Chapter 3 : Plant Kingdom [Download Link]
Exercise : Solutions of Questions on Page Number : 44
Q1 : What is the basis of classification of algae?
Answer :
Algae are classified into three main classes - Chlorophyceae, Phaeophyceae, and Rhodophyceae.
These divisions are based 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
Class I - Chlorophyceae
Common name - Green algae
Major pigments - Chlorophylls a and b
Stored food - Starch
Cell wall composition - Cellulose
Flagella number and position - 2-8; equal and apical
Class II - Phaeophyceae
Common name- Brown algae
Major pigments - Chlorophylls a and c, and fucoxanthin
Stored food - Mannitol and laminarin
Cell wall composition - Cellulose and algin
Flagella number and position - 2; unequal and lateral
Class III - Rhodophyceae
Common name - Red algae
Major pigments - Chlorophylls a and b, and phycoerythrin
Stored food - Floridean starch
Cell wall - Cellulose, pectin, and polysulphate esters
Flagella number - Absent
Q2 : When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?
Answer :
Liverwort- In liverworts, the main plant-body is haploid (gametophytic). It bears the male and female sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops on the gametophytic plant-body to form a sporophyte. The sporophyte is differentiated into the foot, seta, and capsule. Many haploid spores are produced as a result of the reduction division taking place inside the capsule.
Moss- In mosses, the primary protonema (developed in the first stage) develops into the secondary protonema. Both these stages are haploid or gametophytic. The secondary protonema bears the sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops into a sporophyte. Many spores are formed as a result of the reduction division taking place in the capsule of this sporophyte.
Fern- In ferns, the main plant-body is sporophytic. Its leaves are known as sporophylls and these bear the sporangia. Reduction division takes place in these sporangia, thereby producing many spores.
Gymnosperm- In gymnosperms, the main plant-body is sporophytic. They bear two types of leaves - microsporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the microsporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing megaspores).
Angiosperm- In angiosperms, the main plant-body is sporophytic and bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the stamen (producing haploid pollen grains) and in the ovary of the pistil (producing eggs).
Q3 : Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
Answer :
Archegonium is the female sex organ that produces the female gamete or egg. It is present in the life cycles of bryophytes, pteridophytes, and gymnosperms.
Life cycle of a fern (Dryopteris)
Dryopterisis a common fern with pinnately-compound leaves. The main plant-body is sporophytic. Many sporangia are borne on the lower surfaces of its mature leaves. Each sporangium has spore mother cells which undergo meiosis to produce haploid spores. On maturing, these spores dehisce and germinate to give rise to a heart-shaped gametophyte called prothallus. Theprothallus bears the male and female sex organs called antheridia and archegonia respectively. The antheridia produce sperms that swim in water to reach the archegonia. The egg is produced by the archegonia. As a result of fertilisation, a zygote is formed. The zygote forms an embryo, which in turn develops into a new sporophyte. The young plant comes out of the archegonium of the parent gametophyte.
Q1 : What is the basis of classification of algae?
Answer :
Algae are classified into three main classes - Chlorophyceae, Phaeophyceae, and Rhodophyceae.
These divisions are based 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
Class I - Chlorophyceae
Common name - Green algae
Major pigments - Chlorophylls a and b
Stored food - Starch
Cell wall composition - Cellulose
Flagella number and position - 2-8; equal and apical
Class II - Phaeophyceae
Common name- Brown algae
Major pigments - Chlorophylls a and c, and fucoxanthin
Stored food - Mannitol and laminarin
Cell wall composition - Cellulose and algin
Flagella number and position - 2; unequal and lateral
Class III - Rhodophyceae
Common name - Red algae
Major pigments - Chlorophylls a and b, and phycoerythrin
Stored food - Floridean starch
Cell wall - Cellulose, pectin, and polysulphate esters
Flagella number - Absent
Q2 : When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?
Answer :
Liverwort- In liverworts, the main plant-body is haploid (gametophytic). It bears the male and female sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops on the gametophytic plant-body to form a sporophyte. The sporophyte is differentiated into the foot, seta, and capsule. Many haploid spores are produced as a result of the reduction division taking place inside the capsule.
Moss- In mosses, the primary protonema (developed in the first stage) develops into the secondary protonema. Both these stages are haploid or gametophytic. The secondary protonema bears the sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops into a sporophyte. Many spores are formed as a result of the reduction division taking place in the capsule of this sporophyte.
Fern- In ferns, the main plant-body is sporophytic. Its leaves are known as sporophylls and these bear the sporangia. Reduction division takes place in these sporangia, thereby producing many spores.
Gymnosperm- In gymnosperms, the main plant-body is sporophytic. They bear two types of leaves - microsporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the microsporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing megaspores).
Angiosperm- In angiosperms, the main plant-body is sporophytic and bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the stamen (producing haploid pollen grains) and in the ovary of the pistil (producing eggs).
Q3 : Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
Answer :
Archegonium is the female sex organ that produces the female gamete or egg. It is present in the life cycles of bryophytes, pteridophytes, and gymnosperms.
Life cycle of a fern (Dryopteris)
Dryopterisis a common fern with pinnately-compound leaves. The main plant-body is sporophytic. Many sporangia are borne on the lower surfaces of its mature leaves. Each sporangium has spore mother cells which undergo meiosis to produce haploid spores. On maturing, these spores dehisce and germinate to give rise to a heart-shaped gametophyte called prothallus. Theprothallus bears the male and female sex organs called antheridia and archegonia respectively. The antheridia produce sperms that swim in water to reach the archegonia. The egg is produced by the archegonia. As a result of fertilisation, a zygote is formed. The zygote forms an embryo, which in turn develops into a new sporophyte. The young plant comes out of the archegonium of the parent gametophyte.
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