Class 12 Biology Sexual Reproduction in Flowering Plants Notes

Class 12 Biology Sexual Reproduction in Flowering Plants Notes

Sexual Reproduction in Flowering Plants – Short Notes

1. Flower Structure

  • Flower is the reproductive organ of angiosperms.
  • Parts of a flower:
    • Calyx: Sepals – protect the bud.
    • Corolla: Petals – attract pollinators.
    • Androecium: Stamens – male part, consists of anther (pollen producer) + filament.
    • Gynoecium: Carpels/Pistil – female part, consists of stigma, style, ovary (with ovules).

2. Microsporogenesis and Megasporogenesis

  • Microsporogenesis: Formation of male gametes (pollen grains) in anthers.
    • Microspore mother cell → meiosis → 4 haploid microspores → develop into pollen grains.
  • Megasporogenesis: Formation of female gametes in ovules.
    • Megaspore mother cell → meiosis → 4 megaspores (only one functional) → forms embryo sac.

3. Pollination

  • Pollination: Transfer of pollen from anther to stigma.
    • Self-pollination: Same flower or same plant.
    • Cross-pollination: Between different plants.
  • Agents: wind, water, insects, birds.

4. Fertilization

  • Double fertilization:
    • One sperm fuses with egg → zygote (2n).
    • One sperm fuses with polar nuclei → primary endosperm (3n).
  • Syngamy → zygote; Triple fusion → endosperm.

5. Post-fertilization Events

  • Zygote → embryo → seed.
  • Ovary → fruit; Ovule → seed.
  • Seed Structure: Embryo, cotyledons, seed coat, endosperm.
  • Types of fruits: Simple, aggregate, multiple; dry or fleshy.

MCQs

1. Reproduction in Flowering Plants

  1. Which part of the flower is male reproductive organ?
    a) Stigma
    b) Ovary
    c) Androecium
    d) Corolla
    Answer: c) Androecium
  2. The female gametophyte in angiosperms is called:
    a) Pollen grain
    b) Ovule
    c) Embryo sac
    d) Zygote
    Answer: c) Embryo sac
  3. In flowering plants, the process of transfer of pollen grains from anther to stigma is called:
    a) Fertilization
    b) Pollination
    c) Germination
    d) Double fertilization
    Answer: b) Pollination
  4. Which of the following is an example of asexual reproduction?
    a) Cross-pollination
    b) Binary fission
    c) Fertilization
    d) Embryo sac formation
    Answer: b) Binary fission

2. Microsporogenesis and Megasporogenesis

  1. Microspores develop into:
    a) Ovules
    b) Pollen grains
    c) Embryo sacs
    d) Zygotes
    Answer: b) Pollen grains
  2. Megaspore mother cell undergoes meiosis to form:
    a) Four megaspores
    b) Two megaspores
    c) Eight megaspores
    d) One megaspore
    Answer: a) Four megaspores
  3. Out of the four megaspores produced in angiosperms, how many are functional?
    a) 1
    b) 2
    c) 3
    d) 4
    Answer: a) 1

3. Pollination

  1. Self-pollination occurs when pollen is transferred:
    a) From one plant to another
    b) From one flower to another on the same plant
    c) Only by insects
    d) Only by wind
    Answer: b) From one flower to another on the same plant
  2. The agent of cross-pollination in Hibiscus is:
    a) Wind
    b) Water
    c) Insects
    d) Self
    Answer: c) Insects
  3. Wind-pollinated flowers usually have:
    a) Bright petals and nectar
    b) Small, light pollen grains
    c) Sticky pollen
    d) Foul smell
    Answer: b) Small, light pollen grains

4. Fertilization

  1. Double fertilization is characteristic of:
    a) Gymnosperms
    b) Pteridophytes
    c) Angiosperms
    d) Bryophytes
    Answer: c) Angiosperms
  2. In angiosperms, one sperm fuses with the egg to form:
    a) Endosperm
    b) Embryo
    c) Zygote
    d) Seed coat
    Answer: c) Zygote
  3. The fusion of the second sperm with the polar nuclei produces:
    a) Zygote
    b) Embryo
    c) Endosperm
    d) Ovule
    Answer: c) Endosperm
  4. Syngamy refers to:
    a) Fusion of sperm with polar nuclei
    b) Fusion of male and female gametes
    c) Formation of pollen tube
    d) Production of gametes
    Answer: b) Fusion of male and female gametes

5. Post-Fertilization Events

  1. The ovule develops into:
    a) Seed
    b) Fruit
    c) Zygote
    d) Embryo
    Answer: a) Seed
  2. The ovary develops into:
    a) Seed
    b) Fruit
    c) Embryo
    d) Endosperm
    Answer: b) Fruit
  3. The endosperm is triploid (3n) because of:
    a) Single fertilization
    b) Syngamy
    c) Triple fusion
    d) Double fertilization
    Answer: c) Triple fusion
  4. A fruit that develops without fertilization is called:
    a) Simple fruit
    b) Aggregate fruit
    c) Parthenocarpic fruit
    d) Multiple fruit
    Answer: c) Parthenocarpic fruit