Although algae lack structures like flowers, fruits, and seeds for reproduction, they employ a variety of reproductive methods to adapt to their environment. In asexual reproduction, some cells can directly divide in two, such as Spirogyra, which can break into several segments, each of which grows into an independent individual. Some algae can produce numerous flagellated spores that can move freely, with each spore maturing into a new individual. Under unfavorable environmental conditions, some algae can produce thick-walled dormant spores, which germinate and grow into new individuals when conditions become suitable. In sexual reproduction, some algae can produce male and female gametes, which mate to develop into new individuals.
Throughout the life cycle of seaweed, asexual and sexual reproduction often alternate regularly, forming a complex life history. For example, seaweed and kelp, which we commonly eat, exhibit different growth forms of sporophyte and gametophyte. The sporophyte reproduces asexually by producing spores, while the gametophyte produces male and female gametes for sexual reproduction. This alternation of different life forms is called "alternation of generations."
