How Biological Diversity Evolves

How Biological Diversity Evolves
Chapter 14 How Biological Diversity Evolves

Biology and Society: The Sixth Mass Extinction
Over the past 540 million years, the fossil record reveals five periods of extinction when 50–90% of living species suddenly died out. © 2013 Pearson Education, Inc. 2

Figure 14.0 Figure 14.0 A critically endangered species: the black and white ruffed lemur

Biology and Society: The Sixth Mass Extinction
Our current rate of extinction, over the past 400 years, indicates that we may be living in, and contributing to, the sixth mass extinction period. Mass extinctions pave the way for the evolution of new and diverse forms, but it takes millions of years for Earth to recover. © 2013 Pearson Education, Inc. 4

Figure 14.1 PATTERNS OF EVOLUTION Figure 14.1 Galápagos tortoises

THE ORIGIN OF SPECIES In the 150 years since the publication of Darwin’s book On the Origin of Species by Means of Natural Selection, new discoveries and technological advances have given scientists a wealth of new information about the evolution of life. The diversity of life evolved through speciation, the process in which one species splits into two or more species. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 6

Similarity between different species Diversity within one species
Figure 14.2 Similarity between different species Diversity within one species Figure 14.2 The biological species concept is based on reproductive compatibility rather than physical similarity

Reproductive Barriers between Species
Prezygotic barriers prevent mating or fertilization between species. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 8

INDIVIDUALS OF DIFFERENT SPECIES
Figure 14.3 INDIVIDUALS OF DIFFERENT SPECIES Prezygotic Barriers Temporal isolation Habitat isolation Behavioral isolation MATING ATTEMPT Mechanical isolation Gametic isolation FERTILIZATION (ZYGOTE FORMS) Postzygotic Barriers Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown VIABLE, FERTILE OFFSPRING No Barriers Figure 14.3 Reproductive barriers between closely related species

PREZYGOTIC BARRIERS Temporal Isolation Habitat Isolation
Figure 14.4 PREZYGOTIC BARRIERS Temporal Isolation Habitat Isolation Behavioral Isolation Mechanical Isolation Gametic Isolation Figure 14.4 Prezygotic barriers

Reproductive Barriers between Species
Postzygotic barriers operate if interspecies mating occurs and hybrid zygotes form. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 11

Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown
Figure 14.5 POSTZYGOTIC BARRIERS Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown Horse Donkey Mule Figure 14.5 Postzygotic barriers

Mechanisms of Speciation
A key event in the potential origin of a species occurs when a population is somehow cut off from other populations of the parent species. Species can form by allopatric speciation, due to geographic isolation, or sympatric speciation, without geographic isolation. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 13

Allopatric speciation Sympatric speciation
Figure 14.6 Allopatric speciation Sympatric speciation Figure 14.6 Two modes of speciation

Allopatric Speciation
Geologic processes can fragment a population into two or more isolated populations and contribute to allopatric speciation. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 15

Ammospermophilus harrisii Ammospermophilus leucurus
Figure 14.7 Ammospermophilus harrisii Ammospermophilus leucurus Figure 14.7 Allopatric speciation of antelope squirrels on opposite rims of the Grand Canyon

Allopatric Speciation
Speciation occurs with the evolution of reproductive barriers between the isolated population and its parent population. Even if the two populations should come back into contact at some later time, the reproductive barriers will keep them as separate species. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 17

Time Populations become allopatric Populations become sympatric
Figure 14.8 Populations become allopatric Populations become sympatric Populations interbreed Gene pools merge: No speciation Geographic barrier Populations cannot interbreed Reproductive isolation: Speciation has occurred Time Figure 14.8 Has speciation occurred during geographic isolation?

Sympatric Speciation Sympatric speciation occurs in populations that live in the same geographic area. An accident during cell division that results in an extra set of chromosomes is a common route to sympatric speciation in plants. Many polyploid species arise from the hybridization of two parent species. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 19

Sympatric Speciation Many domesticated plants are the result of sympatric speciation, including oats, potatoes, bananas, peanuts, apples, coffee, and wheat. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 20

What Is the Pace of Speciation?
There are two contrasting patterns for the pace of evolution: the gradual pattern, in which big changes (speciations) occur by the steady accumulation of many small changes, and the punctuated equilibria pattern, in which there are long periods of little apparent change (equilibria) interrupted (punctuated) by relatively brief periods of rapid change. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process. 2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years. 3. Students might not have considered how species are “naturally” kept separate and unique. Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home. 2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. 3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation. 4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species. 5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: 6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction. 7. Have your students think of analogous examples of punctuated equilibrium in our culture. Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. 21

Punctuated pattern Time Gradual pattern Figure 14.10
Figure Two patterns for the pace of speciation

THE EVOLUTION OF BIOLOGICAL NOVELTY
What accounts for the dramatic differences between dissimilar groups? © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students are unlikely to appreciate the life history of salamanders and the similarity of a larval salamander to the axolotl form. Students might therefore best understand what happens during salamander paedomorphosis by considering more commonly understood life stages. Ask students to imagine what would result if a caterpillar reproduced and never turned into a winged adult butterfly. Then relate the caterpillar stage to the early larval form of salamanders. 2. Clear examples of evolutionary remodeling include the many variations of the pattern of bones in the vertebrate forelimb. Bat wings, bird wings, penguin flippers, the arms of apes, and the digging forelimbs of moles all show how the ancestral pattern was revised as new functions evolved. Descent with modification is a powerful explanation of such diversity. Teaching Tips 1. Another way to think about evolutionary remodeling is to make an analogy to remodeling a home. A remodeled home retains many of the “ancestral” traits—perhaps the same plumbing and electrical system. But, where there once was a wall might now be an opening into an enlarged family room, or a window to the outside. Evolution can work like the TV show This Old House! 2. When discussing exaptations, have students consider the many new uses for common household items if they were to have them in a survival situation, stranded on an island or lost in the woods. A handkerchief, a screwdriver, and a pair of pliers might take on new functions in this different context. 3. Consider challenging your students to explain why the evolution of a group is not driven in any particular direction, or directed toward any ideal form or function. As a hint, you can ask them to describe the mechanisms by which variety arises in a species. 23

Adaptation of Old Structures for New Functions
Birds are derived from a lineage of earthbound reptiles and evolved flight from flightless ancestors. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students are unlikely to appreciate the life history of salamanders and the similarity of a larval salamander to the axolotl form. Students might therefore best understand what happens during salamander paedomorphosis by considering more commonly understood life stages. Ask students to imagine what would result if a caterpillar reproduced and never turned into a winged adult butterfly. Then relate the caterpillar stage to the early larval form of salamanders. 2. Clear examples of evolutionary remodeling include the many variations of the pattern of bones in the vertebrate forelimb. Bat wings, bird wings, penguin flippers, the arms of apes, and the digging forelimbs of moles all show how the ancestral pattern was revised as new functions evolved. Descent with modification is a powerful explanation of such diversity. Teaching Tips 1. Another way to think about evolutionary remodeling is to make an analogy to remodeling a home. A remodeled home retains many of the “ancestral” traits—perhaps the same plumbing and electrical system. But, where there once was a wall might now be an opening into an enlarged family room, or a window to the outside. Evolution can work like the TV show This Old House! 2. When discussing exaptations, have students consider the many new uses for common household items if they were to have them in a survival situation, stranded on an island or lost in the woods. A handkerchief, a screwdriver, and a pair of pliers might take on new functions in this different context. 3. Consider challenging your students to explain why the evolution of a group is not driven in any particular direction, or directed toward any ideal form or function. As a hint, you can ask them to describe the mechanisms by which variety arises in a species. 24

Artist’s reconstruction
Figure 14.11 Wing claw (like reptile) Teeth (like reptile) Feathers Long tail with many vertebrae (like reptile) Fossil Artist’s reconstruction Figure An extinct bird

