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: Keeping Cool
Our bodies are kept in a narrow temperature range. When we exercise, our bodies are cooled by: Evaporation of sweat on the skin Expansion of blood vessels near the skin surface © 2010 Pearson Education, Inc.

Figure 21.00 Figure 21.0 Thermoregulation

Extreme conditions can lead to:
Loss of consciousness in heat exhaustion Even higher body temperatures, which can disrupt the brain’s control center Heat stroke, a life-threatening emergency

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 Organ systems make up the entire organism Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Organism level: Multiple organ systems functioning together
Cellular level: Muscle cell Tissue level: Cardiac muscle Organ level: Heart Organ system level: Circulatory system Organism level: Multiple organ systems functioning together Figure Figure 21.1 Structural hierarchy in a human (Step 5)

Form Fits Function Analyzing a biological structure gives us clues about: What it does How it works Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

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

Biologists distinguish anatomy from physiology.
Anatomy is the study of the structure of an organism. Physiology is the study of the function of an organism’s structural equipment. Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Tissues In most multicellular animals, cells are grouped into tissues.
A tissue is an integrated group of similar cells that perform a specific function. Animals have four main categories of tissue. Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Epithelial Tissue Epithelial tissue, also known as epithelium:
Covers the surface of the body Lines organs and cavities within the body Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

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

Some examples of organs lined with epithelial tissue:
Heart Lung Stomach Small intestine Large intestine Urinary bladder Figure 21.3a Figure 21.3a Epithelial tissue: examples of organs

Epithelial tissue lining esophagus
Figure 21.3b Figure 21.3b Epithelial tissue: esophagus

Epithelial tissue lining small intestine
Figure 21.3c Figure 21.3c Epithelial tissue: small intestine

Cells of epithelial tissues:
Are bound tightly together Form a protective barrier Fall off and are continuously renewed Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Connective Tissue 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 function: to bind and support other tissues. Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

(a) Loose connective tissue (under the skin) (b) Adipose tissue
Fat droplets Cell Collagen fiber (a) Loose connective tissue (under the skin) (b) Adipose tissue White blood cells Red blood cell Plasma (c) Blood Cell nucleus Collagen fibers (d) Fibrous connective tissue (forming a tendon) Matrix Cells Cells Matrix (f) Bone (e) Cartilage (at the end of a bone) Figure 21.4 Figure 21.4 Types of connective tissue

Loose connective tissue:
Is the most widespread connective tissue Binds epithelia to underlying tissues Holds organs in place Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Adipose tissue: Stores fat Stockpiles energy
Pads and insulates the body Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Blood: Is a connective tissue with a matrix of liquid
Contains red and white blood cells suspended in plasma Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Fibrous connective tissue:
Has a dense matrix of collagen Forms tendons and ligaments Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Cartilage: Has a strong but rubbery matrix
Functions as a flexible, boneless skeleton Forms the shock-absorbing pads that cushion the vertebrae of the spinal column Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Bone: Is a rigid connective tissue
Has a matrix of collagen fibers hardened with deposits of calcium salts Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Muscle Tissue Muscle tissue:
Consists of bundles of long, thin, cylindrical cells called muscle fibers Has specialized proteins that contract when stimulated by a nerve Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

several muscle fibers) Muscle fiber Nucleus
Junction between two cells Muscle fiber (cell) Muscle fiber Unit of muscle contraction Nucleus Nuclei (b) Cardiac muscle (a) Skeletal muscle (short segments of several muscle fibers) Muscle fiber Nucleus (c) Smooth muscle Figure 21.5 Figure 21.5 Three types of muscle tissue

Skeletal muscle is: Attached to bones by tendons
Responsible for voluntary movements Striated because the contractile apparatus forms a banded pattern in each cell or fiber Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Cardiac muscle is: Composed of cells that are branched and striated
Found only in heart tissue Responsible for the contraction of the heart Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Smooth muscle is: Named for its lack of obvious striations
Found in the walls of various organs Involuntary Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

Nervous Tissue Nervous tissue:
Makes communication of sensory information possible Is found in the brain and spinal cord Consists of a network of neurons Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

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

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 lungs. Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

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

Blast Animation: Anatomy of the Kidney
Organ systems: Are teams of organs that work together Perform vital body functions Blast Animation: Anatomy of the Kidney Student Misconceptions and Concerns 1. One of the greatest intellectual challenges for students is gaining a proper understanding of the evolution of form and function relationships. Structure and function relationships appear to have been constructed to meet a purpose, a consequence of deliberate planning and design. However, as the text notes, natural selection is a process of editing, and not creating, diversity. 2. Students are likely to explain that a structure has a certain shape because the organism needs to perform a certain task. However, need cannot cause evolution to occur because need cannot generate diversity. You might point out that if need was an important force of change, organisms would not go extinct. 3. Form and function relationships are all around us. To some of us, the connections are 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. 4. 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, is 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 long-term consequences of a lifetime of sun exposure.

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

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

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

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

Muscular system: moves body Skeletal muscles Figure 21.8d
Figure 21.8d Organ systems of a vertebrate: muscular system

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

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

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

Integumentary system: protects body Hair Skin Nail Figure 21.8i
Figure 21.8i Organ systems of a vertebrate: integumentary system

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

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

EXCHANGES WITH THE EXTERNAL ENVIRONMENT
Every organism is an open system, continuously exchanging chemicals and energy with its surroundings to survive. 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. 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! 2. 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 bite us less on days when there is a good breeze. 3. 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.

