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Structure of the Amniotic Egg. Evolution of eggs with a water-impermeable amniotic membrane surrounding a fluid-filled amniotic cavity permits embryonic development on land without danger of dessication. The main diagram shows the arrangement of membranes in a typical egg-laying oviparous vertebrates. In live-bearing viviparous vertebrates, the ...
21 de nov. de 2023 · The amniotic egg is 'air-breathing', meaning that it exchanges gases with the environment, unlike more primitive egg types. Amniotic eggs were an important adaptation for land dwelling species ...
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Artist Sam Davies. Narrator Addison Anderson. 350 million years ago, eggs could not survive far from water, therefore animals were water-bound. That is, until the amniotic egg, which allowed animals to live a fully terrestrial life. April Tucker peels back each layer of the amniotic egg, revealing how truly extraordinary this evolutionary.
The shelled, amniotic egg could be buried in nests on land, thus freeing early amniotes from the aquatic environment and making possible unfettered conquest of land by vertebrates. Evolution of the first extraembryonic membrane, the yolk sac, actually predates appearance of the amniotes many millions of years.
羊膜卵内有大的卵黄囊（yolk sac）,储存卵黄以保证胚胎发育的营养需求.在胚胎发育至原肠期后,胚胎周围产生向上突起的环状褶皱,环绕胚胎生长,最终将胚胎包在一个具有2层膜的囊中,外层为绒毛膜(chorion),内层为羊膜(amnion).羊膜腔(amniotic cavity)是一个充满羊水的密闭的腔,胚胎浸于其中.这为胚胎提供了 ...
The amniotic egg: An air-breathing egg characterized by a shell and extraembryonic membranes. These enclosed the amniote embryo in a private pond during its development and mediated gas-exchange with the external environment. Claws or nails at the end of digits. This novelty allows digging, and burying of eggs.
17 de abr. de 2019 · The amnion is a membrane derived from fetal tissue which surrounds and protects the fetus. The amnion can be found within the egg, as in lizards and birds, or the amnion can simply enclose the fetus within the uterus. Amniotes include most of the vertebrates, excluding fish and amphibians. Fish and amphibians are anamniotes, meaning “without ...
