UCMP Glossary: T

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taphonomy -- The study of what happens to a fossil, from the time of its initial creation (e.g. the death of an organism or the imprint left by the movement of an organism) and the time that the fossil is discovered by a paleontologist. For example, shells or bones can be moved my running water, and later be compressed by overlying sediment. Taphonomy is often broken into two parts, biostratinomy and the study of diagenesis.

taxon -- n. Any named group of organisms, not necessarily a clade; a taxon may be designated by a Latin name or by a letter, number, or any other symbol; taxa- pl.

taxonomy -- The science of naming and classifying organisms.

tectonic -- adj. Describing the forces that cause the movements and deformation of Earth’s crust on a large scale, also describes the resulting structures or features from these forces.

telson -- The last segment of the abdomen in many arthropods. May be flat and paddlelike, buttonlike, or long and spiny, as in the horseshoe crabs.

temperate -- Region in which the climate undergoes seasonal change in temperature and moisture. Temperate regions of the earth lie primarily between 30 and 60 degrees latitude in both hemispheres.

tentacles -- Appendages which are flexible, because they have no rigid skeleton. Cnidarians and molluscs are two kinds of orgnaisms which may have tentacles.

tepal -- When the sepals and petals of a flower are indistinguishable, they are referred to as tepals. Tepals are common in many groups of monocots. More info?

terrane -- n. A general term used to refer to a piece of the crust that is usually smaller than a continent but larger than an island; exotic terrane- n. terrane that has an unknown origin or a different origin than its surrounding rocks.

terrestrial -- Living on land, as opposed to marine or aquatic.

test -- n. A hard shell produced by some unicellular protists; may be made of calcium carbonate, silica, or sand grains.

Tethys Ocean -- n. A small ocean that existed from the Triassic to the Jurassic; as Pangea was split into Gondwana and Laurasia in the Jurassic, an arm developed westward called the Tethys Seaway or Tethys Sea.

tetrapod -- n. A vertebrae that has (or whose close relatives have) four limbs with digits, not fins.

thalloid -- Plants which have no roots, stems, or leaves are called thalloid, such as liverworts and hornworts.

theca -- General term for any stiff outer covering of a unicellular protist, and usually made up of interlocking plates. dinoflagellates and diatoms are examples of protists with thecae.

thorax -- In insects, the second body region, between the head and thorax. It is the region where the legs and wings are attached.

till -- n. unstratified glacial drift consisting of clay, sand, gravel, and boulders

tissue -- A group of cells with a specific function in the body of an organism. Lung tissue, vascular tissues, and muscle tissue are all kinds of tissues found in some animals. Tissues are usually composed of nearly identical cells, and are often organized into larger units called organs.

topography -- n. The relief features of the Earth's surface, above and below sea level; the set of landforms in a region.

trace fossil -- Evidence left by organisms, such as burrows, imprints, coprolites, or footprints. Trace fossils are not preserved parts of the organism.

tracheae -- Internal tubes through which air is taken for respiration. Vertebrates with lungs have a single trachea carrying air to the lungs, while insects and some other land-living arthropods have a complex network of tracheae carrying air from the spiracles to all parts of the body.

tracheophyte -- Any member of the clade of plants possessing vascular tissue; a vascular plant.

transduction -- Viral transfer of DNA to new host.

transgression -- (n) A rise in sea level relative to the land.

tree -- Any tall plant, including many conifers and flowering plants, as well as extinct lycophytes and sphenophytes.

trichocyst -- Organelle in ciliates and dinoflagellates which releases long filamentous proteins when the cell is disturbed. Used as a defense against would-be predators.

tropical -- Region in which the climate undergoes little seasonal change in either temperature or rainfall. Tropical regions of the earth lie primarily between 30 degrees north and south of the equator.

tube feet -- Extensions of the water-vascular system of echinoderms, protruding from the body and often ending in suckers. May be used for locomotion and/or for maintaining a tight grip on prey or on the bottom.

tuber -- An underground stem which has been modified for storage of nutrients, such as a potato.

tubercle -- Any small rounded protrusion. In pycnogonids and some cheliceramorph arthropods, the central eyes are carried on a tubercle.

tuff -- n. A general term for consolidated rocks made of material ejected from volcanic explosions.

tundra -- n. A vast, mostly flat, treeless Arctic region of Europe, Asia, and North America in which the subsoil is permanently frozen. The dominant vegetation is low-growing lichens, mosses, and stunted shrubs.

turbidite -- n. The sediments or rocks that formed as a result of a turbidity flow.

turbidity current -- n. A bottom fast-flowing current that moves down a slope, depositing suspended sediments over the floor of a body of water

turbidity flow -- n. A flow of dense, muddy water moving down a slope due to a turbidity current

turgor pressure -- Force exerted outward on a cell wall by the water contained in the cell. This force gives the plant rigidity, and may help to keep it erect. More info?