Insects and closely related arthropods are the dominant and most diverse forms of terrestrial and aquatic (non-marine) animal life on the planet. Other than marine systems, insects occupy every conceivable environment and habitat on the Earth. Crustaceans and Annelids (worms) are the dominant and most diverse groups of animals in marine systems. The dominance of insects is true in terms of diversity (number of species), numbers of individuals, and total biomass within a given area. As of this writing, there are approximately one million known species of insects (species that have been scientifically described—they have been provided a scientific name and their evolutionary relationship to other species is relatively well established). The known number of insect species is only a fraction of the estimated total number of species. The total number of insect species has been estimated to be between five and ten million species; most of which have yet to be discovered and scientifically described.