JAMB Biology Note- Reproduction

Sub Topics

a. A sexual reproduction
i. Fission as in Paramecium
ii. Budding as in yeast
iii. Natural vegetative propagation
iv. Artificial vegetative propagation.
b. sexual reproduction in flowering plants
i. Floral parts and their functions
ii. Pollination and fertilization
iii. products of sexual reproduction
c. Reproduction in mammals
i. structures and functions of the male and female reproductive organs
ii. Fertilization and development. (Fusion of gametes)

Table of Contents

• Sub Topics
  • A. Asexual Reproduction
    • 1. Fission (e.g., Paramecium)
    • 2. Budding (e.g., Yeast)
    • 3. Natural Vegetative Propagation
    • 4. Artificial Vegetative Propagation
  • B. Sexual Reproduction in Flowering Plants
    • 1. Floral Parts and Their Functions
    • 2. Pollination and Fertilization
    • 3. Products of Sexual Reproduction
  • C. Reproduction in Mammals
    • 1. Structures and Functions of Male and Female Reproductive Organs
    • 2. Fertilization and Development
  • D. Modern Methods of Regulating Reproduction
  • Summary

A. Asexual Reproduction

Asexual reproduction involves only one parent, and offspring are genetically identical to the parent. It is a simple and rapid form of reproduction.

1. Fission (e.g., Paramecium)

• Process: In binary fission, the parent organism splits into two equal parts, each becoming a new individual.
• Example: Paramecium undergoes binary fission, where the nucleus divides by mitosis, followed by the division of the cytoplasm.

2. Budding (e.g., Yeast)

• Process: A new organism develops from an outgrowth or bud from the parent organism. The bud remains attached to the parent for a period before detaching.
• Example: Yeast reproduces by budding, where a small bud grows on the parent and eventually breaks off to form a new individual.

3. Natural Vegetative Propagation

• Process: Involves the growth of new individuals from vegetative parts such as roots, stems, and leaves.
• Examples:
  • Runner (e.g., strawberries),
  • Bulbs (e.g., onions),
  • Tubers (e.g., potatoes),
  • Rhizomes (e.g., ginger).

4. Artificial Vegetative Propagation

• Process: Humans use techniques like grafting, cutting, and layering to propagate plants.
• Examples:
  • Grafting: Joining parts from two different plants to grow as one (e.g., apple trees).
  • Cutting: Placing a part of a plant (like a stem) in soil to grow roots and form a new plant (e.g., rose).
  • Layering: Bending a branch to the ground to form roots and a new plant.

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B. Sexual Reproduction in Flowering Plants

Sexual reproduction involves the fusion of male and female gametes to form offspring.

1. Floral Parts and Their Functions

• Stamen: Male reproductive organ that produces pollen (which contains male gametes).
  • Anther: Produces pollen.
  • Filament: Holds the anther up to expose pollen.
• Pistil (Carpel): Female reproductive organ that produces the ovule.
  • Stigma: Receives pollen during pollination.
  • Style: Connects the stigma to the ovary.
  • Ovary: Contains ovules, which, when fertilized, develop into seeds.
• Petals: Attract pollinators.
• Sepals: Protect the flower bud before it opens.

2. Pollination and Fertilization

• Pollination: The transfer of pollen from the male anther to the female stigma.
  • Types:
    • Self-pollination: Pollen from the same flower or plant fertilizes the ovule.
    • Cross-pollination: Pollen from one plant fertilizes the ovule of another plant, increasing genetic diversity.
• Fertilization: The fusion of male and female gametes (sperm and egg) to form a zygote, which develops into a seed.

3. Products of Sexual Reproduction

• Fruits: Formed from the ovary after fertilization; they contain seeds.
• Seeds: Formed from the fertilized ovule and contain the embryo, which can grow into a new plant.

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C. Reproduction in Mammals

1. Structures and Functions of Male and Female Reproductive Organs

• Male Reproductive System:
  • Testes: Produce sperm and testosterone.
  • Epididymis: Stores sperm.
  • Vas deferens: Transports sperm to the urethra.
  • Penis: Delivers sperm into the female reproductive tract.
  • Seminal vesicles: Produce fluids that nourish sperm.
• Female Reproductive System:
  • Ovaries: Produce eggs (ova) and hormones (estrogen and progesterone).
  • Fallopian tubes: Transport eggs from the ovaries to the uterus.
  • Uterus: Where the embryo develops.
  • Cervix: The lower part of the uterus that opens into the vagina.
  • Vagina: The birth canal and the passage for sperm during intercourse.

2. Fertilization and Development

• Fertilization: The fusion of sperm from the male and egg from the female, resulting in the formation of a zygote.
• Embryonic Development: The zygote undergoes cell division and differentiation to form an embryo, which develops into a fetus. The fetus grows in the uterus, nourished by the placenta.
• Gestation: The period from fertilization to birth. In humans, it lasts about 9 months.

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D. Modern Methods of Regulating Reproduction

1. In-vitro Fertilization (IVF): A medical procedure where an egg is fertilized by sperm outside the body, and the resulting embryo is implanted in the uterus.
2. Birth Control Methods:
   • Contraceptive Pills: Hormonal methods to prevent pregnancy.
   • Condoms: A barrier method to prevent sperm from reaching the egg.
   • IUDs (Intrauterine Devices): Devices inserted into the uterus to prevent pregnancy.

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Summary

Reproduction is a fundamental biological process that ensures the continuity of species. Asexual reproduction allows organisms to reproduce without the need for a mate, while sexual reproduction involves the fusion of gametes to produce offspring. In plants, sexual reproduction involves pollination, fertilization, and the development of fruits and seeds. In mammals, sexual reproduction involves the male and female reproductive organs, fertilization, and embryonic development. Modern methods such as IVF and birth control allow for the regulation of reproduction.