Ecological Pyramids

Goals for the Lesson

• Students will be able to explain the relationship between the Pyramid of Numbers and the Pyramid of Biomass.
• Students will have the opportunity to examine and be able to calculate the area of a topographic map.
• Students will understand how much land area is need to support life at each level of the food chain.

Materials Needed

• lab sheets
• topographic maps of your area

State Standards Addressed: Ecosystems and their Interactions (4.6)

Subjects Covered: ecology

Topics: ecological pyramids

Method

1. Explain the Pyramid of Numbers. The Pyramid of Numbers defines the feeding relationships in an ecosystem. For example, in this activity the Pyramid of Numbers would show how much plant material is needed to feed the number of deer that would be needed to feed one mountain lion.
2. Explain the Pyramid of Biomass. (Biomass: the total dry weight of all the organisms at a given level.) For example, in this activity the Pyramid of Biomass would give the total weight of all the plant material that would be eaten by the deer, the total weight of the deer eaten by the mountain lion and, at the top, the weight of our one mountain lion.

Activity

1. Read the entire activity before getting started.
2. Break the class into small groups with no more than four people per group. Give each group their lab sheets and topographic maps. Reading the assumptions aloud. Answer questions 1-3.
3. Answer #1: 4.8 can round to 5; Answer #2: 15 deer; Answer #3: 75 square miles for each mountain lion.
4. Using the answer from problem #3 and the topographic map, determine how large an area the maps in each group encompasses. Help students read the scale of the map to calculate the area. Once that is completed, answer questions 1 through 7.

Assessment

• Use the lab sheet as an assessment tool.
• Have the students draw a Pyramid of Numbers and Pyramid of Biomass by following the given assumptions.

Conclusion

• Wrap up this activity by reviewing the definitions of the Pyramids of Numbers and Biomass.
• Have the students relate those definitions to the problem at hand.
• Talk through and explain the answers to problems 1 through 3.
• Go around the room and state the area of each map at hand. Ask, "Do any of these maps encompass enough land to house one mountain lion?" Figure out how many maps it would take to house this mountain lion.
• Review any of questions 1 through 7 that would lead to discussion in the class. Questions 5 and 6 may lead to a good discussion based on your students' personal biases and beliefs.

References

Lederer, Roger (1984). Ecology and Field Biology. Menlo Park, Calif.: Benjamin/Cummings Publishing, Inc.

Author

Melissa Boyer, Wellsboro Area School District