Question

What is meant by haplontic diplontic and haplo-diplontic life cycle?

Answer 1

Haplontic - when sporophytic generation is represented by only one celled zygote and gametophyte is dominant.
Example : volvox,spirogyra,chlamydomonas

Diplontic - When the gametophytic phase is represented by single to few celled haploid gametophyte and sporophyte is dominant.
Example : gymnosperms, angiosperms,fucus

Haplo-diplontic - An intermediate condition between haplontic and diplontic lifecycle where both sporophyte and gametophyte are free living and multicellular but have different dominant phases.
Example : Ectocarpus , polysiphonia , kelps

Answer 2

HAPLONTIC LIFE CYCLE:

In this, sporophytic generation is represented only by the one-celled zygote. There are no free-living sporophytes. Meiosis in the zygote results in the formation of haploid spores. The haploid spores divide mitotically and form the gametophyte. The dominant, photosynthetic phase in such plants is the free-living gametophyte.

E.g. Algae such as Volvox, Spirogyra and some species of Chlamydomonas.

DIPLONTIC LIFE CYCLE:

In this, the diploid sporophyte is the dominant, photosynthetic, independent phase of the plant. The gametophytic phase is represented by the single to few-celled haploid gametophyte.

E.g. All seed - bearing plants (Gymnosperms & Angiosperms).

HAPLO-DIPLONTIC LIFE CYCLE:

Bryophytes and pteridophytes exhibit an intermediate condition (Haplo-diplontic). Both phases are multicellular and often free-living. However, they differ in their dominant phases.Most of the Algae are haplontic, some of them like Ectocrpus, Polysiphonia, and Kelps are haplo-diplontic while Fucus is diplontic.