Unit 6 – Reproduction

1. Sexual Reproduction in Flowering Plants

Flower Structure

• Flowers are the reproductive structures in angiosperms.
• Male Reproductive Part: Stamen (anther and filament).
• Female Reproductive Part: Carpel/Pistil (stigma, style, ovary).

Development of Gametophytes

1. Male Gametophyte:
• Pollen grains develop in the anther.
• Microspores undergo mitosis to form two cells: generative cell and vegetative cell.
2. Female Gametophyte:
• Ovules in the ovary develop into the embryo sac.
• The megaspore undergoes mitosis to form a 7-celled, 8-nucleate embryo sac.

Pollination

• Transfer of pollen from anther to stigma.
• Types:
• Self-pollination: Pollen from the same flower or plant.
• Cross-pollination: Pollen from another flower or plant.
• Agencies: Wind, water, insects, animals.

Outbreeding Devices

• Prevent self-pollination to promote genetic diversity (e.g., dichogamy, herkogamy).

Pollen-Pistil Interaction

• Chemical signaling between pollen and pistil ensures compatibility for fertilization.

Double Fertilization

• Unique to angiosperms.
• One sperm nucleus fuses with the egg (zygote formation), and the other fuses with polar nuclei (endosperm formation).

Post-Fertilization Events

1. Endosperm Development: Provides nutrition to the developing embryo.
2. Embryo Development: Zygote develops into an embryo.
3. Seed Formation: Ovule matures into a seed.
4. Fruit Formation: Ovary develops into a fruit.

Special Modes

• Apomixis: Seed formation without fertilization.
• Parthenocarpy: Fruit formation without fertilization (e.g., banana).
• Polyembryony: Formation of multiple embryos in a seed.

2. Human Reproduction

Male Reproductive System

• Organs:
• Testes (produce sperm and testosterone).
• Epididymis, vas deferens, seminal vesicles, prostate gland, and penis.
• Testes contain seminiferous tubules where spermatogenesis occurs.

Female Reproductive System

• Organs:
• Ovaries (produce ova and hormones like estrogen and progesterone).
• Fallopian tubes, uterus, cervix, and vagina.
• Ovaries contain follicles where oogenesis occurs.

Gametogenesis

1. Spermatogenesis:
• Occurs in seminiferous tubules.
• Spermatogonia → Primary spermatocyte → Secondary spermatocyte → Spermatids → Spermatozoa.
2. Oogenesis:
• Occurs in ovaries.
• Oogonia → Primary oocyte → Secondary oocyte → Ovum.

Menstrual Cycle

• Cyclic changes in the female reproductive system (~28 days).

1. Menstrual Phase (Day 1–5): Shedding of uterine lining.
2. Follicular Phase (Day 6–14): Follicle development; estrogen secretion.
3. Ovulatory Phase (~Day 14): Release of ovum from ovary.
4. Luteal Phase (Day 15–28): Corpus luteum secretes progesterone.

Fertilization and Implantation

1. Fertilization occurs in the fallopian tube when sperm fuses with the ovum to form a zygote.
2. Zygote undergoes cleavage to form a blastocyst, which implants into the uterine wall.

Pregnancy and Placenta Formation

• Placenta forms for nutrient and gas exchange between mother and fetus.
• Hormones like hCG maintain pregnancy.

Parturition and Lactation

1. Parturition: Process of childbirth; involves uterine contractions stimulated by oxytocin.
2. Lactation: Milk production by mammary glands due to prolactin; milk ejection is stimulated by oxytocin.

3. Reproductive Health

Need for Reproductive Health

• Ensures healthy reproductive functions and prevents sexually transmitted diseases (STDs).

Birth Control Methods

1. Natural Methods: Rhythm method, withdrawal method.
2. Barrier Methods: Condoms, diaphragms.
3. Hormonal Methods: Oral contraceptives, injectables.
4. Intrauterine Devices (IUDs): Copper-T, hormonal IUDs.
5. Surgical Methods: Vasectomy (male), tubectomy (female).

Medical Termination of Pregnancy (MTP)

• Legal termination of pregnancy under medical supervision to prevent complications or unwanted pregnancies.

Amniocentesis

• Prenatal diagnostic technique to detect genetic disorders by analyzing amniotic fluid.

Infertility and Assisted Reproductive Technologies (ART)

1. IVF (In Vitro Fertilization): Fertilization outside the body; embryo transferred to uterus.
2. ZIFT (Zygote Intrafallopian Transfer): Zygote transferred to fallopian tube.
3. GIFT (Gamete Intrafallopian Transfer): Gametes transferred to fallopian tube.

Key Diagrams

1. Structure of a flower showing male and female reproductive parts.
2. Human male reproductive system anatomy.
3. Human female reproductive system anatomy.
4. Spermatogenesis and oogenesis processes.

Summary

This unit explores reproduction in plants and humans along with reproductive health:

1. Sexual reproduction in flowering plants involves gametophyte development, pollination, double fertilization, seed/fruit formation, and special modes like apomixis and parthenocarpy.
2. Human reproduction includes gametogenesis, menstrual cycle, fertilization, pregnancy, parturition, and lactation processes.
3. Reproductive health emphasizes birth control methods, prevention of STDs, infertility treatments like IVF/ZIFT/GIFT, and awareness about MTP and amniocentesis.