(N/A) The haplo-diplontic life cycle is characterized by the alternation between a multicellular haploid gametophytic phase and a multicellular diploid sporophytic phase.
This pattern is observed in bryophytes and pteridophytes.
$1$. Gametophytic phase $(n)$: This phase is haploid and produces male and female gametes through mitosis. The male sex organ is the antheridium (producing antherozoids) and the female sex organ is the archegonium (producing an egg).
$2$. Syngamy: The fusion of the male gamete (antherozoid) and the female gamete (egg) results in the formation of a diploid zygote $(2n)$.
$3$. Sporophytic phase $(2n)$: The zygote undergoes mitosis to develop into a multicellular diploid sporophyte. The sporophyte produces sporangia,which contain spore mother cells.
$4$. Meiosis: The spore mother cells undergo meiosis to produce haploid spores $(n)$,which germinate to form a new gametophyte,thus completing the cycle.
This alternation of generations is a hallmark of the plant life cycle.