How is the development of an embryo in an amniotic egg and in a placental mammal different?

The development of an embryo in an amniotic egg occurs outside the mother's body, where the embryo is surrounded by protective membranes and a yolk sac that provides nutrients. In contrast, placental mammals develop their embryos internally, where they are nourished through a placenta that facilitates the exchange of nutrients and waste with the mother's bloodstream. This difference allows placental mammals to have longer gestation periods and more complex developmental stages compared to those in amniotic eggs. Additionally, amniotic eggs typically have a hard or leathery shell that protects the embryo, while placental mammals give birth to live young.