Succession is the
gradual change in a
community over time.
the organisms within
change its abiotic
This allows better
adapted organisms to
colonize the area,
replacing its current
Primary succession occurs when
organisms colonize a lifeless habitat.
Secondary succession occurs
when organisms recolonize
A series of predictable changes that
occur in a community over time due to
events in the environment.
The changes may happen suddenly
or very slowly.
The series of changes that occur in an
area where no ecosystem previously
will lead to
Primary Succession – the
series of changes that
occur in an area where no
An area of rock
uncovered by a
melting ice sheet
A new island formed
by the eruption of an
Human made ponds
The first species to populate an
area are the pioneer species.
They break up rock and begin soil
•Soil starts to form as lichens and
the forces of weather and erosion
help break down rocks into smaller
•When lichens die, they
decompose, adding small amounts
of organic matter to the rock to
Grasses and small
plants – protect the
soil and add more
•The simple plants die, adding more
•The soil layer thickens, and grasses,
wildflowers, and other plants begin to
•These plants die, and they add
more nutrients to the soil
•Shrubs and trees can survive now
•Insects, small birds, and mammals have
begun to move in
•What was once bare rock now supports
a variety of life
Larger plants with deep roots
continue to break up rock and
make more soil.
A diverse forest ecosystem
takes hundreds of years
1. Ground is solid rock
2. Rock begins to weather, pioneer
3. Weeds and grasses grow in soil making thicker, richer soil
4. Eventually trees and shrubs sprout community of organisms develops
5. Ecosystem reaches equilibrium
Reaching a stable community
can take centuries.
The series of
changes that occur
after a disturbance
in an existing
It can occur more
Begins in a place that already has
soil and was once the home of
Occurs faster and has different
pioneer species than primary
abandoned by a
Logging, or mining
Secondary Succession –
The series of changes that
occur after a disturbance
in an existing ecosystem.
1. Varies depending on the type of
A disturbed area returns to its
previous condition, eventually reaches
Soil and seeds are already present
Organisms move in
There is a quick recovery of the
•A stable group of plants and
animals that is the end result of
the succession process
•Does not always mean big trees
– Grasses in prairies
– Cacti in deserts
• Equilibrium restored
• State of balance
• No sudden changes in
Secondary succession usually
requires less time to form a
climax community, since soil is
already in place.
Creates a new
May take a long time
to reach equilibrium
A shorter time to
New land created by
destroyed by fire
How do primary and secondary succession help
maintain equilibrium in an ecosystem?
By fostering stability, over time, in the number and
species of organisms in a community.
What is a pioneer species?
The first species to populate an area.
Identify two natural disturbances and
two human disturbances that can
result in secondary succession.
Natural Disturbances: fire, hurricanes,
volcanoes, tornadoes. Human
Disturbances: farming, logging,
Grass poking through the cracks in the
sidewalk is an example of succession. Is
this primary or secondary succession?
Secondary Succession; before the
sidewalk was built, an ecosystem
Primary Succession occurs where no
previous ecosystem exists and
Secondary succession occurs after a
disturbance restores equilibrium.