of a system to retain its functional and organizational structure and the ability to recover after a perturbation or disturbance. Resilience also expresses the need for persistence although from a management approach it is expressed to have a broad range of choices and events are to be looked at as uniformly distributed. Elasticity and amplitude are measures of resilience. Elasticity is the speed with which a system returns to its original / previous state. Amplitude is a measure of how far a system can be moved from the previous state and still return. Ecology borrows the idea of neighborhood stability and a domain of attraction from dynamical systems theory. Lyapunov stability Researchers applying mathematical models from system dynamics usually use Lyapunov stability. Numerical stability Focusing on the biotic components of an ecosystem, a population or a community possesses numerical stability if the number of individuals is constant or resilient. Sign stability It is possible to determine if a system is stable just by looking at the signs in the interaction matrix. Stability and diversity The relation between diversity and stability has been widely studied. Diversity can operate to enhance the stability of ecosystem functions at various ecological scales. For example, genetic diversity can enhance resistance to environmental perturbations. At the community level, the structure of food webs can affect stability. The effect of diversity on stability in food-web models can be either positive or negative, depending on the trophic coherence of the network. At the level of landscapes, environmental heterogeneity across locations has been shown to increase the stability of ecosystem functions. A stability diversity tradeoff has also been recently observed in microbial communities from human and sponge host environments. History of the concept The term 'oekology' was coined by Ernst Haeckel in 1866. Ecology as a science was developed further during the late 19th and the early 20th century, and increasing attention was directed toward the connection between diversity and stability. Frederic Clements and Henry Gleason contributed knowledge of community structure; among other things, these two scientists introduced the opposing ideas that a community can either reach a stable climax or that it is largely coincidental and variable. Charles Elton argued in 1958 that complex, diverse communities tended to be more stable. Robert MacArthur proposed a mathematical description of stability in the number of individuals in a food web in 1955. After much progress made with experimental studies in