Question Bank — Sexual Reproduction in Flowering Plants

NCERT Class 12 Biology · Chapter 1 · CBSE Board Pattern

Class 12 Biology Chapter 1 Question Bank CBSE Board Pattern

Section A — MCQs (10 questions, 1 mark each)

  1. The hard outer layer of the pollen grain wall is made up of:
    (a) Cellulose (b) Pectin (c) Sporopollenin (d) Lignin

  2. In a typical angiosperm embryo sac, the number of nuclei at maturity is:
    (a) 7 (b) 8 (c) 4 (d) 6

  3. Assertion (A): Cleistogamous flowers ensure assured seed set even in the absence of pollinators.
    Reason (R): In cleistogamous flowers, anthers and stigma lie close to each other and pollination occurs within the closed flower bud.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  4. The process of formation of microspores from pollen mother cell through meiosis is called:
    (a) Megasporogenesis (b) Microsporogenesis (c) Embryogenesis (d) Apomixis

  5. Assertion (A): Wind-pollinated flowers produce enormous quantities of pollen grains.
    Reason (R): Pollination by wind is a chance factor and a large number of pollen grains are lost.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  6. The functional megaspore in most angiosperms develops into the female gametophyte by:
    (a) Bisporic development (b) Tetrasporic development (c) Monosporic development (d) Apomictic development

  7. Which of the following is a post-fertilisation event?
    (a) Pollination (b) Endosperm formation (c) Pollen-pistil interaction (d) Microsporogenesis

  8. The filiform apparatus is present in:
    (a) Antipodal cells (b) Synergids (c) Central cell (d) Egg cell

  9. In angiosperms, double fertilisation involves:
    (a) Two syngamy events (b) Syngamy and triple fusion (c) Two triple fusion events (d) Fusion of three polar nuclei

  10. The persistent nucellus in some seeds (e.g., black pepper) is called:
    (a) Pericarp (b) Perisperm (c) Endosperm (d) Testa

Section B — Very Short Answer (6 questions, 2 marks each)

  1. Differentiate between microsporogenesis and megasporogenesis.
  2. What is the role of the tapetum in pollen grain development?
  3. Define xenogamy. Why is it considered the only type of pollination that brings genetically different pollen to the stigma?
  4. What is meant by monosporic development of the female gametophyte?
  5. Why is endosperm development said to precede embryo development in angiosperms?
  6. Name the two nuclei involved in triple fusion and state the product formed.

Section C — Short Answer (5 questions, 3 marks each)

  1. Describe the structure of a typical angiosperm anther with the help of a labelled diagram of its transverse section.
  2. Explain the events of megasporogenesis and the organisation of a mature 7-celled, 8-nucleate embryo sac.
  3. What are outbreeding devices in flowering plants? Describe any three devices that prevent self-pollination.
  4. Differentiate between albuminous and non-albuminous seeds with suitable examples.
  5. What is pollen-pistil interaction? How does the pistil recognise and accept/reject pollen?

Section D — Long Answer (3 questions, 5 marks each)

  1. Describe the structure of a typical anatropous ovule with a neat labelled diagram. Explain the process of megasporogenesis leading to the formation of the female gametophyte.
  2. Explain double fertilisation in angiosperms. Describe the post-fertilisation changes that lead to the formation of endosperm, embryo, seed and fruit.
  3. What is apomixis? How does it differ from sexual reproduction? Explain its significance in hybrid seed production with reference to polyembryony.

Section E — Case/Source-Based (2 questions, 4 marks each)

Case 1

Hybrid seed production is expensive because hybrid seeds must be produced every year; seeds collected from hybrids segregate in the progeny. Some species of Asteraceae and grasses produce seeds without fertilisation through apomixis. In certain varieties of Citrus and mango, nucellar cells surrounding the embryo sac divide and develop into multiple embryos (polyembryony).

