Reptile egg (amniote)

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Reptile egg (amniote)

Amniotic egg of a reptile (Athena Review).

Fish and amphibians have eggs which are hatched in open water and whose hatchlings, larvae, or tadpoles develop largely unprotected. Reptiles, birds, and mammals, by contrast, have eggs which contain the embryo in a protective, amniotic sac.
The German anatomist Ernst Haeckl added to Linnean classification the evolutionary distinction between amniotic and non-amniotic eggs used in reproduction. This basic trait showed that mammals, reptiles, and birds share a more recent common ancestor than do mammals and amphibians.
Amniotic eggs were first formally defined by Haeckl in 1866 on the basis of the amnion, a protective sheath around the embryo. As also shown in the figure, the allentois is a sac with blood vessels for exchanging liquids with the embryo. The yolk sac, also with blood vessels, contains food for the embyo.
Vertebrates which give birth through amniotic eggs which contain the embryo in a protective, amniotic sac are called amniotes. Examples are a chicken egg, a turtle or crocodile egg, or a mammalian foetus. Thus the group of amniotes includes the classes of birds, reptiles, and mammals, but excludes all members of the classes of fish and amphibians, which are called anamniotes.

Reference:
Haeckl, E. 1866. Generelle Morphologie der Organismen. Allgemeine Grundzüge der organischen Formen-Wissenschaft, mechanisch begründet durch die von C. Darwin reformirte Decendenz-Theorie. Berlin.
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	Reptile egg (amniote) Amniotic egg of a reptile (Athena Review).

	Fish and amphibians have eggs which are hatched in open water and whose hatchlings, larvae, or tadpoles develop largely unprotected. Reptiles, birds, and mammals, by contrast, have eggs which contain the embryo in a protective, amniotic sac. The German anatomist Ernst Haeckl added to Linnean classification the evolutionary distinction between amniotic and non-amniotic eggs used in reproduction. This basic trait showed that mammals, reptiles, and birds share a more recent common ancestor than do mammals and amphibians. Amniotic eggs were first formally defined by Haeckl in 1866 on the basis of the amnion, a protective sheath around the embryo. As also shown in the figure, the allentois is a sac with blood vessels for exchanging liquids with the embryo. The yolk sac, also with blood vessels, contains food for the embyo. Vertebrates which give birth through amniotic eggs which contain the embryo in a protective, amniotic sac are called amniotes. Examples are a chicken egg, a turtle or crocodile egg, or a mammalian foetus. Thus the group of amniotes includes the classes of birds, reptiles, and mammals, but excludes all members of the classes of fish and amphibians, which are called anamniotes. Reference: Haeckl, E. 1866. Generelle Morphologie der Organismen. Allgemeine Grundzüge der organischen Formen-Wissenschaft, mechanisch begründet durch die von C. Darwin reformirte Decendenz-Theorie. Berlin. .
	Athena Review Image Archive™ Main index of Athena Review Copyright © 1996-2020 Rust Family Foundation (All Rights Reserved).

Athena Review Image Archive ™

Reptile egg (amniote)

Amniotic egg of a reptile (Athena Review).

Fish and amphibians have eggs which are hatched in open water and whose hatchlings, larvae, or tadpoles develop largely unprotected. Reptiles, birds, and mammals, by contrast, have eggs which contain the embryo in a protective, amniotic sac.

The German anatomist Ernst Haeckl added to Linnean classification the evolutionary distinction between amniotic and non-amniotic eggs used in reproduction. This basic trait showed that mammals, reptiles, and birds share a more recent common ancestor than do mammals and amphibians.

Reference:

Haeckl, E. 1866. Generelle Morphologie der Organismen. Allgemeine Grundzüge der organischen Formen-Wissenschaft, mechanisch begründet durch die von C. Darwin reformirte Decendenz-Theorie. Berlin..

Athena Review Image Archive ^™

Haeckl, E. 1866. Generelle Morphologie der Organismen. Allgemeine Grundzüge der organischen Formen-Wissenschaft, mechanisch begründet durch die von C. Darwin reformirte Decendenz-Theorie. Berlin.
.