Unifying Concepts of Animal Structure and Function

Unifying Concepts of Animal Structure and Function
Chapter 21 Unifying Concepts of Animal Structure and Function © 2016 Pearson Education, Inc.

Why Animal Structure and Function Matter
Figure Why Animal Structure and Function Matter Figure Why animal structure and function matter

The Structural Organization of Animals
Life is characterized by a hierarchy of organization. In animals, individual cells are grouped into tissues, tissues combine to form organs, organs are organized into organ systems, and organ systems make up the entire organism. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 3

Cellular level: Muscle cell Tissue level: Cardiac muscle
Figure 21.1-s1 Cellular level: Muscle cell Tissue level: Cardiac muscle Figure 21.1-s1 Structural hierarchy in a human (step 1)

Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level:
Figure 21.1-s2 Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level: Heart Organ system level: Circulatory system Figure 21.1-s2 Structural hierarchy in a human (step 2)

Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level:
Figure 21.1-s3 Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level: Heart Organism level: Multiple organ systems functioning together Organ system level: Circulatory system Figure 21.1-s3 Structural hierarchy in a human (step 3)

Structure/Function: Anatomy and Physiology
Biologists distinguish anatomy from physiology. Anatomy is the study of the structure of an organism’s parts. Physiology is the study of the function of those parts. The correlation of structure and function is a fundamental principle of biology that is evident at all levels of life’s hierarchy. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 7

(a) At the organism level Figure 21.2-s1
Figure 21.2-s1 Structure fits function (step 1)

(b) At the organ level (a) At the organism level Figure 21.2-s2
Figure 21.2-s2 Structure fits function (step 2)

(c) At the cellular level
Figure 21.2-s3 (b) At the organ level (a) At the organism level (c) At the cellular level Figure 21.2-s3 Structure fits function (step 3)

Figure Figure Structure fits function (part 1: nerve cell)

Tissues The cell is the basic unit of all living organisms.
In almost all animals, including humans, cells are grouped into tissues. A tissue is an integrated group of similar cells that performs a specific function. Animals have four main categories of tissue: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 12

Epithelial Tissue Epithelial tissue, also known as epithelium,
covers the surface of the body and lines organs. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 13

Examples of organs lined with epithelial tissue Heart Lung Stomach
Figure 21.3 Examples of organs lined with epithelial tissue Heart Lung Stomach Small intestine Large intestine Epithelial cells Epithelial tissue covering body (skin) Urinary bladder Spaces for exchange Epithelial tissue lining capillaries Figure 21.3 Epithelial tissue

Epithelial Tissue The body continuously renews the cells of many epithelial tissues. Such turnover requires cells to divide rapidly, which increases the risk of an error in cell division, a mistake that can lead to cancer. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 15

Connective Tissue Connective tissue contains cells scattered throughout a material called the extracellular matrix. The structure of the matrix varies and matches the function of each tissue. Two major functions of the connective tissue are to support and join other tissues. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 16

Adipose tissue Blood Fibrous connective tissue Bone Cartilage
Figure 21.4 Loose connective tissue Adipose tissue Blood Fibrous connective tissue Bone Cartilage Figure 21.4 Types of connective tissue

Loose connective tissue (under the skin)
Figure Cell Collagen fiber Loose connective tissue (under the skin) Figure Types of connective tissue (part 1: loose connective)

Fat droplets Adipose tissue Figure 21.4-2
Figure Types of connective tissue (part 2: adipose)

White blood cells Red blood cell Plasma Blood Figure 21.4-3
Figure Types of connective tissue (part 3: blood)

Fibrous connective tissue (forming a tendon)
Figure Cell nucleus Collagen fibers Fibrous connective tissue (forming a tendon) Figure Types of connective tissue (part 4: fibrous connective)

Cells Matrix Cartilage (at the end of a bone) Figure 21.4-5
Figure Types of connective tissue (part 5: cartilage)

Matrix Cells Bone Figure 21.4-6
Figure Types of connective tissue (part 6: bone)

Connective Tissue Figure 21.4 illustrates six of the major types of connective tissue. Loose connective tissue is the most widespread connective tissue in the body of vertebrates and binds epithelia to underlying tissues. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 24

Connective Tissue Fibrous connective tissue has a dense matrix of collagen. It forms tendons, which attach muscles to bones, and ligaments, which strongly join bones together at joints. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 25

Connective Tissue Cartilage is strong but flexible,
has no blood vessels, so it heals very slowly, and functions as a flexible, boneless skeleton. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 26

Connective Tissue Bone
is a rigid connective tissue with a matrix of collagen fibers hardened with deposits of calcium salts. This combination makes bone hard without being brittle. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 27

Connective Tissue Adipose tissue
stores fat in closely packed cells of a sparse matrix, functions as an energy bank, and insulates and cushions the body. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 28

