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Warm-up
Describe your favorite ecological interaction discussed in the lecture.
How can biotic and abiotic factors influence an ecosystem?
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4-2: Succession
Photo Credit: ©Michael Fogden/DRK PHOTO
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3. Ecological Succession
As an ecosystem changes:
older inhabitants gradually die out
new organisms move in
 This causes more change in the community.
Ecosystems are constantly changing in response to natural and human disturbances.
As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community.
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4. Ecological Succession
Response is either:
Abrupt due to disturbance
A gradual response due to natural fluctuations in the environment.
Mt. St. Helens
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5. Ecological Succession
Primary Succession
-occurs on surfaces where no soil exists
Pioneer species
-The first species to populate the area
Primary succession = On land, succession that occurs on surfaces where no soil exists. For example, primary succession occurs on rock surfaces formed after volcanoes erupt.
Ex. primary succession occurs on rock surfaces formed after volcanoes erupt.
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6. Ecological Succession
Primary Succession Example:
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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7. Ecological Succession
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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8. Ecological Succession
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. Mosses soon appear, and grasses take root in the thin layer of soil.
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9. Ecological Succession
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. Tree seedlings and shrubs sprout among the plant community as soil builds.
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10. Ecological Succession
Secondary Succession
Restoration of an ecosystem to its original condition after a disturbance-soil is present after the disturbance (ex. fire, floods, etc)
Components of an ecosystem can be changed by natural events, such as fires.
When the disturbance is over, community interactions tend to restore the ecosystem to its original condition through secondary succession. 
Healthy ecosystems usually recover from natural disturbances, but may not recover from long-term, human-caused disturbances.
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