What happens between meiosis i and meiosis ii that reduces the number of chromosomes?

Explanation:

Meiosis occurs in germ cell and produce four haploid cell from a single diploid cell.

Meiosis I begins with diploid cell and there is DNA replication in meiosis I and , and it ends with haploid cells having chromosome number half as compared to parental cells, this is called reductional division.

Meiosis II begins after meiosis I, where two haploid parent cells ends with four haploid daughter cells, after meiosis II, containing the same number of chromosomes in each cell as in meiosis I but half DNA content because there is no DNA replication in meiosis II. In meiosis II, sister chromatids are separated into different chromosomes . This is called equational division.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.