Thi Thử VSTEP Đề 4 Reading Test 4 Part 2

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 3 QUESTIONS 21 - 30

In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection ofdaringadventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; stillothers, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty.

Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some - for example, Fort Davis - had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment andboostedmorale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection.

Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts andinhibitedtheir military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.

PASSAGE 4 QUESTIONS 31 - 40

Anyone who has handled a fossilized bone knows that it is usually not exactly like its moderncounterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone, and other tissues, have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is wrong interpretation; fossils are frequently so dense because theporesand other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up little from their surroundings. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions, the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bones, even in bones as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structures of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too -ithas the same crystal structure as that of modern bone. Although nothing remains of the original collagen, some of its component amino acids are usually stilldetectable, together with amino acids of the non-collagenous proteins of bone.