External Fertilization: Characteristics, Advantages and Disadvantages

External fertilization is the term for fertilization that takes place outside of an organism's body. A body of water is typically necessary for effective fertilization. The environment outside is where the sperm and eggs are released. When the female releases the egg and the male releases the sperm in the same environment during spawning, external fertilization typically happens.

Evolution of life on Earth

Characteristics of External Fertilisation

• The likelihood of fertilisation is extremely low.
• Unlike internal fertilisation, successful reproduction requires both the male and female to produce a lot of gametes.
• To start the process of external fertilisation, a body of water is needed. On land, the sperms would perish.
• For most animals, this presents a reproductive disadvantage because most gametes perish before fertilisation.
• However, external fertilisation is a straightforward reproductive method that does not involve using hormones or ritualised mating.

Evolutionary Biology

External Fertilization's Benefits

• Increased genetic diversity is the result.
• There are more offspring as a result.
• Finding mates is simple because the gametes released can drift.
• Protection from predators: External fertilization allows for the release of a large number of gametes at once, increasing the chances of successful fertilization. Additionally, this can make it harder for predators to consume all of the eggs or sperm in one area.
• Adaptation to changing environments: External fertilization allows for adaptation to changing environments. For example, if a sudden change in temperature or salinity occurs in the environment, organisms that use external fertilization can quickly produce large numbers of eggs or sperm that are adapted to the new conditions.
• Reduced competition for resources: External fertilization allows organisms to reproduce without competing for resources. In contrast, internal fertilization often requires males to compete for access to females, which can be energetically expensive and potentially dangerous.
• No need for complex reproductive structures: Organisms that use external fertilization do not need complex reproductive structures, such as a penis or a vagina. This can reduce the risk of injury or infection during mating.
• Overall, external fertilization can be a highly effective reproductive strategy, especially in aquatic environments.

Evidence Of Evolution

External Fertilization's Drawbacks

• Wastage of gametes: External fertilization involves the release of a large number of gametes into the environment, and there is no guarantee that all of them will find a partner for fertilization. This can result in a waste of gametes.
• Lower fertilization success rate: External fertilization can result in lower fertilization success rates compared to internal fertilization. Environmental factors such as temperature, pH levels, and predation can affect the survival and chances of fertilization of gametes.
• Reduced control over offspring quality: External fertilization can result in many offspring with variable genetic traits, many of which may not benefit survival in the environment. This can result in reduced control over the quality of offspring.

Environmental Issues and Solutions

• Lack of parental care: External fertilization often involves minimal parental care for offspring, which can result in higher mortality rates due to predation or other environmental factors.
• Vulnerability to desiccation: Gametes or embryos released in a dry environment can be vulnerable to desiccation or drying out, which can result in reduced chances of successful fertilization or embryonic development.
• Competition for mates: In species with external fertilization, competition for mates can be intense, resulting in high energy expenditure and increased predation risk.

Essential Mineral Elements

External Fertilization Examples

• Starfish-

• Coy Coral-

• Frogs-

Entomology

• Sea Urchins-

• Salmon-

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Human External Fertilization

Exchange Regulation Of Gases

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