Sub-questions:
(a) What is apomixis and how does it mimic sexual reproduction? (1)
(b) How can apomixis solve the problem of hybrid seed production? (1)
(c) What is polyembryony? Give one example from the case. (1)
(d) Are apomictic embryos genetically identical to the parent plant? Give reason. (1)

Case 2

In Vallisneria, the female flowers reach the water surface by means of a long stalk. Male flowers or pollen grains are released on the water surface and are carried passively by water currents to the female flowers. In contrast, most aquatic plants such as water hyacinth have flowers that emerge above water and are pollinated by insects or wind.

Sub-questions:
(a) Name the type of pollination seen in Vallisneria and state the agent involved. (1)
(b) Why do water-pollinated flowers generally lack bright colours and nectar? (1)
(c) How are pollen grains of many water-pollinated species protected from wetting? (1)
(d) Why is water pollination described as a rare event in flowering plants? (1)

▶ Answer Key Attempt all questions first,
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Section A

  1. (c) Sporopollenin
  2. (b) 8
  3. (a)
  4. (b) Microsporogenesis
  5. (a)
  6. (c) Monosporic development
  7. (b) Endosperm formation
  8. (b) Synergids
  9. (b) Syngamy and triple fusion
  10. (b) Perisperm

Section B

  1. Microsporogenesis: formation of microspores from pollen mother cell by meiosis in anther (1). Megasporogenesis: formation of megaspores from megaspore mother cell by meiosis in nucellus (1).
  2. Tapetum nourishes developing pollen grains; cells are multinucleate with dense cytoplasm (2).
  3. Xenogamy: transfer of pollen from anther of one plant to stigma of another plant (1). It alone introduces genetically different pollen (1).
  4. Development of embryo sac from a single functional megaspore after three mitotic divisions (2).
  5. Endosperm provides nutrition to the developing embryo; zygote divides only after some endosperm is formed (2).
  6. Two polar nuclei + one male gamete (1); forms triploid primary endosperm nucleus (1).

Section C

  1. Anther is bilobed, dithecous, tetrasporangiate (1); wall layers — epidermis, endothecium, middle layers, tapetum (1); sporogenous tissue in centre (1).
  2. MMC undergoes meiosis → 4 megaspores; one functional megaspore → 8-nucleate embryo sac by 3 mitotic divisions (free nuclear) → 7-celled structure (egg apparatus, central cell with 2 polar nuclei, antipodals) (3).
  3. Devices: (i) temporal separation of pollen release and stigma receptivity (1); (ii) spatial separation of anther and stigma (1); (iii) self-incompatibility / unisexual flowers (1).
  4. Albuminous: endosperm persists (castor, maize) (1½); non-albuminous: endosperm completely consumed (pea, groundnut) (1½).
  5. Recognition of compatible/incompatible pollen by chemical dialogue (1); acceptance leads to germination and tube growth; rejection prevents germination or tube growth (2).

Section D

  1. Ovule structure: funicle, hilum, integuments, micropyle, chalaza, nucellus, embryo sac (2); megasporogenesis and monosporic development leading to 8-nucleate embryo sac (3).
  2. Syngamy + triple fusion (double fertilisation) (2); endosperm (PEN → free nuclear → cellular), embryo development, seed (ovule) and fruit (ovary) formation (3).
  3. Apomixis: seed formation without fertilisation (asexual mimic of sexual reproduction) (2); advantage — hybrid characters maintained without segregation every year (2); polyembryony: multiple embryos per seed (e.g., Citrus) (1).

Section E

Case 1

(a) Seed formation without fertilisation (1).
(b) No segregation; hybrid seeds can be reused (1).
(c) Occurrence of more than one embryo per seed; Citrus/mango (1).
(d) Yes; formed from diploid nucellar cells without meiosis/fertilisation (1).

Case 2

(a) Hydrophily (water pollination) (1).
(b) No need to attract biotic agents (1).
(c) Mucilaginous covering (1).
(d) Limited to ~30 genera, mostly monocots; most aquatic plants use wind/insects (1).

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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.