1. Flow of Energy
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2. Flow of Energy Energy flows through a food chain, starting
with a producer.

3. The Sun Producers get their energy from the Sun.
Producers use sunlight,
water, and carbon dioxide (CO2 ) to make food (sugar).
This is called photosynthesis.

4. Trophic levels Each level of a food chain is called a trophic level.
1st trophic level
(producer)
2nd trophic level
(primary consumer)
3rd trophic level
(secondary consumer)

5. Pyramid of Energy
As you go up a food chain, the amount of energy in each
trophic level
becomes
smaller.

6. Example When a mouse eats a plant, it uses most of the energy:
to grow
to move
for chemical reactions
some energy is lost as heat
Only about 10% of the energy eaten moves up to the next trophic level (snake).

7. Size of food chains few hawks many plants Most food chains only
have four or five levels.
There is not enough
energy to have more levels.
There are usually more
organisms at the lower level
of a food chain, and less
organisms at the top of the food chain.
many plants

8. Question to think about…
Do wolves need plants? Why?

9. Add these words to your vocabulary list!
Organism
Photosynthesis
Trophic level
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