Unifying Concepts of Animal Structure and Function

Unifying Concepts of Animal Structure and Function
Chapter 21 Unifying Concepts of Animal Structure and Function

Biology and Society: An Avoidable Tragedy
Our bodies are kept in a narrow temperature range. When we exercise, our bodies are cooled by evaporation of sweat on the skin and expansion of blood vessels near the skin surface. © 2013 Pearson Education, Inc. 2

Figure 21.0 Figure 21.0 Sweating and drinking water are two ways of cooling the human body.

Biology and Society: An Avoidable Tragedy
Extreme conditions can lead to loss of consciousness in heat exhaustion, even higher body temperatures, which can disrupt the brain’s control center, and heat stroke, a life-threatening emergency. © 2013 Pearson Education, Inc. 4

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. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 5

Cellular level: Muscle cell
Figure Cellular level: Muscle cell Figure 21.1 Structural hierarchy in a human (step 1)

Cellular level: Muscle cell Tissue level: Cardiac muscle
Figure Cellular level: Muscle cell Tissue level: Cardiac muscle Figure 21.1 Structural hierarchy in a human (step 2)

Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level:
Figure Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level: Heart Figure 21.1 Structural hierarchy in a human (step 3)

Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level:
Figure Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level: Heart Organ system level: Circulatory system Figure 21.1 Structural hierarchy in a human (step 4)

Organism level: Multiple organ systems functioning together
Figure 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 Structural hierarchy in a human (step 5)

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: The Hierarchical Organization of Animals

Form Fits Function Analyzing a biological structure gives us clues about what it does and how it works. Conversely, knowing the function of a structure provides insight about its construction. In exploring life at its many levels, we will discover functional elegance at every turn. When discussing structure and function, biologists distinguish anatomy from physiology. Anatomy is the study of the structure while Physiology is the study of the function. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 12

Form Fits Function The correlation of form (structure) and function is a fundamental principle of biology that is evident at all levels of life’s hierarchy; it is a principle that will guide us throughout our study of animals. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 13

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

Tissues The cell is the basic unit of all living organisms. In almost all animals, including humans, cells rarely act alone but instead are grouped into tissues. 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. The cells composing a tissue are specialized; they have an overall structure that enables them to perform a specific task. Animals have four main categories of tissue. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 15

1. Epithelial tissue, also known as epithelium
Epidermis of the skin and linings of the heart, blood vessels and digestive tract Sheets of tightly packed cells that are fused together Body continuously renews the cells of epithelial tissues, shedding old cells and growing new ones Exposed to the environment and carcinogens which is why 80% of cancers are epithelial © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 16

Some examples of organs lined with epithelial tissue:
Figure Some examples of organs lined with epithelial tissue: Heart Lung Stomach Small intestine Epithelial cells Large intestine Epithelial tissue lining esophagus Urinary bladder Epithelial tissue lining small intestine Figure 21.3 Epithelial tissue (step 3)

The structure of connective tissue is correlated with its functions:
2. Connective tissues have a sparse population of cells in an extracellular matrix consisting of a web of protein fibers within a uniform foundation that may be liquid, jellylike, or solid. The structure of connective tissue is correlated with its functions: to bind and support other tissues. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 18

(a) Loose connective tissue (d) Fibrous connective tissue
Figure 21.4 (a) Loose connective tissue (b) Adipose tissue (c) Blood (d) Fibrous connective tissue (f) Bone (e) Cartilage Figure 21.4 Types of connective tissue

Loose connective tissue
is the most widespread connective tissue, binds epithelia to underlying tissues, and holds organs in place Held together by a mesh of protein fibers that provide great strength and elasticity. Decrease in the production of collagen can result in wrinkles © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 20

Connective Tissue Adipose tissue stores fat, stockpiles energy, and
pads and insulates the body each adipose cell contains a large globule of fat gaining body fat involves increasing the size of the fat cell, not creating new fat cells © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 21

Connective Tissue Blood is a connective tissue and
contains red and white blood cells suspended in a liquid called plasma. functions mainly in transporting substances from one part of the body to another also plays a role in immunity (white blood cells) © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 22

