1. Chapter 18: Life cycles and reproductive strategies
Birth Control

2. Birth Control
After intercourse, only a few hundred thousand of the millions of sperm ejaculated into the vagina will make it to the uterus.
Only a few hundred sperm will reach the ends of the Fallopian tubes.
Conception occurs in a Fallopian tube.

3. Birth Control
An egg is capable of being fertilised for about two days after ovulation and sperm can last for about three days in the female reproductive tract.
There is about two to five days around ovulation (oestrus) where conception is most likely.

4. Birth Control

5. Birth Control

6. Birth Control
The zygote takes about three to four days to travel down the Fallopian tube and be implanted in the uterus.

7. Birth Control
Humans have practised birth control for thousands of years.
This is before our biological understanding of conception and embryology.
Ancient Egyptians placed foreign objects in the vagina to prevent the sperm entering the uterus.

8. Birth Control Contraception can be practised by women, men or couples.
Traditionally women have been responsible for birth control (most probably because they carry the consequences of failed contraception).

9. Birth Control Today birth control falls into three categories:
Contraception (prevention of release of egg or sperm, blocking transport of egg or sperm, reducing the survival of sperm or preventing the transfer of sperm into the vagina).
Interference with implantation
Pregnancy termination (abortion)

10. Birth Control Contraception
Most effective (apart from complete abstinence from sex)
Females - tubal ligation (cut and tie oviducts)
Males - vasectomy (cut and tie vas deferens)

11. Tubal Ligation
Top of uterus
Fallopian tube
Ovary

12. Vasectomy

13. Birth Control Contraception
The pill, diaphragm and condoms also effective
Small implants containing a hormone such as progesterone can last for up to three years

14. Birth Control Contraception and interference with implantation
Intra-uterine device (IUD) is a flexible plastic device with copper wire wrapped around it.
The copper is toxic to sperm
IUDs also decrease the chance of implantation

15. Birth Control Pregnancy termination
Surgical removal of embryo (termination or abortion)
Laws vary between states and countries