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

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

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

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

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

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

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

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.