Dr. Paul's Virtually Biology Show.
www.jccc.net/~pdecell
U
Uniformitarianism. An important
assumption in science that says that the physical laws that operate today have
operated in the same manner in earlier times, back to close to the beginning of
the universe. It does not mean that conditions have been unchanging in past times.
Urea. The water
soluble nitrogenous waste product of mammals and some other vertebrates that is
formed by a combination of carbon dioxide and ammonia. Urea also has the distinction
of being the first "organic" compound synthesized in the laboratory
from inorganic sources.
Ureter. The duct
that carries nitrogenous waste from the kidney to the bladder.
Urethra. The
duct that carries nitrogenous waste from the bladder to the outside.
Uric acid.
A white, insoluble nitrogenous compound used to store or eliminate nitrogenous
waste in birds and other egg laying organisms.