Both meiosis I and meiosis II are essential processes in sexual reproduction, but they serve different purposes in the formation of gametes.
Similarity
Both meiosis I and meiosis II involve a type of cell division that results in the reduction of the chromosome number by half. This is crucial for maintaining the chromosome number across generations through fertilization. During both processes, DNA is replicated only once before the divisions begin, leading to four non-identical daughter cells by the end of meiosis II.
Difference
The main difference lies in their phases and outcomes. Meiosis I is known as the reductional division because it reduces the chromosome number from diploid (2n) to haploid (n) by separating homologous chromosomes. In contrast, meiosis II is similar to mitosis, as it separates sister chromatids, but it does so in haploid cells, leading to four haploid cells from the two haploid cells produced in meiosis I.