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Community Ecology
Remember:
Community: a group of interacting
populations that occupy the same area at
the same time.
Limiting Factors
Biotic or Abiotic factors that restrict the
existence, numbers, reproduction,
or distribution of organisms.
How might a cold climate be a
limiting factor?
Dry climate?
Salt water?
Limitations
Temperature
Elevation
Winds
Soil
Vegetation is limited to shallow rooted plants like
lichen, ferns, and mosses
Animals must have adaptations to survive and
thrive in cold, harsh environments
Why do organisms live where they
do?
Tolerance range: the ability of an organism
to adjust to environmental fluctuations
-Catfish need little oxygen and can live in
warmer water
-Bass/Trout need more oxygen and need much
colder water
Tolerance
Salt Marsh:
Near the
shore, a few salttolerant species form
salt marshes
Succession
The natural changes and species
replacements that take place in the
communities of an ecosystem over
time.
Succession
Primary succession: the
colonization of new areas by organisms
-pioneer species: the first organisms to
colonize an area (usually mosses and
lichens)
The decay of pioneer species produces
soil
With soil comes the ability to sustain larger
species
 Occurs where
a glacier has
receded.
 Anywhere there
is exposed rock
and no soil.
Succession
Secondary succession: the community
changes that occur after it has been
destroyed by a natural disaster or human
activity
The land already contains soil
The pioneer species will differ from that in
primary succession
Types
Secondary Examples
a hurricane
a farmer abandons a field
a building is demolished and left alone
Final Result
Climax Community
A stable, mature community that undergoes
little or no change.
Succession Observed in Glacier
Bay National Park
Lichen and moss have special adaptations to
tolerate extreme conditions. Despite limiting
factors, the fireweed seeds are well adapted so
that they are easily spread by wind.
Dryas is very good at enriching the soil with nitrogen.
The moss grows close to the ground around the dryas
mat and the cottonwood trees grow up in the middle.
A spruce tree
growing under
an alder thicket
A mature Spruce
and Hemlock Forest
Succession
Will the climax community be the same in all
areas? Why or why not?