Compare amniotic eggs to placentas.

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1. Identify the primary function: Both amniotic eggs and placentas serve the purpose of nurturing and protecting the developing embryo. However, they are found in different groups of animals and have distinct structures and functions.
2. Describe amniotic eggs: Amniotic eggs are found in reptiles, birds, and some mammals like monotremes. They have several layers including a hard or leathery shell that provides protection, and membranes that store waste and facilitate gas exchange.
3. Explain placentas: Placentas are found in most mammals. They are organs formed in the uterus during pregnancy that provide oxygen and nutrients to the growing fetus through the umbilical cord, while also removing waste products.
4. Compare development environments: Amniotic eggs develop externally, where the embryo grows inside the egg outside the mother's body. In contrast, development in species with placentas occurs internally, with the fetus developing inside the uterus connected to the mother.
5. Discuss evolutionary significance: The development of amniotic eggs allowed for reproduction away from water bodies, facilitating the colonization of diverse terrestrial environments. The evolution of the placenta allowed for more direct nurturing of the young, leading to longer gestation periods and more developed offspring at birth.