Ectocarpus has a haplodiplontic life cycle. Two distinct phases are seen in the life cycle of the ectocarpus haploid gametophyte phase and the diploid sporophytic phase. These are called isomorphic because morphologically both phases are similar in structure. Diploid sporophytes produce haploid spores by the meiotic division, then these spores germinate to form a gametophytic body. Gametophytic bodies make gametes which fuse to form diploid bodies called sporophytes. Then these sporophytes again produce spores by meiotic division. This cycle keeps on running.