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1800-102-2727Chapter 3 "Plant Kingdom" is a continuation of the previous chapter in detail. Previously, we had learned about the wide classification of the living organisms in the form of Five Kingdoms Classification, namely Monera, Fungi, Protista, Plantae, and Animalia, which was put forward by Whittaker (1969).
In this chapter, the students will explore in-depth the further classification in the plant kingdom or the 'Kingdom Plantae.' The meaning and concepts on Algae, Pteridophytes, Angiosperms, Bryophytes, Gymnosperms, Alternation of Generations, and Plant Life Cycles are few other topics discussed here. The topics introduced under the chapter Plant Kingdom are as follows:
All the species named above are a part of the plant kingdom, and each of them has been explained extensively under chapter 3, providing information about their life cycle, habitat, etc. The proper meaning of algae and how it is classified into different types have been explained generously. The concept of reductional division has also been discussed, explaining its involvement and importance in the life cycle of moss, liverwort, angiosperms, ferns, and gymnosperms.
The above sub-topics also throw light on the significance of the different uses of algae and gymnosperms for the survival of humanity. The three groups of plants that bear archegonia have been talked about, and they are Bryophytes, Gymnosperms, and Pteridophytes. Descriptions on a series of cells, different types of cell divisions, heterospory, and its importance have also been given under this chapter.
Q1. What is the basis of classification of algae?
Algae are chlorophyll-containing thallus-bearing plants characterised by the absence of embryo stage. A variety of algae are found in a variety of habitats. The various types of algae are classified on the basis of their pigments, flagellation and the reserve food material. Based on these criteria, algae are of three types i.e. red algae, brown algae and green algae.
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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?
In the life cycle of a liverwort reduction division takes place in the capsule for the formation of haploid spores that will grow into gametophytic thallus after germination. In mosses, the gametes fertilise and a zygote is formed. The zygote develops into the sporophyte. In the capsule of the sporophyte, reduction division takes place and haploid spores are formed which on germination give rise to gametophytic thallus. In ferns, reduction division takes place in the sporangia present on leaves for the production of spores. Gymnosperms, which have sporophytic plant bodies show reduction division in their microsporangia and megasporangia for the formation of microspores and megaspores. In the case of angiosperms, the main plant body is diploid and reduction division occurs for the formation of gametes. Therefore, in the life cycle of an angiosperm, reduction division takes place in the anther and ovary at the time of microspore and megaspore formation respectively.
Q4. 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.
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Q5. Write a note on the economic importance of algae and gymnosperms.
Economic importance of algae
Economic importance of Gymnosperms
Q6. Both gymnosperms and angiosperms bear seeds, then why are they classified separately?
Both gymnosperms and angiosperms come under the group spermatophyta or seed- bearing plants. However, angiosperms and gymnosperms are classified separately in spermatophyta because gymnosperms possess naked seeds i.e. their seeds are not enclosed in the ovary whereas angiosperms possess seeds that are enclosed in the ovary.
Q7. What is heterospory? Briefly comment on its significance. Give two examples.
Answer:
Heterospory- It refers to the existence of two types of meiospores i.e. microspores and megaspores in a single plant. These microspores and megaspores are formed respectively within microsporangia and megasporangia which in turn are borne on two distinct sporophylls called microsporophylls and megasporophylls respectively. The microspores and megaspores upon germination give rise to male and female gametophyte respectively. The megaspore is retained in megasporangia and it ensures proper development of the zygote. which is formed after the fusion of microgametes with the megagametes. The zygote is retained on the plant and it is considered to be a precursor of seed habit.
Significance of heterospory- Heterospory is considered to be an important step in evolution as it is a precursor of seed habit which is seen in higher plants. Heterospory was first observed in pteridophyte Selaginella and Salvinia .
Q8. Explain briefly the following terms with suitable examples:-
Answer:
Protonema- It refers to the creeping, green, branched, often filamentous structure which is formed directly after the germination of moss spore. It represents the first stage in the life cycle of moss. Protonema is short-lived and it grows prostrate on the surface. Protonema bears rhizoids for the absorption of materials.
Answer:
Antheridium- It is the male sex organ found in bryophytes, pteridophytes and some algae. Antheridium encloses a mass of cells that give rise to male gametes. Generally, antheridium remains enclosed by a jacket of sterile cells.
Answer:
Archegonium- It is female sex organ found in bryophytes, pteridophytes and gymnosperms. Based on the presence of archegonium, these three groups are referred to as archegoniate. It generally possesses a swollen venter and a tubular neck. The venter possesses ventral canal cells and neck contains neck canal cells. Archegonium also contains the female gamete which is called egg.
Answer:
Diplontic- This is a term utilized for depicting the life cycle of angiosperms and gymnosperms. In this type of life cycle, the plant body is represented by a diploid plant, i.e. sporophyte. It bears sex organs that produce male and female gamete. The gametophyte is of reduced type and it is dependent on the sporophyte. The male and female gametes fuse and form zygote which develops on the diploid plant.
Answer:
Sporophylls- These refer to leaf-like appendages bearing sporangia in pteridophytes, gymnosperms etc. Sporophylls can be either microsporophylls or megasporophylls and respectively they can form either microsporangia or megasporangia.
Answer:
Isogamy- It refers to the process of fertilisation of two gametes which are exactly similar to each other in morphology, physiology, anatomy etc. Such gametes are called isogametes.
Q9. Differentiate between the following:-
(i) red algae and brown algae
Answer:
Differences between red algae and brown algae are as follows:
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(ii) liverworts and moss
Answer:
Differences between liverworts and mosses are as follows
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(iii) homosporous and heterosporous pteridophyte
Answer:
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(iv) syngamy and triple fusion
Answer:
The differences between syngamy and triple fusion are as follows:
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Q10. How would you distinguish monocots from dicots?
Answer:
Differences between monocots and dicots are as follows:
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Q11. Match the following (column I with column II)
Column I Column II
Answer:
Correct matching is (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
Column I Column II
Q12. Describe the important characteristics of gymnosperms
Answer:
Important characteristics of gymnosperms
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