<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="92" name="biodiversity" parent="921" scope="The variety in form, genetics, and ecological roles of organisms within a specific geographic area."/><uf><usefor name="biological diversity"/><usefor name="diversity (biological)"/></uf><bt><term thcode="2" code="921" name="population and community ecology" parent="1174" scope="Interactions of a single species (population) or an association of different species (community) occupying a particular region, including their biotic and abiotic environments."/><term thcode="2" code="1174" name="topics" parent="1" scope="Themes, subjects, and concerns for which USGS information resources are relevant."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="314" name="ecosystem diversity" parent="92" scope="Measure of the variety of biological communities and habitats important for ecological stability."/><term thcode="2" code="432" name="genetic diversity" parent="92" scope="Measure of the variety of genes within a population pool in a given area."/><term thcode="2" code="1089" name="species diversity" parent="92" scope="An ecological concept incorporating both the number of species in a particular sampling area and the evenness with which individuals are distributed among the various species."/></nt><rt><term thcode="2" code="96" name="biogeography" parent="921" scope="The study of the geographic distributions of plants and animals."/><term thcode="2" code="308" name="ecological competition" parent="310" scope="The struggle between members of two or more species for scarce environmental resources."/><term thcode="2" code="311" name="ecology" parent="650" scope="Study of the relations between living plants and animals and their environment."/><term thcode="2" code="332" name="endangered species" parent="841" scope="Any species that is in danger of extinction throughout all or a significant portion of its range."/><term thcode="2" code="333" name="endemic species" parent="768" scope="Plant and animals species native to and confined to specific geographic areas."/><term thcode="2" code="602" name="invasive species" parent="797" scope="Plant, animal, or microbe species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm, or harm to human health."/><term thcode="2" code="650" name="life sciences" parent="1019" scope="Branches of science that study living and fossil organisms."/><term thcode="2" code="768" name="native species" parent="841" scope="Organisms originating in the area where they live."/><term thcode="2" code="797" name="nonindigenous species" parent="841" scope="Organisms accidentally or intentionally introduced into areas where they did not previously originate or live."/></rt></descriptor>