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34 Cards in this Set

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ulcer a lesion of the surface of the skin or a mucous membrane; sometimes occurs in the digestive system
ulcer
ultrasonic describes sounds that have frequencies higher than 20,000 Hz
ultrasonic
ultrasound any sound wave with frequencies higher than 20,000 Hz
ultrasound
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
umbra
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
unconformity
understory a foliage layer that is beneath and shaded by the main canopy of a forest
understory
undertow a subsurface current that is near shore and that pulls objects out to sea
undertow
ungulate a hoofed mammal
ungulate
unicellular describes an organism that consists of a single cell
unicellular
uniformitarianism a principle that geologic processes that occurred in the past can be explained by current geologic processes
uniformitarianism
unit a quantity adopted as a standard of measurement
unit
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
universe
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
uplift
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
upwelling
uracil one of the four bases that combine with sugar and phosphate to form a nucleotide subunit of RNA; uracil pairs with adenine
uracil
urban describes an area that contains a city
urban
urbanization an increase in the ratio or density of people living in urban areas rather than in rural areas
urbanization
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
urea
ureter one of the two narrow tubes that carry urine from the kidneys to the urinary bladder
ureter
urethra the tube that carries urine from the urinary bladder to the outside of the body
urethra
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
urine
uropod a flattened posterior appendage in some crustaceans
uropod
uterus in female mammals, the hollow, muscular organ in which a fertilized egg is embedded and in which the embryo and fetus develop
uterus