Science - Unit 6 Creating Life

Language Learning Goal Define: Reproduce Egg Sperm Fertilize Fetus Uterus

Content Learning Goal Students will learn how humans reproduce (or make more of themselves). We will learn what organ system is in charge of reproducing and how it works.

Creating Life Life begins with one cell. From that one cell, billions of cells are made to form a human body. Humans have organ systems that make them able to make new humans…babies. If we didn’t have these organ systems, the human race would die out.

Starting from One Cell The human body has an organ system to reproduce humans. It is called the Reproductive System. Babies are born with all the parts they need for their reproductive systems, but the system doesn’t start working until around Age 12.

Puberty Around the time kids turn 12 (may be younger or older), another organ system starts sending hormones to the reproductive system. Do you remember what system sends hormones? Right! The Endocrine System. The hormones tell the reproductive system to start producing sex cells. This age in a child’s life is called “puberty”.

Sex Cells In the female, sex cells are called eggs. In the male, sex cells are called sperm. These two kinds of sex cells cannot make new life on their own, they must join together and become one cell. When that happens, we say the sperm fertilizes the egg.

One Cell Continued The sperm and egg combine to make one cell. That one cell divides and becomes two cells. Those cells divide and make four cells and so on. As the cells divide, they form tissues, organs and different body parts. Slowly, the cells build up to make a baby. This forming baby is called a fetus.

Reproductive Organs Male: Testicles make sperm cells. (Men have two testicles). The sperm travel from the testicles through tubes to leave the body. The final portion of the sperm’s journey in a male body goes through the urethra in the penis. (Note: When a male urinates, urine passes through this same tube.)

Reproductive Organs Female: The ovary produces egg cells. (Women have two ovaries – one on each side). The egg cells move through fallopian tubes. If the egg cell joins a sperm cell along the way, it becomes fertilized. It then attaches itself to the wall of the uterus where it will grow and develop into a fetus. (Note: if the egg does not meet a sperm, it is simply absorbed back into the body…this happens very often. Women make eggs every month.)

Reproductive Organs Female: The fetus lives in the uterus. When the fetus is fully developed, it is a baby ready to be born. It leaves the uterus through the vagina in an amazing and painful process. How long do you think it takes a fetus to develop and be ready to be born?

Nine Months It takes 40 weeks (or just over 9 months) for a baby to develop Life starts at one cell. The cell multiplies and attaches itself to the wall of the uterus. At that stage, it is called an embryo. It does not yet look like a human baby, but it is alive (its heart is formed and beating.) Look at the diagram on Page 136 to see how an embryo turns into a fetus.

3 Months In Picture B, the forming baby is 3 months old. It is now starting to look like a human baby. At this stage, it is no longer called an embryo…it is now a fetus. It has nerves, lungs, stomach, intestines, bladder and muscles. The muscles are working and allow the baby to move in the uterus. The baby is still connected to the wall of the uterus, but now it is through a tube to the placenta. Everything a baby needs to grow, it gets from its mother through the placenta.

6 Months Picture C shows a growing fetus at six months old. Its respiratory, circulatory and digestive systems are almost complete. It moves around a lot (kicks, turns and swings its arms) and the mother can feel the baby move. Babies born at 6 months could survive, but they are not ready yet for the outside world and will have trouble breathing and eating.

9 Months Picture D shows a baby that has grown inside its mother for nine months. Do you think it is ready to be born? If it were born now, do you think it would survive? How big do you think it would be?

Review Work on the Review Questions #1-6 on Page 137.

Going Deeper… Earlier we talked about the “placenta”. The placenta is what gives a baby all the good things it needs to grow and passes the waste back to the mother to get rid of. The placenta gives the baby everything it needs, and the placenta gets everything from the mother. This means that everything the mother has in her body is being passed to her baby through the placenta.

What does that mean? That means that a pregnant mother wants to take lots of good things into her body to share with her unborn baby. She also wants to avoid lots of bad things so she doesn’t harm her baby.

Pregnant Mom Examples: Would a pregnant mom want to do these things? What do you think? Why? Eat healthy meals Drink Alcohol Take vitamins Smoke Drink lots of water Do drugs

Parents Let’s talk about what you think it takes to be a good new parent. What do new parents have to do? How are their lives different because they have a new baby?