Editing Content :: Admin Scraper

Chapter

Content type

Position

Value

7.5 Reproductive Phase of Menstrual cycle is controlled by hormones. The cycle includes the Life in Humans maturation of the egg, its release, Adolescents become capable of thickening of uterine wall and its reproduction when their testes and breakdown if pregnancy does not ovaries begin to produce gametes. The occur. In case the egg is fertilised it capacity for maturation and production begins to divide and then gets of gametes lasts for a much longer time embedded in the uterus for further in males than in females. development as you have learnt in In females, the reproductive phase of Chapter 6 (Fig. 6.8). life begins at puberty (10 to 12 years of age) and generally lasts till the age of 7.6 How is the Sex of the approximately 45 to 50 years. The ova begin to mature with the onset of Baby Determined? puberty. One ovum matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus becomes I heard my mother and my thick so as to receive the egg, in case aunt talking about my cousin who is going to have a baby. it is fertilised and begins to develop. They were discussing whether This results in pregnancy. If she would give birth to a boy fertilisation does not occur, the released egg, and the thickened lining or a girl. I wonder what makes the fertilised egg develop of the uterus along with its blood either into a boy or a girl! vessels are shed off. This causes bleeding in women which is called menstruation. Menstruation occurs Boy or Girl? once in about 28 to 30 days. The first Inside the fertilised egg or zygote is the menstrual flow begins at puberty and instruction for determining the sex of is termed menarche. At 45 to 50 years the baby. This instruction is present in of age, the menstrual cycle stops. the thread-like structures, called Stoppage of menstruation is termed chromosomes in the fertilised egg. menopause. Initially, menstrual cycle Chromosomes are present inside the may be irregular. It take some time to nucleus of every cell. All human beings become regular. have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these are the sex chromosomes, named X and Y. A female has two X Paheli says that the chromosomes, while a male has one X reproductive life of a and one Y chromosome. The gametes woman lasts from (egg and sperm) have only one set of menarche to menopause. chromosomes. The unfertilised egg Is she right? always has one X chromosome. But 84 SCIENCE 2024-25