ABSTRACT PAGE
The Issue
Elimination of top predators (e.g. wolves) from regions like the Greater Yellowstone Ecosystem leads to changes in prey population density and behavior, as well as overall community structure. This issue addresses how ecosystems change when predators are removed, and what happens in such a system when the predators are restored. It is designed to address students’ misconception that predators only influence ecosystems directly through predation. In the Greater Yellowstone Ecosystem, wolves exert impacts not only on their prey (elk) but also on lower trophic levels (e.g. willows).
Ecological Content
predation, trophic cascades, keystone species, direct vs. indirect effects, top-down vs. bottom-up effects, predator control, predation risk, prey behavior
Student-active Approaches
pairs share, hypothesis development, informal group work
Student Assessments
formulate hypotheses, essay quiz, minute paper, and concept map
Author
Cynthia Dott Department of Biology, Fort Lewis College, Durango, CO 81301 Dott_C@fortlewis.edu
FIGURE SET HEADER for Set #1
Figure Set 1: Changes in cottonwood and willow abundance in the 20th century.
Purpose: To practice interpreting graphical data; to use the data to generate hypotheses about what could have caused a decline in cottonwood and willow recruitment.
Teaching Approach: “Pairs share” and hypothesis development
Cognitive Skills: (see Bloom's Taxonomy) knowledge, comprehension, interpretation, analysis Student Assessment: generate hypotheses
BACKGROUND for Set #1 (back1.html)
Background
Where have the cottonwoods and willows gone?
FIGURE SET HEADER for Set #2
Figure Set 2: Factors influencing suppression and recrutiment of woody riparian vegetation.
Purpose: To practice interpreting graphical data; to use the data to accept or reject hypotheses about potential causes of cottonwood and willow decline; to refine and revise a hypothesis based on new data.
Teaching Approach: “pairs share” and report out
Cognitive Skills: (see Bloom's Taxonomy) – knowledge, comprehension, interpretation, analysis Student Assessment: essay quiz or minute paper
BACKGROUND for Set #2 (back2.html)
Background
What factors could influence suppression and recruitment of woody riparian vegetation?
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FREE DOWNLOAD
FIGURE SET 4 FIGURE SET HEADER for Set #4 FIGURE SET 3 FIGURE SET HEADER for Set #3
Figure Set 3: Causes of intense elk browsing on cottonwoods and willows during the 20th century.
Purpose: To practice interpreting graphical data; to use the data to address the question of why browsing by elk in Yellowstone was so intense during the 20th century.
Teaching Approach: “pairs share”
Cognitive Skills: (see Bloom's Taxonomy) -- knowledge, comprehension, interpretation
Student Assessment: minute paper or essay quiz
BACKGROUND for Set #3 (back3.html)
Background
Why was elk browsing on cottonwoods and willows so intense during much of the 20th century?
Figure Set 3: Causes of intense elk browsing on cottonwoods and willows during the 20th century.
Purpose: To practice interpreting graphical data; to use the data to address the question of why browsing by elk in Yellowstone was so intense during the 20th century.
Teaching Approach: “pairs share”
Cognitive Skills: (see Bloom's Taxonomy) -- knowledge, comprehension, interpretation
Student Assessment: minute paper or essay quiz
BACKGROUND for Set #3 (back3.html)
Background
Why was elk browsing on cottonwoods and willows so intense during much of the 20th century?
FREE DOWNLOAD
Figure Set 4: How do wolves impact elk and elk browsing, if not by direct population control?
Purpose: To introduce the idea of indirect effects of predator on prey by changing prey behavior, and of trophic cascades – effects of predators on primary producers; to construct a flow diagram of effect of prey behavioral response to predation on vegetation; to use concept mapping to construct a complex food web for the Greater Yellowstone Ecosystem.
Teaching Approach: informal group work
Cognitive Skills: (see Bloom's Taxonomy) -- knowledge, comprehension, interpretation, application, synthesis
Student Assessment: flow diagram and (optional) concept map
BACKGROUND for Set #4 (back4.html)
Background
How do wolves impact elk and elk browsing, if not by direct population control?
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