Fertilization

• Fusion of the egg and the sperm is called fertilization.
• The site of fertilization is oviduct.
• During fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus.
• This results in the formation of a fertilized egg or zygote.
• The new individual inherits some characteristics from the mother and some from the father.
• Fertilization can be of two types: internal and external.

Internal Fertilization:

• Fertilization which takes place inside the female body is called internal fertilization.

Example: humans, cows etc.

• For this sperms from male body enters the female body and reaches the oviduct where the fusion occurs.
• After fertilization, the zygote divides repeatedly and travels down the oviduct to the uterus.
•  As it travels down, many protective layers are formed around it.
• This layer acts as a shield and does not allow further any other sperm to fuse with the egg.
• After this the development of embryo takes place.

External Fertilization:

• Fertilization in which the fusion of a male and a female gamete takes place outside the body of the female is called external fertilization. Example: fish etc.
• In these animals, fertilization takes place in water.
• The female lays many eggs in water and then male releases many sperms over these eggs.
• Many eggs and sperms gets washed away due to flowing water hence few are available for fusion.
• Once zygote is formed it which further undergoes development outside the body only.
• Further the mature organism will develop.