An exaptation is a structure that evolves in one context but becomes adapted for another function and a type of evolutionary remodeling. Exaptations can account for the evolution of novel structures. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students are unlikely to appreciate the life history of salamanders and the similarity of a larval salamander to the axolotl form. Students might therefore best understand what happens during salamander paedomorphosis by considering more commonly understood life stages. Ask students to imagine what would result if a caterpillar reproduced and never turned into a winged adult butterfly. Then relate the caterpillar stage to the early larval form of salamanders. 2. Clear examples of evolutionary remodeling include the many variations of the pattern of bones in the vertebrate forelimb. Bat wings, bird wings, penguin flippers, the arms of apes, and the digging forelimbs of moles all show how the ancestral pattern was revised as new functions evolved. Descent with modification is a powerful explanation of such diversity. Teaching Tips 1. Another way to think about evolutionary remodeling is to make an analogy to remodeling a home. A remodeled home retains many of the “ancestral” traits—perhaps the same plumbing and electrical system. But, where there once was a wall might now be an opening into an enlarged family room, or a window to the outside. Evolution can work like the TV show This Old House! 2. When discussing exaptations, have students consider the many new uses for common household items if they were to have them in a survival situation, stranded on an island or lost in the woods. A handkerchief, a screwdriver, and a pair of pliers might take on new functions in this different context. 3. Consider challenging your students to explain why the evolution of a group is not driven in any particular direction, or directed toward any ideal form or function. As a hint, you can ask them to describe the mechanisms by which variety arises in a species. 26

Bird wings are modified forelimbs that were previously adapted for non-flight functions, such as thermal regulation, courtship displays, and/or camouflage. The first flights may have been only glides or extended hops as the animal pursued prey or fled from a predator. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students are unlikely to appreciate the life history of salamanders and the similarity of a larval salamander to the axolotl form. Students might therefore best understand what happens during salamander paedomorphosis by considering more commonly understood life stages. Ask students to imagine what would result if a caterpillar reproduced and never turned into a winged adult butterfly. Then relate the caterpillar stage to the early larval form of salamanders. 2. Clear examples of evolutionary remodeling include the many variations of the pattern of bones in the vertebrate forelimb. Bat wings, bird wings, penguin flippers, the arms of apes, and the digging forelimbs of moles all show how the ancestral pattern was revised as new functions evolved. Descent with modification is a powerful explanation of such diversity. Teaching Tips 1. Another way to think about evolutionary remodeling is to make an analogy to remodeling a home. A remodeled home retains many of the “ancestral” traits—perhaps the same plumbing and electrical system. But, where there once was a wall might now be an opening into an enlarged family room, or a window to the outside. Evolution can work like the TV show This Old House! 2. When discussing exaptations, have students consider the many new uses for common household items if they were to have them in a survival situation, stranded on an island or lost in the woods. A handkerchief, a screwdriver, and a pair of pliers might take on new functions in this different context. 3. Consider challenging your students to explain why the evolution of a group is not driven in any particular direction, or directed toward any ideal form or function. As a hint, you can ask them to describe the mechanisms by which variety arises in a species. 27

Evo-Devo: Development and Evolutionary Novelty
Evo-devo, evolutionary developmental biology, is the study of the evolution of developmental processes in multicellular organisms. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students are unlikely to appreciate the life history of salamanders and the similarity of a larval salamander to the axolotl form. Students might therefore best understand what happens during salamander paedomorphosis by considering more commonly understood life stages. Ask students to imagine what would result if a caterpillar reproduced and never turned into a winged adult butterfly. Then relate the caterpillar stage to the early larval form of salamanders. 2. Clear examples of evolutionary remodeling include the many variations of the pattern of bones in the vertebrate forelimb. Bat wings, bird wings, penguin flippers, the arms of apes, and the digging forelimbs of moles all show how the ancestral pattern was revised as new functions evolved. Descent with modification is a powerful explanation of such diversity. Teaching Tips 1. Another way to think about evolutionary remodeling is to make an analogy to remodeling a home. A remodeled home retains many of the “ancestral” traits—perhaps the same plumbing and electrical system. But, where there once was a wall might now be an opening into an enlarged family room, or a window to the outside. Evolution can work like the TV show This Old House! 2. When discussing exaptations, have students consider the many new uses for common household items if they were to have them in a survival situation, stranded on an island or lost in the woods. A handkerchief, a screwdriver, and a pair of pliers might take on new functions in this different context. 3. Consider challenging your students to explain why the evolution of a group is not driven in any particular direction, or directed toward any ideal form or function. As a hint, you can ask them to describe the mechanisms by which variety arises in a species. 28