Connective Tissue Blood
consists of cells suspended in a liquid matrix called plasma and transports substances in the plasma from one part of the body to another, plays major roles in immunity, and seals broken blood vessels. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 29

Muscle Tissue Muscle tissue
is the most abundant tissue in most animals, consists of bundles of long, thin, cylindrical cells called muscle fibers, and has specialized proteins arranged into a structure that contracts when stimulated by a signal from a nerve. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 30

Cardiac muscle Skeletal muscle Smooth muscle Figure 21.5
Figure 21.5 Three types of muscle tissue

several muscle fibers)
Figure Unit of muscle contraction Muscle fiber (cell) Nuclei Skeletal muscle (short segments of several muscle fibers) Figure Three types of muscle tissue (part 1: skeletal)

Junction between two cells Muscle fiber Nucleus Cardiac muscle
Figure Junction between two cells Muscle fiber Nucleus Cardiac muscle Figure Three types of muscle tissue (part 2: cardiac)

Muscle fiber Nucleus Smooth muscle Figure 21.5-3
Figure Three types of muscle tissue (part 3: smooth)

Muscle Tissue Skeletal muscle is attached to bones by tendons,
moves your skeleton, and is responsible for voluntary movements. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 35

Muscle Tissue Cardiac muscle is found only in heart tissue. The contraction of the cardiac muscle produces a coordinated heartbeat. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 36

Muscle Tissue Smooth muscle is found in many organs and can contract slowly for a long period of time. The powerful contractions of smooth muscle expel the fetus from the uterus during childbirth. The walls of the intestines are composed of smooth muscle that contracts to move food and waste along. Smooth muscle is also found in blood vessels. Rings of smooth muscle in blood vessels widen, causing blood to quickly flow to your face and neck. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 37

Nervous Tissue Nervous tissue
makes communication of information possible, is found in your brain and spinal cord, and consists of a network of neurons. The basic unit of nervous tissue is the neuron, or nerve cell. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 38

Brain Spinal cord Signal-receiving extensions Cell body Nerve Signal-
Figure 21.6 Brain Signal-receiving extensions Spinal cord Cell body Nerve Signal- transmitting extension LM Figure 21.6 Nervous tissue

Signal-receiving extensions Cell body Signal- transmitting extension
Figure Signal-receiving extensions Cell body Signal- transmitting extension LM Figure Nervous tissue (part 1: nerve cell)

Interconnections within Systems: Organs and Organ Systems
An organ consists of two or more tissues packaged into one working unit that performs a specific function. An organ performs functions that none of its component tissues can carry out alone. Examples include the heart, brain, and small intestines. To see how multiple tissues interconnect in a single organ, examine the layered arrangement of tissues in the wall of the small intestine in Figure 21.7. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 41

Small intestine (cut open) Epithelial tissue Connective tissue
Figure 21.7 Small intestine (cut open) Epithelial tissue Connective tissue (containing blood and lymph vessels) Smooth muscle tissue (two layers) Epithelial tissue Connective tissue Figure 21.7 Tissue layers of the small intestine, an organ

Organ systems are teams of organs that work together and perform vital body functions. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 43

Skeletal system: supports body and anchors muscles Metacarpals Carpals
Figure Metacarpals Carpals Phalanges Radius Ulna Skull Bone Humerus Shoulder girdle Clavicle Scapula Sternum Ribs Cartilage Vertebra Pelvic girdle Skeletal system: supports body and anchors muscles Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges Figure Human organ systems (part 1: skeletal)

transports substances throughout body
Figure Circulatory system: transports substances throughout body Heart Blood vessels Figure Human organ systems (part 2: circulatory)

Respiratory system: exchanges O2 and CO2 between blood and air
Figure Respiratory system: exchanges O2 and CO2 between blood and air Nasal cavity Pharynx Larynx Trachea Bronchus Lung Figure Human organ systems (part 3: respiratory)

Muscular system: moves the body Skeletal muscles Figure 21.8-4
Figure Human organ systems (part 4: muscular)

Digestive system: breaks down food and absorbs nutrients Mouth
Figure Digestive system: breaks down food and absorbs nutrients Mouth Esophagus Liver Stomach Large intestine Small intestine Anus Figure Human organ systems (part 5: digestive)

Urinary system: rids body of certain wastes Kidney Ureter
Figure Urinary system: rids body of certain wastes Kidney Ureter Urinary bladder Urethra Figure Human organ systems (part 6: urinary)

Endocrine system: secretes hormones that regulate body Hypothalamus
Figure Endocrine system: secretes hormones that regulate body Hypothalamus Pituitary gland Parathyroid gland Thyroid gland Adrenal gland Pancreas Ovary (female) Testis (male) Figure Human organ systems (part 7: endocrine)

