Interdependence Within Environmental Systems
Interactions Through Trophic Levels
Student Pages
Purpose
The purpose of this station is to use food chains, food webs, and ecological pyramids
to reinforce your understanding of how matter and energy interact through trophic
levels within an ecosystem.
Before You Begin
Check to see that all the items are present and organized according to the station
information sheet. If you notice a problem, notify the teacher immediately.
Materials
Station Information sheet
Food Chain cards (3 sets in envelopes)
Matter and Energy flow arrows (18 in envelope)
Ecological Pyramid
Activities and Questions
Essential Question
Why is it necessary for the number of prey to be greater than the number of
predators in order for an ecosystem to be balanced?
Discuss the essential question with your teammate(s) and record your answer.
Charles A. Dana Center at The University of Texas at Austin
Student pages-1
Interactions Through Trophic Levels
STAAR Biology Assessments: Module 1
Activities and Questions
1.
Locate the three envelopes containing the food chain cards and the envelope
with the matter and energy flow arrows. Take out four arrows, then remove the
food chain cards from the envelope labeled Set 1. Use all of the cards and the
four arrows to make a food chain.
2.
Analyze and explain the flow of matter and energy in the food chain you just
created?
3.
Remove the second set of food chain cards and make a second food chain,
again using four matter and energy arrows. Do the same with the third set of
food chain cards. There should be three separate food chains on the table.
4.
Record the names of the organisms in each of the three food chains on the
blank chains below.
Student pages-2
Charles A. Dana Center at The University of Texas at Austin
STAAR Biology Assessments: Module 1
Interactions Through Trophic Levels
5.
Examine each of the food chains above. Which food chain is most sustainable?
Support your answer with information from the food chains.
6.
Choose at least 10 of the food chain cards and arrange them to form a food
web. Place the matter and energy flow arrows in the appropriate places within
the food web.
Draw the food web you created.
Charles A. Dana Center at The University of Texas at Austin
Student pages-3
STAAR Biology Assessments: Module 1
Interactions Through Trophic Levels
7.
Illustrate an example of an ecological pyramid by placing each food chain card
at the appropriate trophic level on the Ecological Pyramid.
8.
Using your filled-in pyramid, write the name of the organism on each food chain
card in the appropriate column in the table below.
Trophic Levels in an Ecological Pyramid
Producers
9.
Primary
Consumers
Secondary
Consumers
Tertiary
Consumers
Explain the 10% rule of an ecosystem using the information from the ecological
pyramid and the glossary.
10. Which example, a food chain or a food web, represents a more realistic picture
of the flow of matter and energy in an ecosystem? Support your answer.
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Charles A. Dana Center at The University of Texas at Austin
STAAR Biology Assessments: Module 1
Interactions Through Trophic Levels
11. Now that you have completed these questions, return to the essential question
at the beginning of the activity. Would you like to modify or change your
answer? Write any modifications to your answer below.
NOTE—Because other students are going to do the activity after you, be sure to put
all the materials at the station back as you found them. Sometimes there will be
materials that need to be renewed or replaced. If you need assistance or have any
questions, ask your teacher.
Charles A. Dana Center at The University of Texas at Austin
Student pages-5
Interactions Through Trophic Levels
STAAR Biology Assessments: Module 1
I Need to Remember
Complete this part after the class discussion of the station.
I need to remember . . .
Student pages-6
Charles A. Dana Center at The University of Texas at Austin
STAAR Biology Assessments: Module 1
Interactions Through Trophic Levels
Glossary for Interactions Through Trophic Levels
10% Rule
The 10% rule states that when energy passes from prey to predator, only about
10% of that energy is transferred to the next trophic level. For example, when a
horse eats grass, approximately 10% of the energy that the grass received from
the sun is passed to the horse.
Food chain
A food chain is the simplest representation of energy flow in an ecosystem. Each
organism represented in a food chain feeds on the organism just below it in the
chain. Thus the food chain represents the organisms in an ecosystem in order
from organisms that produce their own food to organisms that are prey to
organisms that are predators.
Food web
A food web represents the complex network of interconnected food chains and
feeding interactions found in an ecosystem.
Primary consumer
A primary consumer is an organism that eats plant material.
Producer
A producer is an organism that can make its own food, usually through
photosynthesis; green plants are examples of producers.
Ecological pyramid
An ecological pyramid shows the number of organisms at each trophic level of an
ecosystem.
Secondary consumer
A secondary consumer is an organism that eats primary consumers.
Tertiary consumer
A tertiary consumer is an organism that feeds on secondary consumers.
Trophic level
A trophic level is one level of energy (such as primary producer, primary
consumer, secondary consumer, etc.) in a food chain.
Charles A. Dana Center at The University of Texas at Austin
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