Evo-Devo: Development and Evolutionary Novelty
Homeotic genes are master control genes that regulate the rate, timing, and spatial pattern of changes in an organism’s form as it develops from a zygote into an adult. Mutations in homeotic genes can profoundly affect body form. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students are unlikely to appreciate the life history of salamanders and the similarity of a larval salamander to the axolotl form. Students might therefore best understand what happens during salamander paedomorphosis by considering more commonly understood life stages. Ask students to imagine what would result if a caterpillar reproduced and never turned into a winged adult butterfly. Then relate the caterpillar stage to the early larval form of salamanders. 2. Clear examples of evolutionary remodeling include the many variations of the pattern of bones in the vertebrate forelimb. Bat wings, bird wings, penguin flippers, the arms of apes, and the digging forelimbs of moles all show how the ancestral pattern was revised as new functions evolved. Descent with modification is a powerful explanation of such diversity. Teaching Tips 1. Another way to think about evolutionary remodeling is to make an analogy to remodeling a home. A remodeled home retains many of the “ancestral” traits—perhaps the same plumbing and electrical system. But, where there once was a wall might now be an opening into an enlarged family room, or a window to the outside. Evolution can work like the TV show This Old House! 2. When discussing exaptations, have students consider the many new uses for common household items if they were to have them in a survival situation, stranded on an island or lost in the woods. A handkerchief, a screwdriver, and a pair of pliers might take on new functions in this different context. 3. Consider challenging your students to explain why the evolution of a group is not driven in any particular direction, or directed toward any ideal form or function. As a hint, you can ask them to describe the mechanisms by which variety arises in a species. 29

EARTH HISTORY AND MACROEVOLUTION
Macroevolution is closely tied to the history of Earth. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60  60  24  365 = 31,536,000) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 2. Students also need to be reminded that 1 billion is 1,000 million. Many students (and too many politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The sequence but not absolute ages are revealed by the stratifications in sedimentary rocks. The authors make an analogy to peeling the layers of wallpaper from the walls of a very old house that has been inhabited by many owners. By the sequence we can tell which layers are older, but not the absolute ages of each layer. Cutting into a layered cake is another analogy. Although we do not know the absolute age of each layer, we know the sequence in which the layers were placed. 2. Consider this analogy to help students understand the biological consequences of speciation as continents drifted apart. As your students left high school, and entered the workforce or continued their education, their high school social groups drifted apart. Your students, in their new circumstances, adapted and changed in different ways, separate from the members of their old social groups. A note of caution: This analogy to individual social changes is not an example of biological evolution, which occurs over generations. 3. The consequences of an asteroid impact, large or small, illustrates the role of random forces influencing evolution. Like throwing a dart at a spinning globe, where the asteroid hits and what continents and life are most greatly affected can change greatly if the impact is delayed by a few hours. An asteroid delayed by 12 hours, in what might be a journey of millions or billions of years, will land on the opposite side of Earth! 30

