Question

Most algal genera show a haplontic lifestyle. Name an alga which is
a) Haplo - diplontic
b) Diplontic

Answer 1

Hint: A biological life cycle in biology is a sequence of shape changes that an organism undergoes, returning to the starting state. In haplontic the mitoses only exist in haploid cells. The formation of single haploid cells or a multicellular haploid organism may result in this. By mitosis, the haplontic life forms create the gametes. A zygote is produced after fertilization.

Complete answer:
Haplo-diplontic: An intermediate state between haplontic and diplontic life cycles, where all sporophytes and gametophytes are free and multicellular but have separate dominant phases.

b)Ectocarpus is a filamentous brown algae genus that is a model organism for multicellularity genomics. Ectocarpus was selected among the potential model organisms in the brown algae due to the relatively small size of its mature thallus and the speed with which it completes its life cycle. Ectocarpus has a haploid-diploid life cycle, like many brown algae, which involves switching between two multicellular generations, the sporophyte and the gametophyte.

Diplontic: When the gametophytic phase is described by single to few haploid gametophytes and the sporophyte is dominant. This type of diplontic biological life cycle is found in plants such as angiosperms and gymnosperms. The diploid sporophyte is the dominant and autonomous step of this life cycle. In addition, the gametes are undergoing meiosis. These gametes are haploid, and they are called gametophytes. The sporophyte is very evident.

b)Fucus is a genus of brown algae found almost all over the globe in the intertidal zones of rocky seashores. The cycle of sexual life is gametic; the stage of free-living is diploid, and the gametes are the only haploid phases. The main plant body in Fucus is saprophytic and shows a diplontic life cycle form.

Note: Polysiphonia is a red, polysiphonous and typically well-branched algae. They are bound to a rocky surface or other algae by rhizoids. Each with a central axial filament supporting pericentral cells, the thallus consists of fine branched filaments. Polysiphonia's life cycle is three-phase and haplo-diplobiontic.