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 📚 Chapter: Principles of Inheritance and Variation – Class 12 Biology Notes --- 🔸 1. Introduction Genetics is the branch of biology that deals with heredity and variation. Heredity: Transmission of characters from parents to offspring Variation: Differences among individuals --- 🔹 2. Mendel and His Experiments Gregor Mendel is known as Father of Genetics He worked on garden pea (Pisum sativum) He selected 7 contrasting traits like tall/dwarf, round/wrinkled etc. --- 🔹 3. Mendel’s Laws of Inheritance a) Law of Dominance Dominant allele expresses itself in F₁ generation b) Law of Segregation Alleles separate during gamete formation c) Law of Independent Assortment Genes for different traits assort independently --- 🔹 4. Monohybrid Cross One trait considered Genotypic ratio: 1:2:1 Phenotypic ratio: 3:1 --- 🔹 5. Dihybrid Cross Two traits considered Phenotypic ratio: 9:3:3:1 --- 🔹 6. Incomplete Dominance F₁ is intermediate Example: Red × White flower = Pink (in Snapdragon) --- ?...

 📚 Chapter: Reproductive Health – Class 12 Biology Notes --- 🔸 Introduction: Reproductive health means a complete physical, emotional, and social well-being in all aspects of reproduction. It includes awareness, safe practices, and control over fertility. --- 🔹 1. Need for Reproductive Health To prevent sexually transmitted infections (STIs) To reduce maternal and infant mortality To control population growth To educate people about sex and contraception --- 🔹 2. Reproductive Health Programmes in India Started in 1951 (RCH Programme) Objectives: Family planning Safe motherhood Adolescent health Prevention of STDs --- 🔹 3. Birth Control Methods a) Natural Methods: Rhythm method (safe period) Withdrawal Lactational Amenorrhea (up to 6 months) b) Barrier Methods: Condoms (male & female) Diaphragms, Cervical caps c) Intrauterine Devices (IUDs): Non-medicated (Lippes loop) Copper releasing (Cu-T) Hormone releasing (Progestasert) d) Oral Contraceptives: Pills containing estrogen...

 📚 Chapter: Human Reproduction – Class 12 Biology Notes --- 🔸 Introduction: Human reproduction is sexual reproduction involving the fusion of male and female gametes. This chapter covers reproductive organs, gamete formation, menstrual cycle, fertilisation and pregnancy. --- 🔹 1. Male Reproductive System Primary organs: Testes (sperm production) Accessory ducts: Epididymis, Vas deferens, Urethra Glands: Seminal vesicles, Prostate, Bulbourethral External genitalia: Penis Spermatogenesis: Formation of sperm in seminiferous tubules Hormone control: FSH, LH, Testosterone --- 🔹 2. Female Reproductive System Primary organs: Ovaries (ovum production) Ducts: Fallopian tubes, Uterus, Cervix, Vagina External genitalia: Vulva Oogenesis: Formation of ovum Hormone control: Estrogen, Progesterone, FSH, LH --- 🔹 3. Menstrual Cycle Average duration: 28 days Phases: 1. Menstrual phase (1-5 days) 2. Follicular phase (6–13 days) 3. Ovulation (Day 14) 4. Luteal phase (15–28 days) Controlled by ho...