Many life-cycle patterns are found in algae. However, there is no regular and fixed alternation of generation, as found in higher plants. In blue-green algae and certain chlorophyceae which reproduced asexually, there is an alternation generation.
Most algae have two recognisable phases - the sporophyte and the gametophyte. The main types of algal life cycles are exhibited by green algae. (Red algae have even more complicated life cycles!)
Complex plants always have a multicellular haploid (gametophyte) stage in their life cycle!