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Difference Between External and Internal Fertilization

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Introduction

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For continuation of life on earth living beings have to undergo the reproduction process. And this reproduction process can be of types either sexual reproduction or asexual reproduction and in both types of the reproduction process, there is a huge difference. In the case of sexual reproduction, the process and development are complex whereas in the case of asexual reproduction it is not that much complex. In sexual reproduction, there is a fusion of sperm with egg (ovum) to produce zygote and this whole process is known as fertilization and this stage is the very first step of sexual reproduction. 


Types of Fertilization:

Based on the fertilization process, it is of two types they are:

1. Internal Fertilization: 

When there is an insertion of male sperm into the female reproductive part, so that sperm can fuse with egg to produce a zygote, this type of fertilization is called internal fertilization. In most of the animals like human beings, cats, lions, pigs, dogs, hens, etc internal fertilization takes place. It is called internal fertilization because the process of reproduction i.e. takes place inside the female body. And in this type of fertilization development of zygote takes place inside the mother’s body only and they get all kinds of nourishment from her. 

2. External Fertilization: 

In this type of fertilization fusion of male and female gametes take place outside the female body. Less percentage of organisms show external fertilization. Some of the organisms which show external fertilization are fish, frogs, etc. In these organisms, female parents deposit their eggs safely at one place and later male parents eject their sperm over the eggs which are then stored by females and due to this fusion takes place. 

But in this type of fusion, there are so many challenges which organisms have to go through. As their eggs and sperms are deposited in the external environment, because of this, the chances of fusion of gametes are very less and there is a risk that predators may eat eggs and the zygote that is formed. To compensate for this loss, organisms like fish and frogs lay hundreds of eggs at a time.


Facts About Internal Fertilization:

Some of the important facts and terms about internal fertilization are discussed below:

A. Fertilization is also known as syngamy so in case of internal fertilization syngamy of gametes occurs inside the female body after insemination through copulation process by the male.

B. This is seen in birds, mammals, birds occurring in terrestrial plants and animals, also in some of the aquatic entities.

C. Further internal fertilization is seen in three different ways, they are ovoviviparity(eggs retained in the female body, hatched when fully developed, oviparity(egg-laying), viviparity (offsprings develop within the female body) observes in plants such as bryophytes, pteridophytes.


Facts About External Fertilization:

Some of the common facts and term about external fertilization are discussed below:

A. In this type of fertilization, syngamy occurs outside the female body i.e. in the outer surrounding like in water bodies.

B. Organisms which show external fertilization have the following characteristics:

Syngamy of gametes outside the female body/outer environment, notably in water bodies.

  • Observed in a few vertebrates, sea urchins, fish, aquatic invertebrates, almost all amphibians.

  • Deposition of sperms and eggs by males and females in open surroundings is known as spawning.

  • Broadcast fertilization – used when sperms swim through the water uniting with eggs to fertilize.