Geologic Time and the Fossil Record
The fossil record is the sequence in which fossils appear in rock strata and an archive of macroevolution. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60  60  24  365 = 31,536,000) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 2. Students also need to be reminded that 1 billion is 1,000 million. Many students (and too many politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The sequence but not absolute ages are revealed by the stratifications in sedimentary rocks. The authors make an analogy to peeling the layers of wallpaper from the walls of a very old house that has been inhabited by many owners. By the sequence we can tell which layers are older, but not the absolute ages of each layer. Cutting into a layered cake is another analogy. Although we do not know the absolute age of each layer, we know the sequence in which the layers were placed. 2. Consider this analogy to help students understand the biological consequences of speciation as continents drifted apart. As your students left high school, and entered the workforce or continued their education, their high school social groups drifted apart. Your students, in their new circumstances, adapted and changed in different ways, separate from the members of their old social groups. A note of caution: This analogy to individual social changes is not an example of biological evolution, which occurs over generations. 3. The consequences of an asteroid impact, large or small, illustrates the role of random forces influencing evolution. Like throwing a dart at a spinning globe, where the asteroid hits and what continents and life are most greatly affected can change greatly if the impact is delayed by a few hours. An asteroid delayed by 12 hours, in what might be a journey of millions or billions of years, will land on the opposite side of Earth! 31

A researcher excavating a fossilized dinosaur skeleton from sandstone
Figure 14.14 A researcher excavating a fossilized dinosaur skeleton from sandstone A sedimentary fossil formed by minerals replacing the organic matter of a tree A 45-million-year-old insect embedded in amber Trace fossils: footprints, burrows, or other remnants of an ancient organism’s behavior Tusks of a 23,000-year-old mammoth discovered in Siberian ice Figure A gallery of fossils

Table 14.1 The geologic time scale
Age (millions of years ago) Relative Time Span Period Epoch Some Important Events in the History of Life Recent Historical time Cenozoic Quaternary 0.01 Mesozoic Pleistocene Ice ages; humans appear 1.8 Pliocene Origin of genus Homo 5 Paleozoic Miocene Continued speciation of mammals and angiosperms Cenozoic era 23 Oligocene Origins of many primate groups, including apes Tertiary 34 Angiosperm dominance increases; origins of most living mammalian orders Eocene 56 Paleocene Major speciation of mammals, birds, and pollinating insects 65 Flowering plants (angiosperms) appear; many groups of organisms, including most dinosaur lineages, become extinct at end of period (Cretaceous extinctions) Cretaceous Mesozoic era 145 Jurassic Gymnosperms continue as dominant plants; dinosaurs become dominant 200 Triassic Cone-bearing plants (gymnosperms) dominate landscape; speciation of dinosaurs, early mammals, and birds 251 Extinction of many marine and terrestrial organisms (Permian extinctions); speciation of reptiles; origins of mammal-like reptiles and most living orders of insects Permian 299 Extensive forests of vascular plants; first seed plants; origin of reptiles; amphibians become dominant Pre- cambrian Carboniferous 359 Devonian Diversification of bony fishes; first amphibians and insects Paleozoic era 416 Silurian Early vascular plants dominate land 444 Ordovician Marine algae are abundant; colonization of land by diverse fungi, plants, and animals 488 Cambrian Origin of most living animal phyla (Cambrian explosion) 542 600 Diverse algae and soft-bodied invertebrate animals appear 635 Oldest animal fossils 2,100 Precambrian Oldest eukaryotic fossils 2,700 Oxygen begins accumulating in atmosphere 3,500 Oldest fossils known (prokaryotes) 4,600 Approximate time of origin of Earth Table 14.1 The geologic time scale

Plate Tectonics and Macroevolution
The continents are not locked in place. Continents drift about Earth’s surface on plates of crust floating on a flexible layer of hot, underlying material called the mantle. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60  60  24  365 = 31,536,000) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 2. Students also need to be reminded that 1 billion is 1,000 million. Many students (and too many politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The sequence but not absolute ages are revealed by the stratifications in sedimentary rocks. The authors make an analogy to peeling the layers of wallpaper from the walls of a very old house that has been inhabited by many owners. By the sequence we can tell which layers are older, but not the absolute ages of each layer. Cutting into a layered cake is another analogy. Although we do not know the absolute age of each layer, we know the sequence in which the layers were placed. 2. Consider this analogy to help students understand the biological consequences of speciation as continents drifted apart. As your students left high school, and entered the workforce or continued their education, their high school social groups drifted apart. Your students, in their new circumstances, adapted and changed in different ways, separate from the members of their old social groups. A note of caution: This analogy to individual social changes is not an example of biological evolution, which occurs over generations. 3. The consequences of an asteroid impact, large or small, illustrates the role of random forces influencing evolution. Like throwing a dart at a spinning globe, where the asteroid hits and what continents and life are most greatly affected can change greatly if the impact is delayed by a few hours. An asteroid delayed by 12 hours, in what might be a journey of millions or billions of years, will land on the opposite side of Earth! 34

