1. Ecological Succession
4-2 What Shapes an Ecosystem?

2. Ecosystems Change
Ecosystems are constantly changing in response to natural and human disturbances.
As an ecosystem changes, older inhabitants die out and new organisms move in.
This is ecological succession.

3. Primary Succession
Succession that occurs on surfaces where no soil exists.
Occurs on the surfaces that are left bare after
Volcanic eruptions
Glaciers melting
Pioneer species – the first species to populate an area
Often lichens because they can grown on bare rock

4. Lichens

5. Primary Succession

6. Secondary Succession
Change in an ecosystem after a disturbance (leaves soil behind)
Examples: after wildfires, clear-cutting a forest, natural disasters
Ecosystems usually recover from natural disasters, but may not always recover from long-term human disturbances.

7. Secondary Succession

8. Boreal Forest Biome - Succession