Fibrous connective tissue
has a dense matrix of collagen and forms tendons (muscle to bone) and ligaments (bone to bone) © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 23

Connective Tissue Cartilage is strong but flexible,
has no blood vessels, so it heals very slowly, functions as a flexible, boneless skeleton, and forms the shock-absorbing pads that cushion the ends of bones including the vertebrae of the spinal column. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 24

Connective Tissue Bone is a rigid connective tissue and
has a matrix of collagen fibers hardened with deposits of calcium salts. makes bone hard without being brittle © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 25

Muscle Tissue 3. 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. Three types of muscle: skeletal, cardiac and smooth © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 26

(b) Cardiac muscle (a) Skeletal muscle (c) Smooth muscle Figure 21.5
Figure 21.5 Three types of muscle tissue

Muscle Tissue Skeletal muscle is attached to bones by tendons,
responsible for voluntary movements, and striated because the contractile proteins form a banded pattern adults have a fixed number of these cells weight training increases size of cell – not number of cells © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 28

Muscle Tissue Cardiac muscle is found only in heart tissue
composed of cells that are branched and striated, involuntary, and responsible for the contraction of the heart. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 29

Muscle Tissue Smooth muscle is named for its lack of obvious stripes,
found in the walls of various organs such as intestines and blood vessels, and involuntary contracts more slowly than skeletal muscle, but can remain contracted for longer period of time © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 30

The basic unit of nervous tissue is the neuron, or nerve cell.
makes communication of sensory 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. with long extension called the axon can transmit electrical signals very rapidly over long distance © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 31

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

Brain Spinal cord Nerve Figure 21.6a
Figure 21.6 Nervous tissue (part 1)

Signal-receiving extensions Cell body Signal- transmitting extension
Figure 21.6b Signal-receiving extensions Cell body Signal- transmitting extension LM Figure 21.6 Nervous tissue (part 2)

Organs and Organ Systems
An organ consists of two or more tissues packaged into one working unit that performs a specific function. Examples include the heart, liver, stomach, brain, and small intestines. An organ performs functions that none of its component tissues can carry out alone. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 35

Examine the layered arrangement of tissues in the wall of the small intestine. - inside wall lined with epithelial tissue - underneath are two layers of connective tissue - layer of smooth muscle - outside wall lined with epithelial tissue © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 36

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. Skeletal, Muscular, Digestive, Circulatory, Respiratory, Urinary, Endocrine, Reproductive, Lymphatic/Immune, Nervous, Integumentary © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of 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 line 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. 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 teeth were not used by these cats for that function (biological role)! Teaching 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 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. 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. 5. 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. 6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk. 7. 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 become self-aware! 38

Skeletal system: supports body and anchors muscles Bone Cartilage
Figure 21.8a Skeletal system: supports body and anchors muscles Bone Cartilage Figure 21.8 Organ systems of a vertebrate: skeletal (part 1)

transports substances throughout body
Figure 21.8b Circulatory system: transports substances throughout body Heart Blood vessels Figure 21.8 Organ systems of a vertebrate: circulatory (part 2)

Respiratory system: exchanges O2 and CO2 between blood and air
Figure 21.8c Respiratory system: exchanges O2 and CO2 between blood and air Nasal cavity Pharynx Larynx Trachea Bronchus Lung Figure 21.8 Organ systems of a vertebrate: respiratory (part 3)

Muscular system: moves the body Skeletal muscles Figure 21.8d
Figure 21.8 Organ systems of a vertebrate: muscular (part 4)

Digestive system: breaks down food and absorbs nutrients Mouth
Figure 21.8e Digestive system: breaks down food and absorbs nutrients Mouth Esophagus Liver Stomach Large intestine Small intestine Anus Figure 21.8 Organ systems of a vertebrate: digestive (part 5)

Urinary system: rids body of certain wastes Kidney Urinary bladder
Figure 21.8f Urinary system: rids body of certain wastes Kidney Urinary bladder Ureter Urethra Figure 21.8 Organ systems of a vertebrate: urinary (part 6)

