Ecology December 2017 Page 1 of 6
Student Handout
Modeling Food Webs in Darién, Panama
This hands-on activity supports the WildCam Darién citizen science website. You will identify producers and
consumers in the tropical forest ecosystem of Darién National Park in Panama. Using a set of “Darién cards,” you
will then create a food chain to show the flow of energy in that system, introduce an ecological force or
disturbance (e.g., fire), and predict how that force would impact energy flow. Lastly, you will construct a more
complex model of the flow of energy by depicting multiple relationships in a food web and again make a
prediction about the impact of introducing an ecological force.
Student Handout
Darién food web cards
All food chains start with a producer such as a plant, which converts light energy from the sun into more useable
chemical energy that is transferred to herbivores and then to carnivores. You will receive a set of cards that
depict some common animals, plant types, and ecological forces or disturbances from the tropical forest
ecosystem in Darién. Use the cards to build models and answer questions as directed on this worksheet. After
building a food chain or food web with the cards, record your version by writing the organism names in the
appropriate spaces on the worksheet and connecting them with arrows.
Part 1: Identifying relationships and creating a food chain
Sort the cards into two piles that represent producers and consumers.
1. How many producers do you have? _________
2. How many consumers do you have? _________
3. A food chain is a model that identifies the feeding relationships and the flow of energy in an ecosystem.
Select a producer and a consumer from your piles, then fill in the blanks below and select which model (A or
B) correctly shows the flow of energy.
A. _______________ _______________
B. _______________ _______________
4. Justify why you chose A or B as the correct model.
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Student Handout
5. Select four cards to create a food chain, starting with a producer. Label the trophic level of each organism in
your food chain as follows: producer, primary consumer, secondary consumer, tertiary consumer. Record
your food chain in the space below using species names and arrows.
6. Ecosystems include both biotic (living) and abiotic (nonliving) components that can influence food chains. In
this activity, the abiotic components are referred to as an ecological force or disturbance. Choose one of the
disturbance cards, read the information provided, and then make a prediction about how it might impact
the food chain you created above.
Ecological Force
(list the title)
Predict how these impacts would affect
each trophic level
Tertiary consumer:
Secondary consumer:
Primary consumer:
Primary producer:
7. Not all disturbances have negative consequences for all trophic levels. In one or two sentences, describe a
possible benefit that one trophic level in your food chain may gain from the disturbance you selected.
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Student Handout
Part 2: Quantifying energy flow and the rule of 10
Three hundred trout are needed to support one man for a
year. The trout, in turn, must consume 90,000 frogs, that
must consume 27 million grasshoppers that live off of
1,000 tons of grass.
-- G. Tyler Miller, Jr., American Chemist (1971)
Only a small fraction of the energy available at any trophic
level is transferred to the next trophic level. That fraction
is estimated to be about 10 percent of the available
energy. The other 90 percent of the energy is needed by
organisms at that trophic level for living, growing, and
This relationship is shown in the energy pyramid above. It suggests that for any food chain, the primary producer
trophic level has the most energy and the top trophic level has the least.
8. Why is a pyramid an effective model for quantifying energy flow?
9. Place the organisms from your original food chain on the pyramid provided.
10. Using the rule of 10 percent in energy transfer, record the species names for each trophic level and the
amount of energy available at that level if your producer level had 3,500,000 kilocalories of energy/area.
11. In one or two sentences, describe how the available energy may affect the population sizes of organisms at
different trophic levels.
Part 3: Creating a food web
Food chains are simple models that show only a single set of energy-transfer relationships, but many organisms
obtain energy from many different sources and in turn may provide energy to several different consumers. A
food web illustrates all these interactions and is a more accurate model of how energy moves through an
ecological community.
12. Starting with your original food chain, add another plant and four more animal cards to construct a food
web that shows how energy flows from producers through primary consumers, secondary consumers,
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Student Handout
tertiary consumers, and possibly a quaternary consumer. When making your food web, you can have more
than one arrow leading to and from each organism. Draw a version of your food web below.
13. In one or two sentences, describe any patterns you notice in the relationships between trophic levels.
14. Now choose and read a different disturbance card and predict its impact on your food web. Complete the
table below:
Ecological Force
(list the title)
Describe four ecosystem impacts
noted on the card
Predict how this impact would be seen in
your food web
Tertiary consumers:
Secondary consumers:
Primary consumers:
Primary producers:
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Student Handout
15. Describe whether some trophic levels benefit from the disturbance while others do not. If the disturbance
was caused by humans, was it negative or positive for each trophic level in the food chain?
Part 4: Model evaluation
In science, models are used to represent explanations and predications. The food chain, food web, and energy
pyramid are all models that show feeding relationships and allow us to make predictions. Compare and contrast
the strengths and weaknesses of each model by filling in the table below.
List two things this model is useful for
illustrating or predicting
Identify one feature that this model
lacks or one that could lead to a
Food web
16. Select the model that you think is most effective in representing relationships among organisms in the
Darién ecosystem and justify your choice in two or three sentences.
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Student Handout