By what mechanism does a diploid animal grow after fertilization?

mitosis

binary fission

isogamous fertilization

meiosis

Mitosis. After fertilization, the cells in the zygote divide rapidly (by mitosis) to form a morula, which becomes the embryo after approximately five days. The fetus is present about eight weeks after the fertilization takes place.

It is mitosis because after fertilization the groth of somatic cells stars