1. Food Webs & Energy Pyramids
Trophic Structures
Food Webs & Energy Pyramids

2. Can be represented or explained using:
Trophic Structure - refers to the feeding relationships within a community.
Can be represented or explained using:
Food Chains
Food Webs
Energy Pyramids

3. Trophic Levels include: Producers - get their energy from the sun
1 - Food Chains - shows the transfer of energy from one level to the next.
Trophic Levels include:
Producers - get their energy from the sun
Plants & phytoplankton
Consumers - eat producers or other consumers for energy
Primary - 1st level - herbivores
Secondary - 2nd level - carnivores or omnivores
Tertiary & Quaternary - 3rd & 4th levels - carnivores
Decomposers - break down dead material; are not shown, but can be found anywhere along a chain.

4. The arrow shows which way energy is being transferred.
2 - Food Webs - diagrams that show multiple food chains in a community.
Multi-branching structure because some consumers eat at several different levels.
Ex: the hawk is both a 2nd & 3rd level consumer.
The arrow shows which way energy is being transferred.
Ex: Energy moves from the cactus to the mouse & from the mouse to the hawk

5. 3 - Energy Pyramid - organizes a food web into a diagram that shows both energy & biomass changes.
Law of 10% - only 10% of the energy is passed on from one level to the next - 90% of the energy is lost as heat or waste.
The amount of E available to top-level consumers is small compared to lower-level consumers.
Most food chains are limited to 4 or 5 levels since there’s not enough energy available at the top to support another level.
Top-level consumers tend to eat more often & need a large feeding area in order to support their energy needs.
The eating of meat by consumers is relatively inefficient, since it provides much less energy than do fruits or vegetables (producers). (It takes 10 pounds of feed corn to produce 1 pound of steak.)