This is an active transport mechanism by which cells pump sodium and potassium ions against the concentration gradient.

Primary active transport

Explanation:

Primary active transport is the transport in which molecules are moved against their gradient, with direct use of ATP as an energy source. Na/K pump  is an example  of primary active transport: Na ions are transported out of cell, K ions are moved into the cell. This pumps maintain concentrations of those ions and also creates voltage across the cell membrane, which can be used for the secondary active transport of other molecules (e.g. glucose).

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genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).