Reproductive system: produces gametes and offspring Seminal vesicles
Figure Reproductive system: produces gametes and offspring Seminal vesicles Prostate gland Oviduct Vas deferens Ovary Penis Uterus Urethra Vagina Testis Figure Human organ systems (part 8: reproductive)

Integumentary system: protects body Hair Skin Nail Figure 21.8-9
Figure Human organ systems (part 9: integumentary)

Lymphatic and immune system: defends against disease Tonsil Thymus
Figure Lymphatic and immune system: defends against disease Tonsil Thymus Spleen Appendix Lymph nodes Lymphatic vessels Figure Human organ systems (part 10: lymphatic and immune)

Nervous system: processes sensory information Brain and controls
Figure Nervous system: processes sensory information and controls responses Brain Sense organ (ear) Spinal cord Nerves Figure Human organ systems (part 11: nervous)

An organism depends on the interconnection of all its organ systems for survival. Your body is a whole, living unit that is greater than the sum of its parts. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to understand the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the lines of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.” 2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. You might begin by simply noting how tools from a hardware store have constructions that match their intended functions (hammers tend to have blunt, heavy ends!). 3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these canines were not used by these cats for that function (biological role)! Teaching Tips 1. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure. 2. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone. 3. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons (with the support of a large amount of supporting cells) have collectively become self-aware! Active Lecture Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet. 2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects. 3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to work in small groups to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.) 4. Most adaptations represent compromise. Ask students to turn to someone near them to think of examples of functional compromises in their own bodies. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. Common examples include (a) chewing which can interfere with hearing, (b) our flexible skin that is more likely to be cut or punctured than a hard outer shell, (c) and walking on two legs, which frees up our hands for other tasks, but makes us less stable than walking on four legs. 5. Students often fail to consider the significance of body size. Consider asking your students to think about the impact of being small. Have they ever had difficulty emerging from a swimming pool because of the adhesive properties of water? Of course not—and yet small insects that land on a pond’s surface may find these forces to be lethal, preventing them from breaking away from the water’s surface! Ask students if they are ever unable to leave their homes because of high winds, which make it impossible for them to walk around outside. The movements of small insects are often hampered by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a nuisance on days when there is a good breeze. 6. To help your students appreciate the functional integration of the major systems of the body, have students turn to someone near them, pick a body system, and discuss its relationships with perhaps three other body systems. Then, working as a class, have your students help create a concept map noting the nature of the interrelationships between body systems. 7. See the Activity Learning to Think Critically Like a Scientist on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 55

Exchanges with the External Environment
Every organism is an open system that continuously exchanges chemicals and energy with its surroundings. An animal’s size and shape affect its exchanges with its surrounding environment. Every living cell of an animal’s body must be bathed in a watery solution, partly because substances must be dissolved in water to cross cell membranes. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. It can be difficult for students to think of their own bodies in such simple terms as surfaces and tubes. Perceiving the digestive tract as one continuous tube, in which food that passes through never technically enters the body, is one such challenge. Illustrate these fundamental principles first using simple animals as examples. Then apply these principles to humans as a final test of comprehension. 2. If students have not previously examined the diversity of animals, consider a brief overview of the fundamental body plans before explaining how these fundamental principles of form and function generally apply to the animal kingdom. Teaching Tips 1. Students often fail to consider the overall significance of body size. Consider asking your students to think about the impact of being small. Do they recall ever having trouble emerging from a swimming pool because of the adhesive properties of water? Yet small insects that land on a pond’s surface may find these forces to be lethal, preventing these organisms from breaking away from the water’s surface! In addition, are your students frequently prevented from leaving their homes because of high winds, simply unable to walk around outside? The movements of small insects are often prevented by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a pest on days when there is a good breeze. 2. The consequences of large size in organisms require transport and exchange systems extending to the deepest inner regions. Whether we think of a whale, a giant redwood, or the United States, these principles apply. By analogy, the railway and highway systems of the United States transport essential products from ocean ports to the deepest interior regions, where other transport systems deliver the goods to stores for sale. A person living near the ocean may obtain food directly, by fishing in the ocean. A person living in the Midwest may purchase ocean fish at a store or at a restaurant. 3. Organisms and individual cells need sufficient surface exchange and transport systems to support their surface-to-volume ratios. Cell size is limited, in part, by the ability of a cell to exchange materials efficiently with its surface. Thus, adaptations that increase surface area can permit cells to reach larger sizes. Active Lecture Tips 1. Ask students to turn to someone near them to list at least four factors that affect heat gain and loss during periods of physical activity. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. These examples will demonstrate how much our homeostatic mechanisms must work to maintain a steady body temperature. These factors include (a) the person’s physical condition, (b) the level of physical activity, (c) the age of the person (younger people tend to have higher metabolic rates), (d) the person’s level of hydration (which in turn affects the amount of sweating and evaporative cooling), (e) the external level of humidity (higher levels decrease evaporative cooling), (f) the intensity of the wind (greater intensity promotes evaporative cooling), (g) the intensity of sunlight, and (h) the color of the person’s clothing (which affects the amount of light energy the body absorbs). 56

