CHAPTER 4
BIODIVERSITY AND EVOLUTION
Outline
4-1 What is biodiversity and why is it important?
A. Biodiversity is a crucial part of the earth’s natural capital
2. Biodiversity includes a number of components.
a. Species diversity, or the number and variety of the species present in any biological
community.
3. SCIENCE FOCUS 4.1: Insects play a vital role in our world.
2. INDIVIDUALS MATTER 4.1: Edward O. Wilson: A champion of biodiversity.
a. Started with studying ants then widened his focus to include the entire biosphere.
b. Proposed the hypothesis that humans have a natural affinity for wildlife and wild places—
4-2 What roles do species play in ecosystems?
A. Each species plays a role in its ecosystem.
1. An ecological niche is a species’ way of life in an ecosystem, everything that affects its
survival and reproduction.
3. Generalist species have broad niches.
4. Specialist species have narrow niches.
a. They live only in very specific environments.
b. This makes them more prone to extinction when environmental conditions change.
c. If the environment is constant, specialists have fewer competitors.
d. China’s giant panda is a specialist with a specialized diet of mostly bamboo.
B. Species can play four major roles within ecosystems
1. Niches can be classified further in terms of specific roles that certain species play within
2. Native species are those that normally live and thrive in a particular ecosystem.
4. Nonnative species can threaten native species.
C. Indicator species serve as biological smoke alarms.
1. Indicator species provide early warnings of damage to a community or an ecosystem.
a. Birds are excellent biological indicators because they are found almost everywhere and
are affected quickly by environmental changes, such as loss or fragmentation of their
habitats and introduction of chemical pesticides.
D. CASE STUDY: Why are amphibians vanishing?
2. Populations of amphibians are declining or disappearing throughout the world; more than
3. The cause of this decline is unknown but scientists have identified a number of factors that
can affect frogs and other amphibians at various points in their life cycles.
a. Habitat loss and fragmentation.
4. Three reasons to care if amphibians become extinct include:
a. Amphibians are sensitive biological indicators of changes in environmental conditions
such as habitat loss and degradation, air and water pollution, UV radiation, and climate
change.
b. Adult amphibians play important ecological roles in biological communities.
c. Amphibians represent a genetic storehouse from which hundreds of pharmaceutical
products could be developed.
E. Keystone species play critical roles in their ecosystems
1. Keystone species are species whose roles have a large effect on the types and abundance of
other species in an ecosystem, even though they may exist in relatively limited numbers in
their ecosystems.
a. Examples are the wolf, leopard, lion, some shark species, and the American alligator
F. CASE STUDY: The American alligator—A keystone species that almost went extinct
1. Between the 1930s and 1960s, hunters and poachers wiped out 90% of the alligators in the
2. The American alligator is a keystone species because it plays a number of important roles that
help to maintain the sustainability in the subtropical wetland ecosystems where it is found.
a. Alligators dig deep depressions, or gator holes, which hold freshwater during dry spells,
3. Since being classified as an endangered species in 1967, American alligators have recovered
4.3 How does the earth’s life change over time?
A. Biological evolution by natural selection explains how life changes over time
1. Fossils reveal the history of life.
3. The theory of evolution by natural selection is a scientific explanation of how the process of
evolution takes place.
4. Natural selection is the process in which individuals with certain traits are more likely to
survive and reproduce under a particular set of environmental conditions than those without
the traits.
B. Mutations and changes in the genetic makeup of populations lead to biological evolution by
natural deflection
2. An adaptation, or an adaptive trait, is any heritable trait that improves the ability of an
3. Natural selection can result in the evolution of genetic resistance, the ability of one or more
organisms in a population to tolerate a chemical designed to kill the population. Examples
include antibiotic-resistant bacteria and pesticide-resistant insects.
C. Adaptation through natural selection has limits.
1. Organisms can adapt to a change in environmental conditions only if the necessary genetic
traits are already present in a population’s gene pool.
2. Another limit is that even if a beneficial heritable trait is present in a population, the
population’s ability to adapt may be limited by its reproductive capacity.
D. SCIENCE FOCUS: How did humans become such a powerful species?
2. Ability to walk upright.
3. Complex brain
E. There are three incorrect ideas about evolution through natural selection
1. “Survival of the fittest” meaning “survival of the strongest”.
3. Evolution by natural selection involves some grand plan of nature in which species become
more perfectly adapted.
