Chapter 3Communities and Biomes

Section 1Communities

Limiting Factors

• Any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms.

• Factors that limit one population directly may also have an indirect affect on other populations.

Tolerance

• The ability of an organism to withstand fluctuations in biotic or abiotic environmental factors.

Succession

• The orderly, natural changes and species replacements that take place in the communities of an ecosystem.

• Occurs in stages.• Each stage has conditions suitable for

some organisms but not for others.

• Takes decades to centuries to occur.

Primary Succession

• The colonization of barren land by communities of organisms.

• The first species to colonize in barren areas are called pioneer species.

• Pioneer species eventually die out.

• After some time, the community reaches equilibrium.

Climax Community

• A stable, mature community that undergoes little or no change.

• May last for hundreds of years.

Secondary Succession

• The sequence of changes that takes place after an existing community is severely disrupted in some way.

• Because soil already exists, secondary succession may take less time than primary succession to reach a climax community.