Ecosystems and Ecosystem Management

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Chapter 6

• Ecosystems and Ecosystem Management

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Basic Characteristics of Ecosystems

• Sustained life on Earth is a characteristic of
  ecosystems, not of individual organisms or
  populations- no member of a community can carry
  out the processes of life alone
• Structure An ecosystem is made up of two major
  parts
• Non-Living (Abiotic)- Physical Environment (Soil,
  Air and Water)
• Living (Biotic)- Ecological community

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Basic Characteristics of Ecosystems

• 2) Processes Two basic kinds of processes must
  occur in an ecosystem a cycling of chemical
  elements and a flow of energy
• 3) Change An ecosystem changes over time and can
  undergo development through a process called
  succession

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Ecological Communities and Food Chains

• Ecological Communities
• A set of interacting species that occur in the
  same place and function together to make possible
  the persistence of life
• Energy, chemical elements and some compounds are
  transferred from creature to creature along FOOD
  CHAINS/FOOD WEBS (Linkage of who feeds on whom)

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Trophic Levels

• A trophic level consists of all those organisms
  in a food web that are the same number of feeding
  levels away from the original source of energy.
• The original source of energy in most ecosystems
  is The Sun.

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Food Chains and Food Webs

• A Terrestrial Food Chain
• 4 trophic levels
• Autotrophs (Photosynthesizing plants, algae and
  bacteria)
• Herbivores (Plant-Eaters)
• Carnivores (Feed directly on Herbivores)
• Carnivores (Feed on other Carnivores) and
  Decomposers (Bacteria and Fungi-Feed on
  everything)
• People are Omnivores (Herbivore Carnivore)

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The Community Effect

• Species interact directly and indirectly
• Community-level interactions
• Example Sea Otters of Pacific Ocean
• Otters eat Sea Urchins
• Sea Urchins eat kelp (important habitat for many
  creatures)
• More Sea Otters Less Sea Urchins More Kelp
  Forests for many sea creatures

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Keystone Species

• A species such as the Sea Otter that has a large
  effect on its community or ecosystem is called a
  Keystone Species
• Removal or change in the role of a keystone
  species within the ecosystem changes the basic
  nature of the community

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Community Interactions with Sea Otter
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Oceanic Food Web
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Food Web of Harp Seal
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Natural and Artificial Ecosystems

• Ecosystems can be natural or artificial or a
  combination of both
• Agriculture can be thought of as partial
  management of certain kinds of ecosystems
• Wildlife Preserves are examples of partially
  managed ecosystems

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Review Questions

• 1) What is the difference between an ecosystem
  and an ecological community?
• 2) In what ways would an increase in the number
  of sea otters and a change in their geographical
  distribution benefit fisherman? In what ways
  would these changes be a problem for fisherman?

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Review Questions

• 3) Based on the discussion in this chapter, would
  you expect a highly polluted ecosystem to have
  many species or few species?
• 4) Is our species a keystone species? Explain.