4-4 What factors affect biodiversity?
A. How do new species evolve?
2. Geographic isolation occurs when different groups of the same population of a species
become physically isolated from one another for a long period of time.
3. Reproductive isolation occurs when mutation and change by natural selection operate in the
gene pools of geographically isolated populations.
B. Sooner or later all species become extinct
2. Local extinction occurs when a population of a species becomes extinct over a large region,
but not globally.
4. Background extinction has occurred over most of Earth’s history.
C. There have been several mass extinctions of life on the Earth
2. Fossil and geological evidence indicate that there have probably been five mass extinctions
during the past 500 million years
3. Mass extinctions have been followed by an increase in species diversity as new species have
4. There is growing evidence that we are experiencing the beginning of a new mass extinction,
with much of the increase in extinctions and loss of biodiversity due to human activities.
D. SCIENCE FOCUS: Changing the genetic traits of populations
1. Humans use artificial selection to change the genetic characteristics of populations with
2. Scientists can now use genetic engineering to manipulate genes.
a. An organism’s genetic material is altered by adding, deleting, or changing segments of
2. Niche is different from habitat, which is the place where an organism lives.
3. Generalist species have broad niches.
4. Specialist species have narrow niches.
a. They live only in very specific environments.
b. This makes them more prone to extinction when environmental conditions change.
c. If the environment is constant, specialists have fewer competitors.
d. China’s giant panda is a specialist with a specialized diet of mostly bamboo.
H. Species can play four major roles within ecosystems
2. Native species are those that normally live and thrive in a particular ecosystem.
4. Nonnative species can threaten native species.
I. Indicator species serve as biological smoke alarms.
1. Indicator species provide early warnings of damage to a community or an ecosystem.
a. Birds are excellent biological indicators because they are found almost everywhere and
are affected quickly by environmental changes, such as loss or fragmentation of their
habitats and introduction of chemical pesticides.
J. CASE STUDY: Why are amphibians vanishing?
2. Populations of amphibians are declining or disappearing throughout the world; more than
3. The cause of this decline is unknown but scientists have identified a number of factors that
can affect frogs and other amphibians at various points in their life cycles.
a. Habitat loss and fragmentation.
b. Prolonged drought.
4. Three reasons to care if amphibians become extinct include:
a. Amphibians are sensitive biological indicators of changes in environmental conditions
such as habitat loss and degradation, air and water pollution, UV radiation, and climate
change.
K. Keystone species play critical roles in their ecosystems
1. Keystone species are species whose roles have a large effect on the types and abundance of
other species in an ecosystem, even though they may exist in relatively limited numbers in
their ecosystems.
a. Examples are the wolf, leopard, lion, some shark species, and the American alligator
L. CASE STUDY: The American alligator—A keystone species that almost went extinct
1. Between the 1930s and 1960s, hunters and poachers wiped out 90% of the alligators in the
2. The American alligator is a keystone species because it plays a number of important roles that
help to maintain the sustainability in the subtropical wetland ecosystems where it is found.
a. Alligators dig deep depressions, or gator holes, which hold freshwater during dry spells,
3. Since being classified as an endangered species in 1967, American alligators have recovered
enough to be removed from the endangered species list.
Objectives
4-1 What is biodiversity and why is it important?
CONCEPT 4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to
sustaining life on earth.
1. Define species diversity, genetic diversity, ecosystem diversity and functional diversity.
3. Describe why humans consider insects to be pests and how insects are beneficial to the ecosystems
where they live.
4-2 What roles do species play in ecosystems?
CONCEPT 4-2A Each species plays a specific ecological role called its niche.
CONCEPT 4-2B Any given species may play one or more of four important roles—native, nonnative,
indicator, or keystone—in a particular ecosystem.
2. Define natural selection and the conditions that are necessary for evolution of a population by natural
4-3 How does the earth’s life change over time?
Instructor’s Manual for Environmental Science, 15th edition
CONCEPT 4-3A The scientific theory of evolution through natural selection explains how life on the
earth changes over time due to changes in the genes of populations.
CONCEPT 4.3B Populations evolve when genes mutate and give some individuals genetic traits that
enhance their abilities to survive and to produce offspring with these traits (natural selection).
4-4 What factors affect biodiversity?
CONCEPT 4-4A As environmental conditions change, the balance between the formation of new
species and the extinction of existing species determines the earth’s biodiversity.
