1. Biodiversity & Ecosystem Stability By: Fareed Bello, Sara Stoneroad, and Kara Kaylor

2. Species Diversity • The variety of different kinds of organisms that make up the community (two components) • Species richness – the number of different species in the community • Relative abundance – a representation of all individuals in the community through the proportion of each species • The species richness is the same for both communities because they both contain four species of trees but the relative abundance would be different

3. Trophic Structure • The structure and dynamics of a community depend to a large extent on the feeding relationships between organisms • Food Chain – The transfer of food energy up the trophic levels from its source in plants and other autotrophic organisms through herbivores, to carnivores, and eventually to decomposers

4. Food Webs & Food Chain Length • A food web allows ecologists to summarize the trophic relationships of a community by diagramming a food web with arrows linking species according to who eats whom • Energetic hypothesis - suggests that the length of a food chain is limited by the inefficiency of energy transfer along the chain • Biomass – The total mass of all individuals in a population

5. Food Webs & Food Chain Length • Dynamic Stability Hypothesis – Proposes that long food chains are less stable than short chains

6. Species With A Large Impact • Specific species help environments because they are more abundant and they play pivotal roles in the community • Dominant species- Species in a community that are the most abundant or that collectively have the highest biomass • Invasive species - Organisms that take hold outside their native range

7. Different Types Of Species • Species that are not necessarily abundant in a community • Foundation Species sometimes act as facilitators since they alter the structure or dynamics of the environment

8. Model Types • Bottom-up model postulates a uni-directional influence from lower to higher trophic levels • Top-down model says that predation mainly controls community organization • Biomanipulation- attempts to prevent algal blooms blooms and eutrophication by altering the density of higher level consumers.