1. Ecological Succession & Niches

2. Are Ecosystem stable?
No, on the time scale of humans, some ecosystems may seem stable, but they are not!

3. Ecosystems & Communities
Are always changing
Sometimes an ecosystem changes in response to an abrupt disturbance:
Volcanoes, Storms, Tornadoes, Human disturbances
Sometimes changes occur as a more gradual response to natural fluctuations in the environment
Temperature change, disease, Fires

4. Ecosystems
As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing the community to change

5. Ecological succession
Changes that occur in a community over time is called:
Ecological succession

6. Primary Succession
Succession that occurs on surfaces where no soil exist.
New surface form after:
Volcanic eruptions
Glaciers melt
Pioneer Species
First species to populate an area
Examples: Lichen
Lichen break down rocks & form soil

7. Primary Succession

8. Secondary Succession
Components of an ecosystem can be changed by natural events:
Fires, Temperature change, farming
These changes affect an ecosystem
When the disturbance is over, community interactions tend to restore the ecosystem to its original condition through secondary succession

9. Secondary Succession Secondary succession occurs after: Wildfires
When land cleared for farming is abandoned

10. Interesting Fact
Fires set by lightening occur in many ecosystems and some plants are so adapted to periodic fires that their seeds won’t sprout unless exposed to fire.