All-American Canal

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All-American Canal, 80 mi (129 km) long, SE Calif.; part of the federal irrigation system of the Hoover Dam. Built between 1934 and 1940 across the Colorado Desert, the canal is entirely within the United States and replaces the Inter-California Canal, which passes through Mexico. The Imperial Dam, NE of Yuma, Ariz., diverts water from the Colorado River into the All-American Canal, which runs W to Calexico, Calif. Smaller canals move water into the Imperial Valley; the Coachella Canal branches NW to the Coachella Valley. This canal system irrigates more than 630,000 acres (254,961 hectares) and has greatly increased crop yield in the area; however, problems of drainage and salinity exist.

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canalization The holding of a developmental process within narrow bounds despite both genetic and environmental disturbing forces. Thus cells will progress along particular developmental pathways until they become differentiated into their final, adult forms. Development is such that all the different genotypes have a standard phenotype over the range of environments common to that species. See also autopoiesis.

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canalization A developmental process that is held within narrow bounds despite both genetic and environmental disturbing forces. Development is such that all the different genotypes have a standard phenotype over the range of environments common to that species.

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canalization The developmental process that is held within narrow bounds despite both genetic and environmental disturbing forces. Thus, cells will progress along particular developmental pathways until they become differentiated into their final, adult forms. Development is such that all the different genotypes have a standard phenotype over the range of environments common to that species.

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canalization (in evolutionary genetics) A developmental mechanism that limits variation of the phenotype within narrow bounds by repressing underlying genetic variation. It thus maintains a fairly uniform phenotype over a range of different environments in which the organism might normally occur. Canalization is achieved by various genes concerned with development and stress responses. Mutation of these, or exposure to extreme environmental stress, will uncover the genetic variation hitherto hidden by canalization, enabling the population to undergo rapid evolution.