Secondary Sexual Characters

key notes:

1. Definition of Secondary Sexual Characters

  • Secondary sexual characteristics refer to the physical traits that differentiate males and females of a species, but are not directly involved in reproduction.
  • These traits emerge during puberty as a result of hormonal changes.

2. Characteristics in Males and Females

  • In Males:
    • Deep voice: Due to the enlargement of the larynx (voice box).
    • Facial hair: Growth of beard and mustache.
    • Muscle development: Increase in muscle mass and strength.
    • Broad shoulders: Increased bone density and broadening of the shoulder region.
    • Body hair: Hair growth on chest, arms, and legs.
  • In Females:
    • Breast development: Growth of breasts due to the increased secretion of estrogen.
    • Wider hips: Pelvic bones widen for childbirth.
    • Increased fat distribution: More fat is stored in the hips, thighs, and breasts.
    • Menstruation: Start of menstrual cycle as a sign of fertility.
    • Softer skin and hair: Changes due to hormonal influence.

3. Hormonal Regulation

  • Estrogen: Responsible for the development of female secondary sexual characteristics.
  • Testosterone: Responsible for the development of male secondary sexual characteristics.
  • These hormones are secreted by the gonads (ovaries in females and testes in males) and cause physical changes during puberty.

4. Purpose of Secondary Sexual Characters

  • These characteristics are typically associated with attracting mates and ensuring reproductive success.
  • They signal to others that an individual is mature and capable of reproduction.

5. Difference from Primary Sexual Characters

  • Primary sexual characters are directly involved in reproduction (e.g., ovaries and testes).
  • Secondary sexual characters are physical traits that arise due to hormonal changes and distinguish males from females but do not directly play a role in reproduction.

6. Variation Across Species

  • In humans, these traits appear during puberty, typically between the ages of 10 and 15, but the exact age varies based on genetics and environmental factors.
  • Secondary sexual characteristics vary widely across species. For example, the peacock’s colorful feathers are a secondary sexual characteristic used to attract mates.

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