Amniotes are a group of vertebrates that include reptiles, birds, and mammals. They are characterized by having an amniotic egg, which allows them to reproduce on land without the need for water. This egg contains a protective membrane that surrounds the developing embryo, providing it with nutrients and a stable environment. The evolution of amniotes marked a significant adaptation to terrestrial life. Unlike their ancestors, which were tied to aquatic environments for reproduction, amniotes can lay eggs in diverse habitats. This adaptation has enabled them to thrive in various ecosystems, making them a dominant group in the animal kingdom.