Diploid zygote may be adapted to surviving winter conditions, as in freshwater green algae. Sexual reproduction is triggered when the cells reach a certain minimal size. Dinobryon Brown algae Phaeophyta Multicellular Reproductive cells, both asexual zoospores and sexual gametes, are usually flagellated. Most have life cycles with an alternation of generations .
Many species show alternation of generations.
These reproduce by spores in sporangia. Water molds Oomycota Coenocytic mycelium Biflagellate zoospores. Asexual and sexual phases.