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The key difference between internal fertilization and external fertilization is that in internal fertilization, a fusion of male and female gametes or fertilization takes place inside the body while in external fertilization fusion of gametes or fertilization takes place outside the body of the organism.
Internal Fertilization vs. External Fertilization
Fertilization is the most important step in sexual reproduction. Fertilization is the process in which male gametes. i.e., sperms unite with the female gamete, i.e., egg to form a new individual. There are two types of fertilization, i.e., internal fertilization and external fertilization. Internal fertilization is the type of fertilization in which fusion of gametes takes place inside the body of the organism while external fertilization is the type of fertilization in which fusion of gametes takes place outside the body of the organism. Mostly, terrestrial organisms show internal fertilization while aquatic organisms show external fertilization. For example, Reptiles and birds, etc. show internal fertilization while fish and amphibians show external fertilization.
What is Internal Fertilization?
Internal fertilization takes place when the male organism directly deposits its sperms into the female body during copulation and syngamy (fusion of male and female gametes) takes place inside the female body. As the individual is present within the body of the mother so female shows more parental care. Moreover, it also protects the individual from harsh external conditions and survival chances of the young one increases. Internal fertilization is divided into three types, i.e., oviparity, viviparity and ovoviviparity.
- Oviparity: A type of internal fertilization in which organism lay egg outside and the offspring get nourishment by the presence of the yolk in the egg, Such animals are called oviparous and its examples are birds, most amphibians, reptiles, bony fish, and some cartilaginous fish, etc.
- Viviparity: Viviparity is a type of internal fertilization in which offspring develops within the body of the female and get nourishment from the mother with the help of placenta. Later on, a developed offspring comes out of the mother’s body. Such animals are called viviparous. For example human etc.
- Ovoviviparity: A type of fertilization in which the offspring develops in an egg within the mother body and get its nourishment from the yolk present within the egg. The egg hatched when the young one is fully developed. Such animals are called ovoviviparous. For example Sharks, lizards and snakes, etc.
What is External Fertilization?
External fertilization is the type of fertilization that takes place when both male and female gametes combine outside the body. Most of the aquatic organisms show this type of fertilization. Both male and female organisms lay their egg in the aquatic environment where syngamy takes place and new offspring is produced. Organisms with external fertilization show little parental care. Moreover, the harsh external environment also reduced the chances of survival of young ones. When egg and sperms are deposited in the open environment by male and female gamete, it is called spawning. For example amphibians, algae and fish, etc. show external fertilization.
- The process or type of fertilization in which fusion of male and female gametes takes place inside the body of the organism is called internal fertilization while external fertilization is the type of fertilization that takes place when both male and female gametes combine outside the body.
- Less number of gametes are released during internal fertilization and get deposited inside the body of the female whereas large numbers of gametes are released during external fertilization into the environment.
- In internal fertilization, further development of the young one takes place inside the body of the organism but in external fertilization further development of the young one takes place outside the body of the organism in the external environment.
- There are three types of internal fertilization, e., Oviparity, Viviparity and Ovoviviparity while there is no any type of external fertilization.
- During internal fertilization, young one gets more parental care and protection from the harsh environment while there are less parental care and more harsh conditions during external fertilization.
- There are more chances of survival due to parental care in internal fertilization while there are fewer chances of survival due to less parental care in external fertilization.
- A small number of offsprings produced during internal fertilization whereas a large number of offspring produced during external fertilization.
- Internal fertilization can occur in any type of environment while external fertilization required wet or aquatic environment.
- Mammals, Reptiles, Birds, Bryophytes and Tracheophytes show internal fertilization while amphibians, algae and fish, etc. are the example of external fertilization.
From the above discussion, it is concluded that internal and external fertilization are two types of fertilization. In internal fertilization, syngamy takes place inside the female’s body while in external fertilization syngamy takes place outside the body in an external aquatic environment. Internal fertilization shows more parental care and has more survival value while external fertilization has less parental care and low survival value.