taphonomy -- n. The study of the death, decay, burial, and fossilization of an organism. Essentially, taphonomy describes everything that happens to an organism between the time it dies and the moment its remains are discovered. Understanding why organisms are or are not preserved over time helps explain the biases seen in the fossil record. Taphonomy is often broken into two parts, biostratinomy and diagenesis.
taxon -- n. A named group of organisms, not necessarily a clade, but linked by shared physical or genetic characteristics. A taxon may be designated by a Latin name or by a letter, number, or any other symbol; taxa- pl.
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.
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.
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. An animal with four limbs that evolved from a common fish ancestor during the Devonian Period (~365 million years ago). Tetrapods include amphibians, reptiles, birds, and mammals. Though "tetrapod" literally translates to "four-footed," many animals in this group have limbs adapted for different modes of transportation. Humans walk upright on two legs; the legs of whales, dolphins, and other marine mammals have evolved into fins and flippers; and snakes have lost their legs all together. Tetrapods are generally thought of as terrestrial animals, but some, like dolphins and whales, have returned to marine habitats.
thalloid -- Plants which have no roots, stems, or leaves are called thalloid, such as liverworts and hornworts.
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.
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.
transduction -- Viral transfer of DNA to new host.
tree -- Any tall plant, including many conifers and flowering plants, as well as extinct lycophytes and sphenophytes.
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.
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.
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?