Page 2 - 2. Lesson notes-Fertilisation

Types of fertilisation

Fertilisation is of two types such as internal and external fertilisation.

Internal fertilisation External fertilisation
Fusion of male and female gametes takes Fusion of male and female gametes takes
place inside female’s body. place outside female’sbody.
It occurs in oviduct of females. It occurs in water.
Less number of gametes is produced by Large number of gametes is produced by
females. females.
Gametes and zygote are well protected. Gametes and zygote are not protected.

The chances of fertilisation is more . The chances of fertilisation areless.
Examples- Hen, Cat, Dog, Humans Examples-Fish, Frog, Star fish

During spring or rainy season, male and female Frogs come together,the female lays
thousands of eggs , the male deposits sperms over eggs . The eggs of frog are not
covered with shell and those are covered by layer of jelly for protection. Fertilisation
occurs in water.

In vitro fertilisation (IVF)

It is a type of artificial fertilisation . If the oviduct is blocked in females, then the freshly
released sperm and ova are kept togather in test tube for fertilisation . After fertilisation
the zygote is allowed to grow for a week and implanted in to mother’s uterus for
complete development .

Such babies are called test tube babies.The term test tube baby is misleading because
only fertilisation takes place in test tube and complete development takes place in
mother’s uterus .