How do the random distribution of chromosomes and crossovers create more variation in the resulting gametes?

When cells divide during meiosis, homologous chromosomes are randomly distributed during anaphase I, separating and segregating independently of each other. This is called independent assortment. It results in gametes that have unique combinations of chromosomes.

Crossing over creates new combinations of genes in the gametes that are not found in either parent, contributing to genetic diversity.