The process of sexual reproduction in which the male gamete is small and motile and the female gamete is large and stationary is called oogamy. A single ovule is produced in the female genitalia. A zygote unites with an egg to form a zygote. Such as Fucus, Oedogonium, Chlamydomonas, Vaucheria, Volvox, Chara, Polysiphonia, Sargassum etc.