Plant kingdom, part 5 –Important awareness ( Algae)

 

·        Life cycle of algae –

 Diphasic

Ø Haplontic

v Primitive and simplest type

v Prominent phase  - Haploid gametophytic phase

v Zygote immediately undergo meiosis to produce haploid zoospore.( zygotic meiosis) 

v Zoospore grows by mitosis to produce Haploid gametophytic generation.

v Gametophytic plant produces male and female gametes by mitosis.

Examples - Spirogyra, Oedogonium, Ulothrix, Chlamydomonas, Volvox, Zygnema , Chara. 

Ø Diplontic  - 

v Prominent phase  - Diploid sporophytic phase

v Gametes are produced in the gametangia by meiosis.(Gametic meiosis) 

v Zygote developed into a Diploid sporophytic phase by mitosis.

Examples- Caulerpa, Fucus, Sargassum , diatom, Cladophora glomerata

Ø Haplo-diplontic -

v Well-developed multicellular haploid and diploid phases, called gametophyte and sporophyte respectively.

v In sporophytic plant, sporangia produce haploid zoospores by meiosis ( Sporic meiosis)

v Zoospores develop into haploid gametophytic generation.

v Two types of Haplodiplontic –

o   Isomorphic –

ü Morphologically similer sporophytic and gametophytic phase

üE.g. Ulva, Chaetophora, Ectocarpus, Cladophora, Fritschiella

o   Heteromorphic –

ü Morphologically dissimilar sporophytic and gametophytic phase

ü E.g. Laminaria ,Urospora, Dictyota

 Triphasic

ØHaplobiontic –

v Triphasic (1 diploid , 2 haploid )

o   Gametophyte phase (n) – Haploid phase 1

o   Zygote (2n) – Diploid phase

o   Carposporophyte - Haploid phase 2

v E.g., Rhodophyceae members (Batrachospermum,Nemalion)

 

Ø Haplo-Diplobiontic-

v Most complex and advanced type

v Triphasic (2 diploid , 1haploid)

o   Carposporophyte (2n) -  Diploid phase 1

o   Gametophyte (n) – Haploid

o   Tetrasporophyte (2n) - Diploid phase 2

v E.g. Ectocarpus, Polysiphonia and Kelps (Laminaria saccharina)

reference

https://biosmartnotes.com/types-of-life-cycle-in-algae/