Question

Write notes on—
1. Adam’s apple.
2. Secondary sexual characters.
3. Sex determination in the unborn baby.

Answer 1

(a) Adam’s apple: The protruding part of the throat is called Adam’s apple. It is the enlarged voice box or larynx which gets enlarged and visible from outside in boys at the onset of puberty. This makes the voice of boys hoarse.

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(b) Secondary sexual characters: Secondary Sexual Characters are those characters which distinguish a male from female. Some of the characters are as follows:
Boys:

• Facial hairs such as beard and moustaches develop.
• Hair develops under the armpit, under chest and in the pubic regions.
• Voice becomes deeper.
• Muscles develop, and shoulder becomes broad.
• Increase in weight.

Girls:

• Development and enlargement of breasts.
• Hair develops under the armpit and in the pubic regions.
• Hips broaden and pelvic region widens.
• Initiation of menstrual cycle.
• Deposition of fat around hips.

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(c) Sex determination in the unborn baby: All human beings have 23 pairs of chromosomes in the nuclei of their cells. Out of these two chromosomes are the sex chromosomes, named X and Y. A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes (egg and sperm) have only one set of chromosomes. The unfertilised egg always has one X chromosome but sperms may have X or Y. When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilisation, the zygote would develop into a male child. This concludes that the sex chromosomes of the father determine the sex of an unborn baby.