Crossing over is an important event in meiosis because it increases genetic diversity among gametes. When homologous chromosomes exchange genetic material during crossing over, they create new combinations of alleles. This genetic variation is crucial for evolution and adaptation, as it enhances the ability of populations to respond to environmental changes and pressures.
Crossing over occurs during prophase I of meiosis. During this phase, homologous chromosomes pair up and exchange segments of their genetic material, leading to the recombination of genes and contributing to genetic variation in the resulting gametes.