8th Science Guide Lesson 20 Reaching the age of Adolescence

8th Std Science Guide Lesson 20  Reaching the age of Adolescence | English Medium

8th Science Guide Unit 20 Reaching the age of Adolescence book back answers. 8th Standard Science Guide English Medium Book Back Answers. 8th Science Samacheer kalvi guide Tamil Medium and English Medium Book Back and additional questions and answers. 8th Text Book download pdf. 8th std All Subject Guide. 

• 8th Science Guide (All Units)- Book Back Answers – TM & EM – Click Here

8th Science Guide Lesson 20 Reaching the age of Adolescence

I. Choose the correct answers:

1. Adolescence is the period of life between _____________ years of age.

1. 10 to 16
2. 11 to 17
3. 11 to 19
4. 11 to 20

Ans : 11 to 19

2. The period at which an organism attains sexual maturity is called _____________

1. puberty
2. adolescence
3. growth
4. maturity

Ans : puberty

3. During puberty, the region below the waist become wider in _____________

1. boys
2. girls
3. Both a and b
4. None of these

Ans : Both a and b

4. Adam’s apple is the growth of the ________

1. pharynx
2. thyroid
3. larynx
4. parathyroid

Ans : larynx

5. External Many adolescent boys and girls get pimples on face, due to the secretions of _________ gland.

1. sweat
2. sebaceous
3. sweat and sebaceous
4. None of these

Ans : sebaceous

6. The sperm is produced by ____________

1. penis
2. ovary
3. uterus
4. testes

Ans : testes

7. ___________ are the chemical substances, secreted by endocrine glands.

1. Hormones
2. Enzymes
3. Proteins
4. Fatty acids

Ans : Hormones

8. Androgen production is regulated by ___________

1. GH hormone
2. LH hormone
3. TSH hormone
4. ACTH hormone

Ans : LH hormone

9. During menstruation, the progesterone level is ___________

1. decreased
2. increased
3. ceased
4. normal

Ans : ceased

10. ___________ intake needs to be increased to prevent osteoporosis in later life.

1. Potassium
2. Phosphorus
3. Iron
4. Calcium

Ans : Calcium

II. Fill in the blanks.

1. ____________ is secreted by the ovaries of female.Ans : Estrogen
2. The hormones secreted by the gonads are controlled by __________Ans : Anterior pituitary.
3. Milk secretion during lactation is controlled by ____________ hormone.Ans : prolactin
4. The male and the female gamete fuse together and form ____________Ans : zygote
5. The first menstrual flow begins at puberty and it is termed as ______________Ans : menarche
6. _____________ usually occurs 14 days after ovulation.Ans : Menstruation
7. __________ includes protein, carbohydrates, fats and vitamins in requisite proportion.Ans : Balanced diet
8. __________ helps to prevent thyroid gland related diseases.Ans : Iodine
9. Iron defciency leads to ____________Ans : Aneamia
10. In women fertilization takes place at ___________Ans : Fallopian tube

III. State True or False. If false, correct the statement.

1. There is a sudden increase in the height of both boys and girls during puberty.Ans : True
2. The release of ovum from the uterus is called ovulation. Ans : False
3. During pregnancy, the corpus luteum continues to grow and produces large amount of estrogen and progesterone.Ans : True.
4. Making use of disposable napkins or tampons may increase the chances of infectionsAns : False.

Cu St. : Making use of disposable napkins or tampons may reduce the chances of infections

5. Using clean toilets for defecation is a good practice.Ans: True.

IV. Match the following

1. Puberty – Testosterone
2. Adam’s apple – Muscle development
3. Androgen – at 45 to 50 years of age
4. ICSH – Sexual maturity
5. Menopause – Change in voice

Ans: 1 – d, 2 – e, 3 – b, 4 – a, 5 – c

V. Answer very briefly:

1. What is adolescence?

• The term adolescence is derived from the Latin word ‘adolescere’ meaning ‘to grow’ or ‘grow to maturity’.
• Biologically it is a physical transition marked by the onset of puberty and termination of physical growth in an individual.

2. List out the changes which occur during puberty.

Puberty transform the body of a child into that of an adult. These changes are:

• Changes in body size
• Changes in body proportion
• Development of primary sex characteristics
• Development of secondary sex characteristics.

3. What is secondary sex characteristics?

• Secondary sex characteristics are the physical features which distinguish male from female.

4. What is fertilization?

• The fusion of the sperm and egg is called fertilization.

5. Explain Menarche.

• The first menstrual flow begins at puberty and is termed menarche.
• It is the beginning of adolescence, during which mental and emotional maturation occurs and physical growth becomes pronounced.

6. Explain the process of pregnancy.

• After ovulation, the ovum reaches the fallopian tube and fertilization takes place.
• The fertilized egg undergoes development and it is implanted in the uterus.
• The corpus luteum continues to grow and produces large amount of progesterone.
• This results in pregnancy. Normally, it lasts for 280 days, at the end of which parturition (child birth) takes place.

7. Explain the importance of cleanliness during the time of menstrual cycle in girls.

• Girls should take special care of cleanliness during the time of menstrual cycle.
• Making use of disposable napkins or tampons may reduce chances of infections. It should be changed frequently depending upon the menstrual flow.

8. How is adolescence different from childhood?

• The period of life from birth till 12 years is also childhood. Adolescence begins from age of 12 -13 years.
• Lot of changes in height, weight, sex organs, muscle mass etc, occur in adolescence.

VI. Answer in detail

1. What are the physical changes that occur in boys and girls during adolescence?

• Secondary sex characteristics are the physical features which distinguish male from female. The Physical changes that occur is boys and girls during adolescence are:

Girls:

• Height and weight increase.
• Fatty and subcutaneous tissues develop.
• Hip broadens.
• Hair grows in arm pits and pubic area.
• Voice becomes shrill.
• Breast develops.

Boys

• Height and weight increase.
• Muscles develop.
• Shoulder broadens.
• Hair grows in the arm pits and pubic area, and facial hair also appears.
• Voice break takes place due to lengthening of vocal cord and enlarging of larynx.
• Size of the penis increases.

2. Explain the role of hormones in reproduction.

• The primary hormones that regulate reproduction are the steroids such as androgens, estrogens and progesterone. which have masculinizing, feminizing and gestational effects respectively.
• These hormones are secreted from the gonads which are regulated by the anterior pituitary adenohypophysis).

Follicle Stimulating Hormone (FSH):

FSH in a female influences the development of the Graafian follicle and secretion of estrogens. In a male, it is necessary for the development of seminiferous tubules, and for spermatogenesis.

Luteinizing Hormone (LH):

In a female, it is the hormone necessary for ovulation, and the secretion of the luteal hormone progesterone, and for the final maturation of the Graafian follicle. In a male, it stimulates the interstitial (Leydig) cells of testes and the secretion of testosterone, and is referred to as the Interstitial Cell Stimulating Hormone (ICSH).

Prolactin (PRL) or Lactogenic Hormone:

The main function of this hormone is milk secretion during lactation.

Oxytocin Hormone:

Oxytocin causes expulsion of milk from the breast and it is also involved in the contraction of smooth muscles of uterus during child birth.

3. Briefly describe the menstrual cycle.

• The beginning of the menstrual cycle marks the onset of puberty in human females. Menstruation occurs if an ovum released by the ovary of a woman is not fertilized during ovulation. This is described below.
• When a girl reaches puberty at the age of about 10, the sex hormones released into her blood cause some of the ova (or egg cells) in her ovaries to become mature (or ripe).
• Usually one mature ovum (or egg) is released ff(jm one of the ovaries into the oviduct once in every 28 days. This is called ovulation.
• Before ovulation (or release of ovum), the inner wall of uterus becomes thick and spongy, and full of tiny blood vessels to receive the fertilized ovum.
• If the ovum does not get fertilized then the thick and soft inner lining of uterus breaks So, the thick and soft inner lining of uterus along with the blood vessels and the dead ovum comes out of the vagina in the form of a bleeding called menstruation.
• Menstruation usually occurs 14 days after ovulation and usually lasts for about 3 to 5
•  
• After menstruation is over, the inner lining of the uterus starts building up again so that it may become ready to receive the next ovum.
• If the ovum does not get fertilized even now, then menstruation takes place again. This cycle of menstruation is repeated again and again in women after every 28 days. The menstrual cycle is controlled by hormones.

Menstruation stops temporarily when the ovum gets fertilized and the women gets pregnant. Menstruation also stops due to nutritional deficiencies, low body weight, stress, eating disorder, excessive weight gain etc.

4. Briefly explain the nutritional needs of adolescence.

1. Adolescence is a stage of rapid growth and development.
2. Balanced diet is very much important during adolescence. Balanced diet includes proteins, carbohydrates, fats and vitamins in requisite proportions.

• A very good amount of proteins and carbohydrates is necessary during this

growth period. Apart from that, adolescents need the following dietary components.

Minerals:

Since there is an increase in skeletal mass and blood volume during adolescence, the body needs calcium, phosphorus and iron.

Calcium:

Calcium intake needs to be increased to prevent osteoporosis in later life.

It is present in milk and milk products or other equivalents.

Iodine:

• It helps to prevent thyroid gland related diseases.

Iron:

• Iron builds blood and iron-rich foods such as green leafy vegetables, jaggery, meat, dates, fish, chicken, citrus, Indian gooseberry (Nelli) and whole pulses are good for adolescents.
• Lack of iron in the diet results in anemia.
• In boys, iron deficiency occurs due to muscle spurt whereas in girls it occurs due to menstruation in addition to muscular growth.