Endocrine system: secretes hormones that regulate body Hypothalamus
Figure 21.8g Endocrine system: secretes hormones that regulate body Hypothalamus Pituitary gland Parathyroid gland Thyroid gland Adrenal gland Ovary (female) Pancreas Testis (male) Figure 21.8 Organ systems of a vertebrate: endocrine (part 7)

Reproductive system: produces gametes and offspring Seminal vesicles
Figure 21.8h Reproductive system: produces gametes and offspring Seminal vesicles Prostate gland Oviduct Vas deferens Ovary Penis Uterus Urethra Vagina Testis Figure 21.8 Organ systems of a vertebrate: reproductive (part 8)

Integumentary System (skin): protects body Hair Skin Nail Figure 21.8i
Figure 21.8 Organ systems of a vertebrate: integumentary (part 9)

Lymphatic and immune system: defends against disease Thymus Spleen
Figure 21.8j Lymphatic and immune system: defends against disease Thymus Spleen Lymph nodes Lymphatic vessels Figure 21.8 Organ systems of a vertebrate: lymphatic and immune (part 10)

Nervous system: processes sensory Brain information and controls
Figure 21.8k Nervous system: processes sensory information and controls responses Brain Sense organ (ear) Spinal cord Nerves Figure 21.8 Organ systems of a vertebrate: nervous (part 11)

EXCHANGES WITH THE EXTERNAL ENVIRONMENT
Every organism is an open system, continuously exchanging chemicals and energy with its surroundings to survive. You eat, breathe, defecate, urinate, sweat and radiate heat – all examples of how you are an open system An animal’s size and shape affect its exchanges with its surrounding environment. All living cells must be bathed in a watery solution so that exchange of materials can occur. © 2013 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 warehouses and other transport systems deliver the goods to stores for purchase. 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. 4. You might note how sponges are well adapted to maximize their surface area exposed to water. Their highly porous system dramatically increases the region engaged in water filtration. 5. The stratified squamous epithelium on most outside surfaces of our body resists abrasions in part because it is keratinized. However, the nonkeratinized epithelial tissues that line our body cavities, such as the mouth, pharynx, esophagus, and anus, are also resistant to abrasion as a result of mucus coatings, which provide friction-reducing lubrication. Students may not realize that the same type of tissue performs similar functions in very different parts of the body.

The entire surface area of a single-celled amoeba is in contact with its watery environment. A hydra has a body wall only two cell layers thick. Both layers of cells are bathed in pond water, enabling exchange with the environment. © 2013 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 warehouses and other transport systems deliver the goods to stores for purchase. 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. 4. You might note how sponges are well adapted to maximize their surface area exposed to water. Their highly porous system dramatically increases the region engaged in water filtration. 5. The stratified squamous epithelium on most outside surfaces of our body resists abrasions in part because it is keratinized. However, the nonkeratinized epithelial tissues that line our body cavities, such as the mouth, pharynx, esophagus, and anus, are also resistant to abrasion as a result of mucus coatings, which provide friction-reducing lubrication. Students may not realize that the same type of tissue performs similar functions in very different parts of the body. 51

(a) Single cell (b) Two cell layers Mouth Gastrovascular cavity
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

Animals with complex body forms face the same basic problems. Every cell must be bathed in fluid and have access to resources from the outside environment. each cell in a multicellular animal has a plasma membrane where exchange of materials occurs © 2013 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 warehouses and other transport systems deliver the goods to stores for purchase. 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. 4. You might note how sponges are well adapted to maximize their surface area exposed to water. Their highly porous system dramatically increases the region engaged in water filtration. 5. The stratified squamous epithelium on most outside surfaces of our body resists abrasions in part because it is keratinized. However, the nonkeratinized epithelial tissues that line our body cavities, such as the mouth, pharynx, esophagus, and anus, are also resistant to abrasion as a result of mucus coatings, which provide friction-reducing lubrication. Students may not realize that the same type of tissue performs similar functions in very different parts of the body. 53

