Class 8 Science Chapter 7 Question Answers - Reaching the Age of Adolescence

Q1:What do you mean by health? What are the factors which help to keep a good health?
Ans. The physical and mental well-being of an individual is regarded as health.
The factors that help to keep good health:
(i) One should take a balanced diet.
(ii) One should care and keep personal hygiene.
(iii) Walking and playing in fresh air keeps the body fit and healthy.
(iv) All young boys and girls should take walks, exercise and play outdoor games to keep good health.
(v) Avoid the alcohol and tobacco.
(vi) Drink clean water, breathe in clean air and eat clean food. 

Q2: What are endocrine glands? Write the names of hormones and the functions of thyroid, pancreas and adrenal glands.
Ans.The glands which have no any duct to pour their secretions (hormones) into blood directly are called endocrine glands.

Thyroid: Thyroid is the endocrine gland. It secretes thyroxine hormone. If thyroid does not produce thyroxine, then thyroid glands increase in size and cause a disease called goitre.

Pancreas: Pancreas is also an endocrine gland which produces insulin hormone. If insulin is not produced sufficient then a person suffers from a disease called diabetes.

Adrenal: The hormone produced by adrenal gland is called adrenalin. This hormone maintains the correct salt balance in the blood. It also adjusts the body to stress when one is very angry, embarrassed or worried.

Q3:Explain the sex determination of a baby in human.
Ans. Inside the fertilised egg or zygote is the instructor for determination of sex of the baby.  All human beings have 23 pairs of chromosomes in the nuclei of their cells. Out of these chromosomes two chromosomes are the sex chromosomes: X and Y. 

• A female has two X chromosomes, while a male has one X chromosome and one Y chromosome.
• The eggs and sperms each contain only one set of chromosomes.
• An unfertilized egg will always have one X chromosome.
• Sperms come in two types: 
  • One type carries an X chromosome.
  • The other type carries a Y chromosome.
• If a sperm with an X chromosome fertilizes the egg, the resulting zygote will develop into a female child.
• If a sperm with a Y chromosome fertilizes the egg, the zygote will develop into a male child.

Q4: How do hormones work? Explain with the help of a flow chart.
Ans.

Q5:Adolescence is also a period of change in a person’s way of thinking. Justify the statement.  

Ans:

• Adolescents become more independent than they were before and often feel self-conscious.
• During this stage, intellectual development occurs, and teenagers spend a lot of time thinking.
• This period is when the brain has the greatest ability to learn.
• Teenagers may feel a stronger attraction to the opposite sex due to the release of sex hormones.
• They might also feel insecure while adjusting to the changes happening in their mind and body.
• It’s important for them to realize that these changes are a natural part of growing up.

Q7:Explain secondary sexual characters and roles of hormones in initiating reproductive function 

Ans: During puberty, many features develop in boys and girls that help to distinguish males from females, which is called secondary sexual character. 

During adolescence, boys experience various changes, including:

• Production of sperm
• Growth of facial hair (beards and moustaches)
• Increased body hair on the chest, underarms, and in the pubic area

Girls undergo different changes, such as:

• Production of ova
• Development of breasts
• Formation of mammary glands inside the breasts
• Growth of hair under the arms and in the pubic region. 

The changes that happen during adolescence are mostly controlled by hormones. 

• In boys, the changes like sperm production, facial hair growth, and body hair growth are due to the release of the male hormone testosterone, produced by testes.
• In girls, the changes such as ova production, breast development, and body hair growth result from the female hormone estrogen, produced by the ovaries. 

Q8: Explain changes occuring in human body at puberty. 

Ans: Changes during puberty are as follows:

1. There is an increase in height as well as mass in both boys and girls.

2. In boys, shoulders are broadened, chest is widened.

3. Voice becomes hoarse in boys.

4. In girls, the region below the waist becomes wider.

5. Body hair appears in areas such as underarms, face, hands, and legs.

6. Boys and girls may go through acne problems.

7. Testes grow and start producing sperms in males, whereas in females, the ovary enlarges and starts producing matured eggs.

8. Menstruation starts during the onset of puberty in girls.

Q9: Mention different types of glands, their functions and hormones secreted by them.

Ans: There are different types of glands in our body and they secrete different types of hormones which control groftoth, behaviour, development and reproduction. 
The following table shows different types of glands, hormones secreted by them and their functions:
Q10: Salma had a very soft and smooth skin during her childhood. As she entered adolescence, she developed pimples on her face, her body became taller compared to her face. She got worried of all of the sudden changes. Her mother explained that all these changes are normal and advised her to wash her face at regular intervals.

A) Why Salma’s mother advised Salma to wash her face at regular intervals?

B) What is the reason for appearance of pimples on her face?

C) Why Salma experienced disproportionate growth of the body?

D) What values do we get from this?

Ans: A) Regular face wash keeps the face clean, dry and oil free. This helps to reduce the pimples.

B) During adolescence, secretion of sweat glands and sebaceous glands increases leading to formation of acne and pimples.

C) During adolescence, all parts of the body do not grow at the same rate. Sometimes the arms and legs or hands and feet of adolescents look oversized and out of proportion with the body.

D) We must be self-aware, must take proper care and diet during the growing period, not get worried or lose our self-esteem.