Fertilization


 
 
Concept Explanation
 

Fertilization

The fusion of male and female gametes to produce new organisms is called fertilization. The sperms made in the testes of man are introduced by penis into the woman's body through vagina. Once, a month an ovum is released from the ovary by a process called ovulation. The ovum moves into the oviduct (fallopian tube). During sexual intercourse, the male transfers sperms in the vagina through the penis. The sperm travels through a narrow opening called cervix into the the uterus and then the oviduct. The tail of sperms helps them in moving and reach the oviducts.

  • If at the same time, the ovary of woman releases an egg (or ovum), then this egg also goes into the oviduct.
  • One of the sperms enters the egg (see Figure 7). The fusion of sperm with egg is called fertilisation.
  • During fertilisation, the nucleus of sperm fuses with the nucleus of egg cell to form a single nucleus.
  • This results in the formation of a fertilised egg called zygote. Thus, a sperm combines with the egg in the oviduct and fertilises it to form a zygote.
  • The zygote (or fertilised egg) is the beginning of the formation of a new baby (or a new individual).
  • There are two types of fertilization: internal and external.

    External fertilization and External Development: Parents release sperms and eggs into the surrounding water, where fertilization occurs and zygotes develop into offspring. For this pattern to succeed, male and female must shed their gametes at the same time and place and in large numbers, e.g. frogs.

    Internal fertilization and External Development: Sperms are passed from the male into the female body. The fertilization takes place within the female body. The zygote, after its information, is surrounded by some secretions, reserve food and even a shell for development and protection of the growing embryo. The development of the chick takes place after the egg has been laid, e.g. hen.

    Internal fertilization and internal Development: Both fertilization and development take place in the female body. This means that both, formation of the zygote and development of the young one take place inside the body of the female, e.g. human beings and elephant.

    Animals that lays egg outside the body are called as oviparous animals(eg: chicken, frogs and butterfly) and animals that give birth to young ones are called as viviparous animals ( Human beings, certain fishes etc.) 

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    Sample Questions
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    Question : 1

    Fertilisation of egg takes place inside ________________

    Right Option : D
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    Question : 2

    Animals laying eggs are known as ____________________

    Right Option : A
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    Question : 3

    After fertilisation the human embryo grows inside the :

    Right Option : A
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