1. How Biological Diversity Evolves
Chapter 14
How Biological Diversity Evolves

2. 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.
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. 2

3. Video: Galápagos Islands Overview
THE ORIGIN OF SPECIES
When Darwin visited the Galápagos Islands, he realized that he was visiting a place of origins.
Although the volcanic islands were geologically young, they were home to many plants and animals known nowhere else in the world.
Darwin thought it unlikely that all of these species could have been among the original colonists of the islands.
Video: Galápagos Islands Overview
© 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. 3

4. 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. 4

5. What Is a Species? Species is a Latin word meaning
“kind” or
“appearance.”
The biological species concept defines a species as “A group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring.”
© 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. 5

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

7. What Is a Species?
The biological species concept cannot be applied in all situations, including
fossils and
asexual organisms.
Some other definitions of species are based on
measurable physical traits,
the use of ecological resources, or
unique adaptations to particular roles in a biological community.
© 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. 7

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

9. INDIVIDUALS OF DIFFERENT SPECIES
Figure 14.3a
INDIVIDUALS OF DIFFERENT SPECIES
Prezygotic Barriers
Temporal isolation
Habitat isolation
Behavioral isolation
MATING ATTEMPT
Mechanical isolation
Gametic isolation
Figure 14.3 Reproductive barriers between closely related species (part 1)

10. INDIVIDUALS OF DIFFERENT SPECIES
Figure 14.3b
INDIVIDUALS OF DIFFERENT SPECIES
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 (part 2)

11. Reproductive Barriers between Species
Prezygotic barriers include
temporal isolation,
habitat isolation,
behavioral isolation,
mechanical isolation, and
gametic isolation.
Video: Albatross Courtship Ritual
Video: Blue-footed Boobies Courtship Ritual
Video: Giraffe Courtship Ritual
© 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

12. Reproductive Barriers between Species
Postzygotic barriers operate if
interspecies mating occurs and
hybrid zygotes form.
Postzygotic barriers include
reduced hybrid viability,
reduced hybrid fertility, and
hybrid breakdown.
© 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. 12

13. 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

14. 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. 14

15. 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?

16. 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. 16

17. 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. 17

18. 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. 18

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

20. Bacteria Earliest organisms Archaea Eukarya Figure 14.UN03
Figure 14.UN03 Summary of Key Concepts: Classification: A Work in Progress

21. The Evolution of Microbial Life
Chapter 15
The Evolution of Microbial Life

22. Biology and Society: Has Life Been Created in the Lab?
How did life first arise on Earth?
To gain insight, scientists have
synthesized from scratch the entire genome of a small bacterium known as Mycoplasma mycoides and
transplanted the artificial genome into the cells of a closely related species called Mycoplasma capricolum.
© 2013 Pearson Education, Inc. 22

23. Biology and Society: Has Life Been Created in the Lab?
The newly installed genome
took over the recipient cells,
began cranking out M. mycoides proteins, and
reproduced to make more cells containing the synthetic M. mycoides genome.
© 2013 Pearson Education, Inc.

