Embedded Files
Phenomenon:
Phenomenon:
While viewing wildlife at Yellowstone NP you notice that elk are abundant and wolves are rare. You discover that elk (the prey) outnumber wolves (the predator) by 50:1.
Student Task:
Student Task:
Construct an explanation for the ratio of predator to prey. (If elk are abundant, why are there not more wolves at Yellowstone National Park?)
Model
Model
Students develop and use a model to describe how matter and energy transfer in an ecosystem (e.g., a food web).
Investigate
Investigate
N/A
Obtain Information
Obtain Information
Students read to obtain information about how energy transfers in an ecosystem.
Analyze Data
Analyze Data
N/A
Explanation:
There are less predators than prey in Yellowstone NP because there is not enough energy to support a larger population of wolves, even when the prey (elk) are abundant. Energy from sunlight transfers three times as it moves from grass to elk to wolves. After each energy transfer, 90% of the energy is lost as heat. Inefficient energy transfer limits the population size of predators in an ecosystem.
NGSS Standard:
NGSS Standard:
MS-LS2-3 Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.
[Clarification Statement: Emphasis is on describing the conservation of matter and flow of energy into and out of various ecosystems, and on defining the boundaries of the system.]
Utah SEEd Standard:
Utah SEEd Standard:
Standard 6.4.3 Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.
[Emphasize food webs and the role of producers, consumers, and decomposers in various ecosystems.]
Recommended Teaching sequence:
Recommended Teaching sequence:
Day 1: Students develop a model of the Yellowstone food web to describe how energy moves in the ecosystem.
Day 2: Students read to obtain information about how energy moves in the ecosystem. Students construct a written explanation for why there are not more wolves at Yellowstone NP.
Assessment:
Assessment:
Use student work in science notebooks as a formative assessment, including the food web and the written explanation for the phenomenon. Do students understand that energy flows in one direction through an ecosystem, usually entering as light and exiting as heat?
Lesson Contributor:
April Mitchell, Science Specialist, Salt Lake City School District
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