reproduction

Page 1

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:

Aspect

Wind-Pollinated

Insect-Pollinated

Size

Smaller

Larger

Weight

Lighter

Heavier

Quantity

More grains produced

Fewer grains

Surface Characteristics

No spikes/hooks

Have spikes/hooks

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:

Aspect

Sperm

Egg

Size

Very small

Large

Structure

Nucleus, mitochondria, flagellum

Round, jelly coat

Motility

Mobile

Immobile

Quantity

Millions released daily

One released monthly

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.