Lakhmir Singh & Manjit Kaur: Reaching The Age Adolescence- 3 | Lakhmir Singh & Manjit Kaur Solutions: Class 8 Science PDF Download

Q.61. Which of the following are endocrine glands?
Salivary gland, Thyroid gland, Adrenal gland, Sweat gland, Pituitary gland, Sebaceous gland (Oil gland)

Thyroid gland, adrenal gland and pituitary gland are endocrine gland as they secrete their secretion directly into the bloodstream. So, they are termed as ductless gland. While salivary gland, sweat gland and sebaceous gland (oil gland) secrete their secretions through ducts.

Q.62. (a) What name is given to the onset of menstruation in human females (or girls)? At what age does this occur?
(b) What name is given to the permanent stoppage of menstruation in women? At what age does this occur?

(a) The onset of menstruation in human females (or girls) is termed menarche. It occurs at puberty (10 to 12 years of age).

(b) The permanent stoppage of menstruation in women is termed menopause. It occurs at 45 to 50 years of age.

Q.63. Who is responsible for the sex of the unborn child: father or mother? Why?

The two chromosomes that determine the sex of the unborn baby are called sex chromosomes named X chromosomes and Y chromosomes. A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes (egg and sperm) have only one set of chromosomes. Thus, in females all the egg cells contain X chromosomes while in males, half sperm have X chromosomes and half sperms have Y chromosomes.
When a sperm containing X chromosome fertilizes the egg, the zygote would have XX chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilization, the zygote would develop into a male child.
Thus, father is responsible for the sex of the baby which is born.

Q.64. What will be the sex of the child born:
(a) if X chromosome carrying sperm fuses with an egg cell carrying X chromosome?
(b) if Y chromosome carrying sperm fertilizes an ovum containing X chromosome?

(a) If X chromosome carrying sperm fuses with an egg cell carrying X chromosome at fertilization, then the zygote will have XX chromosomes and develop into a female child.

(b) If Y chromosome carrying sperm fuses with an egg cell carrying X chromosome at fertilization, then the zygote will have XY chromosomes and develop into a male child.

Q.65. What are hormones? Where are hormones made in the human body?

Hormones are chemical substances which coordinated the activities of the living organisms. Hormones are made and secreted by ductless glands called endocrine glands in the body. The hormones are released directly into the bloodstream and carried to the target site through blood circulatory system.

Q.66. What are sex hormones? Name two sex hormones.

Hormones released by the reproductive organs like testes and ovaries and involved in the development of secondary sexual characteristics are called sex hormones. The two common sex hormones are testosterone and estrogen.

Q.67. Define
(i) menarche, and
(ii) menopause.

(i) The first occurrence of menstruation at puberty is called menarche.

(ii) The permanent stoppage of menstruation is termed menopause. It occurs at 45 to 50 years of age.

Q.68. What is menstruation? Explain.

Menstruation is a process in which blood and mucous flows out every month through the vagina. Menstruation usually lasts for 3 to 5 days in human females. The frequency of menstrual cycle in human females is once in a month if egg is not fertilized.

Q.69. What are sex chromosomes? Name the two types of sex chromosomes.

The two chromosomes that determine the sex of the unborn baby are called sex chromosomes named X chromosomes and Y chromosomes.

A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes (egg and sperm) have only one set of chromosomes.

Q.70. Explain how sex is determined in the unborn baby.

The two chromosomes that determine the sex of the unborn baby are called sex chromosomes named X chromosomes and Y chromosomes. A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes (egg and sperm) have only one set of chromosomes. Thus, in females all the egg cells contain X chromosomes while in males, half sperm have X chromosomes and half sperms have Y chromosomes.
When a sperm containing X chromosome fertilizes the egg, the zygote would have XX chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilization, the zygote would develop into a male child.
Thus, father is responsible for the sex of the baby which is born.

Q.71. What are the various ways in which AIDS virus (HIV) can be transmitted?

Various ways in which AIDS virus (HIV) can be transmitted are as follows:

• By sharing the syringes used for injecting drugs.
• It can be transmitted to an infant from the infected mother through her milk.
• It can be transmitted through sexual contact with a person infected with HIV.

Q.72. Explain how, the use of drugs helps in spreading AIDS disease.

AIDS is caused by a dangerous virus called HIV. This virus can be spread from infected person to healthy person by sharing the syringes used for injecting drugs.

Q.73. State the harmful effects of taking drugs.

Harmful effects of taking drugs are as follows:

• Drugs are addictive. If you take them once, you feel like taking them again and again.
• They harm the body in the long run.
• They ruin health and happiness.