In a single-celled amoeba, every part of the cell’s membrane touches the outside world, where exchange with the watery environment can occur. A hydra has a body wall only two cell layers thick. Both layers of cells are bathed in pond water, which enters the digestive sac through the mouth. Every cell of the hydra can thus exchange materials through direct contact with the aqueous environment. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. It can be difficult for students to think of their own bodies in such simple terms as surfaces and tubes. Perceiving the digestive tract as one continuous tube, in which food that passes through never technically enters the body, is one such challenge. Illustrate these fundamental principles first using simple animals as examples. Then apply these principles to humans as a final test of comprehension. 2. If students have not previously examined the diversity of animals, consider a brief overview of the fundamental body plans before explaining how these fundamental principles of form and function generally apply to the animal kingdom. Teaching Tips 1. Students often fail to consider the overall significance of body size. Consider asking your students to think about the impact of being small. Do they recall ever having trouble emerging from a swimming pool because of the adhesive properties of water? Yet small insects that land on a pond’s surface may find these forces to be lethal, preventing these organisms from breaking away from the water’s surface! In addition, are your students frequently prevented from leaving their homes because of high winds, simply unable to walk around outside? The movements of small insects are often prevented by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a pest on days when there is a good breeze. 2. The consequences of large size in organisms require transport and exchange systems extending to the deepest inner regions. Whether we think of a whale, a giant redwood, or the United States, these principles apply. By analogy, the railway and highway systems of the United States transport essential products from ocean ports to the deepest interior regions, where other transport systems deliver the goods to stores for sale. A person living near the ocean may obtain food directly, by fishing in the ocean. A person living in the Midwest may purchase ocean fish at a store or at a restaurant. 3. Organisms and individual cells need sufficient surface exchange and transport systems to support their surface-to-volume ratios. Cell size is limited, in part, by the ability of a cell to exchange materials efficiently with its surface. Thus, adaptations that increase surface area can permit cells to reach larger sizes. Active Lecture Tips 1. Ask students to turn to someone near them to list at least four factors that affect heat gain and loss during periods of physical activity. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. These examples will demonstrate how much our homeostatic mechanisms must work to maintain a steady body temperature. These factors include (a) the person’s physical condition, (b) the level of physical activity, (c) the age of the person (younger people tend to have higher metabolic rates), (d) the person’s level of hydration (which in turn affects the amount of sweating and evaporative cooling), (e) the external level of humidity (higher levels decrease evaporative cooling), (f) the intensity of the wind (greater intensity promotes evaporative cooling), (g) the intensity of sunlight, and (h) the color of the person’s clothing (which affects the amount of light energy the body absorbs). 57

Mouth Gastrovascular cavity Exchange Exchange Exchange (a) Single cell
Figure 21.9 Mouth Gastrovascular cavity Exchange Exchange Exchange (a) Single cell (b) Two cell layers Figure 21.9 Contact of simple organisms with the environment

Figure Figure Contact of simple organisms with the environment (part 1: amoeba)

Exchange with the environment is more complicated for complex, multilayered animals. Each cell in a multicellular organism has a plasma membrane where exchange can occur. But this exchange only works if all the cells of the animal have access to a suitable watery environment. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. It can be difficult for students to think of their own bodies in such simple terms as surfaces and tubes. Perceiving the digestive tract as one continuous tube, in which food that passes through never technically enters the body, is one such challenge. Illustrate these fundamental principles first using simple animals as examples. Then apply these principles to humans as a final test of comprehension. 2. If students have not previously examined the diversity of animals, consider a brief overview of the fundamental body plans before explaining how these fundamental principles of form and function generally apply to the animal kingdom. Teaching Tips 1. Students often fail to consider the overall significance of body size. Consider asking your students to think about the impact of being small. Do they recall ever having trouble emerging from a swimming pool because of the adhesive properties of water? Yet small insects that land on a pond’s surface may find these forces to be lethal, preventing these organisms from breaking away from the water’s surface! In addition, are your students frequently prevented from leaving their homes because of high winds, simply unable to walk around outside? The movements of small insects are often prevented by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a pest on days when there is a good breeze. 2. The consequences of large size in organisms require transport and exchange systems extending to the deepest inner regions. Whether we think of a whale, a giant redwood, or the United States, these principles apply. By analogy, the railway and highway systems of the United States transport essential products from ocean ports to the deepest interior regions, where other transport systems deliver the goods to stores for sale. A person living near the ocean may obtain food directly, by fishing in the ocean. A person living in the Midwest may purchase ocean fish at a store or at a restaurant. 3. Organisms and individual cells need sufficient surface exchange and transport systems to support their surface-to-volume ratios. Cell size is limited, in part, by the ability of a cell to exchange materials efficiently with its surface. Thus, adaptations that increase surface area can permit cells to reach larger sizes. Active Lecture Tips 1. Ask students to turn to someone near them to list at least four factors that affect heat gain and loss during periods of physical activity. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. These examples will demonstrate how much our homeostatic mechanisms must work to maintain a steady body temperature. These factors include (a) the person’s physical condition, (b) the level of physical activity, (c) the age of the person (younger people tend to have higher metabolic rates), (d) the person’s level of hydration (which in turn affects the amount of sweating and evaporative cooling), (e) the external level of humidity (higher levels decrease evaporative cooling), (f) the intensity of the wind (greater intensity promotes evaporative cooling), (g) the intensity of sunlight, and (h) the color of the person’s clothing (which affects the amount of light energy the body absorbs). 60

