1. Chapter 3 Biology
Communities & Biomes

2. Communities
A community includes all of the populations interacting in an area
Communities are impacted by limiting factors
A limiting factor is any living or non-living factor that restricts the community. It can effect:
Whether or not the community exists
How many organisms are present
The reproduction of the organisms
The distribution of the organisms

3. Limiting Factors Common limiting factors include: Sunlight
Climate
Atmospheric gases
Temperature
Water
Nutrients/food
Fire
Soil chemistry
Space
Other organisms

4. Succession
Succession is the orderly series of changes that take place in an undisturbed ecosystem
This involves the growth of current plants and inclusion of new plants
The organisms in an area will also change based on the current conditions

5. Primary Succession
Primary succession occurs when land has had all life eliminated, for example, after a volcanic eruption
The first stage involves the appearance of pioneer species, such as lichens
These species die off and contribute to soil production
Then small weedy plants and ferns begin to grow
This further contributes to soil production
These plants are fast growing, therefore they appear first
New plant species develop until the area becomes a climax community, when little or no change occurs
Climax community plants are generally slow growing

6. Secondary Succession
Secondary succession occurs when an area already has soil, but life has been eliminated, such as after a forest fire
organisms slowly begin to develop in the area
These will again be the faster growing plants
Larger organisms move in over time and displace many of the smaller organisms
The larger organisms do not grow as quickly
A climax community is again reached, but in a much shorter time span