55.1
What Are Ecological Communities? 1185
Communities are loose assemblages
of species 1185
The organisms in a community use diverse
sources of energy 1186
55.2
What Processes Influence Community
Structure? 1188
Predation and parasitism are universal
1189
Competition is widespread because
all species share resources 1192
Commensal and amensal interactions
are widespread 1193
Most organisms participate in mutualistic
interactions 1194
55.3
How Do Species Interactions Cause
Trophic Cascades? 1195
One predator can affect many different
species 1195
Keystone species have wide-ranging
effects 1196
55.4
How Do Disturbances Affect Ecological
Communities? 1197
Succession is a change in a community
after a disturbance 1197
Species richness is greatest at intermediate
levels of disturbance 1199
Both facilitation and inhibition influence
succession 1199
55.5
What Determines Species Richness in
Ecological Communities? 1200
Species richness is influenced by
productivity 1200
Species richness and productivity
influence ecosystem stability 1200
