Biodiversity glossary: Q-Z

Rehabilitation: The recovery of specific ecosystem services in a degraded ecosystem or habitat.

Restoration: The return of an ecosystem or habitat to its original community structure, natural complement of species, and natural functions.

Seedbank: A facility designed for the ex situ conservation of individual plan varieties through seed preservation and storage.

Selection: Natural selection is the differential contribution of offspring to the next generation by various genetic types belonging to the same populations. Artificial selection is the intentional manipulation by man of the fitness of individuals in a population to produce a desired evolutionary response.

Species: A group of organisms capable of interbreeding freely with each other but not with members of other species.

Species diversity: A function of the distribution and abundance of species. Approximately synonymous with species richness. In more technical literature, includes considerations of the evenness of species abundances. An ecosystem is said to be more diverse, according to the more technical definition, if species present have equal population sizes and less diverse if many species are rare and some are very common.

Species richness: The number of species within a region. A term commonly used as a measure of species diversity, but technically only one aspect of diversity.

Stability: A function of several characteristics of community or ecosystem dynamics, including the degree of population fluctuations, the community's resistance to disturbances, the speed of recovery from disturbances, and the persistence of the community's composition through time.

Subspecies: A subdivision of a species; a population or series of populations occupying a discrete range of differing genetically from other subspecies of the same species.

Succession: The more or less predictable changes in the composition of communities following a natural or human disturbance. For example, after a gap is made in a forest by logging, clearing, fire, or treefall, the initial (or "pioneer") species are often fast-growing and shade-intolerant. These species are eventually replaced by shade-tolerant species that can grown beneath the pioneers. If a community is not further disturbed, the outcome of the successional sequence may be a so-called climax community whose composition is unchanging. In practice, many communities are frequently disturbed and may never reach a climax composition.

Sustainable development: Development that meets the needs and aspirations of the current generation without compromising the ability to meet those of future generations.

Systematics: The study of the historical evolutionary and genetic relationships among organisms and of their phenotypic similarities and differences.

Taxon (pl. taxa): The named classification unit (e.g. Homo sapiens, Hominidae, or Mammalia) to which individuals, or sets of species, are assigned. Higher taxa are those above the species level.

Trophic level: Position in the food chain, determined by the number of energy-transfer steps to that level.

Vascular plants: Plants with a well-developed vascular system that transports water, minerals, sugars, and other nutrients throughout the plant body. Excludes the bryophytes: mosses, hornworts, and liverworts.