Ecological Succession:
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Transcript Ecological Succession:
Communities in Transition
Ecological Succession – The replacement of
one community by another until a climax
community is reached
May take hundreds or thousands of years
Each new community makes it harder for the
old communities to survive.
New environmental conditions allow one group
of species in a community to replace other
groups.
All communities change their structure and
composition in response to changing
environmental conditions.
During succession:
Pioneer species arrive first.
(Examples only – Write what will help you)
A forest hundreds of years old may have been
a shallow lake thousands of years ago.
A dead tree falls and allow sunlight to reach
the forest floor. Sunlight allows seeds to
germinate. Wildflowers and shrubs grow.
Moss, shrubs, and small trees cover the
concrete of an old city building.
Pioneer Species – The first organisms to
colonize any newly available area and begin
the process of ecological succession.
The pioneer organism will alter the environment
so that a bigger and better organism can move in.
Climax Community – A final and stable
community.
A climax community can only be disrupted by
a catastrophe.
After the catastrophe it will then rebuild itself
back up again.
Primary Succession – Succession that occurs
on a surface where an ecosystem did not
previously exist
Secondary Succession – Succession that
occurs on a surface where an ecosystem had
previously existed.
Starting from Scratch
Exposed
rocks
Lichens
and mosses
Fig. 7-11, p. 156
DEFINITION: Succession that occurs on a surface
where an ecosystem did not previously exist
Examples: Bare rock, newly cooled lava, abandoned
highway or parking lot
Takes a long time because there is no fertile soil
to provide the nutrients needed to establish a
plant community.
Begins when pioneer species arrive and attach
themselves to bare rock.
Examples of pioneer species: Lichens and mosses
Exposed
rocks
Lichens
and mosses
Fig. 7-11, p. 156
Starting Over With Some Help
Succession that occurs on a surface where an
ecosystem had previously existed.
Examples: Abandoned farmland, burned/cut
forests, heavily polluted streams, and land that
has been flooded
New vegetation can usually germinate within
a few weeks from seeds in the soil and those
brought in from nearby plants by wind or by
birds and other animals.
Secondary succession occurs in ecosystems
that have been disturbed or disrupted by
humans, animals, or natural processes.
Fig. 7-12, p. 157
Secondary Succession: Post-fire
Secondary Succession: Old Field
Secondary Succession: Post-Volcano