Name __________________________________________________ Pd _________ Date ______________
How Does Energy Flow Through an Ecosystem?
http://www.mhhe.com/biosci/genbio/virtual_labs_2K8/labs/BL_21/index.html
Purpose:
In this exploration, you will study and analyze five simplified model ecosystems: a deciduous forest, a hot desert, a
freshwater lake, grassland, and an Antarctic ocean shore. Many more plant and animal species would be involved in a
real world ecosystem. The field notes for each model ecosystem present a profile of the plant and animal inventory for
each ecosystem.
Procedure:
1. Open the Virtual Lab entitled “Model Ecosystems”.
2. The left side of the page contains background information and instructions in the “Question” area. On the
bottom of the page are the following icons for your use: “Journal” (these are questions that may be
answered/submitted to your instructor), “Calculator” (working calculator function), “Data Table” (where you
may be submitting your collected data from the exercise), “Audio” (turns sound on/off) and “Print” (prints the
screen).
3. Read the background information found under the “Field Guide” first, and then continue on to reading the
procedure information posted there as well.
4. To begin, read the information in the “Field Guide” to learn more about the organization of five selected
ecosystems.
5. You will need to first print the “Model Ecosystems Worksheet”, which can be found in on the P: Drive under
Teachers -> Koffarnus. Click on the “Field Guide” on the lower portion of the activity area and read through the
information presented. When you are ready, please begin by selecting the ecosystem type that you would like
to model from the pull down menu in the laboratory area. Then click and drag the various organisms to their
correct locations on the pyramid (note: you must place them in just the right area of the pyramid or else they
will bounce back or replace another organism…this does not mean that they do not belong there, just try again
in a different area of the pyramid). Remember to follow the directions given to you in the “Question” as well as
in the “Model Ecosystems Worksheet” areas, and refer back to the notes in the “Field Guide” area if necessary.
6. Once you have moved all of the organisms click the “Check” button and fix any incorrect choices if necessary.
7. You must take one last step in the investigation of this ecosystem. It is important to determine the amount of
energy that is transferred from one trophic level to the next. This is called the “energy conversion efficiency”
(E.C.E.), and this ratio is determined by taking the energy value from a higher trophic level and dividing it by
the energy value of the level below it. Please do these calculations as directed and input the data in your “Data
Table” and Table I below.
8. When you are completely finished analyzing the ecosystem, you can then click the “Reset” button and select
another type of ecosystem from the pull down menu. Follow the directions above to investigate this ecosystem
and the three that remain.
Clicking on the “Pyramid of Energy” will reveal how much energy is available at each trophic level. Clicking on the
“Pyramid of Numbers” will show the number of organisms at each trophic level within this type of ecosystem. Fill in
all of the information from this pyramid on Table I below.
Name __________________________________________________ Pd _________ Date ______________
Table I:
Ecosystem
Type
Producers
First Order
Heterotrophs
Second Order
Heterotrophs
Third Order
Heterotrophs
Deciduous
Forest
Organisms present:
Organisms present:
Organisms present:
Organisms present:
Energy:
Energy:
Energy:
Energy:
Numbers:
Numbers:
Numbers:
Numbers:
E.C.E.*:
E.C.E.*:
E.C.E.*:
E.C.E.*:
Organisms present:
Organisms present:
Organisms present:
Organisms present:
Energy:
Energy:
Energy:
Energy:
Numbers:
Numbers:
Numbers:
Numbers:
E.C.E.*:
E.C.E.*:
E.C.E.*:
E.C.E.*:
Organisms present:
Organisms present:
Organisms present:
Organisms present:
Energy:
Energy:
Energy:
Energy:
Numbers:
Numbers:
Numbers:
Numbers:
E.C.E.*:
E.C.E.*:
E.C.E.*:
E.C.E.*:
Organisms present:
Organisms present:
Organisms present:
Organisms present:
Energy:
Energy:
Energy:
Energy:
Numbers:
Numbers:
Numbers:
Numbers:
E.C.E.*:
E.C.E.*:
E.C.E.*:
E.C.E.*:
Organisms present:
Organisms present:
Organisms present:
Organisms present:
Energy:
Energy:
Energy:
Energy:
Numbers:
Numbers:
Numbers:
Numbers:
E.C.E.*:
E.C.E.*:
E.C.E.*:
E.C.E.*:
Hot Desert
Grassland
Antarctic
Ocean Shore
Freshwater
Lake
Name __________________________________________________ Pd _________ Date ______________
Journal Questions:
1. What is the ultimate source of energy for most ecosystems?
2. Define each of the following types of organisms:
a. Autotrophs
b. Heterotrophs
c. Carnivores
d. Decomposers
3. What is Biomass and how is it measured?
4. Describe what happens to nutrients within an ecosystem.
5. Describe what happens to energy within an ecosystem.
6. What is the efficiency of energy transfer from a lower trophic level to the next highest level?
7. According to your data, what is the ratio of third-order consumers to producers? Explain your answer.
8. Compare and contrast two of the ecosystems you studied. How is the energy conversion efficiency similar or
different?
9. Does the population size increase or decrease at higher trophic levels in the pyramid of numbers of an
ecosystem consisting of a tree, insects (that are herbivores) and birds feeding on the insects? Explain your
answer.
10. What might happen to an ecological pyramid of numbers in a forest ecosystem if most of the deer were
killed due to hunting by people and disease?
11. What would happen to an ecosystem if the decomposers disappeared?
12. Could there be a food chain without herbivores and carnivores? Explain.