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CHAPTER 5
EVOLUTION AND BIODIVERSITY
THINKING
Goals
See bulleted list of questions on p. 88 of text.
Objectives
1. Briefly describe the evolution of life from chemical evolution to the development of
eukaryotic cells.
2. Describe the tools available to researchers for learning the evolutionary history of
life.
3. Briefly describe the theory of evolution, being sure to include the roles played by
variation within the gene pool and natural selection, extinction, speciation, and
adaptive radiation.
4. Define natural selection and the three conditions that are necessary for evolution of a
population by natural selection. Summarize and address two common
misconceptions about evolution.
5. Define coevolution.
6. Distinguish between a specialist and a generalist. Evaluate the conditions that favor
these two approaches.
7. Define ecological niche. Distinguish between condition and resource; fundamental
niche and realized niche. List the factors that determine the realized niche.
8. Define speciation and compare allopatric speciation with sympatric speciation.
Indicate which of these mechanisms is more common.
9. Define extinction and distinguish between background extinction and mass
extinction. Discuss the role of humans on the rate of extinction at present.
10. Discuss the pros and cons of artificial selection and genetic engineering. Consider the
possible environmental impacts on resource use, pollution, and environmental
degradation.
11. Indicate what it is that has allowed humans to have such a profound influence on
their environment.
Key Terms (Terms are listed in the same font style as they appear in the text.)
chemical evolution (p. 88)
biological evolution (p. 88)
fossils (p. 88)
biological evolution (p. 88)
evolution (p. 88)
theory of evolution (p. 90)
microevolution (p. 90)
macroevolution (p. 90)
genetic variability (p. 90)
gene pool (p. 90)
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alleles (p. 90)
mutations (p. 90)
mutagens (p. 90)
natural selection (p. 90)
heritable (p. 90)
differential reproduction (p. 90)
Section One: Chapter 5
adaptation (p. 90)
adaptive trait (p. 90)
coevolution (p. 90)
ecological niche (p. 91)
niche (p. 91)
habitat (p. 91)
fundamental niche (p. 91)
realized niche (p. 91)
generalists (p. 91)
specialists (p. 91)
generalist species (p. 91)
evolutionary divergence (p. 93)
fitness (p. 93)
speciation (p. 94)
allopatric speciation (p. 94)
geographic isolation (p. 94)
reproductive isolation (p. 94)
sympatric speciation (p. 94)
extinction (p. 94)
background extinction (p. 95)
mass extinction (p. 95)
mass depletion (p. 96)
adaptive radiations (p. 96)
biodiversity (p. 96)
artificial selection (p. 97)
selective breeding (p. 97)
genetic engineering (p. 97)
gene splicing (p. 97)
genetically modified organisms
(GMOs) (p. 97)
transgenic organisms (p. 97)
clone (p. 97)
biopharming (p. 98)
Outline
5-1 Origins of Life
A. Chemical evolution of organic molecules, biopolymers, and systems of chemical
reactions were needed to form the first cell. It took about 1 billion years
B. Biological evolution followed, from single-celled prokaryotic bacteria to singlecelled eukaryotic organisms to multicellular organisms. Is has been continuing for
3.7 billion years.
C. Knowledge of past life comes from fossils, ice-core drilling, chemical analysis, and
DNA analysis. These records are incomplete
5-2 Evolution and Adaptation
Evolution is the change in a population’s genetic makeup over time.
A. Populations evolve by becoming genetically different.
B. All species descend from earlier, ancestral species—theory of evolution.
C. Microevolution describes the small genetic changes that occur in a population
over time.
1. Over time, a population’s gene pool changes when mutations (beneficial
changes) in DNA molecules are passed on to offspring. There may be several
different forms (alleles) of a single gene.
2. Sexual reproduction leads to random recombination of alleles from individual
to individual.
3. The gene pool consists of all the genes in a population’s offspring.
a. The population develops genetic variability brought about by mutations.
1) Mutations are random changes in the structure/number of DNA
molecules in a cell.
2) Mutations occur in two ways:
a) Gene DNA is exposed to external agents like X rays, chemicals
(mutagens), or radioactivity
b) Random mistakes that occur in coded genetic instructions
b. Only mutations in reproductive cells are passed to offspring.
c. Many mutations are neutral; some are deadly; and a few are beneficial.
D. Natural selection’s role in microevolution occurs when members of a population
have genetic traits that improve their ability to survive and produce offspring
with those specific traits.
1. For natural selection to evolve in a population, three conditions are
necessary:
a. The population must have genetic variability.
b. The trait must be heritable, capable of being passed from one generation
to another.
c. The trait must enable individuals with the trait to produce more offspring
than individuals without the trait; this is differential reproduction.
Evolution and Biodiversity
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2. Adaptation or adaptive traits are heritable traits that help organisms to
survive and reproduce better under prevailing environmental conditions.
3. Environmental changes require adaptations also. Organisms must:
a. adapt to the new conditions,
b. migrate to an area with a more favorable environment, or
c. become extinct.
4. Microevolution follows this process: genes mutate; individuals are selected;
and populations evolve.
