<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="841" name="organism groupings (non-taxonomic)" parent="1174" scope="Used for categories of living organisms that are not taxonomic and that include species from more than one taxonomic group."/><bt><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="1345" name="benthos" parent="841" scope="Animals that live on the bottom of water bodies."/><term thcode="2" code="116" name="biota" parent="841" scope="All living organisms in an area."/><term thcode="2" code="194" name="consumers (organisms)" parent="841" scope="Organisms unable to produce food from nonliving matter and dependent on ingesting other animals, plants, or particulate organic matter."/><term thcode="2" code="238" name="decomposers" parent="841" scope="Organisms, chiefly microorganisms and invertebrates, that feed on dead plant or animal matter breaking it down and recycling the resulting elements and compounds in the 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="423" name="game species" parent="841" scope="Species of wild animals that are hunted for food or sport."/><term thcode="2" code="1795" name="genetically engineered organisms" parent="841" scope="Organisms whose DNA has been modified through the insertion or deletion of DNA fragments from the same or another species, in order to produce or enhance desirable traits such as increased yield, resistance to pests, adaptation to drastically changed environments, or formation of entirely new compounds."/><term thcode="2" code="615" name="keystone species" parent="841" scope="Species whose abundance and ecological role has a dramatic effect on the other species in an ecosystem."/><term thcode="2" code="673" name="macroinvertebrates" parent="841" scope="Invertebrate animals large enough to be studied without a microscope."/><term thcode="2" code="1707" name="microbes" parent="841" scope="Microscopic, typically one-celled organisms."/><term thcode="2" code="744" name="migratory species" parent="841" scope="Species that have a pattern of moving from one geographical area to another, primarily according to the seasons, and usually traveling long distances along established routes."/><term thcode="2" code="768" name="native species" parent="841" scope="Organisms originating in the area where they live."/><term thcode="2" code="779" name="nekton" parent="841" scope="Free-swimming aquatic organisms able to move without depending on waves, currents, and tides."/><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."/><term thcode="2" code="1728" name="nuisance species" parent="841" scope="Organisms whose presence or behavior has undesirable effects on human activities."/><term thcode="2" code="1709" name="parasites" parent="841" scope="Symbiotic organisms that are detrimental to the host."/><term thcode="2" code="903" name="plankton" parent="841" scope="Floating aquatic plants (phytoplankton) and animals (zooplankton) which are often microscopic and drift with the current in lakes, rivers, and oceans."/><term thcode="2" code="916" name="pollinators" parent="841" scope="Organisms that aid in the growth and distribution of plants by transferring pollen as a byproduct of their feeding activities."/><term thcode="2" code="935" name="producers (organisms)" parent="841" scope="Organisms, chiefly green plants, which use inorganic elements, compounds, and light to produce their food (photosynthesis). They are a source of food for animals."/><term thcode="2" code="1056" name="shellfish" parent="841" scope="Aquatic invertebrates with shells, usually mollusks and crustaceans. Includes clams, lobsters, and oysters."/><term thcode="2" code="1164" name="threatened species" parent="841" scope="Any species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range."/><term thcode="2" code="1266" name="vegetation" parent="841" scope="Plant life or general plant cover in an area."/><term thcode="2" code="1331" name="wildlife" parent="841" scope="Undomesticated organisms living in natural settings without dependence on man."/></nt><rt><term thcode="2" code="650" name="life sciences" parent="1019" scope="Branches of science that study living and fossil organisms."/><term thcode="2" code="843" name="organisms" parent="1174" scope="Living individuals that grow, reproduce, and die."/></rt></descriptor>