An ecological community consists of interacting species living in a given area. Organisms in a community can be divided into trophic levels based on how they obtain energy, such as primary producers obtaining energy from sunlight and heterotrophs obtaining energy from consuming primary producers. Ecological interactions between species within a community include predation, competition, mutualism, and others. Disturbances can alter community composition through succession as new species colonize or dominant species are removed.

5. Table 55.1 The Major Trophic Levels

10. Table 55.2 Types of Ecological Interactions

17. Figure 55.7 Batesian and Müllerian Mimicry Systems

23. Figure 55.11 A Single Small Community Demonstrates Many Interactions (Part 2)

30. Figure 55.16 Fires Create Mosaics of Burned and Unburned Patches

32. Figure 55.17 Primary Succession on a Glacial Moraine (Part 1)

37. Species Richness