Section 13.4: Food Chains and Food Webs
Key Concepts
Food chains and food webs model the flow of energy in an ecosystem.
Read the following passage and identify the main ideas
A food chain is a model that shows a sequence of feeding relationships between a producer and
consumers. There are several types of consumers:
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Herbivores eat only plants.
Carnivores eat only animals.
Omnivores eat both plants and animals.
Detritivores eat detritus, or dead organic matter.
Decomposers are Detritivores that break down organic matter into simpler compounds.
Food chains are very helpful in explaining the feeding relationships of very selective eaters. Specialists
are consumers that mainly eat only one specific organism or a very small number of organisms. In
contrast, generalists are consumers that have a varying diet. Trophic levels are the levels of
nourishment in a food chain. Energy flows up the food chain from the lowest trophic level to the
highest. As one moves up a food chain, from trophic-level-to-trophic-level, energy is lost from the food
chain.
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Primary consumers (herbivores) are the first consumer above the producer trophic level.
Secondary consumers (carnivores) eat primary consumers.
Tertiary consumers (carnivores) eat secondary consumers.
A food web is a model that shows the complex network of feeding relationships and the flow of energy
within and sometimes beyond an ecosystem. At each link in a food web, some energy is stored within
an organism, and some energy is lost into the environment.
Vocabulary
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Food chain
Herbivore
Carnivore
Omnivore
Detritivore
Decomposer
Specialist
Generalist
Trophic level
Food web
Review Questions
1. A food chain is a model that shows a sequence of feeding relationships. Complete the following
sentence with the correct terms.
 A food chain follows the connection between one __________________ and a single chain
of ____________________ within an ____________________.
Choose the correct term from the box below to fit each description in the following questions.
carnivore, herbivore, secondary consumer, decomposer, omnivore,
tertiary consumer, detritivore, primary consumer, trophic levels
2. I eat only plants. I am an __________________________?
3. I eat only other animals. I am a _________________________?
4. I eat both plants and animals. I am an __________________________?
5. I eat dead organic matter. I am a _____________________________?
6. I break down organic matter into simpler compounds. I am a ______________________________?
7. I am the first consumer above the producer level. I am a _________________________________?
8. I am a carnivore that eats herbivores. I am a ________________________________?
9. I am a carnivore that eats other carnivores. I am a ___________________________________?
10. The levels of nourishment in a food chain are called ________________________________?
A food web shows a complex network of feeding relationships.
11. How is a food web different from a food chain? Please describe the differences.
12. What happens to energy at each link in a food web? How much energy is lost at each link in a food
web?
13. What type of organism provides the base of a food web?
14. Use your knowledge of words special and general to explain the diets of a specialist and a generalist.
Word part
Herba
Carnus
Omnis
Meaning
Vegetation
Flesh
all
15. Use the word origins in the table above to explain the diets of each of the following consumers:
herbivores, carnivores, and omnivores.