1. Feeding Relationships
Food Chains
Food Webs
Trophic Levels
10% Rule
Biomass

2. Food Webs Food Webs Network of complex of feeding relationships.
Links all the food chains in an ecosystem together.
Trophic Levels
Each step in a food chain or food web.
Each consumer depends on the trophic level below for energy.

3. Trophic Levels
A step in a food chain or web is called a trophic level;
Producers(1st level) plants, trees, grass, algae
Consumers (2nd – 4th level)
Primary grasshopper
Secondary frog
Tertiary snake

4. Food Web Analysis
Are there any primary consumers that can also be a secondary consumer?
What would happen to the food web if -
A) The harvest mice where to die off in the area?
B) The algae died?
C) The grasshopper died?

5. Food Web
Food web – explains all of the feeding relationships at each trophic level in a community.
A food web is more realistic than a food chain since most organisms feed on more that one organism.

6. Food Web Cooper’s Hawk Loggerhead Shrike American Kestrel Shrew
Grass & Seeds
Grasshopper
American Kestrel
Loggerhead Shrike
Cricket
Shrew
Sparrow
Deer Mouse
Cooper’s Hawk

7. Food Chain

8. 10% Rule
10% Rule - as energy is transferred from one trophic level to the next;
90% of the energy is lost as heat to the environment
only 10% of the available energy is transferred to the next trophic level

9. 10% Rule

10. Ecological Pyramids
Ecological pyramids – show the relationships in food chains and food webs.
The bottom of the food pyramid represents the producers, the next level the herbivores, the next the 1st carnivore, and the next and/or top carnivore.

11. Ecological Pyramids
Ecologists recognize three different types of ecological pyramids:
energy pyramids
biomass pyramids
pyramids of numbers

12. Energy Pyramid
Shows the relative amount of energy at each trophic level

13. Energy Pyramid

14. Biomass Pyramid
Biomass- The total amount of living organic matter at each trophic level.

15. Biomass Pyramid

16. Pyramid of Numbers
Shows the relative number of individual organisms at each trophic level

17. Pyramid of Numbers