Figure 21.10 shows a schematic model of an animal body, highlighting the three organ systems (digestive, respiratory, and urinary) that exchange materials with the external environment. The circulatory system connects to nearly every organ system as it transports needed materials from the environment to the body’s tissues and carries wastes away. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. It can be difficult for students to think of their own bodies in such simple terms as surfaces and tubes. Perceiving the digestive tract as one continuous tube, in which food that passes through never technically enters the body, is one such challenge. Illustrate these fundamental principles first using simple animals as examples. Then apply these principles to humans as a final test of comprehension. 2. If students have not previously examined the diversity of animals, consider a brief overview of the fundamental body plans before explaining how these fundamental principles of form and function generally apply to the animal kingdom. Teaching Tips 1. Students often fail to consider the overall significance of body size. Consider asking your students to think about the impact of being small. Do they recall ever having trouble emerging from a swimming pool because of the adhesive properties of water? Yet small insects that land on a pond’s surface may find these forces to be lethal, preventing these organisms from breaking away from the water’s surface! In addition, are your students frequently prevented from leaving their homes because of high winds, simply unable to walk around outside? The movements of small insects are often prevented by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a pest on days when there is a good breeze. 2. The consequences of large size in organisms require transport and exchange systems extending to the deepest inner regions. Whether we think of a whale, a giant redwood, or the United States, these principles apply. By analogy, the railway and highway systems of the United States transport essential products from ocean ports to the deepest interior regions, where other transport systems deliver the goods to stores for sale. A person living near the ocean may obtain food directly, by fishing in the ocean. A person living in the Midwest may purchase ocean fish at a store or at a restaurant. 3. Organisms and individual cells need sufficient surface exchange and transport systems to support their surface-to-volume ratios. Cell size is limited, in part, by the ability of a cell to exchange materials efficiently with its surface. Thus, adaptations that increase surface area can permit cells to reach larger sizes. Active Lecture Tips 1. Ask students to turn to someone near them to list at least four factors that affect heat gain and loss during periods of physical activity. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. These examples will demonstrate how much our homeostatic mechanisms must work to maintain a steady body temperature. These factors include (a) the person’s physical condition, (b) the level of physical activity, (c) the age of the person (younger people tend to have higher metabolic rates), (d) the person’s level of hydration (which in turn affects the amount of sweating and evaporative cooling), (e) the external level of humidity (higher levels decrease evaporative cooling), (f) the intensity of the wind (greater intensity promotes evaporative cooling), (g) the intensity of sunlight, and (h) the color of the person’s clothing (which affects the amount of light energy the body absorbs). 61

Metabolic waste products (such as urine)
Figure 21.10 External environment CO2 Mouth Food O2 Animal Respiratory system Digestive system Interstitial fluid Heart Nutrients Circulatory system Body cells Urinary system Anus Unabsorbed matter (feces) Metabolic waste products (such as urine) Figure Exchange between the external environment and the internal environment of complex animals

