Answer
Like most reproductive adaptations for organisms that live on land, internal fertilization in animals keeps gametes moist and gives them a liquid medium to reach each other with.
Work Step by Step
Aquatic organisms have the benefit of an environment in which gametes can both move and be exposed without being destroyed by the elements. But gametes of land animals cannot swim or be propelled through the air as easily; The reproductive structures and processes of all land organisms have developed to overcome this obstacle.
