In what type of environment is external fertilization commonly found?

External fertilization is commonly found in aquatic environments because many organisms that utilize this reproductive strategy release their eggs and sperm into the water. This setting allows the gametes to meet and fertilize outside of the body, which is essential for species such as fish and amphibians. In these environments, water serves as a medium that facilitates the movement and mixing of the gametes, increasing the chances of successful fertilization.

On the other hand, terrestrial environments are less conducive to external fertilization as land-based organisms might face challenges such as desiccation (drying out) of the gametes, making it more difficult for them to survive outside of the body. Additionally, desert and underground environments further restrict the conditions needed for external fertilization due to their arid nature and limited access to water, which is critical for the fertilization process in species that rely on this method. Thus, the presence of water in aquatic environments is a key factor that supports the effectiveness and prevalence of external fertilization.