Name:___________________________Per:_____
Biology
Building an Energy Pyramid
Standard Addressed: S.1.6 I can use mathematics and computational thinking to support claims
for the cycling of matter and flow of energy through trophic levels in an ecosystem.
Objectives: Students will construct an energy pyramid to show the flow of energy through a food web;
Students will calculate how much energy is transferred from one trophic level to the next trophic level.
Sub-Objective Beginning of Class End of Class
I can identify where each trophic level is represented in an energy 1 2 3 4 5 1 2 3 4 5
pyramid.
I can calculate how much energy is transferred up the energy 1 2 3 4 5 1 2 3 4 5
pyramid.
I can explain which trophic level has the largest and smallest 1 2 3 4 5 1 2 3 4 5
populations AND explain why.
Question: How do energy pyramids model energy transfer and population size within a food web? How
much energy is transferred from one trophic level to the next trophic level?
Materials: Energy Pyramid Template Large container
Food web 3 Cups
Energy Pyramid Student Data Sheet One 1 mL pipette
Calculator
Background: An energy pyramid illustrates how energy flows through an ecosystem. By showing the
trophic (feeding) levels of the ecosystem, it is easy to visualize how energy is transferred from autotrophs
(these are known as producers) to heterotrophs (these are known as consumers). Be aware of the rule of
10’s: only about 10% of energy at any given trophic level is transferred to the next. It is also important to note
that there is more energy available at the bottom end of the pyramid.
Procedure:
Part 1
1. Using the left side of Fig. 1 (the pyramid), label each level of the pyramid with the
appropriate term: producer, primary consumer, secondary consumer, tertiary
consumer.
2. Using the right side of the pyramid, label each level of the energy pyramid with the
appropriate term: trophic level 1, trophic level 2, trophic level 3, trophic level 4.
3. Using the food web poster you have created, find ONE food chain that has four
organisms. Write the names of those organisms into the energy pyramid (inside the
pyramid itself).
Question 1: As mentioned in the background reading, a rule of 10’s exists within this pyramid
and is represented by using the pyramid shape (it starts of wide and narrows moving upward).
What does this imply about the amount of energy available in the third trophic level
compared to the amount of energy in the first trophic level? More energy in the first trophic
level then the third trophic level.
Question 2: Considering the rule of 10’s, why does the pyramid narrow (what happens to the
energy)? The pyramid narrows because there is more energy and the bottom then at the top.
Fig. 1
Energy Pyramid
Trophic level 4 tertiary consumers
fox
Trophic level 3 secondary consumers
robin
Trophic level 2 primary consumers
cricket
Trophic level 1 Plant leaves Autotrophs/producers
Part 2
1. Observe the experimental data in Table 1.
2. Write the names of the organisms you put into your energy pyramid in Part 1 into the
appropriate place on the table (using the examples column).
3. Calculate the percent of energy that is transferred from the first trophic level to the
second trophic level. To do this, divide the amount of energy from trophic level 1 by
trophic level 2, then multiply the answer by 100 to convert it into a percent. This is the
percent of energy transferred. Record this in the appropriate place in the data table.
4. Follow step 3 to complete the percent of energy transferred from trophic level 2 to
trophic level 3, and from trophic level 3 to trophic level 4.
Table 1
Trophic Level Organism Examples Energy Percent Energy
Kcal/m2/year Transferred
Trophic level 1 Producers Plant leaves
200 N/A
Trophic level 2 Primary consumers crickets 9.8%
19.6
Trophic level 3 Secondary Robin 10.2%
consumers
2.0
Trophic level 4 Tertiary consumers Fox 9.5%
0.19
Question 1: In Table 1 above, does the calculated amount of energy transferred fit the Rule of
10%? yes
Explain how it does or does not:
Because the numbers are all small
Question 2: As we can see in Table 1, the amount of energy decreases moving from one trophic
level to the next. Why do you think this energy is lost?
Because it goes to a hole new organism.
Question 3: We previously defined a population as a group of organisms of the same species
living in the same area. In which trophic level would you expect to find the
a. largest populations? Plant leaves
b. The smallest populations? fox
c. Explain your reason:
Because it is the bottom of the food chain.
Part 3: Visual Representation
1. Using the 500 mL beaker, measure out 1000 mL of water into the larger container. I will add
a few drops of food coloring to it, which you will need to stir. The water in this larger
container represents the energy found in the first trophic level (producers).
2. Line up three cups. Looking at your calculations from Table 1, how much energy was
transferred from trophic level one to trophic level two? _______%. Pour that percentage
from the 1000 mL (example: 10% of 1000 is 100 mL) into the first cup.
3. How much energy was transferred from the second trophic level to the third level? _____%.
Pour that percentage from the first cup into the second cup.
4. Repeat for the fourth trophic level/cup 3.
