Wolves of Yellowstone
Phenomenon:
Elk populations change over time in Yellowstone NP. In the 1980's, the size of the elk population was at a record high. Plants were disappearing, especially along river banks.
Student Task:
Construct an explanation for what caused the elk population to increase in the 1980's. Evaluate a solution based on how well it controls elk population size and maintains the stability of the ecosystem at Yellowstone NP.
Model
Students develop and use a kinesthetic model to show that population growth is limited by resource availability.
Investigate
N/A
Obtain Information
Students read to obtain information about the effects of reintroducing wolves to the park.
Analyze Data
Students analyze data to identify factors that cause changes in elk population size.
Explanation:
Wolves had been hunted to extinction in Yellowstone NP. This caused the elk population to triple in just a decade. To control the elk population, scientists reintroduced wolves to Yellowstone NP in 1995. As predicted, the elk population declined. Trees and grasses returned to the park. Biodiversity increased, indicating the return of a healthy and stable ecosystem.
NGSS Standard:
MS-LS2-4 Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.
[Clarification Statement: Emphasis is on recognizing patterns in data and making warranted inferences about changes in populations, and on evaluating empirical evidence supporting arguments about changes to ecosystems.]
Utah SEEd Standard:
Standard 6.4.4 Construct an argument supported by evidence that the stability of populations is affected by changes to an ecosystem.
[Emphasize how changes to living and nonliving components in an ecosystem affect populations in that ecosystem.]
Recommended Teaching sequence:
Day 1: Students ask questions and generate claims. Students develop a model to identify factors that control elk population size.
Day 2: Students use the model (act out the simulation) and collect data.
Day 3: Students graph and analyze the data collected from the model (or simulation). Students construct an explanation for what causes elk populations to change over time.
Day 4: Students propose a solution for controlling the elk population at Yellowstone NP. Students read to obtain information about the reintroduction of wolves.
Day 5: Students analyze data to evaluate the effectiveness of wolf reintroduction. Students develop a written argument based on evidence to support the claim that wolves are necessary to maintain the stability of the Yellowstone ecosystem.
Assessment:
Use what students have written in their science notebooks as a formative assessment, including the data they collected and graphed from their model and the written explanation for the phenomenon. Do students use evidence to support their explanation? evaluate the solution?
Lesson Contributor:
April Mitchell, Science Coach, Salt Lake City School District