\n20<\/td>\n | 173<\/td>\n | 155<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Answer: \n<\/p>\n We conclude that initially, girls grow faster than boys but, by about 18 years of age both reach their maximum height. Boys are, in general, taller than girls. The rate of growth in height varies in different individuals.<\/p>\n NCERT Extended Learning Activities and Projects<\/span><\/p>\nQuestion 1. \nFind out from your elder relatives about their awareness of the legal status of early marriage. You yourself may get information on it from your teacher, parents, a doctor or the internet. Write a two-minute speech explaining why early marriage is not good for the couple. \nHint: \nEarly marriage has a great impact on the body of a woman. Early marriages lead to early pregnancies and because of these pregnancies the life of a girl suffers danger. Marriage needs lots of commitment, understanding and the capability to shoulder numerous responsibilities which cannot be expected from two very young people. Maturity is something that is directly related to age. It may vary from person to person but there\u2019s no doubt that a young couple will have a sense of immaturity. Moreover, getting married in early age means that the couples do not even have financial stability which leads to the collapse of such family. In addition, this also creates obstruction for their studies. Hence, early marriages are not good at all.<\/p>\n Question 2. \nCollect newspaper cuttings and information in magazines about HIV\/ AIDS. Write a one page article of 15 to 20 sentences on HIV\/AIDS. \nHint: \nHIV stands for Human Immunodeficiency Virus. It harms the immune system by destroying the white blood cells that fight infection. This puts a person at risk of serious infections and certain cancers. AIDS stands for Acquired Immunodeficiency Syndrome. It is the final stage of infection with HIV. Not everyone with HIV develops AIDS. HIV most often spreads through unprotected sex with an infected person. It may also spread by sharing drug needles or through contact with the blood of an infected person. Women can give it to their babies during pregnancy or childbirth. The first signs of HIV infection may be swollen glands and flu-like symptoms. These may come and go within two to four weeks. Severe symptoms may not appear until months or years. A blood test can tell if you have an HIV infection. Your health care provider can do the test, or you can use a home testing kit. There is no cure, but there are many medicines that fight HIV infection and lower the risk of infecting others. People who get early treatment can live with the disease for a longer time.<\/p>\n <\/p>\n Question 3. \nIn our country, according to 2011 census, there are 940 adolescent females for every 1000 males. Find out \na. the concerns of the community regarding this low ratio. Remember that the chance of having a boy or a girl is equal. \nb. what amniocentesis is and how useful this technique is. Why is its use for identification of sex of the unborn child banned in India? \nHint: \na. The concerns of the community regarding the low ratio are as follows:<\/p>\n \n- Social imbalance: The decrease in sex ratio would result in social imbalance. In a society the number of male and female should be equal because unequal number would result in social imbalance.<\/li>\n
- Marriage squeeze: With the declining number of sex ratio, the institution of marriage would be worst affected because there will be no girl for marriage.<\/li>\n
- Immoral trafficking: As the sex ratio plunges down, people would resort to immoral trafficking where girls would be sold and bought for marriage. Their status would be degraded.<\/li>\n
- Sexual offences against women would rise with decline in sex ratio. There would also be a rise in sexually transmitted diseases.<\/li>\n<\/ul>\n
b. Amniocentesis is a diagnostic test usually done during pregnancy. This test involves removing small amount of amniotic fluid (the fluid surrounding a developing foetus) from the uterus. The amniotic fluid can be tested to determine if the fetus has certain kinds of birth defects.<\/p>\n Usage of this test is banned because of illegal practice of using it to determine the sex of the child and killing the unborn girl child (female infanticide).<\/p>\n Question 4. \nPut your ideas together and write a short note on the importance of knowing facts about reproduction. \nHint: \nBy knowing the facts about reproduction, humans can either plan to have children or avoid unwanted pregnancies. It helps to remove social superstitions and be better aware of ourselves. It can also reduce the chances and spread of sexually transmitted diseases. It also helps to maintain hygiene and health. Hence, it is important.<\/p>\n Activity 1<\/span><\/p>\nObjective: To study and compare the gain in height of boys and girls at different ages. \nProcedure: Use the data given below to draw a graph. Take age on the X-axis and present growth in height on the Y-axis. Highlight the point representing your age on the graph. Find out the percentage of height you have already reached. Calculate the height you might eventually reach.<\/p>\n \n\n\nAge in years<\/td>\n | % of full height<\/td>\n<\/tr>\n | \nBoys<\/td>\n | Girls<\/td>\n<\/tr>\n | \n8<\/td>\n | 72%<\/td>\n | 77%<\/td>\n<\/tr>\n | \n9<\/td>\n | 75%<\/td>\n | 81%<\/td>\n<\/tr>\n | \n10<\/td>\n | 78%<\/td>\n | 84%<\/td>\n<\/tr>\n | \n11<\/td>\n | 81%<\/td>\n | 88%<\/td>\n<\/tr>\n | \n12<\/td>\n | 84%<\/td>\n | 91%<\/td>\n<\/tr>\n | \n13<\/td>\n | 88%<\/td>\n | 95%<\/td>\n<\/tr>\n | \n14<\/td>\n | 92%<\/td>\n | 98%<\/td>\n<\/tr>\n | \n15<\/td>\n | 95%<\/td>\n | 99.5%<\/td>\n<\/tr>\n | \n16<\/td>\n | 98%<\/td>\n | 99.5%<\/td>\n<\/tr>\n | \n17<\/td>\n | 99%<\/td>\n | 100%<\/td>\n<\/tr>\n | \n18<\/td>\n | 100%<\/td>\n | 100%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Observation: \n \nSuppose your present height is 120 cm and the point of your age is 14 years which touches the 93% mark on height axis. \nSo, \nFull height = \\(\\frac{\\text { Present height }(\\mathrm{cm})}{\\% \\text { of full height at this age }}\\) \u00d7 100 \n= \\(\\frac{120 \\mathrm{~cm}}{93}\\) \u00d7 100 \n= 129 cm \nHence, the height you may eventually reach is 129 cm.<\/p>\n Conclusion: It is evident from the graph that initially, girls grow faster than boys but by about 18 years of age, both reach their maximum height.<\/p>\n Secondary Sexual Characters: Characters which help in distinguishing a male from a female are called secondary sexual characters. The marked difference between the males and females of a species because of apparent physical traits is called sexual dimorphism.<\/p>\n | |