Figure 14.16 Figure A tsunami caused by an earthquake off the coast of Japan in March 2011

About 250 million years ago, plate movements formed the supercontinent Pangaea, the total amount of shoreline was reduced, ocean basins increased in depth, sea levels dropped, the dry continental interior increased in size, and many extinctions occurred. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60  60  24  365 = 31,536,000) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 2. Students also need to be reminded that 1 billion is 1,000 million. Many students (and too many politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The sequence but not absolute ages are revealed by the stratifications in sedimentary rocks. The authors make an analogy to peeling the layers of wallpaper from the walls of a very old house that has been inhabited by many owners. By the sequence we can tell which layers are older, but not the absolute ages of each layer. Cutting into a layered cake is another analogy. Although we do not know the absolute age of each layer, we know the sequence in which the layers were placed. 2. Consider this analogy to help students understand the biological consequences of speciation as continents drifted apart. As your students left high school, and entered the workforce or continued their education, their high school social groups drifted apart. Your students, in their new circumstances, adapted and changed in different ways, separate from the members of their old social groups. A note of caution: This analogy to individual social changes is not an example of biological evolution, which occurs over generations. 3. The consequences of an asteroid impact, large or small, illustrates the role of random forces influencing evolution. Like throwing a dart at a spinning globe, where the asteroid hits and what continents and life are most greatly affected can change greatly if the impact is delayed by a few hours. An asteroid delayed by 12 hours, in what might be a journey of millions or billions of years, will land on the opposite side of Earth! 36

India collides with Eurasia.
Figure 14.17 Present Cenozoic India collides with Eurasia. 65 135 Pangaea splits into Laurasia and Gondwana. Mesozoic 251 million years ago Paleozoic Pangaea is formed. Figure The history of plate tectonics

Plate tectonics helps to explain why Mesozoic reptiles in Ghana (West Africa) and Brazil look so similar and how marsupials were free to evolve in isolation in Australia. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60  60  24  365 = 31,536,000) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 2. Students also need to be reminded that 1 billion is 1,000 million. Many students (and too many politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The sequence but not absolute ages are revealed by the stratifications in sedimentary rocks. The authors make an analogy to peeling the layers of wallpaper from the walls of a very old house that has been inhabited by many owners. By the sequence we can tell which layers are older, but not the absolute ages of each layer. Cutting into a layered cake is another analogy. Although we do not know the absolute age of each layer, we know the sequence in which the layers were placed. 2. Consider this analogy to help students understand the biological consequences of speciation as continents drifted apart. As your students left high school, and entered the workforce or continued their education, their high school social groups drifted apart. Your students, in their new circumstances, adapted and changed in different ways, separate from the members of their old social groups. A note of caution: This analogy to individual social changes is not an example of biological evolution, which occurs over generations. 3. The consequences of an asteroid impact, large or small, illustrates the role of random forces influencing evolution. Like throwing a dart at a spinning globe, where the asteroid hits and what continents and life are most greatly affected can change greatly if the impact is delayed by a few hours. An asteroid delayed by 12 hours, in what might be a journey of millions or billions of years, will land on the opposite side of Earth! 38

CLASSIFYING THE DIVERSITY OF LIFE
Systematics focuses on classifying organisms and determining their evolutionary relationships. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 39

CLASSIFYING THE DIVERSITY OF LIFE
Taxonomy is the identification, naming, and classification of species. Systematics includes taxonomy. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 40

