What happens during metaphase 1 that leads to genetic variation?

In metaphase I, the tetrads line themselves up at the metaphase plate and homologous pairs orient themselves randomly. This variation is due to independent assortment and crossing-over during meiosis, and random union of gametes during fertilization.

Explanation:

primary succession begins with a bare rock and ends with a forest secondary succession begins after a natural disaster where there is a temporary setback after a forest fire or local destruction, but the surrounding area can fill in