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Adolescence-theory Biology-day-8 Target-ssc-cgl-2018

Adolescence-theory Biology-day-8 Target-ssc-cgl-2018

Adolescence-theory Biology-day-8 Target-ssc-cgl-2018


Human beings reproduce after a certain age. The phase in which the reproductive organs of human beings grow is called the adolescence. The phase before the adolescence is known as childhood. And after adolescence, the fully developed human is called an adult. Thus, in simple words, the time period between the childhood and adulthood is called adolescence. A person in the adolescence is called adolescent.


When a girl or a boy matures fully to reproduce, we say, the girl or the boy has reached the puberty. Puberty starts earlier in females than males. At puberty, many changes occur in the body of a boy and girl. All the changes at puberty are brought by various hormones.


  • Increase in height
  • Change in appearance and body shape
  • Voice change
  • Development of acne
  • Development of sex organs
  • Attaining mental, intellectual and emotional maturity


  • The sexual characteristics which are present at birth are called primary sexual characteristics. They include internal and external sex organs.
  • The sexual characteristics controlled by hormones but are not directly involved in reproduction are secondary sexual characteristics.
  • In males, hair grows on face, shoulders and chest broaden, deep voice and Adam’s apple develops. These changes are produced by a hormone called testosterone made in testes.
  • In females, breasts develop, hips broaden and a shrill voice. They are produced by a hormone called estrogen made in ovaries.


Hormones are made and secreted by specialised tissues. They are released directly into the blood and are carried by it throughout the body. They act on specific tissues in the body.

Gland secreting its product in tubes is called an exocrine gland and the gland secreting its product directly into the blood is called an endocrine gland.


  • In men the ability to produce sperms is throughout their life but it females it lasts only up to 45 to 50 years.
  • The bleeding from the uterus occurring in a woman every month is called menstruation.
  • The first occurrence of periods is called menarche.
  • The permanent stoppage of menses is called menopause.
  • The reproductive phase of women start at menarche and ends at menopause.


Chromosomes are present inside the nucleus of every cell. Human beings have 23 pairs of chromosomes in their normal body cells. Out of these one pair is called sex chromosomes which determine the sex of the off spring. XX chromosome is a girl and XY chromosome is a boy.


A female has only X chromosome in her eggs but a male has X as well as Y. If a sperm carrying X chromosome fertilises with the egg, it leads to a girl. If a sperm carrying Y chromosome fertilises with an egg then it is a boy.


There are various glands that secrets hormones other than sex hormones in the body. Various glands are….

Pituitary Gland : 

  • It is attached to the base of the brain.
  • Growth hormone is secreted by this gland. If there is a deficiency of growth hormone, height will not increase and the person becomes a dwarf. Also, if the hormone is secreted in excess, the person may become giant.
  • Pituitary gland is the master gland. It is called master gland because it secretes those hormones which helps other glands to secret other hormones.

Thyroid Gland :

  • It is present in the neck.
  • It makes thyroxine hormone which contains iodine. Thyroxine hormone controls the rate of metabolism.
  • A deficiency of iodine causes a deficiency of thyroxine hormone. Due to this, a person can suffer from a disease called goitre.
  • In frogs, thyroxine hormone helps in metamorphosis.

Pancreas  :

  • It is present below the stomach.
  • Pancreas secretes a hormone called insulin.
  • Deficiency of insulin causes diabetes.

Adrenal Glands :

  • There are two adrenal glands in our body and both are located on the top of each kidney.
  • It produces adrenaline hormone. This hormone prepares our body to function accordingly in emergency situations like fear, shock, surprise, excitement etc.
  • Adrenal gland also produces a hormone called aldosterone. This hormone balances the measure of salt in the blood.


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