Q. What respectively are zygotic gametic meiosis, meiosis and sporic meiosis?
Zygotic meiosis is the one that occurs in the haplontic haplobiontic life cycle and Gametes from adult haploid individuals unite forming the diploid zygote and the zygote generates and undergoes meiosis four haploid cells that by mitosis develop into adult individuals. Consequently in the zygotic meiosis the cell that undergoes meiosis is the gametes and the zygote are formed by mitosis.
Gametic meiosis is that in which meiosis produces gametes, that is haploid cells that each of which can unite with another gamete forming the zygote. It occurs in the diplontic haplobiontic life cycle for example, in humans in whom the individual is meiosis and diploid forms gametes.
Sporic meiosis happens in metagenesis diplobiontic life cycle or alternation of generations. In this life cycle cells from the diploid individual known as sporophyte undergo meiosis producing haploid spores that don't unite with others but instead develop by mitosis into haploid individuals known as gametophytes. In this life cycle the gametes are made by mitosis from cells of the gametophyte.