E. Interactions between species can result in microevolution in each of their
populations, a process called coevolution. Sometimes the predators have the
advantage; sometimes the prey are better adapted.
5-3 Ecological Niches and Adaptation
A. An ecological niche is a species’ way of life in an ecosystem, everything that
affects its survival and reproduction.
1. The niche includes the member’s adaptations, its range of tolerance for
physical and chemical conditions, its interactions with other components of
the ecosystem, and its role in energy flow and matter recycling.
2. This is NOT the same as the organism’s habitat.
3. The habitat is the physical location where a species lives.
4. The fundamental niche is the full potential range of conditions and resources
a species could use. Its realized niche is the part of the potential niche that
allows a species to survive and avoid competition with other species for the
same resources.
B. Some species have broad ecological roles and are termed generalist species.
1. Their living range is broad and includes many different places.
2. They can eat a variety of foods and tolerate a wide range of environments.
3. If the environment is changeable, the generalist will survive better than the
specialist.
C. Some species have narrow ecological roles and are termed specialist species.
1. Specialist species can live only in very specific environments.
2. This makes them more prone to extinction when environmental conditions
change.
3. If the environment is constant, specialists have fewer competitors.
4. Intense competition may lead to evolutionary divergence of a single species
into a variety of similar species with specialized niches.
D. A population’s gene pool and its rate of reproduction limit the population’s ability
to adapt to new environmental conditions.
1. The only genetic traits that can adapt are those already in the gene pool.
2. A population’s reproductive capacity limits those genes that can adapt.
a. Genetically diverse species that reproduce quickly can often adapt quickly.
b. Populations that reproduce slowly take a long time to adapt through
natural selection.
c. For a new favorable trait to predominate, most of an existing population
would have to die prematurely.
E. Evolution is concerned with leaving the most descendants, NOT the strongest
ones.
F. There is no master plan to achieve genetic perfection.
5-4 Speciation, Extinction, and Biodiversity
A. Natural selection can lead to development of an entirely new species.
1. In speciation, two species arise from one when some members of a
population cannot breed with other members to produce fertile offspring.
Allopatric speciation is the most common mechanism and occurs in two
phases:
a. Geographic isolation: physical separation for long time periods
b. Reproductive isolation: the gene pools are so changed that members
become so different in genetic makeup that they cannot produce fertile
offspring
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Section One: Chapter 5
B.
C.
D.
E.
F.
2. Sympatric speciation is less common. It occurs when two species live close
together but can’t interbreed due to a mutation or subtle changes in behavior.
When population members cannot adapt to changing environmental conditions,
the species becomes extinct.
1. A species manages to survive one to ten million years before extinction
occurs.
2. Life has had to cope with many major natural disasters that may reduce or
eliminate species.
3. Introduction of new species into an area has also led to reduction in number
or elimination of species.
When local environmental conditions change, some species will disappear at a
low rate; this is called background extinction.
Mass extinction is a significant rise in extinction rates above the background
extinction level. Usually, from 25–70% of species are lost. Recent evidence
suggests that there have been two mass extinctions on Earth. There appear to
have been three mass depletions on Earth.
Adaptive radiations are recovery periods after mass extinction when numerous
new species evolve to fill niches in changed environments. It takes one to ten
million years to rebuild biological diversity after a mass extinction/depletion.
The Earth’s biodiversity is decreasing because of human activities.
1. Biodiversity equals speciation minus extinction.
2. Humans are causing the premature extinction of species, estimated to be 100
to 1,000 species per million species.
3. It has been predicted that by the end of the 21st century we may see the
extinction of half of the present species now on Earth.
4. Humans and their activities are also destroying/degrading ecosystems that
might be centers for future speciation.
5-5 What is the Future of Evolution?
A. Man has used artificial selection to change the genetic characteristics of
populations.
1. We use selective breeding to obtain specific desired traits.
2. Traditional crossbreeding is a slow process; it takes many generations of
selection for the desired trait.
3. Genetic engineering/gene splicing are techniques that isolate, modify,
multiply, and recombine genes from different organisms. Genes from different
species that would never interbreed in nature are being transferred to each
other.
4. Genetically modified organisms (GMOs)/transgenic organisms are the results
of this gene splicing.
a. Gene splicing takes half as much time to develop a new crop/animal, as
does traditional crossbreeding.
b. Cloning produces a genetically identical version of an individual.
c. Biopharming is a new field where genetically engineered animals act as
biofactories to produce drugs, vaccines, antibodies, hormones, etc.
B. Genetic engineering is an unpredictable process and raises privacy, ethical, legal,
and environmental issues. It is a trial and error process.
1. The average success rate of genetic engineering experiments is about 1%.
2. There are many questions about gene therapy. Who will be helped with
genetic knowledge—only those who can pay for it? If one has a defect, will he
or she be able to get health insurance, or a job? Should we clone spare parts
for people’s bodies?
3. A backlash developed in the 1990s against increased use of genetically
modified food plants and animals.
4. Proponents of more careful control of genetic engineering point out that most
new technologies have had unintended, harmful consequences, so caution
should be practiced regarding genetic engineering.
