Smith

1

• Smith
• Ecology
• Chapter 43

2
The Nature of Ecosystems

• Primary producers
• Consumers
• Decomposers
• Detritivores

3
Structure of Ecosystems

• Trophic Levels
• 1st - Primary producers
• Autotrophs
• 2nd - Primary consumers
• Herbivores, Decomposers, Detritivores
• 3rd - Secondary consumers
• Primary carnivores
• 4th - Tertiary consumers
• Secondary carnivores and parasites

4
Food Webs

• Network of crossing, interlinked food chains
  involving primary producers, consumers, and
  decomposers

5
Ecological Pyramids
Top carnivores
Decomposers
Primary carnivores
Herbivores
Primary Producers
6
In Conclusion

• An ecosystem is an array of producers, consumers,
  detritivores, and decomposers and their
  environment
• Sunlight is the initial energy source for nearly
  all ecosystems
• Feeding relationships are structured as trophic
  levels in an ecosystem

7
In Conclusion

• Isolated food chains of who eats whom in an
  ecosystem are rare in nature
• The rate at which primary producers capture and
  store energy is the primary productivity
• Energy fixed by photosynthesizers passes through
  grazing food webs and detrital food webs

8
In Conclusion

• Primary productivity depends on water and
  nutrients
• Carbon dioxide is the main atmospheric gas in the
  carbon cycle
• Burning fossil fuels and

9
In Conclusion

• Nitrogen availability is a limiting factor for
  the total net primary productivity of land
  ecosystems
• Most mineral elements enter sedimentary cycles
  and become available
• Disturbances of an ecosystem can have unexpected
  effects
• Computer modeling helps identify ecosystem
  relationships and can incorporate them into
  models
• developed by M. Roig