Hello students, in this blog you can find important summary notes from the Chapter 10, Science , NCERT Book of Class 8. These notes can be used for preparation of various school Competitive Exams, Olympiads and also developing strong Fundamentals.
1. It is only after a certain age that human beings and many other animals can reproduce.
2. Adolescence : The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence.
3. Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age.
Since this period covers the teens, adolescents are also called teenagers.
4. Generally the period of adolescence varies from person to person though in girls, adolescence may begin a year or two earlier than in boys.
5. The human body undergoes several changes during adolescence, marking the onset of puberty.
6. The most important change which marks puberty is that boys and girls become capable of reproduction.
7. Puberty ends when an adolescent reaches reproductive maturity.
8. The most conspicuous change during puberty is the sudden increase in height.
9. Initially, girls grow faster than boys but by about 18 years of age, both reach their maximum height.
10. The height of an individual is more or less similar to that of some family member. This is because height depends on the genes inherited from parents.
11. Generally during the age of puberty in boys the shoulders broaden and there is muscular growth, while in girls the region below the waist becomes wider.
12. At puberty, the voice box or the larynx begins to grow. Boys develop larger voice boxes.
13. Adam’s apple : The growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple.
14. During puberty the secretion of sweat glands and sebaceous glands (oil glands) increases.
15. Young people get acne and pimples on the face during puberty because of the increased activity of sweat and sebaceous glands in the
16. A few glands such as sweat glands, oil glands and salivary glands release their secretions through ducts.
17. Endocrine glands release hormones directly into the bloodstream. So, they are also termed ductless glands.
18. At puberty, male sex organs like the testes and penis develop completely. The testes also begin to produce sperms.
19. In girls, the ovaries enlarge and eggs begin to mature. Also ovaries start releasing mature eggs.
20. The testes and ovaries are the reproductive organs that produce the gametes, that is, sperms and ova respectively.