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Name: __________________
“If all mankind were to disappear, the
world would regenerate back to the
rich state of equilibrium that existed
ten thousand years ago. If insects
were to vanish, the environment would
collapse into chaos.”
~Edward O. Wilson
CHAPTER 7
COMMUNITY ECOLOGY: STRUCTURE, SPECIES INTERACTIONS,
SUCCESSION, AND SUSTAINABILITY
Outline
A. Community structure and diverse species help define an ecosystem.
B. Different species’ interactions and influences on their environments
are not completely clear.
C. Ecological communities are constantly changing, establishing communities, responding to
disturbances, and seeking stability.
D. For the continuing survival of our environment, we should remember the adage: “First, do no
harm.”
7-1 Community structure and species diversity
1. Give the four features of community structure. Be ready to describe each.
a.
b.
c.
d.
2.
Describe the "patch effects" that most ecosystems show. Describe the edge effect between two areas.
3.
List the three most species-rich areas of the world and give the three factors that affect the diversity
in those areas.
7-2 General types of species
1. The four types of ecological roles of a species are 1) native, 2) nonnative or alien, 3) indicator, and
4) keystone species. For each be able to define and give one example of each role.
2. Native species:
3.
Non-native - Be ready to discuss the movie Cane Toads
4.
Indicator species vanishing amphibian species (be ready to describe the causes for their decline).
What do these indicate in the environment?
5.
Keystone species and their roles in the ecosystem. Remember the role of top predator and the role
of the elephant.
When species interact there are 3 major types of interactions: Competition, Predation, and Symbiosis (living
together). We will study each in the following sections.
7-3 Species interactions: Competition and predation
A. Intraspecific and interspecific competition
1. Describe why competition occurs. Define the terms niche and habitat in your understanding of
competition.
2.
Copy the graph from the power point in the space below. Describe how resource partitioning
can minimize competition. Recall the discussion of the Tragedy of the Commons.
B.
Describe a predator-prey relationship. Give two examples.
C.
Understand that both predator and prey evolve to survive during the relationship. Describe the
analogy of the "arms race".
D. Be ready to give examples of both defense and weapons used to survive.
1. Defensive methods
a. Camouflage and chemical warfare
b. Warming coloration, mimicry
c. Behavioral strategies
2. Predator Weapons
a. Speed
b. Stealth
c. Claw/Fang
7-4 Species interactions: Symbiosis - Parasitism, mutualism, and commensalism
A. Species interactions provide positive and negative benefits for both interacting parties.
B. One organism is the host.
1.
Describe a parasitic relationship. What are the physical differences between the host and the
parasite? Give two examples.
2.
Describe a commensalistic relationship. What are the physical differences between the host and the
commensal? Give two examples.
3.
Describe a mutualistic relationship. What are the physical differences between the host and the
mutual? Give two examples.
Complete the following table that summarizes the changes in the populations during the different
types of species relations. Use a plus sign (+) to indicate population increase and a minus (-) to
indicate a population decrease.
INTERACTION
CHANGE IN POPULATION
POPULATION A
POPULATION B
COMPETITION
PREDATION
Predator
Prey
PARASITISM
Parasite
Host
Commensal
Host
Mutual
Host
COMMENSALISM
MUTUALISM
7-5 Ecological succession: Communities in transition
A. Biotic communities may either gradually establish a community on ‘nearly lifeless
ground’ or establish a biotic community in an area that already has an established
community.
1. Describe primary succession of plants and animals.
2. Describe secondary succession from an already used area.
B. Disturbances in an ecosystem’s environment can cause an ecological succession to revert.
Give several examples of disturbances caused by nature and several caused by humans.
C. An ecological succession’s progress cannot be predicted. Describe why.
7-6 Ecological stability and sustainability
A. A stable and sustained ecosystem is influenced by Inertia, constancy, and resilience.
a. Describe in your own words the concepts of inertia, constancy, and resilience.
B. Since ecosystems are always changing, it is not possible to predict the necessary creatures
or numbers that would sustain a particular ecosystem.
C. The ‘precautionary principle’ suggests that we should be careful of our environments and
environmental resources; we have no sure knowledge of their inter-connectivity nor of
their long-term importance.