Final answer:
Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis I, leading to genetically unique offspring.
Step-by-step explanation:
The exchange of genetic material in an aligned pair of homologous chromosomes is known as crossing over. This process occurs during prophase I of meiosis I, when homologous chromosomes pair up and form a structure called a tetrad. Genetic material is then swapped between non-sister chromatids of these homologous chromosomes, leading to the creation of new combinations of genes on each chromosome.
This genetic recombination contributes to the genetic diversity in offspring. The process of crossing over is essential for proper chromosomal segregation and creates genetic variation critical for evolution and adaptation.