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1. (iv) Cytokinin

2. (i) YES

3. (i) YES

4. (i) YES

5. (ii) NO

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.

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

When a woman is preganant.

(a) Due to blocked oviducts of the woman, the ovum released by her ovary cannot meet the sperm and get fertilized. 

(b) In vitro fertilization technique is used to help those couples in having babies who can produce sperms and ovum but fertilization does not take place inside the woman’s body due to blocked oviducts.

B. broadening of chest 

During puberty, the region below the waist becomes wider in girls.

(d) Cytokinin.

(i) Insulin is secreted by Pancreas.

(ii) Thyroxin is secreted by thyroid gland.

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.

In the other case, 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. 

Thus, father is responsible for the sex of the unborn child.

(a) Raj Kumar and his wife Sunita have been blessed with a baby girl. It means, X chromosome has been contributed by raj Kumar. 

(b) Sunita also contributed X chromosome. 

(c) Kripa Shanker and his wife Vimla have been blessed with a baby boy, thus, kripa shanker contributed Y chromosome. 

(d) Vimla contributed X chromosome.

The answer is (c)

• Dendrites of a neuron receive electrical impulse from axonal end of another neuron.
• After that, electrical impulse travels through cell body, axon; to the axonal end

Menstrual cycle begins when a girl reaches the age of puberty. At this age, ovaries release sex hormones in the blood which cause maturation of ova in ovaries. One mature egg or ovum is released by one of the ovaries once in about 28 to 30 days. This is termed as ovulation. Before ovulation, uterus prepares itself to receive the fertilized egg. The inner lining of the uterus becomes thick and soft with lots of blood capillaries in it.

If the ovum does not get fertilized, then the inner lining of uterus is not required and hence it breaks down and comes out through the vagina in the form of a bleeding called menstruation.

Menstruation occurs once in about 28 to 30 days and it usually lasts for 3 to 5 days.

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

B. B and C 

There are two conditions which can lead to menstruation in a 21-year-old woman during ovulation. These are: (i) Blocked oviduct and, (ii) sperms not available for fertilization.

A. menstruation starts 

In females, the reproductive phase of life begins at puberty (10 to 12 years of age) and generally lasts till the age of approximately 45 to 50 years. The first occurrence of menstruation at puberty is called menarche. It is the beginning of the reproductive life of a girl.

Thyroxine hormone.

Whales are mammals, not ishes. All other statements are correct.

The answer is (a) Iron is essential for the synthesis of thyroxin

Iodine is essential for the synthesis of thyroxin but not iron hence statement a) is wrong

Secondary sexual characteristics are those which distinguishes sexually mature male from female. These are controlled by hormones. A secondary sex character that distinguishes a boy and a girl is the development of breast in females.

The sex of the unborn child is determined whether the zygote has XX or XY chromosome.

The disorder caused by thyroid is goitre.

Stoppage of mensuration is generally termed as menopause.

The changes that take place during puberty are principally controlled by hormones. Hormones are the chemical substances secreted from endocrine glands. Testosterone or male hormone is secreted by testes at the onset of puberty which principally regulates secondary sexual characteristics. Such female hormone is called estrogen.

The answer is (b) Less secretion of growth hormone

• Growth hormones are responsible for the overall growth of an organism.
• When there will be no secretion of growth hormones it leads to dwarfism.

The answer is (d) his sugar level in blood was high

• Patient suffering from diabetes will have high blood glucose due to non-functioning or lack of insulin hormone. 
• Such patients are administered with insulin injection to regulate blood glucose.

Humans have a total of 23 pairs of chromosomes. Out of them, one pair of chromosome is called sex chromosome.

The most prominent change during puberty is that boys and girls become capable of reproduction.

The most discernible change in the puberty is the sudden increase in height.

Aldosterone hormone maintains the correct salt balance in the blood which is secreted from adrenal gland.

The answer is (c) testosterone from testes and estrogen from ovary

• These are the sex hormones responsible for the secondary character that appear after puberty. 
• Males secrete testosterone and females secrete estrogen.

Changes in puberty are associated with the secretion of oestrogen and testosterone. Oestrogen is secreted from ovary in females and testosterone is secreted in males from testes.

Therefore, correct statement is (c).

The puberty age in human females is 11 – 18.

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.

The changes in body shape of girls during puberty occur in following ways: 

1. In girls, the region below the waist becomes wider. 

2. Girls have high pitched voice.

D. thyroxine 

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.

D. B and D 

Estrogen and testosterone are sex hormones which involved in the development and control of the reproductive organs and secondary sexual characteristics.

At puberty, male sex organs like the testes and penis develop completely. In girls, female sex organs like ovaries and uterus develop completely.

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.

In my opinion, looking after physical health more important at adolescent age since all of a sudden body undergoes various physical, chemical and emotional changes which might upset the system of the body. So to remain healthy in adolescent age one must take important care.

Changes which occur in girls during puberty are: 

1. Rapid increase in height. 

2. The region below the waist becomes wider.

3. Hair grow in armpits and in pubic regions between the thighs. 

4. The ovary enlarges and starts producing matured eggs. 

5. Menstruation begins. 

6. Have high pitched voice. 

7. Development and enlargement of breast.

Mother’s milk is a natural balanced food for infants.

Thyroxine is produced by thyroid gland. It plays main role in regulating BMR, heart rate, muscle control, bone development and digestive functions.

Adrenaline helps the body to adjust to stress when one is very angry, embarrassed or worried. It is secreted by adrenal gland.

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).

C. testosterone 

Testosterone is a male sex hormone which is secreted by testes. This hormone brings changes in boys such as growth of facial hair.

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

1. Early marriage and motherhood cause health problems in the mother and the child. 

2. It reduces curtails employment opportunities for the young woman. 

3. It may cause mental agony as she is not ready for responsibilities of motherhood.

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

The adolescent girls should take special care of personal hygiene during the time of menstrual flow.

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

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.

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

1. Adolescents boys and girls should take bath regularly. 

2. Adolescent girls should take care of cleanliness of the body during the time of periods.