Complex animals have evolved extensively folded or branched internal surfaces that maximize surface area for exchange with the immediate environment. Lungs exchange oxygen and carbon dioxide with the air you breathe. The epithelium of the lungs has a very large total surface area. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. It can be difficult for students to think of their own bodies in such simple terms as surfaces and tubes. Perceiving the digestive tract as one continuous tube, in which food that passes through never technically enters the body, is one such challenge. Illustrate these fundamental principles first using simple animals as examples. Then apply these principles to humans as a final test of comprehension. 2. If students have not previously examined the diversity of animals, consider a brief overview of the fundamental body plans before explaining how these fundamental principles of form and function generally apply to the animal kingdom. Teaching Tips 1. Students often fail to consider the overall significance of body size. Consider asking your students to think about the impact of being small. Do they recall ever having trouble emerging from a swimming pool because of the adhesive properties of water? Yet small insects that land on a pond’s surface may find these forces to be lethal, preventing these organisms from breaking away from the water’s surface! In addition, are your students frequently prevented from leaving their homes because of high winds, simply unable to walk around outside? The movements of small insects are often prevented by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a pest on days when there is a good breeze. 2. The consequences of large size in organisms require transport and exchange systems extending to the deepest inner regions. Whether we think of a whale, a giant redwood, or the United States, these principles apply. By analogy, the railway and highway systems of the United States transport essential products from ocean ports to the deepest interior regions, where other transport systems deliver the goods to stores for sale. A person living near the ocean may obtain food directly, by fishing in the ocean. A person living in the Midwest may purchase ocean fish at a store or at a restaurant. 3. Organisms and individual cells need sufficient surface exchange and transport systems to support their surface-to-volume ratios. Cell size is limited, in part, by the ability of a cell to exchange materials efficiently with its surface. Thus, adaptations that increase surface area can permit cells to reach larger sizes. Active Lecture Tips 1. Ask students to turn to someone near them to list at least four factors that affect heat gain and loss during periods of physical activity. After perhaps two minutes, have pairs of students contribute the examples they came up with for a quick discussion. These examples will demonstrate how much our homeostatic mechanisms must work to maintain a steady body temperature. These factors include (a) the person’s physical condition, (b) the level of physical activity, (c) the age of the person (younger people tend to have higher metabolic rates), (d) the person’s level of hydration (which in turn affects the amount of sweating and evaporative cooling), (e) the external level of humidity (higher levels decrease evaporative cooling), (f) the intensity of the wind (greater intensity promotes evaporative cooling), (g) the intensity of sunlight, and (h) the color of the person’s clothing (which affects the amount of light energy the body absorbs). 63

Figure 21.11 Figure The branched surface area of the human lung

Regulating The Internal Environment
Animals adjust to a changing environment. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 65

Homeostasis The internal environment of vertebrates includes the interstitial fluid that fills the spaces between cells and exchanges nutrients and wastes with microscopic blood vessels. Homeostasis, which literally means “steady state,” is the tendency to maintain relatively constant conditions in the internal environment even when the external environment changes. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 66

Animal’s internal environment
Figure 21.12 Animal’s internal environment External environment 37C HOMEOSTATIC MECHANISMS 39C 38C 4C Large external changes Small internal changes Figure An example of homeostasis

Thermoregulation The homeostatic mechanism that controls temperature is called thermoregulation. The ability to maintain a body temperature substantially warmer than the surrounding environment is characteristic of endotherms, animals such as mammals and birds that derive most of their body heat from their own metabolism. In contrast, ectotherms, which include most invertebrates, fishes, amphibians, and nonbird reptiles, obtain their body heat primarily by absorbing it from their surroundings. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 68

Thermoregulation You have a number of structures and mechanisms that aid in thermoregulation. When your body temperature falls below normal, your brain’s control center sends signals that trigger changes that will bring it back to normal. Blood vessels near your body’s surface constrict (reducing heat loss from your body surface) and muscles contract, causing you to shiver. When body temperature gets too high, the control center sends signals to dilate the blood vessels near your skin and activate sweat glands, allowing excess heat to escape. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 69

Thermoregulation Fever, an abnormally high internal temperature is a body-wide response that usually indicates an ongoing fight against infection. Many people mistakenly believe that the invading microbes themselves cause a fever. In fact, the cause is usually the body’s fight against the microbes. A moderate fever of 38–39°C (100–102°F), however, discourages bacterial growth and speeds the body’s internal defenses. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 70

Body temperature near 37C (98.6F)
Figure 21.14 Skin Response: 1. Blood vessels dilate 2. Sweat is produced Sweat gland Control center in brain activates cooling mechanisms Stimulus: Body temperature is above set point Body temperature drops Set point: Body temperature near 37C (98.6F) Stimulus: Body temperature is below set point Body temperature rises Skin Response: 1. Blood vessels constrict 2. Person shivers 3. Metabolic rate increases Control center in brain activates warming mechanisms Figure Thermoregulation in the human body

Figure Skin Response: 1. Blood vessels dilate 2. Sweat is produced Control center in brain activates cooling mechanisms Sweat gland Stimulus: Body temperature is above set point Body temperature drops Set point: Body temperature near 37C (98.6F) Figure Thermoregulation in the human body (part 1: above set point)

Figure Set point: Body temperature near 37C (98.6F) Stimulus: Body temperature is below set point Body temperature rises Skin Response: 1. Blood vessels constrict 2. Person shivers 3. Metabolic rate increases Control center in brain activates warming mechanisms Figure Thermoregulation in the human body (part 2: below set point)

