.Which of the following plant show haplo-diplontic life cycle?
(1) Chlamydomonas
(2) Ulothrix
(3) Polysiphonia
(4) Fucus
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Answer (3) Polysiphonia exhibits haplodiplontic life-cycle pattern.
Interestingly, while most algal genera are haplontic, some of them such as Ectocarpus, Polysiphonia, kelps are haplo-diplontic. Fucus, an alga is diplontic.
Some commonly found green algae are: Chlamydomonas, Volvox, Ulothrix, Spirogyra and Chara
The common brown algae: Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus.
The common red algae are: Polysiphonia, Porphyra , Gracilaria and Gelidium.
The dominant, photosynthetic phase in some plants is the free-living gametophyte. This kind of life cycle is termed as haplontic. Many algae such as Volvox, Spirogyra and some species of Chlamydomonas represent this pattern.
Bryophytes and pteridophytes, interestingly, exhibit an intermediate condition (Haplo-diplontic); both phases are multicellular. However, they differ in their dominant phases.
Majority of the chloroplasts of the green plants are found in the mesophyll cells of the leaves. These are lens-shaped, oval, spherical, discoid or even ribbon-like organelles having variable length (5-10μm) and width (2-4μm). Their number varies from 1 per cell of the Chlamydomonas, a green alga to 20-40 per cell in the mesophyll.
Asexual reproductive structures: (a) Zoospores of Chlamydomonas; (b) Conidia of Penicillium; (c) Buds in Hydra; (d) Gemmules in sponge
Five kingdom classification:All prokaryotic organisms were grouped together under Kingdom Monera and the unicellular eukaryotic organisms were placed in Kingdom Protista. Kingdom Protista has brought together Chlamydomonas, Chlorella (earlier placed in Algae within Plants and both having cell walls) with Paramoecium and Amoeba (which were earlier placed in the animal kingdom which lack cell wall).
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