NCERT Solutions for Class 8 Science Chapter 10 Reaching the age of adolescence

Q1. What is the term used for chemical secretions of endocrine glands responsible for changes taking place in the body?

Answer:

The hormone is the term used for chemical secretions of endocrine glands responsible for changes taking place in the body. Hormones are chemical substances. These are secretions from endocrine glands or endocrine system. These are responsible for changes taking place in the human body.

Q2. Define adolescence

Answer:

Adolescence : It is a period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence.

Adolescence is a period that begins around the age of 11 and lasts up to 18 or 19 years of age. This period covers the ‘teens’ (13 to 18 or 19 years of age), adolescents are also called ‘teenagers’.

In girls, adolescence may begin a year or two earlier than in boys. And the important thing is, this period of adolescence varies from person to person.

Q3. What is menstruation? Explain

Answer:

In the female body, the ova begin to mature with the onset of puberty (10 to 12 years of age). One of the ova matures and is released by the ovaries (once in 28-30 days). In this period, the wall of the uterus becomes thick so that it can receive the egg if it is fertilised  leading to pregnancy in the female. If the ovum is not fertilised, then the released egg and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women. This process is known as menstruation.

NCERT solutions for class 8 science chapter 10 reaching the age of adolescence

Q4. List changes in the body that take place at puberty.

Answer:

The list of changes that take place at the age of puberty are as follows-

1. Increase in height and weight of the body.
2. Widening of chest and shoulders in males. In females, the region below waist becomes wider.
3. At puberty, the voice box or the larynx becomes larger in males. This larger voice box in males is called Adam's apple. In females, the larynx is small in size.
4. Females develop a high pitched voice, whereas males develop a deep voice.
5. At puberty, there is growth of secondary sexual characters (underarms hair, beards and hair on skins) in males and females.
6. At puberty, the male and female reproductive organs become functional.
7. In males, the testes begin to produce sperms.
8. In females, there is an enlargement of ovaries and maturing of eggs. Menstruation also starts in females.

Q5. Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.

Answer:

Q6. What are sex hormones? Why are they named so? State their function.

Answer:

Sex Hormone- These are chemical substances produced by the sex organs of males and females.examples- Testosterone is a male sex hormone produced by the testis and estrogen is a female sex hormone produced by the ovary.

These hormones are secreted from humans' sex organs and they tend to affect the sexual features of the organism. This is the reason, they are names sex hormones.

Functions of sex hormones-

• The female hormone or estrogen which causes the development of breasts or mammary glands. Milk on which newborn babies feed develops inside these mammary glands. It also causes the development of sex organs.
• The male hormone testosterone brings about secondary sexual characters such as the growth of beard, hairs on the skin, development of sex organs.

Q7. Choose the correct option.

(a) Adolescents should be careful about what they eat, because
(i) A proper diet develops their brains.
(ii) A proper diet is needed for the rapid growth taking place in their body.
(iii) adolescents feel hungry all the time.
(iv) taste buds are well developed in teenagers.

Answer:

Adolescents should be careful about what they eat, because (ii)  proper diet is needed for the rapid growth taking place in their body.

Q7. Choose the correct option

(b) Reproductive age in women starts when their
(i) menstruation starts.
(ii) breasts start developing.
(iii) body weight increases.
(iv) height increases.

Answer:

(b) Reproductive age in women starts when their menstruation starts.

Menstruation is the initiation of the reproductive stage in the female.

Q7. Choose the correct option.

(c) The right meal for adolescents consists of
(i) chips, noodles, coke.
(ii) chapati, dal, vegetables .
(iii) rice, noodles and burger.
(iv) vegetable cutlets, chips and lemon drink.

Answer:

(c) The right meal for adolescents consists of (ii)  chapati, dal, vegetables.

Adolescents should consume a properly balanced diet to compensate for the rapid growth taking place in them.

NCERT solutions for class 8 science chapter 10 reaching the age of adolescence

Q8. Write notes on:

(a) Adam's apple

Answer:

Adam's apple-

At the age of puberty, the voice box or the larynx of humans begin to grow. In the case of boys, it develops larger voice boxes. The developing voice box in boys can be seen as a protruding part of the throat. this protruding part in boys is called Adam’s apple. In girls, the larynx is small in size so that it can barely visible from outside.

Q8. Write notes on-

(b) Secondary sexual characters

Answer:

Secondary sexual characters-

Those features that help to distinguish the male from the female are called their secondary sexual characters. These mostly include physical features that can be visualized in humans at the age of puberty.

Secondary sexual characters in boys include g rowing of mustaches and beard, the appearance of chest hair and also hair growth in the pubic region and other parts of the skin.

Secondary sexual characters in girls include an increase in breast size, growth of hair in the genital area and other parts of the skin.

Q8. Write notes on-

(c) Sex determination in the unborn baby.

Answer:

Sex determination of baby-

All humans have 46 number of chromosomes with 23 pairs. Out of these, two chromosomes, X & Y are the sex chromosomes. A female has two X and a male has one X and one Y chromosome. Female gamete ovum and male gamete sperm have possessed only one set of chromosomes. The unfertilized egg always has one X chromosome, however, sperms can have two different kinds of chromosomes. They can have either an X chromosome or a Y chromosome. When a sperm of X chromosome of male fertilizes the egg (X chromosome), the zygote would have two X chromosomes and develop into a female child. But if the sperm contains a Y chromosome and fertilizes with the egg (X chromosomes), the zygote would develop into a male child (XY).

Hence it is clear that the sex of an unborn baby is determined by the father's sex chromosomes.

Q9. Word game: Use the clues to work out the words.
Across
3. Protruding voice box in boys
4. Glands without ducts
7. Endocrine gland attached to brain
8. Secretion of endocrine glands
9. Pancreatic hormone
10. Female hormone
Down
1. Male hormone
2. Secretes thyroxine
3. Another term for teenage
5. Hormone reaches here through blood stream
6. Voice box
7. Term for changes at adolescence

Answer:

1. TESTOSTERONE
2. THYROID
3. ADOLESCENCE
4. ENDOCRINE
5. TARGET SITE
6. LYRINX
7. PITUITARY
8. HORMONE
9. INSULIN
10. ESTROGEN

NCERT solutions for class 8 science chapter 10 reaching the age of adolescence:

Q10 . The table below shows the data on likely heights of boys and girls as they grow in age. Draw graphs showing height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?

Answer:

The given graph depicts the relationship between age and height of the boys and girls during puberty. As per the graph, initially (4-8 years) the height in girls is less than that in boys. Girls of between 12 to 16 age group girls grows faster than boys and after a particular age, their height has become stable. Boys, on the other hand, shoes a sharp increase in height when they are 16.