The Plant Kingdom chapter in NCERT Class 11 Biology explores the incredible diversity of plant life on Earth. From microscopic algae to towering gymnosperms, this chapter introduces students to the classification, structure, reproduction, and life cycles of major plant groups. It also explains key concepts like alternation of generations, heterospory, and the evolutionary significance of different plant types. These NCERT solutions simplify complex topics, making it easier for students to grasp core ideas and prepare effectively for exams.
Q1. What is the basis for classification of algae?
Answer: Algae are classified primarily based on the type of pigments they possess, which determine their color. This pigment-based classification includes:
- Chlorophyceae (Green algae): Contain chlorophyll a and b.
- Phaeophyceae (Brown algae): Have chlorophyll a, c, and fucoxanthin.
- Rhodophyceae (Red algae): Possess chlorophyll a, d, and phycoerythrin.
Other classification criteria include:
- Type of flagella
- Nature of stored food
- Cell wall composition
- Cellular organization
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: Reduction division (meiosis) occurs during spore formation in all these groups:
- Liverworts: In spore mother cells within the capsule of the sporophyte.
- Mosses: In spore sacs of the capsule during sporophyte stage.
- Ferns: In sporangia located on sporophylls (fertile leaves).
- Gymnosperms: In microspore mother cells of microsporangia (male cones) and megaspore mother cells in ovules.
- Angiosperms: In microspore mother cells (anther) and megaspore mother cells (ovule).
Q3. Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
Answer: Plants with archegonia include:
- Bryophytes
- Pteridophytes
- Gymnosperms
Life Cycle of Bryophytes:
- Dominant phase is haploid gametophyte.
- Male organ (antheridium) produces biflagellate sperm; female organ (archegonium) produces a single egg.
- Fertilization occurs in water, forming a diploid zygote.
- Zygote develops into a sporophyte, which remains attached to the gametophyte.
- Sporophyte undergoes meiosis to produce haploid spores.
- Spores germinate into new gametophytes.
Q4. Mention the ploidy of the following:
| Cell Type | Ploidy |
|---|---|
| Protonemal cell of a moss | Haploid |
| Primary endosperm nucleus in dicot | Triploid |
| Leaf cell of a moss | Haploid |
| Prothallus cell of a fern | Haploid |
| Gemma cell in Marchantia | Haploid |
| Meristem cell of monocot | Diploid |
| Ovum of a liverwort | Haploid |
| Zygote of a fern | Diploid |
Q5. Write a note on the economic importance of algae and gymnosperms.
Answer: Algae:
- Fix atmospheric CO₂ via photosynthesis.
- Increase oxygen levels in aquatic ecosystems.
- Serve as food for aquatic animals and humans (e.g., Laminaria, Sargassum).
- Used in hydrocolloids like agar and carrageenan.
- Chlorella is used in space missions as a protein source.
Gymnosperms:
- Provide timber and paper pulp.
- Source of resins and turpentine.
- Used in landscaping and bonsai.
- Produce edible seeds and essential oils.
- Some species used in traditional medicine.
Q6. Both gymnosperms and angiosperms bear seeds, then why are they classified separately?
Answer: Despite both producing seeds, key differences exist:
- Gymnosperms: Seeds are naked; ovules are exposed.
- Angiosperms: Seeds are enclosed within fruits; ovules are protected inside ovaries.
- Gymnosperms: No double fertilization; haploid endosperm forms before fertilization.
- Angiosperms: Double fertilization occurs; triploid endosperm forms after fertilization.
- Wood in gymnosperms is non-porous; angiosperms have porous wood.
Q7. What is heterospory? Briefly comment on its significance. Give two examples.
Answer: Heterospory is the production of two distinct types of spores:
- Microspores: Develop into male gametophytes.
- Megaspores: Develop into female gametophytes.
Significance:
- Essential for seed development.
- Promotes sexual differentiation and specialization.
Examples: Selaginella, Salvinia
Q8. Explain briefly the following terms with suitable examples:
- Protonema: Early, thread-like stage in moss life cycle; develops from spores.
- Antheridium: Male sex organ producing sperm in bryophytes and pteridophytes.
- Archegonium: Female sex organ producing a single egg; found in bryophytes, pteridophytes, gymnosperms.
