1. Notes: Food Chains and Food Webs

2. FOOD CHAIN
Single sequence that links species by their feeding relationships.
Traces the transfer of energy
Simplest way to look at energy flow in an ecosystem

3. Trophic Levels level in a food chain 1. Producers always first level
2. Primary consumers next level (herbivore)
3. Secondary consumer- eat herbivores (small carnivore or omnivore)
4. Tertiary consumer-carnivores that eat secondary consumers.

4. Large Carnivore Small Carnivore Herbivore Producer
3˚ Consumer (tertiary)
Killer Whale
Small Carnivore
2˚Consumer (secondary)
Ex: Sea Otter
Herbivore
1˚ Consumer (primary)
Ex: Sea Urchin
Producer
Ex: Kelp

5. FOOD WEB Interconnected food chains
Organisms usually have multiple feeding relationships

6. FOOD WEB More realistic display of feeding relationships
Arrows show transfer of ENERGY

7. ENERGY TRANSFER
trophic level: position in a series of energy transfers

8. Only 10% of the total energy is passed onto the next trophic level

9. Only 10% of the total energy is passed onto the next trophic level
1. lost to biological processes (digestion, growth and repair, running, walking etc.)
2. lost as heat

10. 3˚ Consumer Ex: killer whale Small Carnivore 2˚Consumer Ex: sea otter
Large Carnivore
3˚ Consumer
Ex: killer whale
Small Carnivore
2˚Consumer
Ex: sea otter
Herbivore
1˚ Consumer
Ex: sea urchin
Producer
Ex: Kelp
90 % Energy Lost
90 % Energy Lost
90 % Energy Lost

11. Why is a Pyramid used to display Energy transfer between trophic levels? Hint: Why not a square?

12. Video

13. KEYSTONE SPECIES
Has a disproportionately large effect on the ecosystem

14. KEYSTONE SPECIES
Has a disproportionately large effect on the ecosystem
Dictates community structure

15. KEYSTONE SPECIES
Has a disproportionately large effect on the ecosystem
Dictates community structure
Demonstrated by removal of keystone species from community
EX. sea stars in tidepools

16. Sea star feeds on all bivalves
Sea star feeds on all bivalves. When the sea star is removed from the tide pools one bivalve (mussel) out competes the rest for resources and becomes the dominant species.