Life cycle in Algae

Life cycle is the cyclic sequence of events occurring in the life of an organism. The different types of life cycles of algae are Diplontic , Haplontic type, Diplohaplontic type, Diplobiontic type and Haplobiontic.
  • Plants are haploid
  • The main vegetative plant body is gemetophytic and haploid(n).
  • Diploid phase is only represented by zygote (2n)
  • Chlamydomonas, Ulothrix, Oedogonium, Spirogyra 
  • Plants are diploid.
  • Plant body: 2n and sporophytic sex organs are also 2n. By meiosis forms gametes.
  • Haploid stage represented only during gamete formation.
  • Bacillariophyceae, Sargassum, Fucus Phaeophyceae
life cycle in algae
  • Both 1n and 2n plants are present. It is of two types.
  • A)Isomorphic alternations of generation: If both are morphologically similar and shows alternation of Cladophora, Ectocarpus, Ulva
  • B)Heteromorphic alternations of generation: Here 2n plant is large and macroscopic and in plant is microscopic Eg : Laminaria
 4. Haplobiontic Life (Diphasic life cycle):
  • 2 well developed haploid phases are present. Diploid phase represented only by zygote.
  • haploid generation is represented by the independent gametophyte and the parasitic carposporophyte
  • First haploid phase represented by gametophytic plant body, sex organs and gametes.
  • Second haploid phase represented by gonimoblast filaments, carposporangia, carpospores and chantransia stage
  • Also called as diphasic life cycle as two haploid phases are present
  • Haplobiontic seen in Batrachospermum, Nemalion
5. Diplobiontic Life Cycle (Triphasic life cycle):
  • one well developed haploid phases and 2 diploid phases also called as triphasic lifecycle
  • First haploid phase represented by male and female gemetophytic plant body, sex organs and gametes
  • First diploid phase is represented by zygote, gonimoblast filament, carposporangia and carpospores. All these together represent carposporophyte which depends on the gametophyte
  • Second diploid phase represented by tetrasporophytic plant bearing tetrasporangia.
  • Seen in Polysiphonia
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