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Identify the classes of animals that are amniotes Describe the main characteristics of amniotes The reptiles (including dinosaurs and birds) are distinguished from amphibians by their terrestrially adapted egg, which is supported by four extraembryonic membranes : the yolk sac, the amnion, the chorion, and the allantois (Figure 1).
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. The albumin, or egg white, provides the embryo with water and protein, whereas the fattier egg yolk is the energy supply for the embryo, as is the case with the eggs of many other animals, such as amphibians.
Amniotic Animals. In the past, the most common division of amniotes has been into the classes Mammalia, Reptilia, and Aves. Birds are directly descended, however, from dinosaurs, so this classical scheme results in groups that are not true clades.
23 de dez. de 2019 · Amniotes include mammals, reptiles and birds, representing 75% of extant vertebrate species on land. They originated around 318 million years ago in the early Late Carboniferous and their early ...
Inside the egg are a series of fluid-filled membranes which permit the embryo to survive: the amnion, allantois, yolk sac, and chorion. Surrounding and protecting the embryo is the amnion, filled with amniotic fluid, and providing the embryo with a stable fluid environment. The allantois performs two very important functions for the embryo ...
Amniotes are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals. Amniotes are characterized by having an egg equipped with an amnion, an adaptation to lay eggs on land or retain the fertilized egg within the mother. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several ...
Evolutionary Developmental Biology. Zachary S. Morris, Arhat Abzhanov, in Current Topics in Developmental Biology, 2021 Abstract. Amniotes, a clade of terrestrial vertebrates, which includes all of the descendants of the last common ancestor of the reptiles (including dinosaurs and birds) and mammals, is one of the most successful group of animals on our planet.