Complex animals have evolved extensively folded or branched internal surfaces that maximize surface area for exchange with the immediate environment. Example: Lungs have a very large total surface area and exchange oxygen and carbon dioxide with the air you breathe. surface area the size of a tennis court © 2013 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 warehouses and other transport systems deliver the goods to stores for purchase. 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. 4. You might note how sponges are well adapted to maximize their surface area exposed to water. Their highly porous system dramatically increases the region engaged in water filtration. 5. The stratified squamous epithelium on most outside surfaces of our body resists abrasions in part because it is keratinized. However, the nonkeratinized epithelial tissues that line our body cavities, such as the mouth, pharynx, esophagus, and anus, are also resistant to abrasion as a result of mucus coatings, which provide friction-reducing lubrication. Students may not realize that the same type of tissue performs similar functions in very different parts of the body. 54

Figure 21.10 Figure The branched surface area of the human lung

Animals use three organ systems to exchange materials with the external environment: digestive, respiratory, and urinary The circulatory system plays a vital role in moving substances from these three systems to areas throughout the body. © 2013 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 warehouses and other transport systems deliver the goods to stores for purchase. 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. 4. You might note how sponges are well adapted to maximize their surface area exposed to water. Their highly porous system dramatically increases the region engaged in water filtration. 5. The stratified squamous epithelium on most outside surfaces of our body resists abrasions in part because it is keratinized. However, the nonkeratinized epithelial tissues that line our body cavities, such as the mouth, pharynx, esophagus, and anus, are also resistant to abrasion as a result of mucus coatings, which provide friction-reducing lubrication. Students may not realize that the same type of tissue performs similar functions in very different parts of the body. 56

Unabsorbed matter (feces) Metabolic waste products (such as urine)
Figure 21.11 External environment CO2 Mouth Food O2 Animal Respiratory system Digestive system Blood 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

REGULATING THE INTERNAL ENVIRONMENT
Animals adjust to a changing environment. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 58

Homeostasis Homeostasis (“steady” “state”)is the body’s ability to stay relatively unchanged even when the world around it changes. tendency to maintain constant conditions in the internal environment even when external environment changes. body temperature changes less than one degree diabetes – loss of glucose homeostasis Changes due occur, but generally stay within a range that is tolerable for living cells © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 59

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. it is important that the composition of this fluid stay relatively constant – maintaining homeostasis. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 60

HOMEOSTATIC MECHANISMS
Figure 21.12 External environment Animal’s internal environment HOMEOSTATIC MECHANISMS Large external changes Small internal changes Figure Homeostasis

Negative and Positive Feedback
Most mechanisms of homeostasis depend on a principle called negative feedback, in which the results of a process inhibit that same process, such as a thermostat that turns off a heater when room temperature rises to the set point. The result (increased room temperature) of a process (heating the air) inhibits that very process (by switching the heater off). This is the most common type of feedback in animals. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 62

Response: Heating Thermostat stops (control center) turns heater off
Figure 21.13 Response: Heating stops Thermostat (control center) turns heater off Stimulus: Room temperature is above set point Room temperature drops Set point: Room temperature 20°C (68°F) Stimulus: Room temperature is below set point Room temperature rises Thermostat (control center) turns heater on Response: Heating starts Figure An example of negative feedback: control of room temperature

Negative and Positive Feedback
Less common is positive feedback, in which the results of a process intensify that same process, such as uterine contractions during childbirth Contractions start and these contractions stimulate more contractions which stimulate more contractions which stimulate more contractions which stimulate more contractions…..etc. until the baby is born. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 64

https://www. youtube. com/watch. v=ufv9Txb7nU0 Homeostasis (12
Homeostasis (12.40) Negative vs. Positive Feedback (11.43)

Thermoregulation Thermoregulation is the maintenance of internal body temperature. Endotherms such as mammals and birds derive the majority of their body heat from their metabolism. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 66

Thermoregulation Ectotherms
such as most invertebrates, fishes, amphibians, and nonbird reptiles obtain body heat primarily by absorbing it from their surroundings. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 67

Thermoregulation Humans have homeostatic mechanisms that aid in thermoregulation Brain has a control center that keeps the body at a constant 37 Celsius When body temperature falls below normal, brain sends signals that trigger changes that will bring it back to normal: blood vessels near body surface constrict ( conserving heat muscles begin to contract (shivering) © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 68

