Zygote: diploid (2n) cell resulting from the fusion of male and female gametes (fertilization/ aka syngamy) Meiosis occurs during gamete formation, producing cells with half the normal of chromosomes. Sexual life cycles have both haploid and diploid stages. 2 sets of chromosomes are present in the somatic cells of adult individuals, 1 set is present in the gametes= haploid. Zygote undergoing meiosis => haploid cells > mitosis. In most animals, diploid state dominates, zygote first undergoes mitosis to make diploid that then go thru meiosis to make haploid. Germ line cells are set aside early in animal development, Germ line cells: during zygote development, cells set aside from somatic cells that will eventually undergo meiosis to produce. Both somatic cells and germ line cells are diploid. Main difference is that somatic cells go thru mitosis to form identically, diploid daughter cells but germ line goes thru meiosis to make haploid gametes.