NEET Biology: Sexual Reproduction in Flowering Plants One Shot Notes 2027 | Class 12 Chapter 1| NCERT + PYQ

*Sexual Reproduction in Flowering Plants - Notes with Diagram*

*1. Main Reproductive Organ: Flower*  

The flower has male and female parts for sexual reproduction.

*Diagram: L.S. of a Flower*

        Stigma

          |

Anther ---|--- Style

   |      |

Filament  | Ovary --> contains Ovules

   |      |

Stamen    Carpel/Pistil

(Male)    (Female)

        Sepals

        Petals

      Receptacle

         |

       Pedicel

*Label Description:*  

- *Stamen*: Male part. Has *Anther* + *Filament*. Anther makes pollen grains. Pollen grain contains male gametes.  

- *Carpel/Pistil*: Female part. Has *Stigma, Style, Ovary*. Ovary contains *Ovules*.  

- *Ovule*: Has *Embryo sac* inside. Embryo sac = 7-celled, 8-nucleate structure. Contains egg cell = female gamete.

---

*2. Key Steps of Sexual Reproduction*

*Step 1: Pollination*  

Transfer of pollen grains from anther to stigma.  

- *Self-pollination*: Same flower or same plant.  

- *Cross-pollination*: Different plant. Agents: wind, water, insects, birds, animals.  

*Step 2: Pollen Germination*  

*Diagram: Fertilization Process*

Pollen grain on Stigma

        |

        ↓ grows

   Pollen tube

        |

        ↓ through Style

        |

        ↓ enters Ovary

        |

        ↓ reaches Ovule

Male gametes → released in Embryo sac

Pollen grain on stigma absorbs sugar + water → forms *pollen tube*. Tube grows through style and enters ovule through micropyle.

*Step 3: Double Fertilization* - Only in Angiosperms  

One pollen grain has 2 male gametes.  

1. *Syngamy*: Male gamete + Egg → *Zygote* (2n) → develops into embryo.  

2. *Triple Fusion*: Second male gamete + 2 polar nuclei → *PEN* (3n) → develops into *Endosperm*. Endosperm gives nutrition to embryo.

*Diagram: Embryo Sac After Double Fertilization*

Antipodals (3 cells) → degenerate later

Central cell + Male gamete → Endosperm (3n)

Egg + Male gamete → Zygote (2n) 

Synergids (2 cells) → degenerate

*Step 4: Post-Fertilization Changes*

Before Fertilization After Fertilization

Ovule Seed

Ovary Fruit

Zygote Embryo

PEN Endosperm

Ovary wall Pericarp

Integuments Seed coat

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*3. Why Sexual Reproduction?*  

1. *Variation*: Offspring are genetically different from parents. Helps in survival.  

2. *Evolution*: New characters help in adaptation.  

3. *Seed dispersal*: Seeds can remain dormant and spread far.

*4. Quick Revision Formula*  

*P.F.S.F* = *P*ollination → *F*ertilization → *S*eed → *F*ruit

*5. Important Terms*  

- *Gametogenesis*: Formation of gametes.  

- *Microsporogenesis*: Pollen formation in anther.  

- *Megasporogenesis*: Embryo sac formation in ovule.  

- *Parthenocarpy*: Fruit formation without fertilization. Ex: Banana.

You can draw these 2 simple diagrams in exam:  

1. L.S. of Flower  

2. Fertilization showing pollen tube + double fertilization  

*5 Unique Questions - Sexual Reproduction in  flowering Plants*

*Q1. Imagine a flower undergoes Double Fertilization but Pollination never happened. What will happen?*  

*Answer*: Nothing will happen. Without pollination, pollen won't reach the stigma, so no pollen tube forms. Fertilization can't occur. So seed and fruit formation is impossible.

*Q2. Both Gymnosperms and Angiosperms produce seeds, then why are Angiosperms considered more evolved?*  

*Answer*: Because Angiosperms have: 1. Flowers that help in pollination, 2. Double Fertilization which forms endosperm for immediate nutrition to the embryo, 3. Seeds are protected inside fruits. Gymnosperms have naked seeds and no fruit.

*Q3. In P.F.S.F, if we remove 'S' and 'F', what is the biggest loss for the plant?*  

*Answer*: P.F.S.F = Pollination → Fertilization → Seed → Fruit. If Seed and Fruit are removed, the new plant won't form after fertilization. The species can't continue. Seeds are essential for dispersal and dormancy.

*Q4. If insects suddenly disappeared, name 3 major effects on plants that depend on insect pollination.*  

*Answer*: 1. Plants that rely only on insect pollination will stop producing seeds, 2. Genetic variation will reduce because self-pollination will increase, 3. Fruit production will drop, causing food scarcity.

*Q5. The embryo sac is 7-celled, 8-nucleate. If it becomes 6-celled, how will fertilization be affected?*  

*Answer*: Embryo sac has 1 egg cell, 2 synergids, 3 antipodals, and 1 central cell with 2 polar nuclei. If 1 cell is missing, Double Fertilization will be incomplete. Either the zygote won't form or endosperm won't form. If either is missing, the seed won't develop properly.