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Chapter 3
Communities, Biomes, and Ecosystems
3.1 Community Ecology
Communities
 A community is a
group of
interacting
populations that
occupy the same
area at the same
time.
Oasis
Chapter 3
Communities, Biomes, and Ecosystems
3.1 Community Ecology
Ecological Succession
 ecological succession: is the gradual
replacement of one community with another as
a result of changing abiotic and biotic factors.
• There are two types of ecological
succession— primary succession and
secondary succession.
• Primary succession always occurs first!
• Primary Succession: when a new substrate
(rock), devoid of topsoil or vegetation, is
deposited and colonized
• Begins with bare rock exposed by geological
activity
• Pioneer species appear next
• Pioneer species: species which colonize
previously uncolonized land
• Ex. Lichen and grasses
• Example:
• Forrest Succession
• Rock →Grass →Shrubs →Open woods →
Dense woods
Primary Succession
Lava → Rock
Lichen or Grass
Grasses and Shrubs
Open Woods
Dense Woods → Stable Community
Chapter 3
Communities, Biomes, and Ecosystems
3.1 Community Ecology
 A community that forms in an area of exposed rock
that does not have any topsoil is primary succession.
• Animal succession always follows plant
succession
• Example:
• Flora (vegetation):
• Grass → Shrubs → Woods
• Fauna (animals):
• Pheasant → Grouse → Fox
Bog in Minnesota
Later Succession of Bog
• Climax Community: The stable, mature
community that results from little change in
composition of species.
• What does Michigan’s climax community
look like?
• Secondary Succession: occurs after a
community has been removed but the soil
remains intact
• May occur at any point after primary
succession
• Usually occurs after man or nature has
changed the community
• Example: farming, fire, flood, windstorm
Fire
New Growth After Fire
Gopher Tortoise
Chapter 3
Communities, Biomes, and Ecosystems