- Diplontic: Life cycle dominated by diploid phase; gametes are the only haploid cells (e.g., Sargassum).
- Sporophyll: Leaf bearing sporangia; found in ferns and gymnosperms (e.g., Pinus).
- Isogamy: Fusion of similar gametes; may be motile or non-motile (e.g., Ectocarpus).
Q9. Differentiate between the following:
| Feature | Red Algae | Brown Algae |
|---|---|---|
| Pigments | Chlorophyll a & d | Chlorophyll a & c, fucoxanthin |
| Reserve Food | Floridean starch | Laminarin |
| Flagella | Absent | Present |
| Phycobilins | Present | Absent |
| Feature | Liverworts | Moss |
|---|---|---|
| Protonema Stage | Absent | Present |
| Plant Body Structure | Dorsiventral thallus | Leafy shoot-like |
| Feature | Homosporous Pteridophyte | Heterosporous Pteridophyte |
|---|---|---|
| Spore Type | One type | Two types (micro & mega) |
| Feature | Syngamy | Triple Fusion |
|---|---|---|
| Definition | Fusion of male & female gamete | Fusion of male gamete with two polar nuclei |
Q10. How would you distinguish monocots from dicots?
| Feature | Monocots | Dicots |
|---|---|---|
| Cotyledons | One | Two |
| Leaf Venation | Parallel | Reticulate |
| Flower Parts | Multiples of 3 | Multiples of 4 or 5 |
| Vascular Bundles | Scattered | Arranged in a ring |
| Root System | Adventitious | Taproot |
| Vascular Cambium | Absent | Present |
Q11. Match the following:
| Column I | Column II |
|---|---|
| Chlamydomonas | Algae |
| Cycas | Gymnosperm |
| Selaginella | Pteridophyte |
| Sphagnum | Moss |
Q12. Describe the important characteristics of gymnosperms.
Answer: Gymnosperms are seed-producing plants with exposed ovules and no flowers. Key features include:
- Naked Seeds: Ovules are not enclosed in ovaries.
- Cones: Reproductive structures are often cone-shaped.
- Vascular Tissue: Well-developed xylem (mostly tracheids) and phloem.
- Heterospory: Produce microspores and megaspores.
- No Double Fertilization: Unlike angiosperms.
- Adaptations: Needle-like leaves, thick cuticles, and sunken stomata for dry climates.
- Economic Uses: Timber, paper, resins, oils, and ornamental plants.
FAQs – NCERT Class 11 Biology Chapter 3: Plant Kingdom
Q1. What are the main groups covered in the Plant Kingdom chapter?
The chapter covers Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms.
Q2. What is the significance of alternation of generations?
It explains how plants switch between haploid and diploid stages, helping us understand their reproductive strategies and evolution.
Q3. Why are gymnosperms and angiosperms classified separately?
Because gymnosperms have naked seeds and lack double fertilization, while angiosperms have enclosed seeds and undergo double fertilization.
Q4. What is heterospory and why is it important?
Heterospory refers to the production of two types of spores—microspores and megaspores. It’s crucial for seed development and sexual differentiation.
Q5. How do algae contribute to the ecosystem?
Algae fix carbon dioxide, release oxygen, serve as food for aquatic life, and are used in industries for hydrocolloids and bio-products.
Q6. What are the economic uses of gymnosperms?
Gymnosperms provide timber, paper pulp, resins, oils, and are used in landscaping and traditional medicine.
Q7. What is the role of archegonia in plant reproduction?
Archegonia are female reproductive organs found in bryophytes, pteridophytes, and gymnosperms. They produce eggs and facilitate fertilization.
Q8. How are monocots different from dicots?
Monocots have one cotyledon, parallel leaf venation, and scattered vascular bundles. Dicots have two cotyledons, reticulate venation, and ringed vascular bundles.
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Conclusion
Chapter 3 of Class 11 Biology, Plant Kingdom, is a gateway to understanding the vast and vital world of plants. These NCERT solutions help students decode complex biological processes, appreciate plant diversity, and build a strong foundation for higher studies. Whether you’re preparing for board exams or competitive entrances, mastering this chapter is essential. Keep revising, stay curious, and let the green world inspire your scientific journey.
