Class 8 Science

Sex Deteremination

There are many people who blame a woman on the birth of a girl child, because such people think that a woman is responsible for the gender of a child. But the fact is that there is fifty fifty chance of a baby to be a boy or a girl. Let us understand the scientific basis of sex determination in humans.

How is Gender of a Child Determined

Gender of a child is determined by the combination of chromosomes in the zygote. A normal cell in human beings has 46 chromosomes, i.e. 23 pairs of chromosomes. Out of them, chromosomes in 22 pairs are identical. But chromosomes in the 23rd pair may be identical or different.

There are two types of chromosomes in 23rd pair. They are called X and Y chromosomes. The 23rd pair in a male has XY combination, while that in a female has XX combination.

Gametes in humans have 23 chromosomes, i.e. half the number in somatic cells. So, a sperm may have X or Y chromosome as 23rd chromosome. But, an ovum has X chromosome as 23rd chromosome.

Sex Determination in Humans

Hormone other than Sex Hormones

Endocrine GlandHormoneFunction
PituitaryGrowth hormoneNormal growth of body
ThyroidThyroxinNormal metabolism
PancreasInsulinGlucose metabolism
AdrenalAdrenalinPrepares the body for a fight or flight like situation.

Goiter: This disease happens due to iodine deficiency. Iodine deficiency results in less production of thyroxin. This may result in a disease called goiter which is manifested by a permanent swelling in the neck.

Diabetes: Less insulin secretion results in a disease called diabetes. In common language, this disease is called blood sugar. There are two types of diabetes, viz. insulin dependent and non-insulin dependent. As the name suggest, a person suffering from insulin dependent diabetes needs to regularly take insulin injections.

Role of Hormone in Completing the Life Cycle of insects and frogs

Reproductive Health

Balanced Diet

Rapid growth during adolescence necessitates balanced diet. A teenager should take adequate amount of carbohydrates, protein, fat, vitamins and minerals in food. One should avoid eating fried food and junk food. Girls need to take lot of iron-rich food because iron is necessary for formation of RBCs.

Personal Hygiene

You have read that sweat and sebaceous glands show increased activity during this period. If proper hygiene is not maintained, it can lead to many skin diseases in adolescents. Girls need to take special care of hygiene during menstrual period.

Physical Exercise

Physical exercise is helpful not only in making a strong body but also in properly utilizing your energy. A good workout ensures all your systems are working in perfect condition.

Say NO to Drugs

The menace of drugs is spoiling many a life. During this period, one can easily get influenced and carried away by negative stimulations. You need to have a strong will power to say NO to drugs. Addiction to drugs will destroy your career and life.

HIV (Human Immunodeficiency Virus)

This is a virus which causes AIDS (Acquired Immunodeficiency Disease). Till date, there is no cure for this disease. Hence, prevention is the only way to keep away from this dangerous disease. AIDS can spread through sexual contact, through infected needles and from a mother to her unborn child. This can also be transmitted to an infant through mother’s milk.