CONCEPT 4-4B Human activities are decreasing biodiversity by causing the extinction of many
species and by destroying or degrading habitats needed for the development of new species through
natural selection.
2. Define extinction and distinguish among biological extinction, local extinction, background extinction
and mass extinction. Discuss the role of humans in the rate of extinction at the present time.
Key Terms
adaptation
adaptive trait
extinction
fossils
natural selection
nonnative species
Teaching Tips
The notion that climate and geological change can affect evolution is a good way to understand the change
over time in biodiversity. Because climate is ever-present, it has an incalculable effect on our evolution.
Begin this discussion with the topic of populations. It is critical for students to understand that populations
evolve, not individuals, and that a population’s genetic material is in flux relative to environmental
1. Explain the theory of evolution and describe the supporting and detracting fossil and DNA evidence.
What are some of the variables influencing changes in evolution?
2. To what extent should humans take evolution into their own hands? Should there be limits on genetic
engineering or any other technologies?
3. How does the change that humans create through cultural evolution compare to the process of
evolution by natural selection?
4. What is the difference between mass extinction and background extinction? What are some of the
variables that influence mass extinction?
5. How do geological processes and climate change affect evolution? Please include how tectonic plates,
6. What species have been around for a long time and why? What are some of their adaptive features?
7. How do speciation, extinction, and human activities affect biodiversity? What is the benefit of
increased biodiversity?
8. How do species help or hurt specific ecosystems?
9. What characteristics of species make it more likely, or less likely to become extinct?
Activities and Projects
1. As a class exercise, evaluate the diversity of your community using criteria such as ethnic, racial,
religious, and socioeconomic groups; lifestyles; and industries, landscape features, and landscape
forms. What elements of diversity have proved troublesome? What additional elements of diversity
would improve your community? You can compare your observations to the United States census data.
2. Invite an evolutionary biologist to your class or take a field trip to a natural history museum (virtual
3. Arrange a field trip (your campus might provide good examples) providing opportunities to compare
and contrast ecosystems of several different types, including some damaged or stressed by human
activities. Invite an ecologist or biologist along to identify and discuss specific examples of species
adaptation to environmental conditions. Do the boundaries between different kinds of ecosystems tend
to be sharply delineated? Can you identify factors that limit the growth of certain species?
4. As a class, consider the risk factors to the local species. Are there endangered species in your city,
county or state? If so, describe the reasons that they are endangered and any protection or conservation
Instructor’s Manual for Environmental Science, 15th edition
© 2016 Cengage Learning
Attitudes and Values Assessment
1. Do you think biodiversity is an ecosystem service? Explain.
2. Is there more than one way to value biodiversity?
3. Do you think you have a responsibility to sustain biodiversity?
4. Should we worry about every species that is threatened, or should we pick and choose? If you believe
we should protect every species, how would this be funded? If you believe we should pick and choose,
how would you choose which species to protect?
5. Do you think evolution of species has occurred? If so, how?
6. Do you think species have a right to struggle to survive without human interference?
Laboratory Skills
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #7: Community Ecology: Forest Plot
Analysis.
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #9: Butcher the Biomes.
News Videos
Additional Videos
Island of the Sharks: IMAX (Documentary, 1999)
Get up close and personal with sharks off the coast of Costa Rica.
http://www.imax.com/movies/m/island-of–the-sharks/
Web Resources
Tree of Life
Follow evolution and explore the variety of life on the planet with the Interactive Tree of Life
Chapter 4: Biodiversity and Evolution
http://www.open2.net/treeoflife/index.html
IUCN Red List
The IUCN Species Survival Commission’s list of threatened and endangered species around the globe.
http://www.iucnredlist.org
Digital Integration
Correlation to Global Environment Watch
Biodiversity Genetic Engineering
Evolution Global Geoscience Watch
Extinction Invasive Species
Correlation to Virtual Field Trips
Carnivorous Plants
Correlation to Explore More
Biodiversity Extinction
Ecology Genetic Engineering
Environmental History Origin of Life on Earth
Evolution Saving Species
Suggested Answers to End of Chapter Questions
Answers will vary but these represent phrases from this chapter. The following are examples of the material
that should be contained in possible student answers to the end of chapter questions. They represent only a
Review
Core Case Study
1. Describe the threats to many of the world’s amphibian species (Core Case Study) and explain why we
should avoid hastening the extinction of any amphibian species through our activities.
