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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.
- Amniotic sac
The amniotic sac, also called the bag of waters or the...
- Amniotic sac
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.
Amniotic embryo. a=embryo, b=yolk, c=allantois, d=amnion, e=chorion In reptiles , birds , and monotremes , the chorion is one of the four extraembryonic membranes that make up the amniotic egg that provide for the nutrients and protection needed for the embryo's survival.
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.
