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Chapter 26
Ecosystems
CHAPTER OUTLINE
Introduction to ecology
Population ecology
Spacing is an important feature of populations
Population increase is limited by environmental resources
Symbiosis is a close association between species
Benefits are shared in mutualism
Commensalism is taking without harming
Parasitism is taking at another’s expense
Keystone species and dominant species affect the character of a community
Ecological succession is community change over time
In primary succession, a community develops on land not previously inhabited by
plants
In secondary succession, a community develops after removal of an earlier
community
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CHAPTER OBJECTIVES
1. Define ecology and distinguish among population, community, ecosystem, and biosphere.
2. Explain the difference between J-shaped and S-shaped population growth curves.
LECTURE OUTLINE
I. Define and relate the terms ecology, population, community, ecosystem, and biosphere.
II. How does one describe a population and the way it grows?
A. What are the three main types of dispersion?
B. What is the difference between exponential growth and logistic growth?
3. What is a metapopulation?
III. How does one describe a community?
A. Define and give examples of autotroph, heterotroph, producer, consumer, herbivore,
carnivore, omnivore, detritivore, and decomposer. What is the difference between a
primary and a secondary consumer?
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2. What is commensalism? Give an example.
3. What is parasitism? Give an example.
F. What is a keystone species and how does it differ from a dominant species?
G. How do communities change over time?
IV. How does one describe an ecosystem?
A. In what direction is the flow of energy in an ecosystem?
1. Describe food chains and food webs and give an example.
KEY TERMS
biogeochemical cycle, p. 529
biosphere, p. 516
carrying capacity, p. 518
ecosystem, p. 516
energy flow, p. 528
exponential growth, p. 617
metapopulation, p. 520
mutualism, p. 523
niche, p. 521
TEACHING TIPS
1. Ask students why species diversity in an ecosystem is important. Ask them to identify
2. Give groups of students a list of about ten organisms. Along with the list, give them
several food chains which together include all the organisms on the list. Ask them to
3. Look around your locale for examples of succession. Take slides of the area to illustrate
4. Succession in hay infusions can be a good exercise for the lab session. (Preparation of the
hay infusions was described in the Teaching Tips for Chapter 20.) Have students identify
5. Ask students to describe their typical diet, then discuss the energy efficiency of their diet.
This can be done in small discussion groups. Ask them how they could change their diet
to “eat lower on the food chain.”
6. Select an ecosystem familiar to the students, such as one that covers part of the campus,
or even an aquarium or terrarium present in the classroom. Have students work in teams
7. Give students a list of species in a local community and ask them to categorize them as
producers, consumers, decomposers, or detritivores.
8. Examine recently disturbed sites, such as fields, construction sites, roadsides, and