5. Creates multicellular organisms from a zygote. It is the basis of all tissue growth and repair. Chromosome number is conserved. BeLingLiew @ PSS SMK ABC 2011
9. Produces sex cells by reducing their chromosome number by half. This is important because it create genetic variability in the gametes. BeLingLiew @ PSS SMK ABC 2011
52. Sperm is male gamete. It is the smallest cell in the body. It can move about in the semen. It is produced when a boy reaches puberty. It has a head with nucleus, a neck and a long tail which helps it to move. BeLingLiew @ PSS SMK ABC 2011
53. A sperm is about 0.01-0.05 mm long. The function of a sperm is to fertilize an ovum cell. A sperm cannot live longer than 72 hours outside the boy of a male. BeLingLiew @ PSS SMK ABC 2011
54. Changes in a male during puberty BeLingLiew @ PSS SMK ABC 2011
55. A boy reaches puberty about 13 years old. During puberty, physical and emotional changes take place in the boy’s body. In a male, these changes are caused by the production of the sex hormone called testosterone by the testes. BeLingLiew @ PSS SMK ABC 2011
56. The following changes occur in a boy’s body during puberty: BeLingLiew @ PSS SMK ABC 2011
57. His penis and testes become bigger. He begins to produce sperms. Hair begins to grow in the pubic area and on the armpits. He begins to grow a beard. His voice-box (laryn) enlarges and his voice deepens. He begins to show interest in the opposite sex. BeLingLiew @ PSS SMK ABC 2011
64. The function of vagina Receives the penis and sperms during sexual intercourse. Provides a channel for the baby to come out during birth. BeLingLiew @ PSS SMK ABC 2011
83. Egg cell is female gamete. It is the largest cell in the body. It cannot move freely. This makes it easier for sperms which are moving freely to find it for fertilization. It will be produced when a girl reaches puberty at about 11-12 years old. BeLingLiew @ PSS SMK ABC 2011
84. An egg cell is spherical in shape with a diameter about 0.10mm. It has a large nucleus and cytoplasm enclosed by a cell membrane. It is then surrounded by a layer of a jelly-like substance. BeLingLiew @ PSS SMK ABC 2011
85. The 2 ovaries alternately release the egg cells. 1 egg cell is released in about 28 days. The function of an egg cell is to get fertilized by a sperm and form a zygote which will develop into a new individual. An egg cell in the uterus can live for about 36 hours. BeLingLiew @ PSS SMK ABC 2011
86. Changes in a female during puberty BeLingLiew @ PSS SMK ABC 2011
87. A girl reaches puberty at about the age of 11. During puberty, a girl undergoes physical and emotional changes. These changes are brought about by the sex hormone, oestrogen, produced by the ovaries. BeLingLiew @ PSS SMK ABC 2011
88. These changes, called secondary sexual characteristic, include the following: BeLingLiew @ PSS SMK ABC 2011
89. Menstruation begins. The breasts and buttocks increase in size. Develops a feminine voice. Hair grows in the pubic area and on the armpits. Shows interest in boys. BeLingLiew @ PSS SMK ABC 2011
94. Menstruation is the periodic discharge of blood from the uterus through the vagina. Normally this occurs once in 28 days. This is known as menstrual cycle. BeLingLiew @ PSS SMK ABC 2011
95. Menstruation starts from puberty and stops when a woman reaches menopause. Menopause takes place because the ovaries do not produce any more egg cells or ova. BeLingLiew @ PSS SMK ABC 2011
96. The menstrual cycle is due to changes in the lining of the uterus. The menstrual cycle starts with menstruation. It occurs during the first five days of the cycle. BeLingLiew @ PSS SMK ABC 2011
97. After menstruation (from the 6th to the 10th day), the lining of the uterus become spongy with tissues and blood vessels. This is in preparation to receive any egg cell or ovum which is fertilized. BeLingLiew @ PSS SMK ABC 2011
98. The egg cell is usually released from the 13th to the 15th day of the menstrual cycle. Te release of the egg cell is called ovulation. BeLingLiew @ PSS SMK ABC 2011
99. The ovulation period together with two days before and two days after it is considered a fertile period. This is because the chance of fertilizing an egg cell during this period is very high. BeLingLiew @ PSS SMK ABC 2011
100.
101. They are discharged together with the egg cell as menses.BeLingLiew @ PSS SMK ABC 2011
102.
103. The zygote moves into the uterus and becomes implanted in the uterus wall.
111. Fertilization is the process of a sperm fusing with an egg (ovum) to form a zygote. BeLingLiew @ PSS SMK ABC 2011
112. During sexual intercourse, sperms ejaculated into the vagina pass through the cervix into the uterus. The sperms then swim up to the Fallopian tube. BeLingLiew @ PSS SMK ABC 2011
113. If an egg cell (ovum) is present in a Fallopian tube, the sperms surround the egg cell. Only the head of one sperm can break through the membrane of the egg cell. The tail of the sperm is left outside the egg cell. BeLingLiew @ PSS SMK ABC 2011
114. The nucleus in the head of the sperm fuses with the nucleus in the egg cell and forms a zygote. Fertilization has taken place. The woman is said to be pregnant. BeLingLiew @ PSS SMK ABC 2011
116. Fertilization usually takes place at the upper portion of Fallopian tube. Cell division occurs as the zygote moves down the fallopian tube towards the uterus. BeLingLiew @ PSS SMK ABC 2011
117. The zygote first divides into two cells, then four cells and so on until it becomes a small ball of many cells called embryo. BeLingLiew @ PSS SMK ABC 2011
120. By the time, the zygote has developed into an embryo, the embryo has moved into the uterus. The embryo attaches itself to the wall of the uterus. BeLingLiew @ PSS SMK ABC 2011
121. The embryo attaches itself to the uterus wall by means of a structure called placenta. The placenta is connected to the embryo by the umbilical cord. BeLingLiew @ PSS SMK ABC 2011
122. The embryo is surrounded and protected by two membranes containing a type of fluid called amniotic fluid. BeLingLiew @ PSS SMK ABC 2011
123. The fluid has two main functions: It acts as a shock absorber and protects the embryo. It buoys up the embryo so that it can move more freely during its development. BeLingLiew @ PSS SMK ABC 2011
129. Jennings, Terry, The Young Scientist Investigates: The Human Body, Kuala Lumpur : FajarBaktiSdn. Bhd., 1993, pg. 22-25 The World of Science, New York : Golden Press, 1966, pg.157-159 Synergy Keep Fit Series: Menopause, Kuala Lumpur : Sam Publishing Sdn. Bhd., 2002, pg. 1-18 BeLingLiew @ PSS SMK ABC 2011
