During which stage do cells of identical genetic makeup become structurally and functionally different from one another according to the genetically controlled developmental program of the species?

A) cleavage
B) cell differentiation
C) morphogenesis
D) metamorphosis
E) ovulation

Cell differentiation is the stage in which cells of identical genetic makeup become structurally and functionally different from one another according to the genetically controlled developmental program of the species. Cleavage refers to the early rapid cell divisions of the zygote, morphogenesis is the process by which the shape of an organism develops, metamorphosis refers to the transformation of an organism from one developmental stage to another, and ovulation is the release of a mature egg cell from the ovary.