External Fertilization

Introduction

External Fertilization is very common among aquatic habits. The process consists of discharging egg and sperm into the water. In this process, the sperm reaches the egg and it shows diversity. In this factor, the temperature of the water plays a major role. Almost all fish, crustaceans, mollusks, spawn, and squid follows this type of fertilization process. It consists of some features and has some advantages and disadvantages of this factor.

What is External Fertilization?

The fertilization that occurs outside the body of the organisms is called External Fertilization. In this process for having successful fertilization water body is the primary medium. The egg and sperm is discharged in the external environment. This process occurs when the male releases sperms and the female releases eggs in the same environment. The desiccation of eggs is protected in an aquatic environment in this process. This process leads to the mix-up of genes and genetic diversity. That is why the survival of the species increases. Some of the organisms such as sponges have the only process of fertilization namely broadcast spawning.

Examples of External fertilization

These factors of external fertilization have different types of examples. Here, the fertilization process of starfish, coy coral, salmon, frogs, and sea urchins can be given.

• Starfish gather in a group and after that give chemical signals for giving an indication to other members of the group. They give the indication that they are ready to spawn and it increases the chance of fertilization.

• Salmon − show an opening right in front of their anal fin through which the gametes are released and then fertilized. For having fertilization, the male and female frogs spread their eggs on water.

• Sea Urchins − use chemotaxis for attracting the sperms towards the eggs.

Features of External Fertilization

External fertilization has some specific features and they described the characteristics of this kind of fertilization.

• In this type of fertilization, water body is required for the survival of the sperms. It is because they can die on land and another feature of it is that this fertilization’s success rate is very low.

• A large number of gametes by the female and males are required for determining the success of the reproduction.

• It is a simple process because there is no involvement of any mating rituals or hormones.

• Most of the gametes can be destroyed without having fertilized and this is the most disadvantage part of reproductive animals.

Advantages of External fertilization

External fertilization has some advantages as this process increases genetic variation. It also helps in producing a large number of offspring. The released gametes can drift and that is why it is easy to find mates. The advantage of this factor is that it is a simple process.

Disadvantages of External fertilization

There are some disadvantages of the factor of external fertilization.

• It is seen that in this process, a majority of gametes are left unfertilized and they get wasted.

• The chances of fertilization in this process are diminished by predators and natural hazards.

• There is a possibility that sperms and eggs may not come in contact for the process of fertilization.

• There is also a possibility of desiccation of gametes or zygotes.

External Fertilization in Humans

Humans use the external fertilization process, but it is not a natural process. It is seen that in some females’ ovarian ducts have been obstructed. Then the sperms are not able to reach the eggs and therefore the woman is unable to conceive. In this case, doctors collect sperms, eggs, and keep them together for some hours in vitro-fertilization. After the fertilization process, the zygote is delivered to the uterus of the female. Then the process of development happens within the body of the female and it takes one-week time.

Facts about External Fertilization in Animals

Some factors about animal’s external fertilization can be described here and they are -

• The female counterparts have fewer gametes compared to males.

• In this fertilization, external unfertilized eggs can never be laid.

• Most of the fish species fertilize externally.

• Algae show three types of external fertilization such as oogamy, anisogamy, and isogamy.

• Variations in genes can see in this type of fertilization process.

• The fertilization process of coral animals is different because they send them effs and sleep separately. The currents of water carry the gamete for fertilization.

Conclusion

Therefore, it is seen that external fertilization is an easy process and it occurs outside the body of an organism. The female releases eggs, the male releases sperms in this process in the external environment, and the fertilization happens. In the process the water body is the most important part as the sperm dies without water. The fertilization of fish, frogs, corals, and Sea Urchins are examples of this factor. This process has both advantages and disadvantages. It is seen that all amphibians and fishes fertilize externally and in this process, risk is high.

FAQs

Qns 1. What are the examples of External Fertilization?

Ans. Some examples of External Fertilization are the fertilization of salmon, frogs, corals, starfish, and urchins of the sea, mollusks, and squid. The process happens when male gametes come in proximity to the female gametes.

Qns 2. What is the difference between internal and external fertilization?

Ans. The main difference between internal and external fertilization is that the first one takes place inside the female body whereas the next one occurs outside the female body.

Qns 3. Does External Fertilization happen inland?

Ans. Water plays important role in this type of fertilization process. Water helps in the movement of the games and in the fertilization process. Although water is the most important part of this process, it can also happen without the presence of water.