What is Fertilization?

Fusion of sperm with egg to form zygote is called fertilization,

During fertilization,the nuclei of the sperm and the nuclei of the egg fuse to form a single nucleus

This fertilised egg is called zygote

Zygote is the beginning of a new individual


Different Types of Fertilization

It is of 2 types

  • Internal Fertilization
  • External Fertilization

Difference between Internal and External Fertilization


Internal Fertilization

External Fertilization

Fertilization of male and female gametes takes place inside female body

Fertilization of male and female gametes takes place outside female body

Chances of survival of offspring is more, so small number of eggs are produced

Chances of survival of offspring is less, so large number of eggs are produced


Human Beings

Animals like Dogs,Cat


Frogs, Starfish

Procedure followed

Male sperm cells enter body from vagina

They go into uterus and from their into oviducts

Ovaries produce egg or ova

Ovaries release single egg every month to oviduct

In oviduct,one of male sperm cells fertilize with the ova to form zygote

Zygote multiples repeatedly to form embryo

Embryo develops into foetus in few months in uterus of  the female

After few months,baby is formed

Procedure followed

Female frogs and star fish lays hundreds of eggs in water.

Male deposit sperms over them.

Sperm swims in water with the help of its long tail.

When it comes in contact with eggs,fertilization takes place




NCERT Question 4 (e) - Indicate whether the following statements are True (T) or False (F):

Egg laid after fertilization is made up of a single cell. (T/F)

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NCERT Question 10 (1) - Complete the cross-word puzzle using the hints given below

The process of the fusion of the gametes.

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NCERT Question 3 (a) - Choose the most appropriate answer:

(a) Internal fertilization occurs

(i) in female body.

(ii) outside female body.

(iii) in male body.

(iv) outside male body.

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NCERT Question 3 (c) - The number of nuclei present in a zygote is

(i) none. (ii) one. (iii) two. (iv) four.

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NCERT Question 9 - Differentiate between internal fertilization and external fertilization.

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo