1. Meiosis
Let’s Make A Baby!!!!

2. Mitosis VS. Meiosis Mitosis: Meiosis:
When one cell divides to become two daughter cells.
Used for growth and to repair injury.
When unicellular organisms use mitosis to reproduce, it is called binary fission.
NOT INVOLVED WITH EGGS OR SPERM!!!!
Meiosis:
When a normal cell becomes a gamete (eggs and sperm).
The number of chromosomes is reduced from the diploid (2N) number to the haploid (N) number.

3. Meiosis Worksheet

4. When Does Meiosis Happen?
If you’re a boy, it begins to happen at puberty and continues for the rest of your life!
If you’re a girl, it happens when you’re still a fetus in your mothers belly and is done by the time you’re born!

5. Crossing Over
Sometimes, during meiosis, the genes from your mother and the genes from your father become spliced together. This is called
crossing over.

6. Sexual Reproduction & Crossing Over
What is the advantage of sexual reproduction?
It means that the offspring get a larger variety of traits.
Crossing over increases this variety even more!

7. Fertilization
When the egg and sperm unite, it is called fertilization.
A fertilized egg is called a zygote.

8. How does fertilization happen?
Boys can release sperm at any time. Girls can only release an egg(s) only a few days a month. When a female releases an egg, it is called ovulation.
The egg is released from the ovary and travels through the fallopian tubes to the uterus.

9. Fertilization Continued
Usually, a female will ovulate from one ovary one month, and the other ovary the next month, releasing only one egg each time.
Sometimes, however, she will release two eggs at a time. If both of these eggs become fertilized, it will result in fraternal twins! Fraternal twins are no more alike than any other siblings.
If she only releases one egg, but the egg splits into two, it will result in identical twins! Identical twins have the same DNA. They are essentially clones of each other!

10. Fertilization Continued
If an egg is released, but there is no sperm available to fertilize it, the egg (along with the lining of the uterus) is shed from the body at the end of the woman’s cycle.
We all know what this is called!!!

11. What About Birth Control/Morning After Pill?
Birth control works essentially by tricking your body into thinking you are already pregnant, so you won’t ovulate every month. No ovulation means no egg. No egg means NO BABY!!!
But you have to be on birth control for 2 to 4 weeks before it completely kicks in, and if you miss a dose, pregnancy is possible!
The morning after pill works in two ways. First, it keeps a woman from ovulating that month if she hasn’t yet. If she has already ovulated, it keeps the egg from attaching to the uterus, so it comes out with the woman’s next period.
Birth control is good, but it’s never 100%, and it CANNOT protect you from STDs. If you’re going to have sex, it’s ALWAYS best to use birth control AND a condom at the same time!