The Process of Science: How Does a Python Warm Her Eggs?
Observation: A female Burmese python incubating her eggs wraps her body around them and frequently contracts the muscles in her coils. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 74

Hypothesis: The snake’s muscle contractions elevate its body temperature for transfer of heat to its eggs. Experiment: Researchers placed a python and her eggs in a chamber and varied the chamber’s temperature. They monitored the rate of the python’s muscle contractions and took into account the snake’s oxygen uptake, a measure of the rate of cellular respiration. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 75

Results: The python’s oxygen consumption increased when the temperature in the chamber decreased. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 76

O2 consumption (mL O2/hr) per kg
Figure 21.15 120 100 80 O2 consumption (mL O2/hr) per kg 60 40 20 5 10 15 20 25 30 35 Contractions per minute Figure Oxygen consumed by a Burmese python as it constricts its muscles

Osmoregulation Living cells depend on a precise balance of
water and solutes. Osmoregulation is the control of the gain or loss of dissolved solutes, such as the ions of NaCl and other salts. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 78

Osmoregulation Saltwater fish lose water by osmosis because there is less salt in their tissues than the water they swim in. Freshwater fish have the opposite problem: The external solute concentration is low, so water enters the fish by osmosis. Most land animals lose water through urinating, defecating, breathing, and perspiring but can counterbalance the loss by eating and drinking © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 79

Figure 21.16 Figure Counterbalancing water loss through drinking

Interconnections within Systems: Homeostasis in the Urinary System
The urinary system plays a central role in osmoregulation, regulating the amount of water and solutes in body fluids by retaining water when we are dehydrated and expelling it when we are hydrated. Besides osmoregulation, the urinary system plays another important role—the excretion of wastes. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 81

In humans, the two kidneys are the main processing centers and contain nearly 100 miles of thin tubes called tubules and an intricate network of capillaries. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 82

As blood circulates through the kidneys, a fraction of it is filtered and plasma enters the kidney tubules, forming filtrate. Filtrate contains valuable substances that need to be reclaimed (such as water and glucose) and substances to be eliminated, such as urea. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 83

The human urinary system includes the circulatory system, the kidneys, nephrons, the functional units within the kidneys, and the urinary bladder, where urine is stored. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 84

(b) Kidney (cutaway view) (c) Blood supply to a nephron
Figure 21.17 Filter Tubule Renal artery (red) and renal vein (blue) Branch of renal artery Collecting duct Kidney Branch of renal vein Ureter Urinary bladder To ureter Urethra Ureter (b) Kidney (cutaway view) (c) Blood supply to a nephron (a) Urinary system Figure Anatomy of the human urinary system

Renal artery (red) and renal vein (blue) Kidney Ureter Urinary bladder
Figure Renal artery (red) and renal vein (blue) Kidney Ureter Urinary bladder Urethra (a) Urinary system Figure Anatomy of the human urinary system (part 1: urinary system)

(b) Kidney (cutaway view) (c) Blood supply to a nephron
Figure Filter Tubule Branch of renal artery Collecting duct Branch of renal vein To ureter Ureter (b) Kidney (cutaway view) (c) Blood supply to a nephron Figure Anatomy of the human urinary system (part 2: kidney and nephron)

Nephrons carry out the functions of the urinary system, consist of a tubule and its associated blood vessels, and number more than a million in a kidney. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 88

Nephrons perform four key functions: Filtration occurs as water and other small molecules are forced out of the blood when it passes through capillary walls into the kidney tubule, forming filtrate. Reabsorption reclaims water and valuable solutes from the filtrate and returns them to the blood. Secretion of certain substances, such as some ions and drugs, that are transported into the filtrate. Excretion of urine from the kidneys to the outside. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 89

Filtration Renal artery Filtrate Renal vein Capillaries Tubule
Figure 21.18 Filtration Renal artery Filtrate Reabsorption Renal vein Secretion Capillaries Tubule Excretion Urine Figure Major functions of a nephron

Hormones regulate the kidney’s nephrons to maintain water balance and are central to the interconnections of the nervous, endocrine, and urinary systems. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 91

Understanding filtration, reabsorption, and secretion will help you see why urine samples are often used to assess health. The presence of glucose in a urine sample suggests diabetes, a serious condition in which the blood glucose level is elevated. Drugs are secreted into urine and can be detected there. Pregnancy can be confirmed by the presence of a specific hormone excreted only in the urine of pregnant women. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 92

Factors affecting urine composition include the environment, presence of disease, secretions from the various harmless microbes that can live in the lower part of the urethra, and diet. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 93

Figure 21.19 Figure A typical urine test strip used to detect diabetes and kidney malfunction

Evolution Connection: Adaptations for Thermoregulation
Natural selection has promoted a wide variety of adaptations for thermoregulation including anatomical, physiological, and behavioral adaptations. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 95

