Species Evenness

	Species Evenness Species evenness refers to how close in numbers each species in an environment is. Mathematically it is defined as a diversity index, a measure of biodiversity which quantifies how equal the community is numerically. So if there are 40 foxes and 1000 dogs, the community is not very even. But if there are 40 foxes and 42 dogs, the community is quite even. The evenness of a community can be represented by Pielou's evenness index: :J'= Where H^\prime is the number derived from the Shannon diversity index and H_\max^\prime is the maximum possible value of H^\prime (if every species was equally likely), equal to: :H^\prime_\max = - \sum_^S \ln = \ln S. ''J is constrained between 0 and 1. The less evenness in communities between the species (and the presence of a dominant species), the lower ''J is. And vice versa. Other indices have been proposed by authors where H_\min^\prime > 0 e.g. Hurlburt's evenness index. S is the total number of species. Species evenness requires ecolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Diversity Index A diversity index is a quantitative measure that reflects how many different types (such as species) there are in a dataset (a community), and that can simultaneously take into account the phylogenetic relations among the individuals distributed among those types, such as ''richness'', ''divergence'' or ''evenness''. These indices are statistical representations of biodiversity in different aspects ( richness, evenness, and dominance). Effective number of species or Hill numbers When diversity indices are used in ecology, the types of interest are usually species, but they can also be other categories, such as genera, families, functional types, or haplotypes. The entities of interest are usually individual plants or animals, and the measure of abundance can be, for example, number of individuals, biomass or coverage. In demography, the entities of interest can be people, and the types of interest various demographic groups. In information science, the entities can be charac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Measurement Of Biodiversity Conservation biologists have designed a variety of objective means to measure biodiversity empirically. Each measure of biodiversity relates to a particular use of the data. For practical conservationists, measurements should include . For others, a more economically defensible definition should allow the ensuring of continued possibilities for both adaptation and future use by humans, assuring environmental sustainability. As a consequence, biologists argue that this measure is likely to be associated with the variety of genes. Since it cannot always be said which genes are more likely to prove beneficial, the best choice for conservation is to assure the persistence of as many genes as possible. For ecologists, this latter approach is sometimes considered too restrictive, as it prohibits ecological succession. Taxonomic Diversity Biodiversity is usually plotted as taxonomic richness of a geographic area, with some reference to a temporal scale. Whittaker described three c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Diversity Index A diversity index is a quantitative measure that reflects how many different types (such as species) there are in a dataset (a community), and that can simultaneously take into account the phylogenetic relations among the individuals distributed among those types, such as ''richness'', ''divergence'' or ''evenness''. These indices are statistical representations of biodiversity in different aspects ( richness, evenness, and dominance). Effective number of species or Hill numbers When diversity indices are used in ecology, the types of interest are usually species, but they can also be other categories, such as genera, families, functional types, or haplotypes. The entities of interest are usually individual plants or animals, and the measure of abundance can be, for example, number of individuals, biomass or coverage. In demography, the entities of interest can be people, and the types of interest various demographic groups. In information science, the entities can be charac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') level. Biodiversity is not distributed evenly on Earth; it is usually greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than 10% of earth's surface and contain about 90% of the world's species. Marine biodiversity is usually higher along coasts in the Western Pacific, where sea surface temperature is highest, and in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, but will be likely to slow in the future as a primary result of deforestation. It encompasses the evolutionary, ecological, and cultu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]