Unit III Compendium review 1
How is a new organism started? Why do we develop and age?)
Human Life Cycle
Meiosis eggs and sperm
Fetal development and birth.
How is a new organism started? Why do we develop and age?)
Human Life Cycle
Meiosis eggs and sperm
Fetal development and birth.
This is a pic of a sperm reaching the egg, fertilizing it.
Human Life Cycle:
As humans we are born an infant and grow into a child. Eventually we hit puberty which is the onset of maturing into an adult. It isn’t till after puberty that a person can reproduce. For girls this happens between the ages of 11 and 13. For boys it’s between 14 and 16. After a human has reached adulthood they can reproduce until the reach 45-55 for women. Men can usually still reproduce into their senor years.
Meiosis eggs and sperm:
Usually cells reproduce in a process called mitosis. In normal mitosis new cells are made as an exact copy of the original carrying 46 chromosomes. Human reproduction involves a different kind of cell division, meiosis. Meiosis takes place in the reproductive organs, the testes and the ovaries. In meiosis each person only produces 23 chromosomes. The mother’s is in an egg or ovum, and the father’s is in sperm. After a sperm enters an egg it is called a zygote. So once the two combine the new cell has 46 chromosomes.
Sperm are produced in the male’s testes. Sperm have three parts the head which contains the nucleus, the middle which is made up of mitochondria and the tail that is a flagellum. The mitochondria and the flagellum help the sperm propel its way up the vaginal canal threw the cervix of a woman and to find the egg. Once it reaches the egg its tail breaks of and the head enters the egg.
Eggs are produced in a women’s ovary. When a woman ovulates (usually once a month) the ovary releases an egg. Once the egg is released it if swept up by the oviduct and sent down toward the uterus. The egg will only for 6-24 hours unless it is fertilized. Once it is fertilized it is called a zygote. After several days the fertilized egg will attach or implant it’s self into the wall or lining of the uterus.
As humans we are born an infant and grow into a child. Eventually we hit puberty which is the onset of maturing into an adult. It isn’t till after puberty that a person can reproduce. For girls this happens between the ages of 11 and 13. For boys it’s between 14 and 16. After a human has reached adulthood they can reproduce until the reach 45-55 for women. Men can usually still reproduce into their senor years.
Meiosis eggs and sperm:
Usually cells reproduce in a process called mitosis. In normal mitosis new cells are made as an exact copy of the original carrying 46 chromosomes. Human reproduction involves a different kind of cell division, meiosis. Meiosis takes place in the reproductive organs, the testes and the ovaries. In meiosis each person only produces 23 chromosomes. The mother’s is in an egg or ovum, and the father’s is in sperm. After a sperm enters an egg it is called a zygote. So once the two combine the new cell has 46 chromosomes.
Sperm are produced in the male’s testes. Sperm have three parts the head which contains the nucleus, the middle which is made up of mitochondria and the tail that is a flagellum. The mitochondria and the flagellum help the sperm propel its way up the vaginal canal threw the cervix of a woman and to find the egg. Once it reaches the egg its tail breaks of and the head enters the egg.
Eggs are produced in a women’s ovary. When a woman ovulates (usually once a month) the ovary releases an egg. Once the egg is released it if swept up by the oviduct and sent down toward the uterus. The egg will only for 6-24 hours unless it is fertilized. Once it is fertilized it is called a zygote. After several days the fertilized egg will attach or implant it’s self into the wall or lining of the uterus.
This is a pic of the inside of a women's uterus. The fetus is attaching it's self to the wall.
Fetal development and birth:
After a fertilized egg implants it’s self into the uterine wall it becomes an embryo. A pregnancy is calculated from the first day of the last menstrual cycle. So when the egg is implanted is actually considered 2 weeks pregnant. An average pregnancy last 40 weeks. A women doesn’t relies she is pregnant until the third week when she misses her period. The heart can be heard beating at 4 weeks. The buds of curtain systems form. In the fifth week a woman uterus is growing larger. By six weeks fingers and toes are present. The child has a skeleton but it is only cartilage. At 2 mths the uterus has grown large enough to be felt over the pubic bone. The embryo is only about 1 ½ inches in length. At three months the uterus has got very large. By four months the mother can feel slight movement and the baby is inches long. At 5 months it is usually obvious that the woman is pregnant. By seven months the eyes have opened and the uterus is close to reaching the rib cage. At 8 mths the baby is gaining about a pound a week. Finally at nine months the baby is fully developed and ready to be born.
Work Cited:
All Pictures were taken from: http://search.live.com/images/results.aspx?q=Ovum&mkt=en-US#
Madder, Sylvia S. “Human Biology” 10th ed. New York: McGraw-Hill, 2007.
Fetal development and birth:
After a fertilized egg implants it’s self into the uterine wall it becomes an embryo. A pregnancy is calculated from the first day of the last menstrual cycle. So when the egg is implanted is actually considered 2 weeks pregnant. An average pregnancy last 40 weeks. A women doesn’t relies she is pregnant until the third week when she misses her period. The heart can be heard beating at 4 weeks. The buds of curtain systems form. In the fifth week a woman uterus is growing larger. By six weeks fingers and toes are present. The child has a skeleton but it is only cartilage. At 2 mths the uterus has grown large enough to be felt over the pubic bone. The embryo is only about 1 ½ inches in length. At three months the uterus has got very large. By four months the mother can feel slight movement and the baby is inches long. At 5 months it is usually obvious that the woman is pregnant. By seven months the eyes have opened and the uterus is close to reaching the rib cage. At 8 mths the baby is gaining about a pound a week. Finally at nine months the baby is fully developed and ready to be born.
Work Cited:
All Pictures were taken from: http://search.live.com/images/results.aspx?q=Ovum&mkt=en-US#
Madder, Sylvia S. “Human Biology” 10th ed. New York: McGraw-Hill, 2007.
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