NCERT Class 11 Biology chapter 10 notes give significance as follows,

Gametes are produced through meiotic division. If it isn't present, the number of chromosomes doubles or quadruples, resulting in monstrosities (abnormal forms). Meiosis keeps the number of chromosomes in a species constant from generation to generation. Crossing over results in the exchange of genetic material, resulting in genetic variants, which are the basic ingredients for evolution.