Sexual Reproduction

Key Notes :

Definition:

Sexual reproduction is a biological process in which two parents contribute genetic material to produce offspring, ensuring genetic diversity.

Key Features:

  1. Two Parents: Involves a male and a female organism.
  2. Gametes:
    • Male gamete: Sperm (in animals) or Pollen grains (in plants).
    • Female gamete: Egg or Ovule.
  3. Fertilization: The fusion of male and female gametes to form a zygote.
  4. Genetic Variation: Offspring inherit traits from both parents, leading to diversity.

Process of Sexual Reproduction:

  1. Gamete Formation:
    • Male and female gametes are formed in specialized reproductive organs.
    • Examples:
      • Animals: Testes (male) and ovaries (female).
      • Plants: Anthers (male) and ovules (female).
  2. Fertilization:
    • External fertilization: Occurs outside the body (e.g., in frogs).
    • Internal fertilization: Occurs inside the body (e.g., in humans).
  3. Zygote Development:
    • The zygote divides and differentiates to form an embryo.
    • In plants, the zygote develops into a seed.
  4. Growth:
    • The embryo grows into a new organism with traits from both parents.

Sexual Reproduction in Animals:

  1. Examples: Humans, mammals, birds, reptiles, etc.
  2. Male Reproductive System:
    • Testes produce sperm.
    • The sperm is transported through reproductive ducts.
  3. Female Reproductive System:
    • Ovaries produce eggs.
    • Fertilization occurs in the oviduct (fallopian tube in humans).
  4. Development: The embryo grows in the uterus in mammals.

Sexual Reproduction in Plants:

  1. Flower Structure:
    • Stamen: Male part; produces pollen.
    • Carpel: Female part; contains ovary with ovules.
  2. Pollination:
    • Transfer of pollen from stamen to carpel.
    • Types:
      • Self-pollination: Pollen lands on the same flower.
      • Cross-pollination: Pollen transferred between different flowers.
  3. Fertilization:
    • Pollen reaches the ovule, and fertilization occurs.
  4. Seed Formation: The fertilized ovule develops into a seed.

Importance of Sexual Reproduction:

  1. Promotes genetic variation, enabling adaptation to environmental changes.
  2. Reduces the risk of genetic disorders.
  3. Ensures species survival over generations.

Examples:

  • Animals: Humans, cats, frogs, and fish.
  • Plants: Sunflowers, mango trees, and roses.

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