1. Survival of species
Fertilization

2. Fertilization is the union of two gametes: an ovum and spermatozoon.
What is fertilization
Fertilization is the union of two gametes: an ovum and spermatozoon.
This Photo by Unknown Author is licensed under CC BY-NC-SA

3. Ovulation
For fertilization to happen, the female body first needs to produce an ovum

4. Fertile period
Women are not fertile (able to have a baby) all the time
An ovum can be fertilized only during a short window that starts a few days before ovulation and ends the day after ovulation.

5. Menstrual cycle
From the end of menstruation until ovulation, the endometrium thickens in anticipation of receiving a fertilized ovum.
If fertilization does not occur, the endometrium detaches from the uterus approximately two weeks after ovulation.
Endometrium = a lot of blood vessel
The blood exists through the vagina.

6. Menstrual cycle In a 28 day cycle, menstruation usually last 5 days.
The ovulation always occurs 14 days before the first day of menstruation.
During ovulation, an ovum is released from the ovary.
An ovum can stay alive only for around 24 hours.
Spermatozoa can live for 3 to 5 days.

7. Spermatozoa and fertilization

8. Spermatozoa and fertilization

9. Spermatozoa and fertilization

10. Pregnancy is the time when a woman carries an embryo (then a fetus) in her uterus
What is pregnancy

11. Zygotes and embryos

12. Zygotes and embryos

13. Fetus
After eight weeks of pregnancy, the embryo is called a fetus. It will keep this name until birth.

14. Fetus