What is Internal Fertilization?
This process is the union of the egg and sperm during the reproduction process inside the female body. This is different from external fertilization and brings more control to the female part during the process of fertilization. For this process to happen we need to make the male to introduce the sperm into the female tract which is used for reproduction.
In some mammals and reptiles this is done by the process of copulation which is done by an organ which is introduced to the vagina or cloaca. In some birds also there is this process and here two animals are transferring sperms. Salamanders, spiders etc also go through the internal fertilization process which is done by transferring the spermatophore. This is a bundle of sperms which goes from male to female. After the fertilization process the egg are being laid which are basically the embryo and thus they continue to develop inside the tract of the females and later develop into the organisms.
Advantages for internal fertilization process.
- This allows the females to choose the process of reproduction and also gives her the freedom to choose her partner and also after and before mating. This does not happen with external fertilization because there she has no control and this is because in external process it is not sure who is fertilizing her eggs. Also when they are being fertilized is not known to her.
- She can decide the location and time when she can reproduce and engage in the process.In the process of external fertilisation she can only choose when she can release her eggs but not when she can get it fertilised.
- There is protection of her eggs and also for some oviparous animals these eggs are inside the hard shell of the egg and thus internal fertilisation does help in the development of the eggs and offspring’s inside.
- There is great protection from predators and dehydration on the dry land. Hence there is great chance of survival for them and also there is more regulated temperature.
Disadvantages for Internal Fertilisation:
- The process involves gestation and also thus risky for the mother. There is extra energy demands for the same.
- The process also involves sexual reproduction and also this process is very risky. There is intercourse along with this process and so is dependent on high ovulation periods and also is very infrequent.
- In external fertilisation some animas release the eggs to the water and does not need any partner to reproduce.
- As compared to external fertilisation in internal fertilisation there are fewer offspring’s produced. This is because the mother will not hold the offspring’
Internal Fertilisation in Fishes:
The process of internal fertilisation in fish and the process involves where the male will insert a fin which is like acute into the female reproductive organ and thus put his sperms into the tract. Other species also are mouthbrooders and this process where one fish will put the eggs in the mouth for the process of incubation. There is another species which also makes the female lay her eggs and pick it up in her mouth. Then the males will make the females to open the mouth and fertilise the egg. Internal fertilisation also helps fishes to internally fertilise.
Birds: This process is very common in Birds via cloacal contact. Here males and females also contact their cloacal together and transfer the sperms into the females. Water fowls and geese use their male organs for internal fertilisation.
Amphibians: Most of the amphibians are using external fertilisation but there is some exception like the Salamanders which have internal fertilisation. They have encapsulated for sperms and they deposit the sperms to the females. There is a nutrient called the spermatophore.The male will put a spermatophore into the ground which is picked up by female with her cloaca. Her eggs are fertilised with it. Over the period of time the internal fertilisation process is found to be evolving in amphibians. This is particularly true for amphibians since this process is rapid and more developed in its stages in Amphibians. There is transition from water to land during the evolution of vertebrate.This is also advantageous for amphibians who internally fertilise and it allows the selection of time and place for the process of reproduction.
Learn more:Reproduction In Organisms from Class 12 Biology