What is the difference between internal and external fertilization?
Fertilization led to the development of new species from the existing ones. It occurs when there is a fusion of male and female gametes. It is further divided into internal and external fertilization.
The lesson provides detailed insight into the difference between internal and external fertilization with examples as well as a comparison chart. Take time to read through and learn more about the similarities between internal and external fertilization.
What Is an Internal Fertilization?
Internal fertilization refers to the fusion of male gametes (sperms) and female gametes (ovum) inside the body of the female by the insemination through copulation. Here are internal fertilization examples:
Ovoviviparity is a method where the egg is retained in the body of the female and the embryo is nourished by the content of the yolk. The eggs later hatch to give rise to young ones. This method is common in sharks, lizards, and snakes.
Oviparity is a method where the female lays eggs outside and get nourished by the yolk. These animals experiencing the method are known as oviparous such as birds, most amphibians, reptiles, bony fish, and some cartilaginous fish.
Viviparity is a method where the offspring developed inside the female and receives nourishment from the placenta of the mother. The method is quite common in mammals, some reptiles and amphibians. These animals are known as viviparous.
Advantages of Internal Fertilization
- More offspring tend to survive
- High chance of successful fertilization
Disadvantages of Internal fertilization
- Requires more energy to find the mate
- Less number of offspring produced
- Require large investment for the female counterpart
What Is an External Fertilization?
External fertilization refers to the fusion of male gametes and female gametes taking place from the outside of the body. An example of external fertilization occurs in frogs, fish, mollusks, and crustaceans.
Advantages of External Fertilization
- Little energy required to find the mate
- Many offspring produced
- Offspring do not compete with parents
Disadvantages of External Fertilization
- High chances of unsuccessful fertilization
- Zygote and embryos not protected
- High chances of not surviving due to lack of parental care
Comparison Chart: Internal Vs External Fertilization
| Basic Terms | Internal Fertilization | External Fertilization |
| Meaning | It occurs inside the body | It occurs outside the body |
| Fertilization | Inside the female organism | Outside the female organism |
| Methods | Oviparity, viviparity, and ovovivipary | External environment |
| Examples | Mammals, reptiles, some birds, and some fish. | Frog, fish, mollusks, and crustaceans. |
| In Plants | Bryophytes, pteridophytes, gymnosperms, and angiosperms. | Most algae. |
| Rates of Survival | High survival rates of the embryo. | Lower survival rates of the embryo and egg. |
| Importance | Quite successful in harsh environmental conditions | Quite successful in moistened environments |
| Number of Gametes | Less number of gametes | a large number of gametes |
| Genetic Diversity | The male gametes are received by a selected individual | Typically results in a great genetic diversity |
| Parental Care | More | Less |
Core Differences between Internal and External Fertilization
- Examples of internal fertilization occur in mammals, reptiles, birds, bryophytes, and tracheophytes whereas examples of external fertilization are shown in amphibians, algae, and fish, etc.
- Internal fertilization occurs in all type of environment whereas external fertilization occurs in a wet environment
- External fertilization results in a large number of offspring while internal fertilization results in a small number of offspring
- The offspring of internal fertilization can greatly survive in a harsh condition unlike those of external fertilization
- Internal fertilization require more energy to find a mate while external fertilization require less energy to find a mate
- There is more chance of survival in internal fertilization due to parental care while a low chance of survival in external fertilization due to no parental care
- Types of internal fertilization are Oviparity, Viviparity, and Ovoviviparity while external fertilization has no any type
- Young ones of internal fertilization develop in the womb of females while those of external fertilization develop from outside the womb of the female
- External fertilization result in great diversity unlike internal fertilization
- Internal fertilization in plants takes place in bryophytes, pteridophytes, gymnosperms, and angiosperms while external fertilization in algae
Core Similarities between Internal and External Fertilization
- Both are the mechanism of fusing male and female gametes
- Both occur in animals as well as plants
- Both result in mobile sperm and immobile egg
- The final result of both is a zygote
Comparison Video
Summary
The core difference between internal and external fertilization is internal fertilization occurs inside the body of the female while external fertilization occurs outside the body of the female. Internal fertilization entails parental care while external fertilization has no parental care hence low chances of offspring survival.