A major anatomical adaptation in mammals and birds is insulation, consisting of hair (fur), feathers, or fat layers. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 96

Some adaptations are physiological, such as land mammals and birds reacting to cold by raising their fur or feathers, hormonal changes tending to boost the metabolic rate of some birds and mammals, increasing their heat production in cold weather, shivering to produce heat as a metabolic by-product of the contraction of skeletal muscles, and panting and sweating to greatly increase cooling. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 97

METHODS OF THERMOREGULATION
Figure 21.20 METHODS OF THERMOREGULATION Anatomical Adaptations (such as hair, fat, and feathers) Physiological Adaptations (such as panting, shivering, and sweating) Behavioral Adaptations (such as bathing, basking, hibernating, and migrating) Figure Methods of thermoregulation in animals

Anatomical Adaptations (such as hair, fat, and feathers)
Figure Anatomical Adaptations (such as hair, fat, and feathers) Figure Methods of thermoregulation in animals (part 1: anatomical)

Physiological Adaptations (such as panting, shivering,
Figure Physiological Adaptations (such as panting, shivering, and sweating) Figure Methods of thermoregulation in animals (part 2: physiological)

Behavioral Adaptations (such as bathing, basking,
Figure Behavioral Adaptations (such as bathing, basking, hibernating, and migrating) Figure Methods of thermoregulation in animals (part 3: behavioral)

Figure Figure Methods of thermoregulation in animals (part 4: dung beetle)

A variety of behavioral responses can regulate body temperature. Some birds and butterflies migrate seasonally to more suitable climates. Other animals, such as desert lizards, bask in the sun when it is cold and find cool, damp areas or burrows when it is hot. Emperor penguins huddle together to stay warm. Many animals cool themselves by bathing. © 2016 Pearson Education, Inc. Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help. 2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store. Teaching Tips 1. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep your body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 2. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 3. Students might better understand a problem faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. 4. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst! 5. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation. Active Lecture Tips 1. Challenge your students to work in small groups to think of other examples of negative and positive feedback. Students from diverse disciplines may think of many new examples, including mechanisms in an automobile. 2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm. Encourage students to work in small groups to discuss why endotherm and ectotherm are preferred terms. (In part, some ectotherms, such as tropical marine organisms, maintain warmer bodies than some endotherms such as bats and hummingbirds, which sometimes allow their temperatures to drop.) 3. Ask your students to work in small groups to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about ten times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? (Endotherms can remain active during colder temperatures at night and during the winter, when they can hunt ectotherms more easily!) 103

HIERARCHICAL ORGANIZATION OF ANIMALS
Figure 21.UN01 HIERARCHICAL ORGANIZATION OF ANIMALS Level Description Example Cell The basic unit of all living organisms Muscle cell Tissue A collection of similar cells performing a specific function Cardiac muscle Organ Multiple tissues forming a structure that performs a specific function Heart Organ system A team of organs that work together Circulatory system Organism A living being, which depends on the coordination of all structural levels for homeostasis and survival Person Figure 21.UN01 Summary of key concepts: hierarchical organization

A collection of similar cells performing a specific function
Figure 21.UN01a HIERARCHICAL ORGANIZATION OF ANIMALS Level Description Example Cell The basic unit of all living organisms Muscle cell Tissue A collection of similar cells performing a specific function Cardiac muscle Organ Multiple tissues forming a structure that performs a specific function Heart Figure 21.UN01a Summary of key concepts: hierarchical organization (part 1)

HIERARCHICAL ORGANIZATION OF ANIMALS
Figure 21.UN01b HIERARCHICAL ORGANIZATION OF ANIMALS Level Description Example Organ system A team of organs that work together Circulatory system Organism A living being, which depends on the coordination of all structural levels for homeostasis and survival Person Figure 21.UN01b Summary of key concepts: hierarchical organization (part 2)

Muscle (contracts) Connective (supports organs) Epithelial (covers
Figure 21.UN02 Muscle (contracts) Connective (supports organs) Epithelial (covers body surfaces and organs) Nervous (relays and integrates information) Figure 21.UN02 Summary of key concepts: tissue types

molecules enter the tubule.
Figure 21.UN03 Blood Capillaries Filtration Water and small molecules enter the tubule. Tubule Reabsorption Water and valuable solutes are returned to the blood. Secretion Specific substances are removed from the blood. Excretion Urine exits the body. Urine Figure 21.UN03 Summary of key concepts: homeostasis in the urinary system

Ambient (environmental)
Figure 21.UN04 40 River otter 30 Body temperature (C) 20 Largemouth bass 10 10 20 30 40 Ambient (environmental) temperature (C) Figure 21.UN04 Process of science, question 12 (thermoregulation)

Unifying Concepts of Animal Structure and Function

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