reproduction

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Page 2: Asexual Reproduction

• Definition: Production of genetically identical offspring (clones) from one parent.

• Common in: Plants and some animals (e.g., starfish).

Advantages:

• Only one parent required.

• Rapid reproduction leads to large offspring numbers.

• Less energy needed for reproduction.

Disadvantages:

• Lack of genetic diversity.

• Increased extinction risk due to shared vulnerability to pathogens.

• Inability to adapt to environmental changes.

• Overpopulation and habitat overcrowding.

Page 3: Sexual Reproduction

• Definition: Requires two parents; offspring are genetically diverse.

• Process: Fusion of two gamete nuclei during fertilisation.

• Diploid cells (most body cells) vs. haploid cells (egg and sperm).

Advantages:

• High genetic diversity among offspring.

• Enhances survival through adaptation and evolution.

Disadvantages:

• Requires two parents; can be difficult in low population.

• Generally fewer offspring produced compared to asexual reproduction.

Page 4: Plant Reproductive System in Insect-Pollinated Flowers

• Sepals: Protect unopened flowers.

• Petals: Brightly colored to attract pollinators.

• Stamen: Male part; includes anthers and filaments.

  • Anthers: Produce pollen (male sex cells).

  • Filaments: Support anthers.

• Carpel: Female reproductive organ; includes ovary, stigma, and style.

  • Style: Path for pollen tubes.

  • Stigma: Collects pollen.

  • Ovary: Contains ovules (female sex cells).

Page 5: Wind-Pollination vs. Insect-Pollination

Wind-Pollination:

• Stigmas extend outside and are feathery for catching pollen.

• Anthers are external to release pollen easily.

Pollen Grains:

Page 6: Sexual Reproduction in Plants

• Pollination: Transfer of pollen from anther to stigma.

• Types: Cross-pollination and self-pollination.

• Cross-Pollination: More genetic diversity, higher resilience to diseases.

• Self-Pollination: Less energy required, doesn't depend on pollinators.

Structural Adaptations:

• Insect-Pollinated Flowers: Bright petals, sticky stigmas, nectar produced.

• Wind-Pollinated Flowers: Dull petals, feathery stigmas, lack of nectar.

Page 7: Fertilisation Process in Plants

1. Pollen lands on stigma.

2. Pollen tube grows if pollen matches species.

3. Pollen moves to ovule.

4. Fertilisation occurs (pollen nucleus + ovule nucleus).

5. Develops into a zygote.

Factors Affecting Seed Germination:

• Water: Absorbed, causing seed to swell.

• Oxygen: Required for respiration.

• Temperature: Affects enzyme activity; seeds dormant in winter.

Page 8: Male Reproductive System in Humans

• Testes: Produce sperm and testosterone.

• Scrotum: Contains testicles.

• Sperm Ducts: Transport sperm to urethra.

• Prostate Gland: Produces fluid that combines with sperm (semen).

• Urethra: Excretes urine and semen.

• Penis: Allows semen transfer and urine excretion.

Page 9: Female Reproductive System in Humans

• Ovaries: Develop egg cells; females have undeveloped eggs from birth.

• Oviducts: Transport eggs; fertilisation occurs here.

• Uterus: Where fetus develops.

• Cervix: Holds baby in place; separates uterus and vagina.

• Vagina: Receives penis during intercourse.

Page 10: Fertilisation in Humans

• Fusion: Sperm and egg cell nuclei fuse.

• Sperm Adaptations: Flagellum for movement, many mitochondria.

• Egg Characteristics: Larger, immobile, jelly coat prevents multiple fertilizations.

Comparing Male and Female Gametes:

Page 11: Development of the Foetus

• Umbilical Cord: Nutrient and waste exchange.

• Placenta: Nutrient exchange; produces hormones.

• Amniotic Sac: Surrounds foetus; produces protective fluid.

Nutrient Exchange:

• Nutrients (e.g., glucose, amino acids) from mother to foetus.

• Waste products (toxins) from foetus diffuse to mother.

Page 12: Sexual Hormones in Humans

• Testosterone: Influences male characteristics (muscle, voice).

• Oestrogen: Influences female characteristics (hips, breasts).

Menstrual Cycle:

• Occurs every 28 days; involves egg release and uterus preparation.

• Hormones Involved:

  • FSH: Stimulates egg development.

  • LH: Triggers egg release.

  • Progesterone: Maintains uterus lining.

  • Oestrogen: Regulates FSH and LH.

Page 13: Sexually Transmitted Infections (STIs)

• Definition: Transmitted via bodily fluids during sexual contact.

• Prevention: Abstinence, avoiding risky behaviors, using protection.

HIV:

• A type of STI affecting lymphocytes; leads to AIDS.

• Reduces immune function, making infection more likely and can be fatal.