Lewis/Life - Glossary

T

taiga TI-e-gah The northern coniferous forest, north of the temperate zone. 876

taproot system A plant in which the first root enlarges to form a major root that persists through life. 546

target cell A cell that a hormone binds and directly affects. 660

taste receptors Specialized neurons that detect taste. 647

taxonomy tax-ON-o-mee Classification of organisms on the basis of evolutionary relationships. Taxonomic levels include, in order: domain, kingdom, phylum (or division), class, order, family, genus, and species. 12

T cell receptor A cell surface molecule that binds a T cell. 797

T cells T lymphocytes; a component of the immune system 716, 790

tectorial membrane tek-TOR-ee-al MEM-brane The membrane above hair cells in the cochlea of the inner ear that is pressed by hair cells responding to the basilar membrane's vibration in the presence of sound waves. 654

tegument TEG-yew-ment The protective body covering of certain flatworms. 517

telocentric tell-o-SEN-trik A chromosome with the centromere at the tip. 296

telomerase tell-OM-er-ase An enzyme that extends chromosome tips using RNA as a template. 175

telomere TELL-o-meer A chromosome tip. 175

telophase TELL-o-faze The final stage of cell division, when two cells form from one and the spindle is disassembled. 171

telophase I TELL-o-faze I Arrival of homologs at opposite poles in meiosis I. 201

telophase II TELL-o-faze II Nuclear envelope formation around meiotic products. 201

temperate deciduous forest temp-er-et de-SID-u-us FOR-est A terrestrial biome with a temperate climate where one or two species of deciduous trees predominate. 873

tendon TEN-din A heavy band of fibrous connective tissue that attaches a muscle to a bone. 694

tendril TEN-dril Shoot or modified leaf that supports plants by coiling around objects. 541

teratogen teh-RAT-eh-jen Something that causes a birth defect. 246

territoriality ter-eh-tor-ee-AL-it-ee An animal's marking and defending of a piece of land. 828

tertiary consumers TER-she-air-ee con-SOOM-erz Carnivores that eat other carnivores. 862

tertiary (3_) structure TER-she-air-ee STRUK-sure The shape a protein assumes when amino acids far apart in the primary structure chemically attract one another. 49

test Calcium-containing shell of protozoa. 458, 523

test cross Breeding an individual of unknown genotype to a homozygous recessive individual to reveal the unknown genotype. 266

testes TES-teez Paired male gonads containing seminiferous tubules, where sperm are manufactured. 196

testosterone tes-TOS-tur-own A sex hormone. 663

thalamus THAL-eh-mus A tight gray package of nerve cell bodies and glia beneath the cerebrum that relays sensory input to the appropriate part of the cerebrum. 627

thalli THALL-i Nonsexual parts of algae and fungi. 464, 477

theory An explanation for observations and evidence of natural phenomena. 18

thermal stratification THER-mal STRAH-tah-fah-KAY-shun Layers within lakes that have different temperatures. 879

thermocline THER-mo-kline A middle layer of a lake where water temperature changes rapidly and drastically. 879

thermodynamics THERM-o-di-NAM-ix Study of energy transformations in nature. 112

thermogenesis therm-o-JEN-i-sis Generating heat metabolically. 772

thermophiles THERM-o-files Archaea of genus Thermoplasma, which live under conditions of high heat and acid. 451

thermoregulation THERM-o-reg-u-LAY-shun Ability of an animal to balance heat loss and gain with the environment. 771

thigmomorphogenesis THIG-mo-MOR-fo-GEN-ah-sis A plant's responses to mechanical disturbances, including inhibition of cellular elongation and production of thick-walled supportive tissue. 582

thigmonasty THIG-mo-NAS-tee A nastic response to touch. 581

thigmotropism THIG-mo-TRO-piz-um A plant's growth response toward touch. 579

thorns Stems modified for protection. 541

thrombin THROM-bin A blood-clotting protein. 717

thromboplastin THROM-bo-PLAS-tin A protein released from blood vessel walls following injury that converts prothrombin to thrombin. 717

thrombus THROM-bus A blood clot that blocks a blood vessel. 717

thylakoids THI-lah-koydz Disclike structures that make up the inner membrane of a chloroplast. 75

thymine THI-meen One of the two pyrimidine bases in DNA. 51

thymus THY-mis A lymphatic organ in the upper chest where T cells learn to distinguish foreign from self antigens. 728

thyroid gland THI-roid GLAND In humans, a gland in the neck that manufactures thyroxine, a hormone that increases energy expenditure. 669

