1. Changes in Ecosystems: Ecological Succession
Chapter 2 Section 3

2. Ecosystems Change Many factors affect the populations in a community.
Some factors have to do with the organisms.
Other factors relate to habitat.

3. Population growth and decline
Birth rate and death rate affect population size
Predator-prey interactions
Biotic factors like food
Abiotic factors like water, light or space

4. Limiting Factor
Any condition that limits the growth of a population in an ecosystem.
Lack of nutrients in the soil will limit plant growth.
A large population of predators will limit the population of prey.

5. Maintaining Balance
All ecosystems have a maximum number of organisms it can support.
Carrying Capacity – the maximum number of individuals that an ecosystem can support.

6. Carrying Capacity
The moose population is limited even when there are no wolves. They are limited by space and food that is available.

7. Succession Definition:
Natural, gradual changes in the types of species that live in an area; can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time
Abandoned farms are now forests

8. Primary Succession Begins in a place without any soil
Sides of volcanoes
Landslides
Glaciers
Starts with the arrival of living things such as lichens that do not need soil to survive
Called PIONEER SPECIES

10. (1) 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

12. (2) Primary Succession
Simple plants like mosses and ferns can grow in the new soil

13. (3) Primary Succession
The simple plants die, adding more organic material
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

14. Primary Succession
These plants die, and they add more nutrients to the soil
Shrubs and trees can survive now

15. (4) Primary Succession
Insects, small birds, and mammals have begun to move in
What was once bare rock now supports a variety of life

16. Secondary Succession
Takes place after a major disturbance, but the soil remains
Fire
Flood
Human activity (forest cleared, farm abandoned)

17. Secondary Succession Only the surface is damaged
There are still seeds and plant roots below the surface
Grasses and small shrubs sprout and grow
Animals begin to return
Trees start to take root

18. Secondary Succession

19. Review What is primary succession?
Plants moving into an area that has no soil
Life moving into a barren, soilless area
What can trigger primary succession?
Lava flow, glacier retreat, major landslide that removes soil

20. Review What is secondary succession?
Regrowth after a disturbance when the soil is left behind
What can trigger secondary succession?
Floods or fire