Chapter 54 Community Ecology How many interactions between species can you see in this picture? -Community Interactions are classified by whether they are harmful, helpful, or have no effect -Dominant or Keystone species exert control over whole community -Disturbance influences species diversity and composition -Biogeographic factorsaffect community biodiversity

A community is the sum of all local overlapping/nonoverlapping niches -Includes interspecific interactions 1. Interspecific Competition (-/-) can lead to the competitive exclusion principle or one species will out compete another and can lead to character displacement Fundimental Niche – Niche a species could have Realized Niche – Portion of the Fundimental Niche a species lives in 2. Predation (+/-) 3. Herbivory (+/-) 4. Symbiosis Parasitism (+/-), Mutualism (+/+), or Commensalism (+/=)

Which community is more diverse? (Community 1) 1.Abundance 2.Richness

Trophic Structure of a Community: Plays a large role in community dynamics 1. Food Chains 2. Food Webs

What organism controls the dynamics of an ecosystem? P = Predators H = Herbivores V = Plants N = Nutrients Top Down (Predator controlled ) P – H – V – N Bottom Up (Nutrient Controlled) N – V – H – P Types of Species that can control an ecosystem 1.Dominant = Most Biomass in the ecosystem 2.Keystone = Organism that controls the diversity of a ecosystem by its unique niche (p. 1208) 3.Foundation = An organism that changes the physical nature of an ecosystem due to its unique niche (Beaver Dams)

Disturbances that influence the physical nature of an ecosystem 1.Fire (Natural Process) 2.Storm 3.Drought 4.Flood 5.Human Disturbance

Stages of Succession after a disturbance Stage 1 Stage 4Stage 3 Stage 2

Biogeographic factors that influence an ecosystem. 1.Latitude – Tropical Areas are generally more diverse due to moderate temperatures and higher precipitation 2.Size of the environment – The bigger the environment the more species and diversity 3.Island Biogeography – Isolation, and the equilibrium model