Download Ecological Succession

Changes in Ecosystems:
Ecological Succession
EQ: How do communities
change over time?
Succession is…
• a series of predictable changes
in types of species that occurs
in a community over time
• Two types: primary and
secondary
Primary Succession
• Occurs on surfaces where no soil exists
• Events which expose bare rock:
– volcanoes
– flooding
– glaciers
• Begins with arrival of organisms
such as lichens that do not need soil
• Lichen are the pioneer species (first
organisms to arrive in an area)
Primary Succession
• Soil starts to form as lichens, weathering,
and erosion break down rocks into smaller
pieces
• When lichens die, they decompose, adding
small amounts of organic matter to the rock
to make soil
• Over time, the soil layer thickens, and
grasses, wildflowers, and other plants begin
to take over
Primary Succession
• In time insects, birds, and mammals
move in
• What was once bare rock now supports
a variety of life, including trees
Secondary Succession
• Occurs in an area with soil that contains
seeds, spores, roots, or other plant parts
• Events that destroys most of an
ecosystem
• forest fire
• harvesting
• Hurricane
• Happens faster and weeds are a typical
pioneer species in secondary
succession
Secondary Succession
http://www.ux1.eiu.edu/~cfruf/bio3002/secondary_succession.htm
Climax Community
• Climax Community = mature
community made up of plants and
animals
• Does not always mean big trees
– tall grasses in prairies
– cacti in deserts
• Species can continue to change in
response to climate and other factors
Succession: summary
Primary
Secondary
• No soil is available
and must be created
by pioneer species
• Lichens are usually
the pioneer species
• Usually the result of a
volcano or glacier
• Soil is still available
and pioneer species
can take root
• Weeds/plants are
usually the pioneer
species
• Usually the result of a
forest fire or hurricane