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thyroxine

(Encyclopedia)thyroxine thīrŏkˈsēn [key], substance secreted by the thyroid gland. The hormone thyroxine forms by combining the amino acid tyrosine with iodine. Complexed to a protein, it is stored in the folli...

tropism

(Encyclopedia)tropism trōpˈĭzəm [key], involuntary response of an organism, or part of an organism, involving orientation toward (positive tropism) or away from (negative tropism) one or more external stimuli. ...

heredity

(Encyclopedia)heredity, transmission from generation to generation through the process of reproduction in plants and animals of factors which cause the offspring to resemble their parents. That like begets like has...

sickle cell disease

(Encyclopedia)sickle cell disease or sickle cell anemia, inherited disorder of the blood in which the oxygen-carrying hemoglobin pigment in erythrocytes (red blood cells) is abnormal. This “hemoglobin-S” crysta...

osmosis

(Encyclopedia)osmosis ŏzmōˈsĭs [key], transfer of a liquid solvent through a semipermeable membrane that does not allow dissolved solids (solutes) to pass. Osmosis refers only to transfer of solvent; transfer o...

Maddox, Lester G.

(Encyclopedia)Maddox, Lester G. (Lester Garfield Maddox, Sr), 1915–2003, U.S. public official, governor of Georgia (1967–71), b. Atlanta. He achieved national notoriety in 1964 when he drove African Americans f...

Chlorophyta

(Encyclopedia)Chlorophyta klōrŏfˈətə [key], phylum (division) of the kingdom Protista consisting of the photosynthetic organisms commonly known as green algae. The organisms are largely aquatic or marine. The ...

perennial

(Encyclopedia)perennial, any plant that under natural conditions lives for several to many growing seasons, as contrasted to an annual or a biennial. Botanically, the term perennial applies to both woody and herbac...

battery, electric

(Encyclopedia)CE5 Lead storage cell: At the lead-dioxide electrode, electrons from the circuit combine with lead dioxide and sulfuric acid to form lead sulfate and water. At the spongy-lead electrode, lead react...

Hartline, Haldan Keffer

(Encyclopedia)Hartline, Haldan Keffer, 1903–83, American physiologist, b. Bloomsburg, Pa., M.D. Johns Hopkins, 1927. From 1931 to 1949 (except for 1940–41), he was a researcher at the Eldridge Reeves Johnson Fo...