Download Ecological Succession

Warm Up
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Cycle Posters
• 10 mins!
• 1 min presentations each
Objective of the day
Analyze how events and processes during ecological succession
can change populations and species diversity.
Homework
Write definitions for:
ecology
habitat
community
ecosystem
abiotic factor
biotic factor
biodiversity
pioneer species
succession
primary succession
secondary succession
Ecological Succession ws
Quiz Mon/Tues
Concept: Disturbance influences species
diversity and composition
• Decades ago, most ecologists favored the view that communities
are in a state of equilibrium
• Recent evidence of change has led to a nonequilibrium model,
which describes communities as constantly changing after being
buffeted by disturbances (such as fire)
Yellow stone national park- 1988
(a) Soon after fire
(b) One year after fire
Ecological Succession
• Ecological succession is the sequence of community and ecosystem changes
(colonized by a variety of species, gradually replaced by other species) after a
disturbance: volcanic eruption or a glacier, strip away all the vegetation.
• Primary succession occurs where no soil exists (lifeless area) when
succession begins. Autotrophic and heterotrophic prokaryotes and protists.
Lichens and moss will first colonize the land when soil develops gradually.
Then grasses, shrubs, trees will sprout.
• Secondary succession begins in an area where soil remains after a
disturbance. Recolonization starts with herbaceous species.
• Early-arriving species and later-arriving species may be linked in one of three
processes:
– Early arrivals may facilitate appearance of later species by making the
environment favorable
– They may inhibit establishment of later species
– They may tolerate later species but have no impact on their establishment
Human Disturbance
• Humans have the greatest impact on biological communities
worldwide
• Human disturbance to communities usually reduces species
diversity
• Humans also prevent some naturally
occurring disturbances, which can be
important to community structure
• Logging and clearing for
urban development, mining,
farming, deep sea trawlers.
Changes in Ecosystems:
Ecological Succession
What is Ecological Succession?
• Make up of a community changes
over time.
• Can be primary or secondary
• The gradual replacement of one
plant community by another
through natural processes over
time
Primary Succession
• Begins in a place without any soil:
»Sides of volcanoes
»Landslides
»Flooding
• First, lichens that do not need soil to
survive grow on rocks
• Next, mosses grow to hold newly
made soil
• Known as PIONEER SPECIES
Pioneer Species
Lichens break down rock to
form soil.
Low, growing moss
plants trap moisture
and prevent soil
erosion
Primary Succession
• Soil starts to form as lichens and
the forces of weather and erosion
help break down rocks into
smaller pieces
• When lichens die, they
decompose, adding small amounts
of organic matter to the rock to
make soil
Primary Sucession
• Purpose to build and rebuild 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 (nutrients to the soil)
• 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 trees can survive now
Primary Succession
• Insects, small birds, and mammals
have begun to move into the area
• What was once bare rock, now
supports a variety of life
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
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