Plant Kingdom

  • Question 1
    CBSEENBI11001625

    What is the basis of classification of algae?

    Solution

    Algae are classified on the following factors:
    (a) Major photosynthetic pigments present.
    (b) Form of stored food.
    (c) Cell wall composition.
    (d) Number of flagella and position of insertion.
    (e) Habitat.  

    Question 2
    CBSEENBI11001626

    When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?

    Solution

    Liverwort: In liverworts, the reduction division takes place in the capsule during the sexual reproduction.
    Moss: In mosses the reduction division takes place in the capsule during the sexual reproduction.
    Fern: Reduction division takes place in the sporangia, thereby producing many spores during the sexual reproduction.
    Gymnosperm: Reduction division takes place in the microsporangia present and in the megasporangia during sexual reproduction.
    Angiosperm: In angiosperms, reduction division takes place in the anthers of the stamen (producing haploid pollen grains or male gametes) and in the ovary of the pistil (producing eggs or female gametes ) during the sexual reproduction phase.

    Question 3
    CBSEENBI11001627

    Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.

    Solution

    Archegonium is the female sex organ that produces the female gamete or egg. It is present in the life cycles of mosses (bryophytes), pteridophytes, and gymnosperms.
    Life cycle of a moss.
    Gametophytic stage is the predominant stage of the moss lifecycle. The Gametophytic stage consists of two stages
    (i). Protenema stage – this is the first stage which develops directly from a spore.
    (ii). Leafy stage – this is the second stage which develops from the secondary protonema as a lateral bud.
    They consist of upright slender axes which bears spirally arranged leaves. Rhizoids are the multicellular structure that attaches the mosses to the soil. This stage bears the sex organs. The male (antheridia) and female (archegonium ) sporangia are formed at the apex of the leafy shoots. Cells within the sporangium of the sporophyte undergo meiosis to produce male and female spores, respectively. These spores divide mitotically to produce multicellular male and female gametophytes. The sperm and eggs are produced mitotically in the antheridia and archegonia, respectively. Sperm are carried to the archegonia in water droplets. After fertilisation, the sporophyte generation develops in the archegonium and remains attached to the gametophyte and the cycle is completed. 

    Question 4
    CBSEENBI11001628

    Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a ferm; gemma cell in Marchantia; meristem cell of monocot, ovum of a liverwort, and zygote of a fern.

    Solution

    The ploidy of the following are:
    (a) Protonemal cell of a moss – Haploid
    (b) Primary endosperm nucleus in a dicot – Triploid
    (c) Leaf cell of a moss – Haploid
    (d) Prothallus of a fern – Haploid
    (e) Gemma cell in Marchantia – Haploid
    (f) Meristem cell of a monocot – Diploid
    (g) Ovum of a liverwort – Haploid
    (h) Zygote of a fern – Diploid

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