The biflagellate sperm in the above illustration is characteristic of a moss.
Human sperm have a single flagellum.
Cytoplasmic division or cytokinesis involves a cleavage furrow in animal cells and a cell plate in plant cells. Egg formation and sperm formation are referred to as oogenesis and spermatogenesis. In the second and final division the chromatids of each doubled chromosome separate from each other forming the haploid gametes. During the first and second divisions of meiosis nondisjunction can occur, as shown in the following illustration. The XXX and XXY chromosome anomalies can also result from an XX-bearing egg.