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NCERT Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence:
NCERT Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence are the most important of class 8 science NCERT Solutions for the students not only for the CBSE exams but also for understanding the changes which are occurring just now in them because the age of the most students would be more than 12 years in class 8, this is the age of puberty in which changes starts in the body like hair starts to grow on the skin, the sound of boys become heavier, the girls sound become more shrilled and their period starts.
NCERT Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence
Study it in Hindi: कक्षा 8 विज्ञान अध्याय 10 का एनसीईआरटी सौल्युशन (हिन्दी में)किशोरावस्था की ओर
Q1.What is the term used for chemical secretions of endocrine glands responsible for changes taking place in the body?
Answer: The chemical secretions of endocrine glands which is responsible for changes taking place in the body is known as hormones.
Q2. Define adolescence.
Ans. The period between childhood to adulthood is known as adolescence which starts with the onset of puberty and ends at the stage of adulthood. Adolescence starts at the age of 11-12 years and ends at the age of 18 or 19 years which can vary from individual to individual in girls and boys.
Q3. What is menstruation? Explain
Ans. On reaching the age of puberty a female hormone estrogen released by the sexual part ovary that activates the uterus to prepare it for pregnancy, in this regard inner linings of the uterus is thickened due to the supply of blood in order to provide nutrition to the embryo but when pregnancy doesn’t occur these linings sheds and blood is released through the vagina since female experiences this every month it is that’s why known as a monthly cycle or menstruation.
Q4. List changes in the body that take place at puberty
Ans.At age of puberty which starts from 11-12 years in males and females due to the release of the female hormone estrogen and male hormone testosterone which results in the following changes in males and females.
a) Increase in height and weight.
b)Fats are deposited in some parts of the body, in girls, it is deposited in the thigh, buttock, and face, and in boys it is deposited around the shoulders.
c)Changes in body structures, in girls the hip broadens and the size of the breast increases and in boys pelvis becomes narrow and stronger.
f) Female voice becomes highly pitched and the male voice becomes low-pitched or deeper.
g)Size of sexual organs increases, in boys size of the testes and scrotum increases, and in girls size of the labia increases
h)Girls starts making egg cells and boy starts making sperm cells.
i)Hair grows on some body parts
Q5. Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.
| Endocrine glands | Hormones |
| Testis | Testosterone |
| Ovary | Oestrogen |
| Pituitary | Growth Hormone |
| Adrenal | Adrenaline |
| Thyroid | Thyroxine |
| Pancreas | Insulin |
Q6. What are sex hormones? Why are they named so? State their function
Ans. On achieving the age of puberty chemical substances are released by the female and male due to which the changes that occur in their body are known as sex hormones, in females estrogen is released by the ovary, and in males, testosteron is released by the testis.
These hormones are named so because they are responsible to develop male and female secondary sexual characteristics like enlargement of reproductive organs, growth of hair, change in voice, etc.
The function of Estrogen: Estrogen is responsibe to increase the size of breast in female,broaden the size of hip and growth of hair under the arm and around the vagina etc.
The function of Testosterone: Testosterone is responsible to increase the size of penes and testes, growth of hair on the face like a beard and mustache and around the testes, change in voice etc.
Q7.Choose the correct option.
(a) Adolescents should be careful about what they eat, because
(i) proper diet develops their brains.
(ii) 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.
(a) (ii) proper diet is needed for the rapid growth taking place in their body.
(b) Reproductive age in women starts when their
(i) menstruation starts.
(ii) breasts start developing.
(iii) body weight increases.
(iv) height increases.
(b)(i) menstruation starts.
(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.
(c)(ii) chapati, dal, vegetables.
Question 8.
Write notes on:
(a) Adam’s apple
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.
(a) Adam’s Apple: In boys, at the onset of puberty, the larynx (larynx) becomes larger and can be seen bulging out of the throat. This raised portion is known as the Adam’s Apple. In boys, the larynx enlarges under the influence of sex hormones. This increases the thickness and length of the vocal cords, making the voice hoarse. On the other hand, in women, the larynx becomes shorter and thinner. Therefore, the voice of girls tends to be higher pitched while that of boys tends to be lower pitched.
(b) Secondary sexual characteristics Those characteristics which usually appear from the onset of puberty are called secondary sexual characteristics. These are the characteristics that differentiate male and female bodies from each other.
characteristics seen in men: hoarseness of voice, appearance of beard, enlargement of chest, growth of pubic hair.
characteristics observed in females: voice deepening, onset of menstrual cycle, enlargement of breasts, growth of pubic hair.
(c) Sex determination in the unborn baby: The sex determination of the unborn baby depends on the pair of sex chromosomes present in the cells of the baby.
X and Y chromosomes are the sex chromosomes in humans. Females always have an X chromosomes in their egg, and males have an X chromosome and a Y chromosome in their sperm. When a sperm with an X chromosome fertilizes an egg, the zygote possess two X chromosomes and the zygote develops into a female child.
When a sperm with Y chromosome fertilizes the egg, the zygote has X and Y chromosomes and the zygote develops into a male child. That’s it , sex determination is determined by the chromosomes of the father.
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 the brain
8. Secretion of endocrine glands
9. Pancreatic hormone
10. Female hormone
Down
1. Male hormone
2. Secretes thyroxine
3. Another term for teenage
4. Hormone reaches here through the bloodstream
5. Voicebox
6. Term for changes at adolescence
Ans.
Across
1. Adam’s apple
2. Endocrine
3. Pituitary
4. Hormone
5. Insulin
6. Estrogen
Down
1. Testosterone
2. Thyroid
3. Adolescence
4. Target site
5. Larynx
6. Puberty
न
Direct and Indirect Narration rules Tenses wise and Sentences wise
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