Page 4 - Reproduction in Animals

female lays hundreds of eggs. Unlike
Have you heard of
test tube babies? hen’s egg, frog’s egg is not covered by a
shell and it is comparatively very
Boojho and Paheli’s teacher once told delicate. A layer of jelly holds the eggs
them in the class that in some women
oviducts are blocked. These women together and provides protection to the
are unable to bear babies because eggs (Fig. 6.7).
sperms cannot reach the egg for
fertilisation. In such cases, doctors
collect freshly released egg and
sperms and keep them together for a
few hours for IVF or in vitro
fertilisation (fertilisation outside the
body). In case fertilisation occurs,
the zygote is allowed to develop for
about a week and then it is placed in
the mother’s uterus. Complete
development takes place in the uterus
and the baby is born like any other
baby. Babies born through this
technique are called test-tube
babies. This term is actually
misleading because babies cannot Fig. 6.7 : Eggs of frog
grow in test tubes.
As the eggs are laid, the male
deposits sperms over them. Each
You will be surprised to know that
in many animals fertilisation takes sperm swims randomly in water with
place outside the body of the female. the help of its long tail. The sperms
In these animals, fertilisation takes come in contact with the eggs. This
place in water. Let us find out how results in fertilisation. This type of
this happens. fertilisation in which the fusion of a
male and a female gamete takes place
Activity 6.1 outside the body of the female is called
external fertilisation. It is very
Visit some ponds or slow-flowing
streams during spring or rainy common in aquatic animals such as
season. Look out for clusters of fish, starfish, etc.
frog’s eggs floating in water.
Write down the colour and size of
the eggs.
Why do fish and
During spring or rainy season, frogs frogs lay eggs in
hundreds whereas a
and toads move to ponds and slow-
hen lays only one
flowing streams. When the male and egg at a time?
female come together in water, the

REPRODUCTION IN ANIMALS 69

Rationalised-2023-24