ECOLOGICAL COMMUNITIES

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ECOLOGICAL COMMUNITIES
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HOW ORGANISM INTERACT IN COMMUNITIES
WHAT SHAPES A COMMUNITY??
PREDATION COMPETITION for Resources!! (food,
habitat, light, nutrients, water, etc.)
Five Basic Interactions Between Species

• Interspecific competition between two or more
  species
• Intraspecific competition between members of
  same species
• Predation
• Parasitism
• Mutualism
• Commensalism

symbiosis
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What is the niche?

• set of conditions
• within which an organism
• can maintain a viable
• population
• multi-dimensional
• with as many
• dimensions as their
• are limiting conditions

ecological niche
light intensity
okay
salinity
temperature
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NICHE (fundamental vs. realized)

• Fundamental Niche - the full potential range of
  conditions and resources it could theoretically
  use if there were no competition from other
  species. niches of a species overlap with those
  of other species.
• Realized Niche - that part of a fundamental niche
  that an organism occupies.

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INTERSPECIFIC COMPETITION niches of two
different species overlaps

• Migrate
• Shifts its feeding habits
• One of the species suffers population decline
  (even to extinction)

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How can we determine the realized niche of each
barnacle?
Where do they grow when competition is present?
Balanus and Chthamalus
growth rate
Balanus realized niche
Chthamalus realized niche
low
high
middle
Location in intertidal zone
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competitive release niche of the
competitively-inferior species
expands in the absence of the
competitively-superior species
competitive release
growth rate
Chthamalus with Balanus
Chthamalus alone
realized niche
fundamental niche
low
high
middle
Location in intertidal zone
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If the niches of two species overlap completely
or significantly how long can they both last?
competitive exclusion principle
Whats an organism to do?
Remember Move, adapt, or die
Avoid or weaken competition by
Symbiosis
Resource partitioning
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Streams with only Planaria species A
Streams with only Planaria species B
Streams with both Planaria species
What are the fundamental and realized niches
for each species?
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Predation
populations will fluctuate based on resource
availability and predation