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34 Cards in this Set

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  • Back
ulcer a lesion of the surface of the skin or a mucous membrane; sometimes occurs in the digestive system
ultrasonic describes sounds that have frequencies higher than 20,000 Hz
ultrasound any sound wave with frequencies higher than 20,000 Hz
ultraviolet catastrophethe failed prediction of classical physics that the energy radiated by a blackbody at extremely short wavelengths is extremely large and that the total energy radiated is infinite
ultraviolet catastrophe
umbilical cord the structure that connects an embryo and then the fetus to the placenta and through which blood vessels pass
umbilical cord
umbra a shadow that blocks sunlight, such as the conical section in the shadow of the Earth or the moon
uncertainty principle the principle that states that determining both the position and the velocity of an electron or any other particle simultaneously is impossible
uncertainty principle
unconformity a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
understory a foliage layer that is beneath and shaded by the main canopy of a forest
undertow a subsurface current that is near shore and that pulls objects out to sea
ungulate a hoofed mammal
unicellular describes an organism that consists of a single cell
uniformitarianism a principle that geologic processes that occurred in the past can be explained by current geologic processes
unit a quantity adopted as a standard of measurement
unit cell the smallest portion of a crystal lattice that shows the three-dimensional pattern of the entire lattice
unit cell
universe the sum of all space, matter, and energy that exist, that have existed in the past, and that will exist in the future
a hydrocarbon that has available valence bonds, usually from double or triple bonds with carbon
unsaturated hydrocarbon
unsaturated solution a solution that contains less solute than a saturated solution does and that is able to dissolve additional solute
unsaturated solution
unshared pair a nonbonding pair of electrons in the valence shell of an atom; also called lone pair
unshared pair
uplift the elevation of regions of the Earth's crust
upslope fog ground fog that develops when air flows up a slope and is cooled to or below its dew point without any transfer of heat taking place
upslope fog
upwelling the movement of deep, cold, and nutrient-rich water to the surface
uracil one of the four bases that combine with sugar and phosphate to form a nucleotide subunit of RNA; uracil pairs with adenine
urban describes an area that contains a city
urbanization an increase in the ratio or density of people living in urban areas rather than in rural areas
urban sprawl the rapid spread of a city into adjoining suburbs and rural areas
urban sprawl
urea the principal nitrogenous product of the metabolism of proteins that forms in the liver from amino acids and from compounds of ammonia and that is found in urine and other body fluids
ureter one of the two narrow tubes that carry urine from the kidneys to the urinary bladder
urethra the tube that carries urine from the urinary bladder to the outside of the body
urinary bladder a hollow, muscular organ that stores urine
urinary bladder
urinary system the organs that produce, store, and eliminate urine; consists of the two kidneys, the two ureters, the urinary bladder, and the urethra
urinary system
urine the liquid excreted by the kidneys, stored in the bladder, and passed through the urethra to the outside of the body
uropod a flattened posterior appendage in some crustaceans
uterus in female mammals, the hollow, muscular organ in which a fertilized egg is embedded and in which the embryo and fetus develop