Chapter 6
Ecosystems
and
Ecosystem
Management
Botkin and Keller
Environmental
Science 5e
Basic Characteristics of
Ecosystems
•
1)
•
•
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
Botkin and Keller
Environmental
Science 5e
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
Botkin and Keller
Environmental
Science 5e
Ecological Communities and
Food Chains
Ecological Communities:
1) 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)
Botkin and Keller
Environmental
Science 5e
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.
Botkin and Keller
Environmental
Science 5e
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)
Botkin and Keller
Environmental
Science 5e
Botkin and Keller
Environmental
Science 5e
Botkin and Keller
Environmental
Science 5e
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
Botkin and Keller
Environmental
Science 5e
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
Botkin and Keller
Environmental
Science 5e
Community
Interactions
with Sea Otter
Botkin and Keller
Environmental
Science 5e
Oceanic
Food Web
Botkin and Keller
Environmental
Science 5e
Food Web of
Harp Seal
Botkin and Keller
Environmental
Science 5e
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
Botkin and Keller
Environmental
Science 5e
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?
Botkin and Keller
Environmental
Science 5e
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.
Botkin and Keller
Environmental
Science 5e