Student
Biology HSL Page 45 Curriculum and Instruction
Designing Food Chains and Food Webs
NGSSS:
SC.912.L.17.9 Use a food web to identify and distinguish producers, consumers, and decomposers.
Explain the pathway of energy transfer through trophic levels and the reduction of available energy at
successive trophic levels. (AA)
Background: (Source: www.epa.gov)
All organisms in an ecosystem need energy to survive. This energy is obtained through food. Producers
obtain energy by making their own food whereas consumers must feed on other organisms for energy. This
dependence on other organisms for food leads to feeding relationships that interconnect all living things in
an ecosystem. A food chain illustrates the simplest kind of feeding relationship. For example, in a forest
ecosystem, a grasshopper feeds on plants. The grasshopper is consumed by a spider and the spider is
eaten by a bird. Finally, that bird is hunted by a hawk. A food chain clearly shows this pathway of food
consumption.
You could probably think of another food chain for a forest ecosystem. In fact, many different food chains
exist in ecosystems. Although there are many different kinds of food chains, each food chain follows the
same general pattern. A link in a food chain is called a trophic, or feeding level. The trophic levels are
numbered as the first, second, third, and fourth levels, starting with the producers.
Each of the trophic levels is occupied by a certain kind of organism. Producers are always in the first trophic
level since they do not feed on another organism. Consumers occupy the rest of the trophic levels. The
second trophic level is the first consumer in the food chain and is called a primary consumer. Primary
consumers eat plants and are therefore herbivores or omnivores. The next consumer in the food chain is
the secondary consumer. The secondary consumer is in the third trophic level. Since the secondary
consumer feeds on another animal, it is a carnivore or an omnivore. Similarly, the tertiary consumer
occupies the fourth trophic level, and is a carnivore. The last link in a food chain is also referred to as the
top carnivore since it is at the top of the food chain and is not hunted by other animals. Student
Biology HSL Page 46 Curriculum and Instruction
Problem Statement: Are food chains and food webs the same? How do organisms transfer energy?
Vocabulary: food chain, food web, producer, consumer, decomposer, energy transfer, trophic level
Materials (per group):
butcher paper or poster paper
markers
Procedures:
Group Assignment
Work in small groups of 3 – 4 to draw each of the connections in a food web of a shoreline coastal
ecosystem of the Everglades (mangrove).
1. On a piece of butcher-block paper, construction paper, or poster board, write the names of each
shoreline organism randomly over the entire piece of paper. (See accompanying list.)
2. Identify the role of each organism in the ecosystem by writing one of the following letters beneath the
name of the organism: (P) Producer, (C) Consumer, (D) Decomposer, (S) Scavenger, and (Dt) Detritivore.
3. Circle the name and letter of each organism. Color code their role and include a key.
4. Draw an arrow between each food source and the organism that eats that food. Remember that the
arrow represents the flow of energy.
Observation/Data Analysis:
Individual Assignment
1. Find and write as many food chains as you can from your team‘s food web (minimum of 6). Two of the
food chains must include a producer and three levels of consumers (primary, secondary, tertiary). Label
them.
2. Sketch a trophic pyramid using the food chains you created and place the names of your organism at the
proper level.
Results/Conclusion:
1. Explain what would happen if all of the primary consumers became extinct.
2. Predict what would happen if a non-native species is introduced into the food web.
3. Explain why food webs with many species (biodiverse) are more resilient than those with few species.
4. Review your trophic pyramid, do you think there are more organisms at the base and less organisms as
you travel up the pyramid.
5. In theory, the earth could support many more people if we ate at a lower trophic level.
a. List 2 benefits of doing this.
b. List 2 drawbacks of eating lower on the food chain.
6. Large predatory fish usually are found at the 3rd or 4th trophic level of an energy pyramid. What does this
mean in terms of energy loss?
7. Large predatory animals can also be problematic to eat because of bioaccumulation and
biomagnifications of toxins such as lead or mercury in their habitats. What do those two big words mean
and why should this be considered when discussing food chains and trophic levels.
Student
Biology HSL Page 47 Curriculum and Instruction
Shoreline Organisms
Plants
ankton)
Red
Copepods
mangr
(zooplankton)
ove
Snook (fish)
White
Mullet (fish)
mangr
Snapper (fish)
ove
Crested Goby
Black
(fish)
mangr
Barracuda (fish)
ove
Bull Shark (fish)
Button
Tarpon (fish)
wood
Hermit Crab
Seasi
(arthropods)
de
Osprey (bird)
Daisy
Great Blue
Seagr
Heron (bird)
ass
Egret (bird)
Glass
Ibis (bird
wort
Bald Eagle
(bird)
Anim
als
Lady Fish (fish)
Shrim
Seatrout (fish)
p
Queen Conch
(arthro
(mollusk)
pods)
Otter (mammal)
Lobste
Fiddler Crab
r
(arthropods)
(arthro
Water Moccasin
pods)
(reptile)
Ameri
Bottlenose
can
Dolphin
Croco
(mammal)
dile
Mosquito
(reptil
Larvae (insect)
e)
Garfis
h
(fish)
Racco
on
(mam
mal)
Oposs
um
(mam
mal)
Amphi
pods
(zoopl
ankton
)
Mysid
s
(zoopl
Other
Algae
(phytoplankton)
Protozoa
Bacteria
Fungi