Transcript Ecological Succession

UNIT 3
Changes in Ecosystems:
Ecological Succession
• Ecological Succession - The
Natural, gradual change in the
types of species that live in an
area; can be primary or
secondary
• Primary succession is a type of
succession that occurs on a surface
where no ecosystem existed before. It
begins in an area that previously did not
support life.
– can occur on rocks, cliffs, or sand dunes.
• Primary Succession begins in a place
without any soil such as:
– Sides of volcanoes
– Landslides
– Flooding
• It starts with the arrival of living things
such as lichens that do not need soil to
survive
• This is called a PIONEER SPECIES
Primary Succession
• Soil starts to form as lichens and the
forces of weather and erosion help break
down rocks into smaller pieces.
• Lichens consiss of a fungus and a
photosynthetic partner growing together in
a symbiotic relationship.
• When lichens die, they decompose,
adding small amounts of organic matter to
the rock to make soil.
Primary Succession
• Simple plants like mosses and ferns can
grow in the new soil
Primary Succession
• The simple plants die, adding more
organic material
• The soil layer thickens, and grasses,
wildflowers, and other plants begin to take
over
Primary Succession
• These plants die, and they add more
nutrients to the soil
• Shrubs and tress can survive now
Primary Succession
• Insects, small birds, and mammals have
begun to move in
• What was once bare rock now supports a
variety of life
• Secondary succession occurs on a
surface where an ecosystem has
previously existed. It is the process by
which one community replaces another
community that has been partially or
totally destroyed.
• Secondary succession can occur in
ecosystems that have been disturbed or
disrupted by humans, animals, or by
natural process such as storms, floods,
earthquakes, or volcanic eruptions.
Secondary Succession
• Begins in a place that already has soil and
was once the home of living organisms
• Occurs faster and has different pioneer
species than primary succession
• Example: after forest fires
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• A pioneer species is a species that colonizes an
uninhabited area and that starts an ecological cycle
in which many other species become established.
• Over time, a pioneer species will make the new area
habitable for other species.
• A climax community is the final, stable community
in equilibrium with the environment.
• Even though a climax community may change in
small ways, this type of community may remain the
same through time if it is not disturbed.
Climax Community
• 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