C. Humans have become such a powerful species so quickly due to two evolutionary
adaptations: a complex brain and strong opposable thumbs.
Evolution and Biodiversity
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1. Humans have quickly developed powerful technologies to meet our needs and
wants.
2. Humans need to change our ways in order not to be called Homo ignoramus
instead of Homo sapiens sapiens, the doubly wise.
Summary
1.
Life emerged on the earth through two phases of development: a chemical evolution
of the organic molecules, biopolymers, and systems of chemical reactions to form
the first cells and the biological evolution from single-celled prokaryotic bacteria to
single-celled eukaryotic creatures, then to multicellular organisms.
2.
Evolution is the change in a population’s genetic makeup over time. Evolution forces
adaptations to changes in environmental conditions in a population. The diversity of
life on Earth reflects the wide variety of adaptations necessary and suggests that
environmental conditions have varied widely over the life of the earth.
3.
An ecological niche is a species’ way of life or its functional role in a community.
Everything that affects its survival and reproduction (temperature tolerance, water
needs, space needs, interactions with other organisms, etc.) is a part of that niche.
The ecological niche helps a population survive by the adaptive traits that its
organisms have acquired.
4.
Extinction of species and formation of new species constantly change the
biodiversity of the earth
5.
In the future, evolution will continue to influence our environment. Man’s use of
artificial selection and genetic engineering to evolve species may have unintended
consequences because evolution is a long, slow process and is unpredictable.
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Section One: Chapter 5
Test Items
See Instructor’s Manual, Section Two, p. 344.
More Depth: Conceptual Term Paper Topics
1. Evolution: the theory of evolution, supporting and detracting evidence, fossils;
embryological homologies, structural homologies; biochemical evidence; DNA
evidence. Contrast the views of slow, gradual change and relatively rapid
(punctuated) change.
2. Biological Evolution: endosymbiont hypothesis; Gaia hypothesis; extinctions and
radiations; natural selection and genetic drift; adaptations and their limits;
gradualism and punctuated equilibrium.
3. Diversity of species: choose a kingdom.
4. Genetic engineering: how humans are changing the course of evolution.
More Breadth: Interdisciplinary 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?
2. Invite an evolutionary biologist to your class. Ask about evidence for different parts
of the theory of evolution, including the endosymbiont hypothesis. Ask about the
Gaia hypothesis.
3. Arrange a field trip 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?
Multisensory Learning: Audiovisuals
Biodiversity (Rediscovering Biodiversity series). 2003. 30 min. ACPB.
Continental Drift: Legacy of Fire; 1998; 50 min.; geologists explore the Pacific Rim with
earthquakes, volcanoes, and rich mineral deposits, all clues to continental drift;
FHS.
Death of the Dinosaurs; 1998; 50 min.; exploration of a theory that a series of volcanic
eruptions lead to the demise of the dinosaurs; FHS.
The Evidence for Evolution. DVD/VHS. FHS.
Evolving Ideas: Isn’t Evolution Just a Theory? 2001. 6 min. PBS.
Gene Blues: dilemmas of DNA Testing. 1997. 30 min. BFF.
Human Evolutions. PBS.
Is There a Crisis? biodiversity in decline. (State of the Planet series) DVD/VHS. FHS.
Land above the Trees; 1988; 19 min.; ecological connections and special adaptations to
the alpine zone; NFB.
Nature’s Numbers: Assessing Species Extinction; 1998; 47 min.; scientists attempting to
quantify loss of species; FHS.
NOVA: origins. VHS. PBS.
Oxygen: the poison gas. 1998. 50 min. FHS.
Toxic Newts. 2001. 5 min. VHS. PBS.
Understanding Biodiversity. 1996. 25 min. VHS/DVD. EVN
See Appendix A for suppliers.
Evolution and Biodiversity
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Section One: Chapter 5
ATTITUDES/VALUES
Assessment
1. Do you think that biodiversity is an ecosystem service? Explain.
2. Do you think you have a responsibility to sustain biodiversity?
3. Do you think evolution of species has occurred? If so, how?
4. Do you think species have a right to struggle to survive without human interference?
More Depth: Discussion and Term Paper Topics
1. To what extent should humans take evolution into their own hands?
2. Should there be limits on genetic engineering?
3. How does the change that humans create through cultural evolution compare to the
process of evolution by natural selection?
(Also, see text, Critical Thinking, p. 100 and Critical Thinking and the Environment.)
PARTICIPATION
More Depth: Action-oriented Term Paper Topics
1. Scientific methods: genetic engineering; DNA analysis.
SKILLS
Environmental Problem-solving Skills: Projects
1. As a class, consider the crops that provide the majority of our food. Brainstorm a list
of “designer genes” that would improve those crops for human consumption. Reflect
on how genetic engineering alters the relationship between humans and evolution.
Consider the power and the limits of that relationship.
Laboratory Skills
Replicate some of Oparin’s experiments adding energy to atmospheric gases that
probably existed before the formation of organic molecules.
Computer Skills
Sim Earth: The Living Planet, Will Wright and Fred Haslam, Software @1990, Maxis and
Will Wright.
Also, see Introduction to the Internet.
Evolution and Biodiversity
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