An animal’s size and shape affect how it exchanges energy and materials with its surroundings.
All living cells must be bathed in a watery solution so that exchange of materials can occur. 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. 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! 2. 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 bite us less on days when there is a good breeze. 3. 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.

The entire surface area of an amoeba is in contact with the environment.
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. 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! 2. 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 bite us less on days when there is a good breeze. 3. 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.

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

A hydra has a body wall only two cell layers thick.
Both layers are bathed in pond water, enabling exchange with the environment. 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. 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! 2. 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 bite us less on days when there is a good breeze. 3. 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.

Animals with complex body forms face the same basic problems
Animals with complex body forms face the same basic problems. Every cell must: Be bathed in fluid Have access to essential nutrients from the outside environment 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. 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! 2. 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 bite us less on days when there is a good breeze. 3. 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.

Complex animals have extensively folded or branched internal surfaces that maximize surface area for exchange with the environment. Lungs: Have a very large total surface area Exchange oxygen and carbon dioxide with the air 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. 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! 2. 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 bite us less on days when there is a good breeze. 3. 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.

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 Urinary The circulatory system transports materials inside the body from these exchange surfaces. 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. 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! 2. 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 bite us less on days when there is a good breeze. 3. 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.

Figure 21.11 Mouth Food CO2 O2 External environment Animal Blood
Respiratory system Digestive system Interstitial fluid Heart Nutrients Circulatory system Body cells Urinary system Anus Unabsorbed matter (feces) Metabolic waste products (such as urine) Figure 21.11 Figure Exchange between the external environment and the internal environment of complex animals

REGULATING THE INTERNAL ENVIRONMENT
Every living organism has the ability to respond to its environment. 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Homeostasis Homeostasis is the body’s tendency to maintain relatively steady conditions in the internal environment when the external environment changes. The internal environment of vertebrates is the interstitial fluid, which fills the spaces between cells. 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Negative and Positive Feedback
Most mechanisms of homeostasis depend on a common 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. Animation: Negative Feedback Animation: Positive Feedback 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

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

Less common is positive feedback in which the results of a process intensify that same process, such as uterine contractions during childbirth. 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Thermoregulation Thermoregulation is the maintenance of internal body temperature. Endotherms derive the majority of their body heat from their metabolism. Ectotherms obtain body heat primarily by absorbing it from their surroundings. 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Blast Animation: Negative Feedback: Body Temperature
Humans have homeostatic mechanisms that aid in thermoregulation, which: Cool or Heat the body Blast Animation: Negative Feedback: Body Temperature 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

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

Fever: Is an abnormally high internal body temperature
Usually indicates an ongoing fight against infection 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Osmoregulation Living cells depend on a precise balance of:
Water Solutes Osmoregulation is the control of the gain or loss of: Dissolved solutes, such as salt 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Osmoconformers: Osmoregulators
Have internal and external environments with similar water concentrations Include most marine invertebrates Osmoregulators Actively regulate their water loss or gain Include freshwater animals, most marine vertebrates, and all land animals 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Osmocomformer Osmoregulator Figure 21.16
Figure Osmoconformer and osmoregulator

Homeostasis in the Urinary System
Plays a central role in homeostasis Forms and excretes urine Regulates the amount of water and solutes in body fluids 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

In humans, the two kidneys:
Are the main processing centers Contain many fine tubes called tubules Include an intricate network of capillaries 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

As blood circulates through the kidneys:
A fraction of it is filtered Plasma enters the kidney tubules, forming filtrate Filtrate contains: Valuable substances that need to be reclaimed (such as water and glucose) Substances to be eliminated, such as urea 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Animation: Nephron Introduction
The human urinary system includes: The circulatory system The kidneys Nephrons, the functional units of the kidney The urinary bladder, where urine is stored Animation: Nephron Introduction 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

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

Nephrons: Carry out the functions of the urinary system
Consist of a tubule and its associated vessels Number more than a million in a kidney 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

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

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 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

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

Hormonal control of the nephrons allows the body to control its internal concentration of:
Water Dissolved molecules 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

Kidney failure can be caused by:
Injury Illness Prolonged use of pain relievers, alcohol, or other drugs One option for treatment of kidney failure is dialysis, filtration of blood by a machine. 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

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

Evolution Connection: Adaptations for Thermoregulation
Animals regulate their body temperatures using adaptations that are: Anatomical Physiological, and / or Behavioral © 2010 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) high humidity level—which decreases evaporative cooling, (g) intensity of wind—to promote evaporative cooling, and (h) the physical condition of the person. 6. Ask students to explain how blood vessels 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 over distended, it may 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 by located by a quick Internet search. The National Kidney Foundation site ( includes information on kidney donation.

METHODS OF THERMOREGULATION
Anatomical Adaptations Physiological Adaptations Behavioral Adaptations Fat Hair Panting Bathing Figure 21.20 Figure Methods of thermoregulation in animals

HIERARCHICAL ORGANIZATION OF ANIMALS
Level Description Example Cell The basic unit of all living organisms Muscle cell Tissue A collection of similar cells that perform 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 Figure 21.UN1 Summary: hierarchical organization of animals

Unifying Concepts of Animal Structure and Function

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