Page 6 - Reproduction in Animals
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parts such as hands, legs, head, eyes, place inside the egg shell during this
ears etc. The stage of the embryo in period? After the chick is completely
which all the body parts can be developed it bursts open the egg shell.
identified is called a foetus (Fig. 6.9). In animals which undergo external
When the development of the foetus is fertilisation, development of the embryo
complete, the mother gives birth to takes place outside the female body. The
the baby. embryos continue to grow within their
egg coverings. After the embryos develop,
the eggs hatch. You must have seen
numerous tadpoles swimming in ponds
Uterus
and streams.
Viviparous and Oviparous Animals
We have learnt that some animals give
birth to young ones while some animals
lay eggs which later develop into young
ones. The animals which give birth to
young ones are called viviparous
animals. Those animals which lay eggs
are called oviparous animals. The
following activity will help you
understand better and differentiate
Fig. 6.9 : Foetus in the uterus between viviparous and oviparous
animals.
Internal fertilisation takes place in
hens also. But, do hens give birth to Activity 6.2
babies like human beings and cows? You
Try to observe eggs of the following
know that they do not. Then, how are
organisms – frog, lizard, butterfly
chicks born? Let us find out.
or moth, hen and crow or any other
Soon after fertilisation, the zygote
bird. Were you able to observe eggs
divides repeatedly and travels down the of all of them? Make drawings of the
oviduct. As it travels down, many eggs that you have observed.
protective layers are formed around it.
The hard shell that you see in a hen’s The eggs of a few animals are easy
egg is one such protective layer. to observe because their mothers lay
After the hard shell is formed around them outside their bodies. These are
the developing embryo, the hen finally examples of oviparous animals. But you
lays the egg. The embryo takes about 3 would not be able to collect the eggs of
weeks to develop into a chick. You must a dog, cow or cat. This is because they
have seen the hen sitting on the eggs to do not lay eggs. The mother gives birth
provide sufficient warmth. Did you know to the young ones. These are examples
that development of the chick takes of viviparous animals.
REPRODUCTION IN ANIMALS 71
Rationalised-2023-24