Instructor’s Manual for Environmental Science, 15th edition
• Amphibian species are having difficulty adapting to rapid changes that have taken place in
their water and land habitats during the past few decades.
Section 4-1
2. What is the key concept for this section? Define biodiversity (biological diversity) and list and describe its
four major components. Why is biodiversity important? Summarize the importance of insects. Define and
give three examples of biomes. Summarize the scientific contributions of Edward O. Wilson.
• CONCEPT 4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital
to sustaining life on earth.
• Biological diversity, or biodiversity, is the variety of the earth’s species, the genes they contain, the
ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling
that sustain all life.
• The four components of biodiversity are:
o Species diversity, or the number and variety of the species present in any biological
community.
• Biodiversity provides us with food, wood, fibers, energy from wood and biofuels, and medicines, and
plays critical roles in preserving the quality of the air and water, maintaining the fertility of topsoil,
decomposing and recycling waste, and controlling populations of species that we call pests.
• Insects play a vital role in helping to sustain life on Earth, such as through pollination, soil
conditioning, and pest control.
• Biomes are large regions such as forests, deserts, and grasslands with distinct climates and certain
species (especially vegetation) typically occurring within them.
o Three examples are prairie grasslands, coniferous forests, and desert.
• Edward O. Wilson:
o Is an expert on ant biology,
Section 4-2
3. What are the two key concepts for this section? Define and distinguish between a niche, or ecological niche,
and a habitat. Distinguish between generalist species and specialist species and give an example of each.
• CONCEPT 4-2A Each species plays a specific ecological role called its niche.
• CONCEPT 4-2B Any given species may play one or more of four important roles—native,
nonnative, indicator, or keystone—in a particular ecosystem.
4. Define and distinguish among native, nonnative, indicator, and keystone species and give an example
of each. What major ecological roles do many amphibian species play (Core Case Study)? List six
factors that contribute to the threats of extinction for frogs and other amphibians. Describe the role of
the American alligator as a keystone species. Explain why we should protect sharks.
• Native species are those species that normally live and thrive in a particular ecosystem.
An example is the bald eagle. Other species that migrate into, or are deliberately or
accidentally introduced into an ecosystem are called nonnative species. An example is
African bees.
• Species that provide early warnings of environmental change in a community or an
ecosystem are called indicator species. An example would be amphibians. Keystone
species are species whose roles have a large effect on the types and abundance of other
species in an ecosystem. An example is wolves.
Section 4-3
5. What are the two key concepts for this section?? What are fossils and how do scientists use them?
Define biological evolution and natural selection and explain how they are related. What is the
scientific theory of biological evolution through natural selection?
• CONCEPT 4.3A The scientific theory of evolution through natural selection explains how life
on the earth changes over time due to changes in the genes of populations.
• CONCEPT 4.3B Populations evolve when genes mutate and give some individuals genetic
traits that enhance their abilities to survive and to produce offspring with these traits
(natural selection).
Instructor’s Manual for Environmental Science, 15th edition
• Fossils are mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and
seeds, or impressions of such items found in rocks.
• Scientists use fossils to interpret the long history of life on the earth.
6. What is a mutation and what role do mutations play in evolution through natural selection? What is an
adaptation, or adaptive trait? Explain how harmful bacteria can become genetically resistant to
antibiotics. What three genetic adaptations have helped humans to become such a powerful species?
What are two limitations on evolution through natural selection? What are four common myths about
evolution through natural selection, and for each of them, why is it a myth?
• Mutations are random changes in the DNA molecules of a gene in any cell, which can
possibly result in a new genetic trait, which can be passed from one generation to the
next. This can cause populations develop differences among individuals, including
genetic variability.
• Limitations:
o First, a change in environmental conditions can lead to such an adaptation only
for genetic traits already present in a population’s gene pool or for traits
resulting from mutations, which occur randomly.
• Myths about evolution:
o Survival of the fittest means survival of the strongest. To biologists, fitness is a
measure of reproductive success, not strength.
o Evolution explains the origin of life. It does not. However, it does explain how
species have evolved after life came into being.
Chapter 4: Biodiversity and Evolution
Section 4-4
What are the two key concepts for this section? Define speciation. Distinguish between geographic
isolation and reproductive isolation, and explain how they can lead to the formation of a new species.
