1. Sexual reproduction evolved around 1.2 million years ago and involves the combination of genetic material from two sexually differentiated organisms, usually male and female gametes. 2. Early organisms reproduced asexually through processes like binary fission and mitosis. Limited genetic recombination was possible in bacteria through conjugation and plasmid transfer. Eventually, haploid cells began fusing (syngamy) and meiosis evolved allowing for genetic mixing. 3. Specialized reproductive cells called gametes evolved, with motile sperm cells fertilizing stationary egg cells. This led to the development of separate gonads and coordinated mating behaviors involving simultaneous gamete release.