Energy Flow in Ecosystems
Unit Plan
Energy Flow in Ecosystems
Objectives
In this unit, students will explore the flow of energy through the organisms in ecosystems, using the food chain, food web, and energy pyramid models. Students will investigate limiting factors on population size. Students compare energy flow with cycles of matter in ecosystems. Students will:
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explain how energy moves through trophic levels in ecosystems.
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describe predator-prey relationships in ecosystems.
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investigate how limiting factors affect populations.
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compare cycles of matter with conservation of energy in ecosystems.
Essential Questions
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Related Materials & Resources
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Materials haven't been entered into the unit plan.Formative Assessment
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Multiple Choice Items:
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1. Which best describes the two animals where a lion eats a gazelle, and the gazelle eats plants?
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A
The lion is the predator and the gazelle is the prey.
B
The lion is the prey and the gazelle is the predator.
C
The lion is the primary consumer and the gazelle is the secondary consumer.
D
The lion is the primary consumer and the gazelle is the producer.
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2. Which kind of organisms in an ecosystem feeds on decomposing matter?
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A
bacteria/fungi
B
insects/spiders
C
squirrels/chipmunks
D
grass/trees
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3. Which of these describes the flow of energy through the food chain below?
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sun → clover → field mice → garter snakes
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A
directly from clover to garter snakes
B
directly from garter snakes to clover
C
from clover to field mice to garter snakes
D
from garter snakes to field mice to clover
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4. In the following food chain, which organisms are autotrophs?
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algae → mosquitoes → salmon → bears
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A
bears only
B
algae only
C
salmon and bears
D
algae and mosquitoes
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5. Frogs are predators of flies. What will most likely happen to the frog population if the fly population increases?
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A
The frog population will increase.
B
The frog population will decrease.
C
The size of the frog population does not depend on the fly population.
D
The frog population will increase for awhile and then decrease.
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6. Which best describes the transfer of energy in a food web?
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A
The producers and consumers transfer energy among each other so that there is no energy loss within the food web.
B
The transfer of energy results in an increase in overall energy due to the accumulation of energy in each consumer.
C
Some of the energy is lost to the environment as heat, and there is an overall decrease in energy when it is transferred.
D
The consumers transfer energy stored in their bodies to the producers, which use the energy for life processes.
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7. Which is an example of a density-dependent limiting factor?
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A
volcanic eruption
B
Hunting
C
flooding
D
forest fire
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8. If the producers in an ecosystem store 400,000 Calories of energy, about how much of that energy is available to the herbivores that eat the producers?
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A
400 C
B
4,000 C
C
40,000 C
D
400,000 C
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9. A chicken eats grain and then a person eats the chicken. What happens to the energy that the chicken obtains from the grain?
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A
Almost all of the energy is passed on to the person.
B
The chicken uses the energy to produce more energy.
C
The chicken uses all of the energy to carry out life processes.
D
Most of it is used for life processes and given off as heat energy.
Multiple Choice Answer Key:
1. A
2. A
3. C
4. B
5. A
6. C
7. B
8. C
9. D
Short-answer items:
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10. Why is a food web a more accurate description of the energy flow in an ecosystem than a food chain?
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11. Why are there fewer consumers at the top level of an energy pyramid than there are at the lower level(s)? Use the terms “trophic level” and “energy” in your answer.
Short-answer key and Scoring Rubrics:
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10. Why is a food web a more accurate description of the energy flow in an ecosystem than a food chain?
Points
Description
2
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Student correctly differentiates between “food chain” and “food web.”
- Student explains that few organisms eat or are eaten by only one other type of organism (i.e., feeding relationships are more complicated than a food chain can show.)
1
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Student correctly differentiates between “food chain” and “food web.”
- Student explains that food webs are more complex than food chains, but does not discuss feeding relationships.
0
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Student does not correctly describe “food chain” or “food web.”
- Student does not explain the answer in terms of complex feeding relationships in an ecosystem.
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11 Why are there fewer consumers at the top level of an energy pyramid than there are at the lower level(s)? Use the terms “trophic level” and “energy” in your answer.
Points
Description
2
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Student correctly uses the terms “trophic level” and “energy” in the context of the answer.
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Student describes the flow of energy through a food chain/web correctly.
- Student explains that about 90 percent of the energy consumed by organisms at each trophic level is used for life processes and released to the environment as heat energy.
1
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Student correctly uses one of the terms “trophic level” and “energy” in the context of the answer.
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Student describes the flow of energy through a food chain/web correctly.
- Student explains that most of the energy consumed by organisms at each trophic level is used for one of the following: either life processes, or released to the environment as heat energy.
0
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Student incorrectly uses both the terms “trophic level” and “energy” in the context of the answer.
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Student describes the flow of energy through a food chain/web correctly.
- Student does not explain that only some energy is transferred between each trophic level.
Performance Assessment:
Energy Flow in a Local Food Web
Have students research organisms in the local ecosystem and create a food web. (Note: Alternatively, have students research ecological relationships in a marine or desert ecosystem).
Have students create a booklet entitled “My Local Ecosystem” that includes:
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Illustrated food web diagram that includes at least 10 organisms’ specific names and ecological roles (red fox, secondary consumer). The food web should also include the Sun, and it should have arrows between each organism to show the flow of energy.
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A paragraph describing one predator-prey relationship in the food web, and explain what would happen to the prey population if the predator species was removed by humans (e.g., due to hunting or loss of habitat due to housing developments).
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Diagram of an energy pyramid that shows the organisms in one food chain from the food web. The energy pyramid should be labeled with trophic levels and percentage of energy that is transferred between each level.
Performance Assessment Scoring Rubric:
Points
Description
5
The student completes all five of the requirements:
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Food web diagram that includes at least 10 types of organisms from the local ecosystem and also the Sun.
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Food web diagram is illustrated and its organisms’ names and roles are correctly labeled.
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Analysis of predator-prey relationship is correct and clearly stated.
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Energy pyramid displays organisms from one food chain in the food web.
- Energy pyramid is labeled correctly (trophic levels and energy transfer).
4
The student completes four of the requirements.
3
The student completes three of the requirements.
2
The student completes two of the requirements.
1
The student completes one of the requirements.
0
The student demonstrates lack of understanding or does not attempt to complete the assessment.
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DRAFT 11/19/2010
