Life cycles differs in the duration of haploid and diploid phase. There are three types of life cycles:
(A) Haplontic life cycles:
(i) Gametophytes is dominant, haploid and independent plant body where as sporophyte is dependent on gametophyte and draws nutrition from it.
(ii) Maximum part of life cycle is represented by haplo-phases. E.g. Spirogyra, Volvox, Chlamydomonas and Dinoflagellate.
(B) Diplontic life cycles:
(i) Sporophyte is dominant, diploid, independent plant body where as gametophyte is highly reduced and dependent on sporophyte.
(ii) Maximum part of life cycle is represented by diplo-phase. e.g., Fucus, Sargassum , All gymnosperms and angiosperms and Diatoms etc.
(C) Haplo-diplontic/Diplohaplonitic life cycles:
(i) Nearly equal existence of sporophyte as well as gametophyte
(ii)Both of them are photosynthetic and free living.
e.g., Ulva, , All bryophytes, all Pteridophytes, Liminaria
(iii)Red algae have two or more phases in their life cycle called
- Haplobiontic/Haplohaplontic type
- Diplobiontic/Diplohaplontic type