Significance of meiosis

Meiosis keeps the chromosome number of each species constant from one generation to the next in sexually reproducing organisms, even though the division itself halves that number.

Halving in meiosis followed by restoring at fertilisation is what keeps the count steady.

Meiosis also increases genetic variability in the population from one generation to the next; crossing over in prophase I, for instance, produces new combinations of genetic material on the chromosomes.

Variation is very important for the process of evolution.

Mitosis versus meiosis in short: mitosis is one division giving two identical diploid cells; meiosis is two divisions after one DNA replication, giving four haploid cells, with pairing and crossing over of homologues in prophase I.