thyroid-stimulating hormone THY-roid STIM-u-lay-ting HOR-moan (TSH) A hormone made in the anterior pituitary gland in humans that stimulates the thyroid gland to release two hormones. 667

thyroxine thy-ROX-in A thyroid hormone that increases the rate of cellular metabolism. 665

tidal volume Volume of air inhaled or exhaled during a normal breath. 742

tissue Groups of cells with related functions. 5

tonsils Collections of lymphatic tissue in the throat. 728

trace element An element an animal requires in small amounts. 32

trachea TRAY-kee-ah The respiratory tube just beneath the layrnx. The windpipe. 736

tracheae TRAY-kee-i Branching system of tubules that brings the outside environment in close contact with an organism's cells so that gas exchange can occur. 733

tracheids TRAY-kee-idz Less specialized conducting cells in plants that are elongated, dead at maturity, and have thick walls. 538

transcription tranz-SKRIP-shun Manufacturing RNA from DNA. 326

transcription factor tranz-SCRIPT-shun fac-tor A protein that turns on and off different genes in a particular cell. 327

transfer RNA (tRNA) A small RNA molecule that binds an amino acid at one site and an mRNA codon at another site. 329

translation tranz-LAY-shun Assembly of an amino acid chain according to the sequence of base triplets in a molecule of mRNA. 326

translocation TRANZ-lo-KAY-shun Exchange of genetic material between nonhomologous chromosomes. 301

transplantation tranz-plan-TAY-shun Replacing a diseased or damaged organ with one from a donor. 603

transposable element tranz-POSE-a-bull EL-e-ment Jumping gene. 343

transverse (T) tubule TRANZ-verse TU-bule Part of the sarcolemma that juts from the sarcoplasmic reticulum of a skeletal muscle cell. 694

trichome TRI-koam Outgrowth of a plant's epidermis that protects. 537

triglyceride tri-GLI-sir-ide A type of fat that consists of one glycerol and three fatty acids. 45

triiodothyronine tri-i-ode-o-THY-ro-neen A thyroid hormone that increases the rate of cellular metabolism. 669

trilobite TRI-low-bite Extinct arthropod that was once very abundant. 522

triploblastic trip-lo-BLAS-tik An animal whose adult tissues arise from three germ layers in the embryo. 511

trisomy TRI-som-mee A cell with one extra chromosome. 298

trocophore TRO-ko-for A mollusk larva. 519

trophic level TRO-pik LEV-l A feeding level in an ecological community. 859

trophoblast TRO-fo-blast A layer of cells in the preembryo that develops into the chorion and then the placenta. 218

trophozoites tro-fo-ZO-ites Form of the protozoan Giardia lamblia in a person's small intestine. 461

tropical rain forest A warm, moist terrestrial biome with a tree canopy. 872

tropic hormone TRO-pik HOR-moan A hormone that effects another hormone's secretion. 666

tropism TRO-piz-um Plant growth toward or away from an environmental stimulus. 578

tropomyosin TRO-po-MI-o-sin A type of protein in thin myofilaments of skeletal muscle cells. 695

troponin tro-PO-nin A type of protein in thin myofilaments of skeletal muscle cells. 695

true ferns The largest group of seedless vascular plants. 497

tube feet Cuplike structures on echinoderms that draw water in. 524

tube nucleus TOOB NEW-klee-us A haploid cell resulting from the mitotic division of a microspore in male plant reproduction. 563

tuber TU-ber Swollen region of stem that stores nutrients. 541

tubulin TOOB-u-lin Protein that makes up microtubules. 99

tumor necrosis factor TOOM-er nek-RO-sis FAC-tor (TNF) An immune system biochemical with varied functions in cancer, infection, and inflammation. 797

tumor suppressor gene TOO-mer sup-PRESS-er JEAN A gene which, when inactivated or suppressed, causes cancer. 183

tundra TUN-drah A band of land across the northern parts of Asia, Europe, and North America, where the climate is harsh and life is sparse. 878

tunicates TOON-i-catz One of three groups of chordates, including the sea squirts. 525

turgor pressure TER-ger PRESH-er Rigidity of a plant cell caused by water pressing against the cell wall. 90

twitch Rapid contraction and relaxation of a muscle cell following a single stimulation. 699

tympanal organ tim-PAN-al OR-gan A thin part of an insect's cuticle that detects vibrations and therefore sound. 645

tympanic membrane tim-PAN-ik MEM-brane The eardrum, a structure upon which sound waves impinge. 653

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