Thermoregulation Fever
is an abnormally high internal body temperature and usually indicates an ongoing fight against infection When immune system cells encounter microbes, they send chemicals that travel through the bloodstream to the brain stimulating your brain to raise the body temperature. Moderate temperature (38-39 C) discourages bacterial growth and speeds body’s internal defenses. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 69

Osmoregulation Living cells depend on a precise balance of water and solutes. Cell cannot survive if too much water enters or leaves. Cell may exchange water with the environment as long as the total amount leaving and entering is the same. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 70

Osmoregulation Osmoregulation is the control of the gain or loss of water and dissolved solutes, such as the ions of NaCl and other salts. Always a net movement of water from the solution with lower solute concentration to the one with higher solute concentration. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 71

Osmoregulation Osmoconformers Osmoregulators
have internal and external environments with similar solute concentrations and include most marine invertebrates. Osmoregulators actively regulate their water loss or gain and include freshwater animals, most marine vertebrates, and all land animals. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 72

Osmoconformer Osmoregulator Figure 21.16
Figure Osmoconformers and osmoregulators

Homeostasis in the Urinary System
The human urinary system plays a central role in homeostasis, forms and excretes waste-carrying urine, and regulates the amount of water and solutes in body fluids. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 74

In humans, the two kidneys are the main processing centers and contain many fine tubes called tubules and an intricate network of capillaries. every day all of the blood in the body passes through the capillaries of the kidneys hundreds of times © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 75

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. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 76

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. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 77

(c) A nephron and collecting duct (b) Kidney
Figure 21.17 (c) A nephron and collecting duct (b) Kidney (a) Urinary system Figure Anatomy of the human urinary system

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. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 79

(c) A nephron and collecting duct
Figure 21.17c Filter Tubule Branch of renal artery Collecting duct Branch of renal vein To ureter (c) A nephron and collecting duct Figure Anatomy of the human urinary system (part 3)

Nephrons perform four key functions. Filtration, forcing water and other small molecules from the blood to form filtrate Reabsorption of water and valuable solutes back into the blood Secretion of certain substances, such as ions and drugs, into the filtrate Excretion of urine from the kidneys to the outside © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 81

Filtration Reabsorption Secretion Renal artery Filtrate Renal vein
Figure 21.18 Filtration Reabsorption Secretion Renal artery Filtrate Renal vein Capillaries Tubule Excretion Urine Figure Major functions of the urinary system

Hormonal control of the nephrons allows the body to control its internal concentration of water and dissolved molecules. When the solute concentration of body fluids rises too high (meaning that not enough water is present) the brain increases levels of a hormone called ADH (antidiurectic hormone). This hormone signals the nephrons to reabsorb more water from the filtrate, effectively increasing the water content. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 83

Kidney failure can be caused by injury, illness, or prolonged use of pain relievers (including over-the-counter medicines such as aspirin), alcohol, or other drugs. One option for treatment of kidney failure is dialysis, filtration of blood by a machine that mimics the action of a nephron. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 84

Line from artery to apparatus Pump Dialyzing solution
Figure 21.19 Line from artery to apparatus Pump Tubing made of a selectively permeable membrane Dialyzing solution Line from apparatus to vein Fresh dialyzing solution Used dialyzing solution (with urea and excess salts) Figure A dialysis machine

Evolution Connection: Adaptations for Thermoregulation
Animals regulate their body temperatures using adaptations that are anatomical, physiological, and/or behavioral. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 86

A major anatomical adaptation in mammals and birds is insulation, consisting of hair (fur), feathers, or fat layers. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 87

Some adaptations are physiological, such as changes in metabolic rate, shivering, or panting and sweating. © 2013 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. Challenge your students 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 discuss why endotherm and ectotherm are preferred. 3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms? 4. 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 the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating. 5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment. 7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever. 8. Students might better understand the problems 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. 9. 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! 10. 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. 88

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 Fat Hair Panting Bathing Figure Methods of thermoregulation in animals

Unifying Concepts of Animal Structure and Function

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