Final answer:
Spirogyra can reproduce asexually through fragmentation or spore dispersal, and sexually via conjugation leading to the formation of zygospores.
Step-by-step explanation:
Spirogyra can reproduce in both asexual and sexual ways. Asexually, it reproduces by fragmentation or the dispersal of spores, which are reproductive cells that can grow into new individuals without fertilization. These spores are often formed during times of stress, such as in very dry environments, and can withstand harsh conditions.
Sexually, Spirogyra engages in the process of conjugation, where two filaments of Spirogyra line up side by side and form conjugation tubes connecting their cells. The contents of one cell, the male gamete, then passes through the tube into the adjoining cell, fusing with the female gamete to form a diploid zygote known as a zygospore. This zygospore can undergo meiosis to produce haploid cells that can then start a new life cycle.