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Indeed, many modern-day amniotes require moisture to keep their eggs from desiccating. Although some modern amphibians lay eggs on land, all amphibians lack advanced traits like an amnion. The amniotic egg formed through a series of evolutionary steps.
- Cleidoic egg
The cleidoic egg (from Greek kleistos = closed) is the type...
- Cleidoic egg
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 origin of amniotes is therefore anchored by two disparate disciplines: developmental biology and vertebrate paleontology. The amniotic egg is at the center of the great evolutionary success of the crown group Amniota.
Amniote. The amniotes are a taxonomic group of animals: all the tetrapods except the amphibians . They are the land vertebrates which lay cleidoic eggs. [1] Two super-groups make up the amniotes: the Synapsida ( Pelycosaurs, Theriodonts and mammals) and the Sauropsida (all reptiles, including dinosaurs and birds ).
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.
