Reproduction was the biological process by which offspring are produced. The known methods of biological reproduction were broadly grouped into two main types: sexual and asexual.
While on an away mission on Gamma Trianguli VI, Pavel Chekov and Martha Landon discussed their desire to be alone together in a place described as the Garden of Eden, Captain James T. Kirk, who overheard their flirtations, interjected, stating "I know you find each other fascinating, but we're not here to conduct a field experiment in Human biology." Later, when the Feeders of Vaal witnessed the affection between Chekov and Landon, they described the need for "replacements" to be unnecessary, and such acts to be "forbidden by Vaal." (TOS: "The Apple")