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:-
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’ 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 mensuration? Explain.
Answer:-
In the female body, the ova begins 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 linning of the uterus along with its blood vessels are shed off. The cause bleeding in women. This process is known as mensuration.
Q4. List changes in the body that take place at puberty.
Answer:-
The list of changes that take place at the age of puberty area s follows-
- Increase in height and weight of the body.
- Widening of chest and shoulders in males. In females , the region below waist becomes wider.
- At puberty , the voice box or the larynx becomes large in males. This larger voice box in males is called Adam’s apple. In females , the larynx is small in size.
- Females develops a high pitched voice, whereas males develops a deep voice.
- At puberty there is the growth of secondary sexual character in males and females.
- At puberty , the male and female reproductive organs become functional.
- In males, the testes begin to produce sperms.
- In females, there is a enlargement of ovaries and maturing of eggs.
Q5. Prepare a Table having two columns depicting names if endocrine glands and hormones secreted by them.
Answer:-
| Endocrine Glands
1. Testis 2. Ovary 3. Thyroid 4. Pancreas 5. Pituitary 6. Adrenal |
Hormones
1. Testosterone 2. Oestrogen 3. Thyroxine 4. Insulin 5. Growth hormone 6. Adrenalin |
Q6. What are sex hormone ? Why are they named so? State their function.
Answer:-
Sex hormone – These are chemical substances produced y the sex organs of males and females. Example – 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 human sex organs and they tend to affect the sexual features of the organisms . This is the reason, they are names sex hormones.
Function of the hormones-
- The female hormone or estrogen which cause 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 character such as the growth of bears , hairs on the skin development of sex organs.
Q7. Choose the correct option.
- Adolescents should be careful about what they eat, because
- A proper diet develops their brains.
- A proper diet is needed for the rapid growth taking place in the their body.
- Adolescents feel hungry all the time.
- Taste buds are well developed in teenagers.
- Reproductive age in women starts when their
- Mensuration starts.
- Breasts start developing.
- Body weight increases
- height increases
( c ) The right meal for adolescents consists of
- Chips, noodles coke.
- Chapati , dal , vegetables.
- Rice, noodles and burger.
- Vegetable cutlets chips and lemon drink.
Answer:-
- (ii) A proper diet is needed for the rapid growth.
- (i) Mensuration starts.
- (ii) Chapati,dal,vegetables.
Q8. Write a short note on:
- Adam’s Apple
Answer:-
At the age of puberty, the voice box or the larynx of humans begins 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 parts in boys is called Adam’s apple. In girls, the larynx is small in size so that it can barely visible from outside.
- Secondary sexual characters-
Answer:-
Those features that help to distinguish the male from the female called their secondary sexual characters These mostly include physical features that can be visualize in humans at the age of puberty.
Secondary sexual character in boys include growing of moustaches and beard, the appearance of chest hair and also hair growth in the public region and other parts of the skin.
Secondary sexual character in girls include an increase in breast size growth of hair in the genital area and other parts of the skin.
( c ) Sex determination of baby:-
All humans have 46 number of chromosomes with 23 pairs Out of these , two chromosomes , X and Y are the sex chromosomes A female has two X and male has one X and Y chromosomes. Female gametes ovum and male gamete sperm have possessed only one set of chromosomes. The unfertilized egg always has one X chromosomes , however, sperms can have two different different kinds of chromosomes. They can have either an X chromosomes or a Y chromosomes Whe a sperm of X chromosomes of male fertilizers the egg ( X chromosomes) the zygote would have two X – chromosomes and develop into a female child. But if the sperm contains a Y – chromosomes and fertilizes with the egg (X chromosomes) the zygote would develop into a male child. (XY).
Q9. Word game: Use the clues to work out the words.
Across
- Protruding voice box in boys boys
- Glands without ducts
- Endocrine gland attached to brain
- Secretion of endocrine glands
- Pancreatic hormone
- Female hormone
Down
- Male hormone
- Secrets thyroxine
- Another term for teenagers
5.Hormone reaches here through blood stream
- Voice box
- Term for changes at adolescence
Answer:-
- Testosterone
- Thyroid
- Adolescence
- Endocrine
- Target Site
- Lyrinx
- Pituitary
- Hormone
- Insulin
- Estrogen
Q10. The table below shows the data on likely heights of boys and girls as they grow in age. Draw a graph showing height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?
| Age ( Years) | Height |
| 0 | Boys Girls |
| 4 | 53 53 |
| 8 | 96 92 |
| 12 | 114 110 |
| 16 | 129 133 |
| 20 | 173 165 |
