Food chains, food webs, trophic levels and energy transfer

1. Trophic Levels,
Energy transfer
and Pyramids

2. Vocabulary
 Trophic Levels – is the position an
organism occupies in a food chain. It
refers to food or feeding.
 Apex predator – top level predators with
few or no predators of their own.
 Detritavore – feeds on dead organisms,
helps with decomposition
 Review Vocab – carnivore, omnivore,
herbivore, scavenger, decomposer

3. Food Chain

4. Food Chains
The energy flow from one trophic level to the
other is know as a food chain
Producers are at the first TROPHIC LEVEL
Primary Consumers are the SECOND TROPHIC
LEVEL
Secondary consumers are at the THIRD
TROPHIC LEVEL
Tertiary consumers are at the FOURTH
TROPHIC LEVEL
In some ecosystems you can go out to
Quaternary consumers

5. Trophic Levels (feeding levels)
3
2
1

6. Food Web
Most organisms eat more than JUST
one organism
When more organisms are involved
it is know as a FOOD WEB
Food webs are more complex and
involve lots of organisms

7. Food webs

8. Trophic Level Producer, primary
consumer, secondary
consumer, tertiary
consumer
Grass 1st Producer
Mouse 2nd Primary consumer
Grasshopper 2nd Primary
consumer
Frog 3rd Secondary
consumer
Owl 3rd
and 4th Secondary and
tertiary consumer
Hawk 3rd Secondary
consumer

9. Terrestrial Food Web

10. Aquatic Food web

11. Transfer Between
Ecosystems
 If an organism that lives in a terrestrial
ecosystem consumes an organism in an
aquatic (or aquatic to terrestrial) energy is
transferred between the two.
 Ex. Bear eats a fish (energy from aquatic
to terrestrial) or fish eats a caterpillar
(energy from terrestrial to aquatic)

12. Transfer of Energy
When a lion eats a zebra, it does
not get all of the energy from the
zebra.
Energy lost is usually in form of heat
Energy lost from chain “link” to “link”
is significant!

13. from grass to sheep, loss is about
90%!
10% Original
Energy! 1% Original
Energy!
100% Energy
Available
HEAT
90%
HEAT
90%

14. Energy lost from one trophic level
(energy level) to the next level can be
represented by a pyramid
PRODUCERS
1° CONSUMERS
2° CONSUMERS
3°
CONSUMERS
4⁰°
CONSUMERS

15. ♦ Each level above only gets 10% of the
energy from below
− Ex: 10,000 J of producers (plants) only give 10% of
energy to primary consumers
> 1,000 J to primary consumers (snails,
minnows, dragonflies)
> 100 J to secondary consumers (small fish)
> 10 J to tertiary consumers (big fish)
> 1 J to quaternary consumers (fish hawk)

16. ENERGY PYRAMID
10,000 J10,000 J
1,000 J1,000 J
100 J100 J
10 J10 J
1 J1 J

17. Energy Pyramid

18. Three hundred trout are needed to
support one man for a year. The trout, in
turn, must consume 90,000 frogs, that
must consume 27 million grasshoppers
that live off of 1,000 tons of grass.
-- G. Tyler Miller, Jr., American Chemist
(1971)

19. Usually no more than 5 trophic
levels since 6th level would have
very little energy to keep it alive

20. Ecological Pyramid
• Which level has the most energy?
• Which level has the most organisms?
• Which level has the least organisms?
• Which level has the least energy?

21. Pyramid of Numbers
• Shows the numbers of individual organisms at each
trophic level in an ecosystem.
tertiary
consumers
secondary
consumers
primary
consumers
producers
5
5000
500,000
5,000,0005,000,000producers
• A vast number of producers are required to support even a few
top level consumers.

22. Biomass pyramid
• Biomass is a measure of the total dry mass of
organisms in a given area.
tertiary
consumers
secondary
consumers
primary
consumers
producers
75 g/m2
150g/m2
675g/m2
2000g/m2producers 2000g/m2