24. MAJOR EPISODES IN THE HISTORY OF LIFE
Earth was formed about 4.6 billion years ago.
Prokaryotes
evolved by about 3.5 billion years ago,
began oxygen production about 2.7 billion years ago,
lived alone for more than a billion years, and
continue in great abundance today.
© 2013 Pearson Education, Inc.
Student Misconceptions and Concerns
1. Students often have difficulty grasping the enormity of time. Perhaps surprisingly, many students do not understand that a billion is a thousand times greater than a million. Exercises and examples that help students comprehend such large numbers should be considered, so that students can understand these tremendous periods for evolutionary diversification. Here are just a few examples to consider:
a. If an earthquake or volcano erupts just once every thousand years or so, how often will this event occur in a million years? (One thousand times.) Note that what is rare to us becomes “common” in geological terms.
b. Have students calculate the age of a human when they reach their 1 billionth second of life. (Starting with birth, the answer is years.) 1,000,000,000 (seconds) = (years)  (days in a year)  24 (hours in a day)  60 (minutes)  60 (seconds).
c. Then have students calculate how long it takes to live 1,000,000 seconds. (About days.)
Teaching Tips
1. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall. Mark these proportional periods: The full length of time is 4.6 billion years. The percentages below were calculated using the textbook’s approximate dates for each of these events.
0.0%—The Earth forms.
13%—The Earth’s crust solidifies.
24%—The first life appears.
41%—Photosynthetic prokaryotes start producing an oxygen-rich atmosphere.
54%—The first eukaryotes appear.
74%—The first multicellular eukaryotes appear.
89%—Plants first invade land.
2. Students may need to be reminded about the reactive properties of oxygen. Note that rust is the result of oxygen interacting with iron and could be seen in the fossil record. Oxygen is highly reactive and could interfere with life-forming chemical processes today. 24

25. MAJOR EPISODES IN THE HISTORY OF LIFE
Single-celled eukaryotes first evolved about 2.1 billion years ago.
Multicellular eukaryotes first evolved at least 1.2 billion years ago.
© 2013 Pearson Education, Inc.
Student Misconceptions and Concerns
1. Students often have difficulty grasping the enormity of time. Perhaps surprisingly, many students do not understand that a billion is a thousand times greater than a million. Exercises and examples that help students comprehend such large numbers should be considered, so that students can understand these tremendous periods for evolutionary diversification. Here are just a few examples to consider:
a. If an earthquake or volcano erupts just once every thousand years or so, how often will this event occur in a million years? (One thousand times.) Note that what is rare to us becomes “common” in geological terms.
b. Have students calculate the age of a human when they reach their 1 billionth second of life. (Starting with birth, the answer is years.) 1,000,000,000 (seconds) = (years)  (days in a year)  24 (hours in a day)  60 (minutes)  60 (seconds).
c. Then have students calculate how long it takes to live 1,000,000 seconds. (About days.)
Teaching Tips
1. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall. Mark these proportional periods: The full length of time is 4.6 billion years. The percentages below were calculated using the textbook’s approximate dates for each of these events.
0.0%—The Earth forms.
13%—The Earth’s crust solidifies.
24%—The first life appears.
41%—Photosynthetic prokaryotes start producing an oxygen-rich atmosphere.
54%—The first eukaryotes appear.
74%—The first multicellular eukaryotes appear.
89%—Plants first invade land.
2. Students may need to be reminded about the reactive properties of oxygen. Note that rust is the result of oxygen interacting with iron and could be seen in the fossil record. Oxygen is highly reactive and could interfere with life-forming chemical processes today. 25

26. Ancestor to all present-day life
Figure 15.1a
Precambrian
Ancestor to all present-day life
Atmospheric oxygen begins to appear
Origin of Earth
Earth’s crust solidifies
Oldest prokaryotic fossils
4,500
4,000
3,500
3,000
2,500
Millions of years ago
Figure 15.1 Some major episodes in the history of life (part 1) 26

27. 27 Precambrian Oldest eukaryotic fossils
Figure 15.1b
Precambrian
Oldest eukaryotic fossils
Origin of multicellular organisms
Oldest animal fossils
2,000
1,500
1,000
Millions of years ago
Figure 15.1 Some major episodes in the history of life (part 2) 27

28. 28 Precambrian Paleozoic Cenozoic Bacteria Prokaryotes Archaea
Figure 15.1c
Precambrian
Paleozoic
Meso- zoic
Cenozoic
Bacteria
Prokaryotes
Archaea
Protists
Eukaryotes
Plants
Fungi
Animals
Cambrian explosion
Extinction of dinosaurs
Oldest animal fossils
Plants colonize land
First humans
1,000
500
Millions of years ago
Figure 15.1 Some major episodes in the history of life (part 3) 28