The amniotic egg first evolved in which of the following groups?

The evolution of the amniotic egg is a significant adaptation that allowed certain vertebrates to reproduce successfully in terrestrial environments. Amniotic eggs are characterized by their protective membranes and structures, which prevent desiccation and provide a controlled environment for embryo development, facilitating reproduction away from water.

Reptiles were the first group to develop the amniotic egg, which allowed their eggs to be laid on land without the risk of drying out, unlike amphibians that typically require water for their eggs. This advancement gave reptiles an evolutionary advantage, enabling them to colonize a wider range of habitats. The amniotic egg contains several key features, such as the amnion, which encases the embryo in a fluid-filled cavity, and the chorion and allantois, which play roles in respiration and waste storage, respectively.

While birds and egg-laying mammals (monotremes) also possess amniotic eggs, they are considered derived groups that evolved this trait after reptiles. Amphibians, on the other hand, typically lay eggs in water and do not have amniotic eggs, highlighting the importance of this evolutionary step in the history of vertebrate reproduction. Thus, the correct answer indicates the origin of the amniotic egg