Class 8 Science · 28 questions · 27 with answers
The belief that the mother is completely responsible for the sex of the child is wrong because the child
(c) gets one sex chromosome from the mother and the other from the father.
AIDS can spread from an infected person to another person through
(b) blood transfusion
Given below are events that lead to pregnancy and development of embryo. (i) Fertilization of egg (ii) Maturation of egg (iii) Release of egg (iv) Embedding of embryo in thickened uterine wall. Which of the following options gives the correct order of sequence in which they occur?
(d) ii, iii, i, iv.
For the metamorphosis of tadpoles which of the following elements must be available in water?
(d) iodine
The most conspicuous visible change that occurs in boys during puberty is:
(b) increase in height. 54 E XEMPLAR PROBLEMS
Structures present in a cell which is responsible for determination of the sex of a baby is
(d) chromosome
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.
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 __________.
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.
Name the hormone that is released by testes at the onset of puberty.
Testosterone.
Name the female hormone produced by ovaries that helps in development of mammary glands. R EACHING THE AG E O F ADOLESCENCE 55
Estrogen. SHORT ANSWER QUESTIONS
Match the hormones given in Column A with their deficiency disease given in Column B. Column A Column B (a) thyroxine
(i) salt imbalance (b) growth hormone
(ii) diabetes (c) Insulin
(iv) Dwarfism
(iii) goitre (d) Adrenal hormone
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?
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.
Mention any two features each that are seen in boys and girls each to distinguish them from each other at puberty.
Two features seen in boys at puberty are: (i) Growth of facial hairs (ii) Voice becomes hoarse. Two features seen in girls at puberty are: (i) Development of breasts. (ii) Region below the waist becomes wider. 136 E XEMPLAR PROBLEMS
We should avoid taking medicines/drugs unless prescribed by a doctor. Give reasons.
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.
A few of Paheli’s classmates eat potato chips and burgers regularly during the recess at school. Are they healthy eating habits? Give reasons.
No. They are not healthy eating habits because potato chips and burgers have very little nutritional value.
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. 56 E XEMPLAR PROBLEMS
Fill the blank circles in figure 10.1 and identify the sex of child A and B. Fig.10.1
This question refers to a figure in the original PDF.
LONG ANSWER QUESTIONS
During adolescence, the body of boys and girls undergoes certain changes. Given below are a few of those changes.
Body Changes Boys Girls Broad shoulders Wider region below waist Wider chests Development of mammary glands Growth of muscles Acne and pimples on face Growth of facial hair Development of sex organs Acne and pimples on face High-pitched voice Development of sex organs Development of pubic hair Development of pubic hair ANSWERS 137
In Fig.10.2 mark the positions of the endocrine glands which release the hormones that:
This question refers to a figure in the original PDF.
Given below are certain food items required for proper nourishment of adolescents. Name the nutrients present in the food items and write their functions. S. No. Food items Major Nutrient Functions 1. Pulses and nuts 2. Oranges and Amla 3. Sugar, Roti 4. Oils 5. Vegetables
S. No. Food items Major Nutrient Functions 1. Pulses and nuts Proteins Growth, repair of body cells 2. Orange and Amla Iron and Formation of blood keeps Vitamins the body healthy 3. Sugar, Roti Carbohydrates Provide energy 4. Oils Fats Provide energy 5. Vegetables Vitamins and Keeps the body healthy Minerals and disease free 138 E XEMPLAR PROBLEMS
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.
In human females, each time during maturation and release of egg the inner wall of uterus thickens. Is this thickening permanent? Give reasons.
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.
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?
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.
Observe the chart and graph given in Fig. 10.3 carefully and answer the following questions. R EACHING THE AG E O F ADOLESCENCE 59 Age in % of full height Years Boys Girls 8 72% 77% 9 75% 81% 10 78% 84% 11 81% 88% 12 84% 91% 13 88% 95% 14 92% 98% 15 95% 99% 16 98% 99.5% 17 99% 100% 18 100% 100% Fig.10.3 60 E XEMPLAR PROBLEMS
This question refers to a figure in the original PDF.
(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?
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?
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.
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.
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.
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?
(Open Ended) students may write about the effects of nutrition, hormones, exercises, disease, etc. on the height. ANSWERS 139