The scientific name for humans is Homo sapiens,
Naming Species Each species is assigned a two-part Latinized name or binomial, consisting of the genus and a name unique for each species. The scientific name for humans is Homo sapiens, a two part name, italicized, given a Latin ending, and with the first letter of the genus capitalized. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 41

Leopard (Panthera pardus) Tiger (Panthera tigris)
Figure 14.19 Leopard (Panthera pardus) Lion (Panthera leo) Tiger (Panthera tigris) Jaguar (Panthera onca) Figure The four species within the genus Panthera

Hierarchical Classification
The taxonomic hierarchy extends to progressively broader categories of classification, from genus to family, order, class, phylum, kingdom, and domain. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 43

Leopard (Panthera pardus) Species Panthera pardus Genus Panthera
Figure 14.20 Leopard (Panthera pardus) Species Panthera pardus Genus Panthera Family Felidae Order Carnivora Class Mammalia Phylum Chordata Kingdom Animalia Domain Eukarya Figure Hierarchical classification

Classification and Phylogeny
The goal of systematics is to have classification reflect evolutionary relationships. Biologists use phylogenetic trees to depict hypotheses about the evolutionary history of species and reflect the hierarchical classification of groups nested within more inclusive groups. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 45

Order Family Genus Species Panthera pardus (leopard) Felidae Panthera
Figure 14.21 Order Family Genus Species Panthera pardus (leopard) Felidae Panthera Mephitis mephitis (striped skunk) Mephitis Carnivora Mustelidae Lutra lutra (European otter) Lutra Canis latrans (coyote) Canidae Canis Canis lupus (wolf) Figure The relationship of classification and phylogeny for some members of the order Carnivora

Molecular Biology as a Tool in Systematics
Molecular systematics compares nucleotide and amino acid sequences between organisms and can reveal evolutionary relationships. The more recently two species have branched from a common ancestor, the more similar their nucleotide and amino acid sequences should be. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 47

Molecular Biology as a Tool in Systematics
Some fossils are preserved in such a way that DNA fragments can be extracted for comparison with living organisms. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 48

Figure 14.22 Figure Studying ancient DNA

The Cladistic Revolution
In cladistics, organisms are grouped by common ancestry. A clade consists of an ancestral species and all its evolutionary descendants and forms a distinct branch in the tree of life. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 50

Iguana Outgroup (reptile) Duck-billed platypus Hair, mammary glands
Figure 14.23 Iguana Outgroup (reptile) Duck-billed platypus Hair, mammary glands Kangaroo Ingroup (mammals) Gestation Beaver Long gestation Figure A simplified example of cladistics

The Cladistic Revolution
Cladistics has changed the traditional classification of some organisms, including the relationships between dinosaurs, birds, crocodiles, lizards, and snakes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 52

Lizards and snakes Crocodilians Pterosaurs Common ancestor of
Figure 14.24 Lizards and snakes Crocodilians Pterosaurs Common ancestor of crocodilians, dinosaurs, and birds Ornithischian dinosaurs Saurischian dinosaurs Birds Figure How cladistics is shaking phylogenetic trees

Classification: A Work in Progress
Phylogenetic trees are hypotheses about evolutionary history. Linnaeus divided all known forms of life between the plant and animal kingdoms. This two-kingdom system prevailed in biology for over 200 years. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 54

In the mid-1900s, the two-kingdom system was replaced by a five-kingdom system that placed all prokaryotes in one kingdom and divided the eukaryotes among four other kingdoms. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 55

In the late 1900s, molecular studies and cladistics led to the development of a three-domain system, recognizing two domains of prokaryotes (Bacteria and Archaea) and one domain of eukaryotes (Eukarya). © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer. 2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names! 3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups. Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household. 2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity. 3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process. Homologous relationships reflect modifications of an ancestral form for many functions. Analogous relationships reflect modifications of many forms for one common function. 4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies. 5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems. 6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, contains a great deal of useful information. 56

How Biological Diversity Evolves

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