1. Production of Gametes: Both internal and external fertilization involve the production of gametes by the reproductive organs of the organisms involved. In internal fertilization, the male produces sperm, and the female produces eggs, while in external fertilization, both gametes are released into the external environment.
2. Union of Gametes: The fundamental goal of both internal and external fertilization is the union of the male gamete (sperm) with the female gamete (egg) to form a zygote. This process is essential for the creation of a new individual.
3. Genetic Variation: Both internal and external fertilization contribute to genetic variation in offspring. The fusion of genetic material from the sperm and egg during fertilization leads to genetic diversity, which is crucial for the survival and adaptation of species in changing environments.
4. Evolutionary Significance: Internal and external fertilization have evolved as reproductive strategies in different animal species. While external fertilization is commonly found in aquatic environments, where the availability of water provides a suitable medium for gamete interaction, internal fertilization has evolved in terrestrial environments, where protection and control over the fertilization process are necessary due to the absence of water.
However, it's important to note that internal and external fertilization differ significantly in the location where fertilization occurs and the level of parental involvement and control over the process. Internal fertilization provides greater protection and control over the developing zygote, while external fertilization involves a higher degree of exposure and potential hazards in the external environment.