Q.74. Name one hormone secreted by pituitary gland. State the function of this hormone.

Growth hormone is secreted by pituitary gland. Growth hormone is necessary for the normal growth of a person.

Q.75. Explain why, people are advised to use iodized salt in cooking food.

Iodine is needed continuously by thyroid gland to make thyroxine hormone. If people do not have enough iodine in their die, they will get goiter disease caused by lack of thyroxine. So, people are advised to use iodized salt in cooking food.

Q.76. What is goiter? What causes goiter?

The deficiency of thyroxine hormone in adults causes a disease called goiter. The main symptom of disease is that the neck of the person suffering from Goitre appears to be swollen.

Q.77. Which hormone lowers the blood sugar in humans? Name the gland which secretes this hormone.

Insulin hormone lowers the blood sugar in humans. Pancreas gland secretes insulin hormone.

Q.78. Name the hormone secreted by pancreas. What is the function of this hormone?

Insulin hormone is secreted by pancreas. The function of insulin hormone is to lower the blood sugar level.

Q.79. What is the function of adrenaline hormone in the body?

There are two adrenaline glands in the body and are located on the top of the kidneys. Adrenaline glands secretes adrenaline hormone which helps the body to adjust to stress when one is very angry, embarrassed, or worried.

Q.80. Name six endocrine glands in the human body. Also name the hormones secreted by each one of these glands.

Six endocrine glands in the human body are as follows:

• Pituitary gland: It secretes growth hormone.
• Thyroid gland: It secretes thyroxine hormone.
• Pancreas: Secretes insulin hormone.
• Adrenal gland: Secrete adrenaline hormone.
• Testes: Secrete testosterone.
• Ovaries: Secrete estrogen.

Q.81. Where are the following glands located in the human body?

(i) Pituitary
(ii) Thyroid
(iii) Pancreas
(iv) Adrenals

(i) Pituitary gland is attached to the base of brain.

(ii) Thyroid gland is present in the neck.

(iii) Pancreas is just below the stomach in our body.

(iv) There are two adrenal glands in our body and are located on the top of the kidneys.

Q.82. What will happen if the water in which tadpoles are growing does not contain sufficient iodine?

In frog, metamorphosis is controlled by thyroxine hormone and thyroxine production requires the presence of iodine. So, if the water in which tadpoles are growing does not contain sufficient iodine, the tadpole cannot become adult.

Q.83. What is acne?

Acne is a skin condition marked by eruption of numerous red pimples on the face.

Q.84. What are pimples? How are pimples formed?

Pimples are small red spots on the face of a person. Many adolescent boys and girls may get acne and pimples on the face during puberty due to the increased activity of sebaceous glands and sweat glands in the skin.

The excess oil secreted by sebaceous glands and sweat secreted by sweat glands get collected in the tiny pores of the skin. The accumulation of oil, sweat and dead skin cells block the tiny pores in the face skin. Then, bacteria grow in the blocked skin pores causing swelling and redness of skin which leads to the formation of pimples.

Q.85. Name two food items each which provide mainly:
(a) carbohydrates for energy
(b) fats for energy
(c) Proteins for growth
(d) vitamins and minerals for good health

(a) Rice and roti.

(b) Butter and ghee.

(c) Milk and pulses

(d) Fruits and vegetables.

Q.86. Why is iron mineral needed by our body? Name some of the iron-rich foods.

Iron mineral is needed by our body as it builds our blood. Some of the iron rich foods are leafy vegetables, meat, jaggary, citrus, Indian gooseberry (amla).

Q.87. State any two practices which can be adopted by adolescents to maintain personal hygiene.

Two practices which can be adopted by adolescents to maintain personal hygiene are given below:

• Adolescents boys and girls should take bath regularly.
• Adolescent girls should take care of cleanliness of the body during the time of periods.

Q.88. Why is the more necessary for adolescents to take bath regularly (at least once everyday)?

It is more necessary for adolescents to take bath regularly (at least once everyday) because increased activity of sweat glands sometimes makes the body smelly.

Q.89. What will happen if personal hygiene (Cleanliness of body) is not maintained by adolescents?

If personal hygiene (Cleanliness of body) is not maintained by adolescents, it will increase the chances of catching bacterial infection.

Q.90. State the various ways in which early marriage and motherhood is harmful to the girls.

The various ways in which early marriage and motherhood is harmful to the girls are as follows:

• Early marriage and motherhood cause health problems in the mother and the child.
• It reduces curtails employment opportunities for the young woman.
• It may cause mental agony as she is not ready for responsibilities of motherhood.