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Chapter 6
Ecosystems and
Ecosystem Management
Basic Characteristics of
Ecosystems
• Sustained life on Earth is a characteristic of
ecosystems, not of individual organisms or
populations
• Structure:
– Living (Ecological Communities)
– Non-living
• Processes
– Cycling of chemical elements
– Flow of energy
• Change (Succession)
Ecological Communities and
Food Chains
• Ecological Communities are defined in 2
ways:
– 1. A set of interacting species that occur in the
same place
• Food chains, food webs, trophic levels (autotrophs)
– A set of species found in one area
Food Chains and Food Webs
• A Terrestrial Food Chain
– 4 trophic levels:
•
•
•
•
Autotrophs
Herbivores
Carnivores
Decomposers
– People are omnivores
• An Oceanic Food Chain
• The Food Web of the Harp Seal
The Community Effect
• Species interact directly and indirectly
• Community-level interactions
• Keystone species
– Have large effects on it’s community or
ecosystem
– Its removal changes the basic nature of the
community
• Holistic View
How Do You Know When You
Have Found an Ecosystem?
• Vary greatly in structural
complexity.
• The watershed is a
common, practical
delineation.
• Common to all ecosystems
is energy flow and cycling
of chemical elements.
Ecosystem Management
• Ecosystem management is the key to
conservation of life on Earth.
• If ecosystems cease to function we must
supplement with our own actions.
• Must consider chemical cycling, energy
flow, community-level interactions, and
natural changes.