The embryo in mammals depend on the umbilical cord to survive, while amphibian embryos depend on the placenta and the protection of the shell of the egg. These two materials perform the same functions of providing the embryo with the necessary nutrients it needs to grow into a mature organism.
Through the umbilical cord, the embryo receives nutrients that are ingested or taken in by the mother. While the egg absorbs its nutrients from the encapsulated placenta inside its walls, where water and most nutrients are found.
