Transcript Succession in Ecosystems - ESC-2

Succession
in
Ecosystems
What caused this?
What caused this?
Equilibrium
• What did the events do to the earth?
• How did the events do this?
• What part of the earth was affected?
• What differences were there between the
two events?
Equilibrium
• Ecosystems try to maintain equilibrium
– Equilibrium is a state of balance (similar to
homeostasis)
– Major events in an ecosystem can upset the
equilibrium
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tornado/hurricane
flood
fire
drought
disease
Succession
• Series of predictable changes that occur in
a community over time
• Succession allows an area to recover after
a catastrophic event
– Primary succession
– Secondary succession
Succession
• Begins with a pioneer species
– can usually perform photosynthesis
• Once equilibrium is reached, it is called a
climax community
• Climax communities are different for each
area
Primary Succession
• Occurs on an area of newly exposed rock,
sand, lava, or any area that has not been
occupied by a living (biotic) community.
– New island created by volcano
– Rock uncovered by glacier
• Takes a very long time
Steps of Primary Succession
1. Pioneer species come in
a. Mosses and lichens that help break down
rock to form soil
2. Plant seeds come in on birds, animals,
wind, water and begin to grow
3. Eventually, primary succession will lead
to a community of organisms in
equilibrium
Primary Succession
Example of Primary
Succession
Glaciers scrape the Earth as it moves. Some
land may have been buried under ice for
thousands of years.
Example of Primary
Succession
As the glacier melts, rocks are left behind.
After about a year, lichens begin to grow on
the rock surface. Lichens slowly weather the
rock, creating the beginning of soil.
Example of Primary
Succession
After the lichens create cracks in the rocks,
mosses begin to grow in the cracks. The moss
further weathers the rock, forming more soil.
Both lichens and moss are pioneer species
Example of Primary
Succession
Once enough soil has been formed, weeds
and small shrubs may follow.
Example of Primary
Succession
As the soil is built up and enriched by dead
plant material, it can support small trees that
will mature into a forest.
Primary Succession
Secondary Succession
• Series of changes that occur after a
disturbance to an existing ecosystem
• Can be a plowed field, a forest or pasture
after a fire etc…
• Occurs faster than primary succession
because there is already soil
Secondary Succession
A wildfire goes through a grassland burning
all of the plant life. Many of the animals are
able to escape by running, flying, or
burrowing in the ground.
Example of Secondary
Succession
The pioneer community is usually made up
of grasses and weeds. Insects, small
mammals, and reptiles make their homes
there.
Example of Secondary
Succession
Small shrubs and trees come in next. Larger
mammals sometimes begin moving in to the
area.
Example of Secondary
Succession
As the shrubs and trees grow taller and
begin to reproduce, the ecosystem becomes
stable.
Secondary Succession
Yellowstone Fires
http://earthobservatory.nasa.gov/Features/WorldOfChange/yellowstone.php?src=yt