Question

The life cycle of algae such as Spirogyra is
A. Haplontic
B. Diplontic
C. Haplo-diplontic
D. Diplo-haplontic

Answer 1

Hint: Spirogyra is a filamentous charophyte green algae that has gametophyte as its dominant phase in its life cycle. It is a free-living phase in its life-cycle.

Complete answer: In Spirogyra, sexual reproduction has a cycle that alternates between a haploid gametophyte phase and a diploid zygospore phase.
The diploid phase is formed during the end of the growing season.
The gametophyte filament produces aplanogametes in vegetative cells which are known as gametangia. Then, the gametes fuse to form a zygospore 2n.
This zygospore germinates and gives rise to a gametophyte.
This type of life cycle is known as the haplontic life cycle.

Additional information: In many Asian countries, Spirogyra spp. is valued for human consumption, and is known as an important source of natural bioactive compounds for an antibiotic, antiviral, antioxidant, anti-inflammatory, and cytotoxic uses.

Hence, the correct option is A Haplontic.

Note: Spirogyra is unbranched and has cylindrical cells connected to form long filaments. It is a free-living phase that forms gametes by meiotic division.
The gametes fuse and give rise to a single-celled zygote.
Under favorable conditions, spores germinate and form a gametophyte. This is a haplontic life cycle.