Chapter 10: Cell – Reaching the age of Adolescence

Science

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  Chapter 10: Cell – Reaching the age of Adolescence

  Class: VIII

  Exemplar Solutions 

MULTIPLE CHOICE QUESTIONS

Question 1

The belief that the mother is completely responsible for the sex of the child is wrong because the child

(a) gets sex chromosome only from the mother.

(b) develops in the body of the mother.

(c) gets one sex chromosome from the mother and the other from the father.

(d) gets sex chromosome only from the father.

Answer 1 (c)

Question 2

 AIDS can spread from an infected person to another person through

(a) sharing food  (c) sharing comb

(b) blood transfusion  (d) a mosquito bite

Answer 2 (b)

Question 3

 Given below are events that lead to pregnancy and development of embryo.

• Fertilization of egg
• Maturation of egg
• Release of egg
• Embedding of embryo in thickened uterine wall.

Which of the following options gives the correct order of sequence in which they occur?

 (a) i, ii, iii, iv,  (b) ii, i, iii, iv

(c) i, iv, ii, iii  (d) ii, iii, i, iv.

Answer 3 (d)

 

Question 4

For the metamorphosis of tadpoles which of the following elements must be available in water?

(a) chlorine   (c) sulphur

(b) carbon   (d) iodine

Answer 4 (d)

Question 5

 The most conspicuous visible change that occurs in boys during puberty is:

 (a) development in voice box.

(b) increase in height.

(c) production of sperms.

(d) increased sweating.

Answer 5 (b)

Question 6

Structures present in a cell which is responsible for determination of the sex of a baby is

(a) cytoplasm   (c) nucleus

(b) cell membrane   (d) chromosome

Answer 6 (d)

 

 VERY SHORT ANSWER QUESTIONS

Question 7

 Unscramble the underlined words in the following sentences.

(a) Reproductive life of a woman lasts from hacreemn to spauoemen.

(b) The development of a caterpillar to an adult butterfly is termed as poommertaissh.

 (c) The overgrowth of sumselc in xalnyr leads to the hoarse voice in adolescent boys.

(d) Dannalier helps the body to adjust and fight the stress.

 

Answer 7

(a) menarche, menopause  (b) metamorphosis

(c) muscles, larynx  (d) Adrenalin

Question 8

Complete the following sentences.

 (a) In females, the uterine wall thickens to receive the __________.

 (b) Endocrine glands release hormones directly into___________for transportation to the __________.

(c) The sex hormones,_______________________ and estrogen are responsible for the development of __________ characters.

 (d) Release of sex hormones is under the control of a hormone secreted from the __________.

Answer 8

(a) fertilised egg.

(b) blood stream, target site.

(c) Testosterone, estrogen, secondary sexual.

(d) pituitary gland.

Question  9

 Give a suitable word for each of the following statements.

 (a) The site which responds to a hormone.

(b) Name of a gland which transports secretions through ducts.

(c) Chemicals which control changes at adolescence stage.

 (d) It marks the beginning of reproductive period.

Answer 9

(a) Target site

(b) Sweat glands/salivary glands/oil glands (any one)

 (c) Hormones

(d) Puberty

Question 10

 Name the hormone that is released by testes at the onset of puberty.

Answer 10

Testosterone.

Question 11

 Name the female hormone produced by ovaries that helps in development of mammary gland.

Answer 11

Estrogen.

SHORT ANSWER QUESTIONS

Question 12

 Match the hormones given in Column A with their deficiency disease given in Column B.

Answer 12

a-i; b-iv; c-ii; d-i.

Question 13

 Lila always eats only dal and rice in every meal. She often falls ill and has become prone to diseases. Can you suggest changes in her diet which can make her healthy and free from disease?

Answer 13

Lila’s diet is not a balanced diet because her meals does not contain the adequate nutritional requirement. She takes only proteins and carbohydrates in every meal. She requires to take vitamins and minerals in her meals to protect her from various diseases. Thus, I would suggest her to include fruits and vegetables in her meals.

 

Question 14

 Mention any two features each that are seen in boys and girls each to distinguish them from each other at puberty.

Answer 14

Two features seen in boys at puberty are:

• Growth of facial hairs
• Voice becomes hoarse.

Two features seen in girls at puberty are:

• Development of breasts.
• Region below the waist becomes wider.

 

Question 15

 We should avoid taking medicines/drugs unless prescribed by a doctor. Give reasons.

Answer 15

Several medicines have adverse side effects and have specific dosage levels which if not followed may harm the body. Drugs can be addictive too and can ruin our health and happiness.

 

Question 16

 A few of Paheli’s classmates eat potato chips and burgers regularly during the recess at school. Are they healthy eating habits? Give reasons.

Answer 16

No. They are not healthy eating habits because potato chips and burgers have very little nutritional value.

Question 17

Read the statements given below and fill up the blanks with the correct words listed in the box. 

deep, ductless, nutrients, thyroxine

(a) The meal that includes all __________ is a balanced diet.

(b) Insufficient production of __________ in the tadpoles leads to their incomplete development.

(c) Endocrine glands are also called __________ glands.

(d) After attaining puberty boys develop a__________ voice.

