This lesson explores reproduction, the fundamental process by which organisms create offspring, ensuring the survival of their species. It covers both plant and human reproduction.

1. Short Notes: Core Concepts

A. Types of Reproduction

B. Plant Reproduction

1. Asexual (Vegetative Propagation): Creating new plants from parts of the parent plant.

   • Natural Methods:

     • Underground Stems: Ginger (rhizome), Potato (tuber), Onion (bulb).

     • Runners: Stems that run along the ground (e.g., Gotukola).

     • Suckers: New shoots from the base (e.g., Banana, Pineapple).

     • Leaves: New plants grow from leaves (e.g., Akkapana).

   • Artificial Methods:

     • Cuttings: Planting a piece of stem (e.g., Rose, Shoe flower).

     • Layering: Rooting a branch while it's still attached to the parent plant.

     • Grafting: Joining a scion (twig/bud) onto a stock (rooted plant).

     • Tissue Culture: Growing a whole plant from a tiny piece of tissue in a lab.

2. Sexual Reproduction in Plants: Involves the flower.

   • Parts of a Flower:

     • Calyx (Sepals): Outer green leaves that protect the bud.

     • Corolla (Petals): Often colourful to attract pollinators.

     • Androecium (Stamen): Male part; consists of anther (produces pollen) and filament.

     • Gynoecium (Pistil): Female part; consists of stigma (receives pollen), style, and ovary (contains ovules/eggs).

   • Pollination: The transfer of pollen from the anther to the stigma.

     • Self-Pollination: Pollen transfer within the same flower.

     • Cross-Pollination: Pollen transfer between different flowers.

     • Agents: Wind, water, insects, birds. Flowers have adaptations (e.g., bright petals, nectar for insects; light pollen, feathery stigmas for wind).

   • Fertilization: The fusion of the male gamete (from pollen) with the female gamete (ovule).

   • After Fertilization: The ovary develops into the fruit, and the ovules develop into seeds.

   • Seed Dispersal: Spreading seeds away from the parent plant (by wind, water, animals, explosion) to reduce competition.

C. Human Reproduction

1. Puberty: The stage when a person becomes sexually mature. Secondary sexual characteristics appear (e.g., voice deepening in males, breast development in females).

2. Male Reproductive System: Produces sperm in the testes. Sperm travels through the vas deferens and is released through the penis.

3. Female Reproductive System: Produces ova (eggs) in the ovaries. An egg travels down the fallopian tube to the uterus.

4. Menstrual Cycle: A ~28-day cycle in females.

   • Ovulation: Around day 14, an ovary releases an egg.

   • Uterine Lining: The wall of the uterus thickens to prepare for a potential pregnancy.

   • Menstruation: If fertilization doesn't occur, the uterine lining breaks down and is discharged.

5. Fertilization & Implantation: If sperm meets the egg in the fallopian tube, fertilization occurs, forming a zygote. The zygote divides and travels to the uterus, where it implants in the uterine wall.

6. Pregnancy & Birth: The embryo develops in the uterus for about 9 months, receiving nutrients from the mother via the placenta and umbilical cord. Birth (parturition) is the process of the baby being pushed out of the uterus.

D. Sexually Transmitted Diseases (STDs)

• Diseases spread through sexual contact. Examples include Gonorrhoea, Syphilis, and AIDS (caused by the HIV virus).

2. Tips & Tricks for the Exam

• Diagrams are Crucial: You must be able to draw and label the parts of a flower and the male/female reproductive systems.

• Know the Flow: Trace the path of pollen from anther to ovule in plants. Trace the path of sperm from testes to the egg in humans.

• Compare and Contrast: Be ready to list differences between sexual/asexual reproduction, self/cross-pollination, and wind/insect pollinated flowers.

• Menstrual Cycle Graph: Understand what happens to the uterine wall and hormones (Oestrogen, Progesterone) during the cycle. The peak of hormones around day 14 is linked to ovulation.

3. Important Points & Common Exam Questions

• Label the Flower: A diagram of a flower will be given, and you'll be asked to label the stigma, anther, ovary, and petals.

• Adaptations for Pollination: "List two features of a flower that is pollinated by insects."

  • Answer: Brightly coloured petals, has nectar.

• Vegetative Propagation: "Name a plant that can be propagated by a stem cutting."

  • Answer: Rose / Shoe flower.

• Human Reproduction: "Where does fertilization take place in the human female reproductive system?"

  • Answer: In the fallopian tube.

• Menstrual Cycle: "What happens to the uterine wall during the first few days of the menstrual cycle if fertilization has not occurred?"

  • Answer: It breaks down and is discharged (menstruation).