The Cambrian Period marks an important point in the history of life on Earth; it is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the "Cambrian Explosion," because of the relatively short time over which this diversity of forms appears
Answer:
Prophase 1
Explanation:
In prophase 1, homologous chromosomes pair up and exchange sections of DNA in a process called crossing over.
