1. CHAPTER 53 COMMUNITY ECOLOGY Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A: What Is a Community? 1.Contrasting views of communities are rooted in the individualistic and interactive hypotheses 2. The debate continues with the rivet and redundancy models

2. What is a Community? A community is defined as an assemblage of species living close enough together for potential interaction. Communities differ in their species richness, the number of species they contain, and the relative abundance of different species. Introduction Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3. An individualistic hypothesis depicts a community as a chance assemblage of species found in the same area because they happen to have similar abiotic requirements. 1. Contrasting views of communities are rooted in the individualistic and interactive hypotheses Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 53.1a

4. An interactive hypothesis depicts a community as an assemblage of closely linked species locked in by mandatory biotic interactions. Fig. 53.1b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

5. These two very different hypotheses suggest different priorities in studying biological communities. In most actual cases, the composition of communities does seem to change continuously. Fig. 53.1c Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

6. The rivet model of communities is a reincarnation of the interactive model. The redundancy model states that most species in a community are not closely associated with one another. No matter which model is correct, it is important to study species relationships in communities. 2. The debate continues with the rivet and redundancy models Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings