Name: ______________________________________ Date: ___________________________________Period:______
Activity 79: Eating for Energy
Before you read:
1. What food do humans use as a source of energy?
CARBOHYDRATES, PROTEIN, FRUITS, VEGETABLES, FAT, MILK
2. Define:
Ecosystem: An area that contains living and non-living factors.
Consumer: feed on other organisms
Producer: use photosynthesis to get their energy
Reading Directions:
1. Read Pages E-43-E-48 with your group. Take turns reading each section, stopping at the questions to answer
as a group.
2. Write down the answers that your group comes up with.
Reading Questions:
Stopping to Think 1: Brainstorm ways in which zebra mussels might accidentally be spread from one lake to another.
NOTE: LARVAL STAGE OF ZEBRA MUSSELS IS PLANKTON (MICROSCOPIC!)
IN BALLAST WATER (ships suck in water to keep them at a certain level,
and then get rid of it when they don’t need that level anymore.)
Stopping to Think 2: Why are producers, such as plants, an essential part of any ecosystem?
They are the base of the food chain.
NOTE: WITHOUT THE PRODUCERS THE CONSUMERS DO NOT HAVE
ANYTHING TO EAT!
Name: ______________________________________ Date: ___________________________________Period:______
Activity 79: Eating for Energy
Stopping to Think 3:
a.
Copy Figure 3 here. Identify each organism as either a producer(P) or consumer (C).
C
C
C
C
C
C
C
P
b. Think about the kinds of food that people eat. Use this knowledge to add humans into this lake food web.
c. In the lake food web, humans are consumers. Are humans always consumers? Explain.
YES, WE DO NOT PRODUCE OUR OWN ENERGY, we have to get it from
other organisms—the trait of a consumer!
Name: ______________________________________ Date: ___________________________________Period:______
Activity 79: Eating for Energy
NOTE: THE
DIRECTION OF THE
ARROW SHOWS THE
DIRECTION OF THE
ENERGY!
Name: ______________________________________ Date: ___________________________________Period:______
Activity 79: Eating for Energy
Stopping to Think 4: Using Figure 3 as a guide, the pictures provided, glue and scissors, create a lake food web that
includes zebra mussels. Be sure to show how zebra mussels get their energy and how other organisms get energy from
them.
NOTE: ENERGY IN THE SYSTEM GETS LESS AS YOU GO UP THE FOOD CHAIN.
The most energy is in producers.
Then, as they are eaten and transfer energy to the next organism, energy in that primary
consumer is less
than in the producer.
As the primary consumer is eaten, the secondary consumer gets less energy, so on.
Name: ______________________________________ Date: ___________________________________Period:______
Activity 79: Eating for Energy
Stopping to Think 5: Look at Figure 4: the lines across the U.S. represent large rivers. Where do you predict zebra
mussels will be found in the next 10 years? Explain.
FURTHER INTO LAKES, RIVERS THAT ARE ATTACHED TO THE CURRENT PLACES
The next 20 years? Explain. Even further…
The next 50 years? Explain. Even further…
Analysis:
1. A volcano erupts 40 miles from the lake ecosystem whose food web you drew in Stopping to Think 4. Ash from
the eruption blocks sunlight over your ecosystem for several months. Explain what happens to each population
within the lake food web in the weeks that follow the eruption.

PHYTOPLANKTON WOULD DIE WITHOUT SUNLIGHT BECAUSE THEY COULD NOT
PHOTOSYNTHESIZE.

AS THEY DISAPPEARED, ZOOPLANKTON (PRIMARY CONSUMER) WOULD DIE WITHOUT
SOMETHING TO EAT.
SECONDARY CONSUMERS AND UP WOULD EAT SOMETHING ELSE.

THE SECONDARY CONSUMERS WOULD DIE WITHOUT SOMETHING TO EAT BUT FIRST THEY
WOULD PROBABLY CHANGE THEIR DIETS.

WITHOUT SECONDARY CONSUMERS, TERTIARY CONSUMERS WOULD DIE.

HUMANS COULD MOVE AWAY OR EAT OTHER ORGANISMS.
2. The ash clears and several more months go by. Think about what is now happening to your ecosystem. Identify
what factors will affect how quickly it recovers.
Factors: season, climate, availability of light, size of surviving populations, the opportunity
for organisms to migrate into the area, the possibility of human intervention.
After a few years the ecosystem may be full of life, although somewhat different.
Name: ______________________________________ Date: ___________________________________Period:______
Activity 79: Eating for Energy
REAL LIFE: Mt. St. Helens
https://www.youtube.com/watch?v=4RsMyVavT2Q
https://www.youtube.com/watch?v=W2sUFP9zrbg
3. Reflection: Think about what you have learned about introduced species as well as ecosystems. What effect(s)
can an introduced species have on an ecosystem?
It can completely change the ecosystem depending on where it inserts itself.

It can out-compete natural organisms.

It can provide food for an organism which would then grow more and feed on another
organism more.