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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.
- Amniosinas
- D000650
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.
The embryos of amniotes are either laid as eggs or develop in the female. These embyros are protected by several membranes, and have a much larger food supply than amphibian eggs. The 'invention' of the cleidoic egg, and its embryonic membranes, is the main reason why the eggs of an amniote do not need to be laid in water.
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.
