Question

explain the life cycle of Selaginella (Phylum Lycopodiophyta).

Answer 1

It reproduces by producing two types of spores hence is heterosporous .

Its main body is a sporophyte which is differentiated into true root,stem and leaves . The sporophyte bear sporangia that are subtended by leaf like appendages called sporophyll . This sporophyll form distinct structure called strobili or cones. The sporangia produces spores by meiosis in spore mother cell . The spore germinate to give rise to free living photosynthetic thalloid gametophyte called prothallus . The gametophyte bear male and female sex organ called antheridia and archegonia . Water is required for transfer of antherozoids . Fusion of gamete result in formation of zygote . Zygote produces a multicellular well differentiated sporophyte dominant phase in Selaginella which produces two types of spores - macro and micro . The mega and micro spore give rise to female and male gametophytes respectively . The female gametophyte retain on parent sporophyte for a variable period . The development of zygote into young embryo take place within female gametophyte.