equatorial land.
BThey identified the types of plants that lived in that period as well as the structural changes they developed against fire.
CThey explained why Carboniferous charcoal formed primarily from plant parts above ground rather than from long tubers deep in the soil.
DThey questioned the established notion that plants had developed fire-resistant features before the Carboniferous era.
8
The Carboniferous was a green world of mosses, vines, horsetails, and ferns, and vast areas of equatorial land were given over to forest swamps. But the oxygen-rich atmosphere brought something else. This is the time when charcoal first appears in the fossil record, and charcoal results from organic matter exposed to high temperatures, which tells us that the atmosphere now had sufficient oxygen to support fire. From around 365 million years ago, ferocious wildfires swept across the land and they were fires like no other, for in air that was 30 percent oxygen, even the damp swamps would have burned. Today, studies of Carboniferous charcoal reveal not only the great intensity of the fires but the nature of the plants that were consumed by them. This, along with fossil evidence, reveals that the plants had adapted to become resistant to fire, with thick bark, high crowns, and long tubers that were protected deep in the soil. Destructive as the wildfires that swept the planet must have been, they were also part of the mechanism that kept the atmosphere in balance, because they would have consumed oxygen and prevented levels from rising too high while also, by burning the forests, injecting carbon dioxide back into the air.
It can be inferred from paragraph 3 that charcoal did not appear in the fossil record before the Carboniferous because before that period
Athere were no mosses,vines,horsetails,or ferns
Bintense humidity in the atmosphere prevented fires from spreading
Cthere was not enough oxygen for wildfires to occur
Dthe land was too damp and swampy to burn