Explain how geological processes can affect biodiversity.
7. Define and distinguish between artificial selection and genetic engineering and give an example of each.
Define synthetic biology.
• CONCEPT 4.4A As environmental conditions change, the balance between the formation
of new species and the extinction of existing species determines the earth’s biodiversity.
• CONCEPT 4.4B Human activities are decreasing biodiversity by causing the extinction of
many species and by destroying or degrading habitats needed for the development of
new species through natural selection.
• Geographic isolation occurs when different groups of the same population of a species
become physically isolated from one another for a long period of time.
• In reproductive isolation, mutation and change by natural selection operate
independently in the gene pools of geographically isolated populations.
• Geological processes can separate populations, an example being the shift of tectonic
plates separating the huge land mass of Pangea.
• In artificial selection, we select one or more desirable genetic traits in the population of
a plant or animal such as a type of wheat, fruit, or dog. Then we use selective breeding,
8. What is extinction? What is an endemic species and why can such a species be vulnerable to
extinction? Define and distinguish between the background extinction rate and a mass extinction.
What is one of the leading causes of the rising rate of extinction?
• Extinction is a process in which an entire species ceases to exist (biological extinction)
or a population of a species becomes extinct over a large region, but not globally (local
extinction).
9. What are this chapter’s three big ideas? How are ecosystems and the variety of species they contain
related to the three principles of sustainability?
• This chapter’s three big ideas are:
• Populations evolve when genes mutate and give some individuals’ genetic traits that
enhance their ability to survive and to produce offspring with these traits (natural
selection).
Critical Thinking
1. How might we and other species be affected if all of the world’s amphibians (Core Case Study) were
to go extinct?
2. Is the human species a keystone species? Explain. If humans were to become extinct, what are three
species that might also become extinct and what are three species whose populations would probably
grow?
• Since Keystone species are species whose roles have a large effect on the types and abundance of
3. If you were forced to choose between saving the giant panda from extinction and saving a shark
species, which would you choose? Explain.
3. How would you respond to someone who tells you that: a. he or she does not believe in biological
evolution because it is “just a theory”? b. we should not worry about air pollution because natural
selection will enable humans to develop lungs that can detoxify pollutants?
• Biological evolution through natural selection is a theory that is supported by evidence. A theory
is not a “guess” but it is a widely held conviction. Through additional and ongoing research and
4. How would you respond to someone who says that because extinction is a natural process, we should
not worry about the loss of biodiversity when species become extinct as a result of our activities?
Chapter 4: Biodiversity and Evolution
It is true that as environmental conditions change some species may begin to disappear at a low rate.
This is the background extinction rate, and annually is around one to five species for every million
5. What role does each of the following processes play in helping to implement the three scientific
principles of sustainability: (a) natural selection, (b) speciation, and (c) extinction?
• The three scientific principles of sustainability are:
• Dependence on solar energy
6. List three aspects of your lifestyle that could be contributing to some of the losses of the earth’s
biodiversity. For each of these, what are some ways to avoid making this contribution?
• Student answers may vary but could include:
o Being a consumer
▪ Practice Reduce, Reuse, Recycle (Rethink).
7. Congratulations! You are in charge of the future evolution of life on Earth. What are the three things
that you would consider to be the most important to do?
Student answers will vary but could include:
• increased conservation, preservation
• protection of habitat that allows for greater biodiversity and ecosystem stability through
continuing evolutionary processes
Search for Amphibians to find out more about the current state of these species with regard to threats to
their existence (Core Case Study). What actions are being taken by various nations and organizations to
protect amphibians? Write a short summary report on your research.
Instructor’s Manual for Environmental Science, 15th edition
Data Analysis Answers
The following table is a sample of a very large body of data reported by R. A. Alford and S. J. Richards in
their book Extinction in Our Times–Global Amphibian Decline. It compares various areas of the world
in terms of the number of amphibian species found and the number of amphibian species that were
1. Fill in the fourth column to calculate the percentage of amphibian species that are endemic to each area.
83
37
40
63
56
51
77
22
2. Which two areas have the highest numbers of endemic species? Name the two areas with the highest
percentages of endemic species.
• Numbers:
3. Which two areas have the lowest numbers of endemic species? Which two areas have the lowest
percentages of endemic species?
• Numbers:
o Southern Coastal Plain of the United States at 27
4. Which two areas have the highest percentages of non-endemic species?