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The amniotic egg formed through a series of evolutionary steps. After internal fertilization and the habit of laying eggs in terrestrial environments became a reproduction strategy amongst the amniote ancestors, the next major breakthrough appears to have involved a gradual replacement of the gelatinous coating covering the amphibian egg with a fibrous shell membrane.
It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective environment for the developing embryo. The amnion, along with the chorion, the yolk sac and the allantois protect the embryo.
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the animal hatches.
22 de ago. de 2023 · The amniotic egg is the innovation that apparently allowed amniotes to complete the transition from an aquatic to a terrestrial environment and not rely on the aquatic habitat for reproduction, as Reisz 1997 describes.
The amniotic egg is the key characteristic of amniotes. In amniotes that lay eggs, the shell of the egg provides protection for the developing embryo while being permeable enough to allow for the exchange of carbon dioxide and oxygen.
They are the land vertebrates which lay cleidoic eggs. Two super-groups make up the amniotes: the Synapsida (Pelycosaurs, Theriodonts and mammals) and the Sauropsida (all reptiles, including dinosaurs and birds). The embryos of amniotes are either laid as eggs or develop in the female.
14 de mar. de 2019 · The origin of the amniote egg is a topic of great significance because it represents one of the major evolutionary innovations in vertebrate evolution, allowing the group to complete their...
