Editing Chlorophyta (section)

=== Reproduction and life cycle ===

[[Asexual reproduction]] is widely observed in chlorophytes. Among core chlorophytes, both unicellular groups can reproduce asexually through [[autospore]]s,{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=17-8}} wall-less zoospores,{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=17-11}} fragmentation, plain cell division, and exceptionally budding.{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=17-9}} Multicellular thalli can reproduce asexually through motile zoospores,{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=18-8}} non-motile [[aplanospore]]s, autospores, filament fragmentation,{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=19-3}} differentiated resting cells,{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=18-19}} and even unmated gametes.{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=18-29}} Colonial groups can reproduce asexually through the formation of autocolonies, where each cell divides to form a colony with the same number and arrangement of cells as the parent colony.{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=19-14}}

Many chlorophytes exclusively conduct asexual reproduction, but some display [[sexual reproduction]], which may be [[isogamy|isogamous]] (i.e., [[gamete]]s of both sexes are identical), [[anisogamy|anisogamous]] (gametes are different) or [[oogamy|oogamous]] (gametes are sperm and egg cells), with an evolutionary tendency towards oogamy. Their gametes are usually specialized cells differentiated from [[vegetative cell]]s, although in unicellular [[Volvocales]] the vegetative cells can function simultaneously as gametes. Most chlorophytes have a [[Biological_life_cycle#Diplontic_life_cycle|diplontic life cycle]] (also known as zygotic), where the gametes fuse into a [[zygote]] which germinates, grows and eventually undergoes [[meiosis]] to produce [[haploid]] [[spore]]s (gametes), similarly to [[ochrophyte]]s and [[animal]]s. Some exceptions display a [[Biological_life_cycle#Haplodiplontic_life_cycle|haplodiplontic life cycle]], where there is an alternation of generations, similarly to land plants.{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=16-13}} These generations can be isomorphic (i.e., of similar shape and size) or heteromorphic.{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=18-14}} The formation of reproductive cells usually does not occur in specialized cells,{{Sfn|Lee|2018|p=318}} but some [[Ulvophyceae]] have specialized reproductive structures: gametangia, to produce gametes, and sporangia, to produce spores.{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=18-14}}

The earliest-diverging unicellular chlorophytes (prasinophytes) produce walled resistant stages called [[microbial cyst|cysts]] or 'phycoma' stages before reproduction; in some groups the cysts are as large as 230 μm in diameter. To develop them, the flagellate cells form an inner wall by discharging mucilage vesicles to the outside, increase the level of lipids in the cytoplasm to enhance [[buoyancy]], and finally develop an outer wall. Inside the cysts, the nucleus and cytoplasm undergo [[cell division|division]] into numerous flagellate cells that are released by rupturing the wall. In some species these daughter cells have been confirmed to be gametes; otherwise, sexual reproduction is unknown in prasinophytes.{{Sfn|Graham|Graham|Wilcox|Cook|2022|p=16-17}}