Final answer:
The amnion is the extraembryonic membrane with the same function in both reptiles and humans, offering protection and a hydrated environment to the developing embryo.
Step-by-step explanation:
The extraembryonic membrane that shares the same function in both reptiles and humans is the amnion. The amnion protects the embryo in reptiles as it does in humans, against mechanical shocks and desiccation, while providing a hydrated environment for the developing embryo. In both humans and reptiles, the amnion forms a protective cushion filled with amniotic fluid encasing the embryo.
Although the chorion and allantois have roles in gas exchange and waste management and contribute to placenta formation in humans respectively, their functions are not completely analogous between these two groups. The yolk sac, which provides nutrients in reptiles, is not heavily utilized for this purpose in humans as it is greatly reduced; instead, it serves primarily in blood cell formation and as the primitive source of germ cells.