1. Unit 6: Lesson 3 Changes in Ecosystems
-~ Ecological Succession ~

2. TEKS: 7.10C
Observe, record, and describe the role of ecological succession such as in a microhabitat of a garden with weeds.

3. Ecological Succession:
The process of natural gradual changes of an ecological community over time.
Plants replace plants; animals replace animals
Two types:
Primary Succession
Secondary Succession

4. Primary Succession:
Occurs on a newly exposed area of rock, sand, or lava or any area that has not been previously occupied by a biotic (living) community.
Begins in an area without soil
First plants are lichens, which grow directly on rock surfaces
Lichens slowly break rock creating cracks
Moss grows in cracks and breaks down rock to create new soil
Both lichens and mosses are pioneer species.
Pioneer species create soil in primary succession.

5. Primary succession: Formation of Soil
Soil starts to form as the lichens, moss, weathering, and erosion help break down the rock into smaller pieces.
When the pioneer species die, they decompose, and add small amounts of organic matter to the surface of the area.

6. Primary succession continues:
Simple plants like herbs, ferns, and grasses can grow in the new soil.
Simple plants die, adding more organic material
The soil layer thickens, and other plants begin to take over

7. Primary succession stabilizes:
As more nutrients are added to the soil, shrubs and trees can now survive
Insects, small birds, and small mammals have now begun to move into the ecosystem
What was once bare rock now supports a growing biodiversity
A climax community, a stable biological community of a diverse number of species, is now established!
Climax community is the last stage of succession and creates stability

8. Picture slide of succession
Picture slide of succession

9. Environmental Disturbance!!
Numerous events can cause an environmental disturbance which can destroy the climax community
Fire
Deforestation
Natural disaster
The surviving community must recover by new steps of ecological succession

11. Secondary Succession:
Takes place where a community has been removed
Occurs faster because it already has soil and was once the home of biotic factors

12. Secondary Succession:
Has different pioneer species than primary succession –
Grasses and weeds develop first and secure the soil
Insects, small mammals, and reptiles make their home here
Shrubs and bushes begin to grow.
Birds and rabbits join the community
A climax community of trees support a greater biodiversity
Fox, badgers, deer, and more larger mammals increase over time

13. Picture slide of succession

14. Climax Community:
Made up of plants and animals that can reproduce successfully and maintain a stable community within a specific type of ecosystem
Does not always mean big trees
Grasses in prairies
Cacti in deserts