Answer 17

(a) nutrients, (b) thyroxine, (c) ductless,

(d) high-pitched, deep

 

Question 18

 Fill the blank circles in figure 10.1 and identify the sex of child A and B.

Answer 18

 

LONG ANSWER QUESTIONS

 

Question 19

During adolescence, the body of boys and girls undergoes certain changes. Given below are a few of those changes.

 (a) Broad shoulders

 (b) Wider chests

(c) Wider region below waist

 (d) Development of muscles

 (e) Development of mammary glands

(f) Growth of facial hair

 (g) Acne and pimples on face

 (h) Development of sex organs

 (i) High-pitched voice

(j) Growth of pubic hair.

Categorise these changes into those that occur in boys and those that occur in girls and fill in the table given below.

Answer 19

Body changes during Adolescence
Boys	Girls
Broad shoulders Wider chests Growth of muscles Growth of facial hair Acne and pimples on face Development of sex organs Development of pubic hair	Wider region below waist Development of mammary glands Acne and pimples on face Development of sex organs High-pitched voice Development of pubic hair

Question 20

In Fig.10.2 mark the positions of the endocrine glands which release the hormones that:

 (a) controls the release of sex hormones.

 (b) is responsible for the secondary sexual characters in boys.

 (c) prevents diabetes.

(d) maintains the correct salt balance in the blood.

Answer 20

 

Question 21

 Given below are certain food items required for proper nourishment of adolescents. Name the nutrients present in the food items and write their functions.

Answer 21

S.No	Food Items	Major Nutrient	Functions
1.	Pulses and nuts	Proteins	Growth, repair of body cells
2.	Oranges  and Amla	Iron and Vitamins	Formation of blood keeps the body healthy
3.	Sugar, Roti	Carbohydrates	Provide energy
4.	Oils	Fats	Provide energy
5.	Vegetables	Vitamins and Minerals	Keeps the body healthy and disease free

 

Question 22

 Name the hormone which would be released during the following situations:

 (a) a frightened person.

 (b) growth of a child to adult.

(c) development of caterpillar to moth.

(d) development of tadpole to frog.

Answer 22

(a) Adrenaline   (b) Growth hormone

(c) Insect hormones  (d) Thyroxine

Question 23

 In human females, each time during maturation and release of egg the inner wall of uterus thickens. Is this thickening permanent? Give reasons.

Answer 23

No, this thickening of the uterine wall is not permanent.

If the egg gets fertilised, it starts developing and gets embedded in the uterine wall resulting in pregnancy. During pregnancy no more eggs are released and the thickened lining is discharged only when the baby is born. However, if fertilisation does not occur, the released egg and the thickened lining are shed off resulting in menstruation.

Question 24

 John and Radha were classmates since childhood. When Radha became eleven years old, she developed a little swelling on her neck. She visited the doctor who started medication for her. After a few years, John also developed a slight protrusion on his throat. He got worried and went to the doctor. But, the doctor assured him that it was a normal feature in boys while they are growing up. Can you think of any reasons for the difference in diagnoses?

Answer 24

The swelling on the neck of Radha may have been because of goiter, a condition of the thyroid gland during which the gland produces insufficient quantity of thyroxine. However, the protrusion in John’s throat would be Adam’s apple, a result of growth of voice box in adolescent boys.

Question 25

 Observe the chart and graph given in Fig. 10.3 carefully and answer the following questions.

 

(a) Which of the line represents the height of boys?

 (b) Which line represents the height of girls?

(c) What is the difference between the pattern of increase in the height of boys and girls?

 (d) Is this pattern true for each individual?

Answer 25
(a) The red line represents the height of boys.

 (b) The blue line represents the height of girl.

 (c) At the onset of puberty, girls grow faster in height than the boys and by the age of 18 years, approximately both reach their maximum height.

(d) No, the rate of growth in height varies among individuals. Some may grow in height suddenly at puberty and then slow down, while others may grow gradually.

Question 26

 Salma had a very soft and smooth skin during her childhood. As she entered adolescence, she developed pimples on her face. The skin specialist advised her to wash her face at regular intervals. Can you explain the reasons for the appearance of pimples on her face and suggest ways to prevent them?

Answer 26

During adolescence, the secretion of sweat glands and sebaceous glands increases leading to formation of acne and pimples. Regular face wash keeps the face clean and dry and helps to reduce the pimples.

Question 27

 Our government has legalised the age for marriage in boys and girls. Give reasons as to why one should get married after a certain age.

Answer 27

In our country, the legal age for marriage is 18 years for girls and 21 years for boys. This is because teenage mothers are not prepared mentally or physically for motherhood. Early marriage and motherhood causes health problems in both mother and the child. It also curtails employment opportunities for the young woman and may cause mental agony as she is not ready to shoulder responsibilities of motherhood.

Also, the boys before that age may not be mentally matured and financially secure enough to take on the responsibilities of a family

Question 28

 It is believed that height of a child depends upon the genes inherited from parents. However, it is often seen that tall parents may have short children and vice-versa. Are there factors other than genes, that can cause these variations?

Answer 28

(Open Ended) students may write about the effects of nutrition, hormones, exercises, disease, etc. on the height.