542 Glossary Trochophore A type of larva characteristic especially of annelids and mollusks, swimming freely by means of a ciliated girdle around the middle Troglobiont Terrestrial species that are obligate subterranean dwellers; the term is sometimes used for aquatic species as well Troglobitic Describing cave-dwelling organisms that are adapted to life in complete darkness Troglobite An organism whose entire life cycle takes place in a cave or other subterranean environment Contrasted with a TROGLOPHILE (see below) Troglomorphic Pertaining to the morphological, behavioral, and physiological characters that are convergent in subterranean species Troglophile A cave lover; a terrestrial species that lives in a cave or other subterranean environment but that also can live and reproduce in surface environments; sometimes used for aquatic species as well Such an organism is troglophilic Trophic Relating to feeding; describing types of food consumed and patterns of feeding behavior Trophic cascade The effect of predatory feeding on prey that propagates down more than one link in a food web Trophic cascades cause inverse patterns in the abundance or biomass of trophic groups at successive levels of a food web Trophic complexity The number and types of organisms that feed at different trophic levels within a community Trophic downgrading Ecological and environmental consequences associated with losses of apex predators from ecosystems Trophic input Energy entering a community via pathways other than local primary production, and often at higher levels in the food chain For example, nutrients from salmon carcasses are a periodic trophic input to the forest community adjacent to salmon streams Trophic interaction A feeding relationship between two species; these include predation, herbivory, parasitism, bacterivory, frugivory, or any other interaction that involves individuals of one species consuming individuals or parts of individuals from another species Trophic level An abstract classification to describe subsets of species that acquire energetic resources in a similar way on a subset of species (e.g., top carnivores feed on primary carnivores which feed on herbivores which feed on primary producers) In natural systems, most species not feed strictly on the level below them, making the concept of trophic level a difficult term to assign operationally to species Trophic status A ranking system for aquatic ecosystems, based on the amount of organic production and nutrient (N, P) levels Trophic web Another term for a FOOD WEB Trophogenic Describing a region where net production of organic matter occurs by photoautotrophy or chemoautotrophy Tropholytic Describing a region where respiration and decomposition of organic matter occur in the absence of primary production Tropical Located in the region lying between the Tropic of Cancer (23.51 N) and Tropic of Capricorn (23.51 S) More generally, involving the climates and landscapes characteristic of this region The Tropics are essentially frost free in the lowlands and permit biological activity as long as water is available Tropical dry forest A type of forest found in tropical to subtropical regions that has distinct rainy and dry seasons Many tropical dry forest plants are adapted to withstand high temperatures and seasonal droughts Tropical rainforest A forest that occurs below 1000 m in elevation, experiences high, relatively constant temperatures, and receives at least 200 mm of rainfall per year TRY A global database of plant functional traits, maintained by the Max Planck Institute for Biogeochemistry in Jena, Germany and governed by an international steering committee Tuberculum interglenoideum An anterior projection of the first (cervical) vertebra in salamanders It bears articular facets that insert into the foramen magnum of the skull and provide additional articulation points between the skull and the vertebral column Tundra The vegetation characteristically occupying the Arctic Turnover A measure of the amount by which the species composition changes among subunits in a data set Type The specimen, culture, or other element on which the scientific name of an organism is based and that fixes the name’s application Type I community An assemblage of species in which the richness is a constant proportion of the number of species occurring in a larger geographic unit where the community is embedded Type II community An assemblage of species in which the richness is independent of the number of species in a larger geographic unit where the community is embedded Typification The practice of designating a single specimen (or, formerly, a series) as the name-bearer for a species; or a species for a higher taxon, especially genera Ultraviolet radiation Radiation with wavelengths shorter than violet light and with more energy Umbrella species A species with large habitat needs or other requirements whose conservation results in many other species also being conserved at the ecosystem or landscape level, thus it acts as an ‘‘umbrella’’ protecting these species Uncultured Describing prokaryotic organisms whose presence has been detected by molecular methods in the environment but that have not been cultured under artificial laboratory conditions Understory The broad spectrum of plants at the ground level of forests that often provide forage for grazing animals These transitory plants are often relatively sparse in dense forests with closed canopies Underutilized Describing a species whose potential for contributing to food security, health (nutritional/medicinal), income generation, and environmental services has not been exploited Unguligrade Walking only on a hoof or tip of the digit An organism that walks in this manner; i.e., the hoofed mammals such as deer, horses, and cattle Compare DIGITIGRADE, PLANTIGRADE Uniramous Relating to or having an extension of the body (usually an appendage) with one branch