Honors/Scholars Biology
Trophic Levels/ Food Web Activity Instruction Sheet
DO NOT WRITE ON THIS SHEET. RETURN AT THE END OF THE PERIOD.
Background
Communities are groups of organisms (populations) that maintain persistent associations with each other. The
members of a typical community include plants, animals, and other organisms that are biologically interdependent
through predation, parasitism, and symbiosis. The structure of a biotic community is largely characterized by the
trophic (feeding) relationships among its member species. These relationships are often represented simplistically as
a food chain. Each link in the food chain represents a trophic level encompassing either producers or consumers.
In most communities, green plants are the dominant producers. They represent the first level in a typical food chain.
Plants capture kinetic energy from sunlight and, through the process of photosynthesis, manufacture organic molecules
(e.g. simple sugars) from carbon dioxide and water. The captured energy is "stored" in the chemical bonds of these
molecules. Most of the stored energy is used by plants for their own survival and growth, some is lost as heat, and
only a small amount passes on to consumers when the plant is eaten, or to decomposers when the plant dies.
Primary consumers occupy the second level of a food chain. These animals, often called herbivores, survive by
feeding exclusively on plants or plant products. The third link includes primary carnivores, secondary consumers
that live as predators or parasites of herbivores. Any remaining levels in the food chain are occupied by secondary or
tertiary carnivores (predators or parasites of other carnivores). Since energy becomes limiting at the uppermost
trophic levels, there are seldom more than four or five links in a terrestrial food chain.
Procedure:
1. Write the following labels in the proper location/level of the trophic level chart on the following page:
producers, primary consumers, secondary consumers, tertiary consumers
2. Determine each organism’s trophic level and write the name of the appropriate organism in the correct trophic
level of the chart on the attached page. If you do not know the feeding relationships of each organism,
research it using an Ipad.
3. Once you have completed the trophic levels, build/draw a food web from the chart and make sure to use all
the organisms in each level. Draw lines with an arrow moving from each predator to all the prey they
consume.
Place the following organisms in the proper trophic level on the chart:
bacteria
walnut tree
vulture
owl
flowers
bear
soybean plant
rat
pecan tree
grass
hawk
moth
blue jay
pig
deer
chicken
fungus
mountain lion
turtle
moss
horse
robin
chestnut tree
frog
ferns
insect
snake
oats
opossum
human
chipmunk
cow
eagle
beaver
lettuce
corn
human
maple tree
oak tree
dogwood tree
squirrel
bob cat
tobacco plant
worms
rabbit
fox
grasshopper
sparrow
Name ____________________________________
Lab Report Trophic Level/ Food Web Activity
Trophic Level Chart
Name of level:
Organisms:
Name of level:
Organisms:
Name of level:
Organisms:
Name of level:
Organisms:
In this space, draw a food web using the above levels and organisms within each level. Make sure to place them
in the proper hierarchical order and place lines with arrows from predators to all the prey they consume to
show the feeding relationships.
Analysis
1. What relationship exists between trophic levels and a food chain/web?
2. Name the group of organisms that occupies each trophic level of an ecosystem.
3. What happens to the number of organisms as they go up through the trophic levels. Explain why this occurs.
4. What factor limits the number of trophic levels in any food web? Explain.
5. What would be the greatest number of trophic levels an ecosystem can hold.
Explain.
6. What percent of energy is available to each level above in any energy pyramid? Why?
7. What does the direction of an arrow in a food chain or food web indicate?
8. What is the importance of decomposers and detrivores in an ecosystem?
ANSWER KEY