Food chains show how organisms are linked through feeding relationships, with energy flowing from producers to primary, secondary, and tertiary consumers. Food webs depict a more complex and realistic set of interlocking food chains in an ecosystem. Within food chains and webs, organisms can be grouped into trophic levels based on their position - with producers on the first trophic level and top carnivores on the highest level. Significant changes to populations within an ecosystem, such as removing producers, can destabilize food chains and negatively impact other organisms.

1. Food Chains
"There's always a bigger fish."
– Qui-Gon Jinn

2. Food Chains
A food chain is a diagram which shows how organisms
are linked together by feeding relationships.
seed  mouse  cat

3. Food Chains
A food chain is a diagram which shows how organisms
are linked together by feeding relationships.

4. Food Chains
They always begin with a producer.

5. Food Chains
The arrows point in the direction of energy (food) flow.

6. Food Chains
Other Abiotic
Components

7. Food Chains
When organisms die, they are eaten by scavengers
(ex. vultures, crabs, hyenas).

8. Food Chains
Then they are
broken down by
decomposers
and detritivores
(bacteria and
fungi).

9. Food Chains
Other Abiotic
Components

10. Food Webs

11. Food Webs:
- the connection of several
food chains.
- more realistic view of
energy transfer.
- show organisms as part of
an interlocking relationship.

12. Food Webs

13. Food
Webs

14. Trophic Levels

15. Trophic Levels
Are the feeding levels that describe the positions of
organisms along a food chain.

16. Trophic Levels

17. 1st tropic  2nd tropic  3rd tropic  4th tropic 
level level level level
Producer primary secondary tertiary
consumer consumer consumer
secondary

18. Think. Pair. Share.
Name an organism that:
- eats rabbits
- is on trophic level 2
- is an autotroph
- is a top carnivore

19. Impacts on Food Webs
What would happen if an organism in a food chain
suddenly has a drastic change in population?

20. Think. Pair. Share.
What would happen if all
of the mangroves in
this ecosystem were
cut down by
humans?
There would be no food
for the fish or crabs
to eat, so they
would all die off.
After the fish and crabs
die, the seabirds and
pied oyster catchers
would also starve.

21. Think. Pair. Share.
What would happen if a
virus invaded this
ecosystem and
killed-off all of the
seabirds?
There would be no
predators to eat the
fish and the fish
population would
become very large.
If there are too many fish
in the ocean, they
may out-compete the
pied oyster catchers
for crabs and drive
them to starvation.