REPRODUCTION
जनन
Complete NCERT Guide for Class 12 Biology
NCERT-Based Content | CBSE | RBSE | Board Exam 2025-26
All Three Chapters with Summaries, Comparisons & Practice Questions
Unit Overview: Unit 6 carries 11 Marks (approx 16%) in the Board Exam. It connects the fundamental processes of life continuity across plants and humans, ending with social health aspects.
Sexual Reproduction in Flowering Plants 5 Marks
Chapter Overview
Explores the reproductive cycle of angiosperms, emphasizing the unique 'Double Fertilization' event where two male gametes participate in fusion.
🔑 Key Concepts (NCERT)
- Double Fertilization: Unique to angiosperms. Syngamy (formation of zygote) + Triple Fusion (formation of 3n Endosperm).
- Pollination Types: Autogamy (Self), Geitonogamy (Functionally cross, genetically self), Xenogamy (True cross).
- Outbreeding Devices: Mechanisms to prevent self-pollination (e.g., Self-incompatibility, Dichogamy, Unisexuality) to encourage genetic variation.
- Pollen-Pistil Interaction: A dynamic process involving pollen recognition followed by promotion or inhibition.
- Apomixis & Polyembryony: Formation of seeds without fertilization (Apomixis) and multiple embryos in one seed (Polyembryony).
📖 Full Chapter Link: Read Detailed Notes for Chapter 1
Human Reproduction 4 Marks
Chapter Overview
Details the human reproductive systems, gametogenesis (sperm & ovum formation), menstrual cycle, and embryonic development.
🔑 Key Concepts (NCERT)
- Gametogenesis: Spermatogenesis (continuous in males) vs Oogenesis (discontinuous in females).
- Menstrual Cycle: Regulated by LH, FSH, Estrogen, Progesterone. LH Surge causes Ovulation.
- Fertilization: Occurs in the Ampullary-Isthmic junction. Acrosome reaction is key.
- Placenta: Structural and functional unit between fetus and mother. Acts as an endocrine gland (hCG, hPL).
- Parturition & Lactation: Childbirth reflex (Fetal Ejection Reflex). Initial milk Colostrum contains IgA antibodies essential for newborn immunity.
📖 Full Chapter Link: Read Detailed Notes for Chapter 2
Reproductive Health 2 Marks
Chapter Overview
Focuses on social aspects of reproduction: population control, contraception, STIs, and infertility treatments.
🔑 Key Concepts (NCERT)
- Contraceptive Methods: Condoms (protect from STIs), IUDs (CuT, LNG-20), Oral Pills (Saheli - non-steroidal, once a week).
- MTP Amendment Act 2017: Legal abortion up to 12 weeks (1 doctor's opinion) and 12-24 weeks (2 doctors' opinion) for specific cases.
- STIs: Infections like Syphilis, Gonorrhea. Hepatitis-B, Genital Herpes and HIV are incurable; others are curable if treated early.
- ART (Infertility): IVF-ET (Test tube baby), ZIFT (Zygote transfer), IUT (Embryo >8 cells), GIFT, ICSI.
- Amniocentesis: For detecting genetic disorders, but legally banned for sex determination.
📖 Full Chapter Link: Read Detailed Notes for Chapter 3
Comparative Analysis Table
| Feature | Chapter 1 (Plants) | Chapter 2 (Humans) |
|---|---|---|
| Gametes | Pollen Grain, Egg Cell | Sperm, Ovum |
| Fertilization | Double Fertilization (Syngamy + Triple Fusion) | Single Fertilization (Sperm + Ovum) |
| Site | Embryo Sac (Ovule) | Fallopian Tube |
| Product | Seed & Fruit | Fetus & Baby |
| Nutrition | Endosperm (3n) | Placenta (Maternal connection) |
Practice Questions (Board Pattern)
Q1. Colostrum is rich in which antibody?
- (A) IgG
- (B) IgA ✓
- (C) IgM
- (D) IgE
Q2. Under MTP Act 2017, abortion is legal up to 24 weeks with the opinion of:
- (A) One Doctor
- (B) Two Doctors ✓
- (C) Three Doctors
- (D) Not permitted
Q3. Which of the following is an outbreeding device?
- (A) Cleistogamy
- (B) Homogamy
- (C) Self-incompatibility ✓
- (D) Bud pollination
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