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Food Chains & Webs
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2. An organism is a living thing. An organism:
Energy Flow in Nature
An organism is a living thing.
Includes: Plants, animals, micro-organisms, fungi, insects
An organism:
Obtains energy from the environment
Contributes energy to the environment
Plants are called “producers” because they produce carbohydrates from carbon dioxide, water and the sun’s energy (in photosynthesis).
E.g., flower
“Consumers” get their energy by feeding on producers or other consumers.
E.g., bee (feeds on flower)
Decomposition (or biodegradation) is the break-down of wastes and dead organisms. It is done by organisms called “decomposers” or “detrivores.”
E.g., bacteria, fungus, earthworm
See pages

3. Examples of terrestrial and aquatic food chains
Different methods are used to represent energy moving through ecosystems:
Food chains
Food webs
Food pyramids (future class)
Food chains show the flow of energy in an ecosystem
Each step is a trophic level
Producers = 1st trophic level
Primary consumers = 2nd trophic level
Secondary consumers = 3rd trophic level
Tertiary consumers = 4th trophic level
Top level = Top consumers or Top carnivores
Examples of terrestrial and aquatic food chains
See pages

4. Food Chains (continued)
Consumers in a food chain can be classified as:
Detrivores - consumers that obtain energy and nutrients from dead organisms and waste matter
Includes small insects, earthworms, fungi
Detrivores feed at every trophic level
Detrivores have their own, separate food chains, and are very numerous
This dung beetle is a detrivore.
See page 61

5. Food Chains (continued)
Detrivores
Herbivores - primary consumers
herbivores eat plants (producers) only
Carnivores - secondary or tertiary consumers
Secondary consumers eat herbivores
Tertiary consumers eat secondary consumers
Omnivores - consumers that eat both plants and animals
Examples include humans and bears

6. Which is it: herbivore, carnivore or omnivore?
Venus Fly Trap?

7. Most organisms are part of many food chains.
Food Webs
Most organisms are part of many food chains.
Food webs represent many interconnected food chains.
Arrows represent the direction that energy flows.
Following the arrows leads to the top carnivore(s).
This food web represents a terrestrial ecosystem that could be found in British Columbia.
See page 62

8. FOOD WEBS
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To Do Now
Practice Package
Read & Highlight
Do the Questions
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