1/19/2024 0 Comments Rhinoceros viper amniotic egg![]() ![]() Anapsids include extinct organisms and may, based on anatomy, include turtles. Anapsids have no temporal fenestrae, synapsids have one, and diapsids have two. Temporal fenestrae are post-orbital openings in the skull that allow muscles to expand and lengthen. The key differences between the synapsids, anapsids, and diapsids are the structures of the skull and the number of temporal fenestrae behind each eye ( Figure). Sauropsids include reptiles and birds, and can be further divided into anapsids and diapsids. Synapsids also include therapsids, which were mammal-like reptiles from which mammals evolved. Synapsids include all mammals, including extinct mammalian species. The initial split was into synapsids and sauropsids. The early amniotes diverged into two main lines soon after the first amniotes arose. The first amniotes evolved from amphibian ancestors approximately 340 million years ago during the Carboniferous period. The amniotic cavity is filled with albumen.Īdditional derived characteristics of amniotes include waterproof skin, due to the presence of lipids, and costal (rib) ventilation of the lungs.The yolk provides food for the growing embryo.The allantois stores nitrogenous waste and facilitates respiration.Which of the following statements about the parts of an egg are false? ![]() Art Connection The key features of an amniotic egg are shown. In mammals, membranes that are homologous to the extra-embryonic membranes in eggs are present in the placenta. The allantois stores nitrogenous wastes produced by the embryo and also facilitates respiration. The amnion protects the embryo from mechanical shock and supports hydration. ![]() The chorion facilitates exchange of oxygen and carbon dioxide between the embryo and the eggâs external environment. While the inner amniotic membrane surrounds the embryo itself, the chorion surrounds the embryo and yolk sac. Extra-embryonic membranes are membranes present in amniotic eggs that are not a part of the body of the developing embryo. However, the eggs of amniotes contain three additional extra-embryonic membranes: the chorion, amnion, and allantois ( Figure). 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. ![]() 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 amniotic egg is the key characteristic of amniotes. Instead, the embryo grows within the motherâs body however, even with this internal gestation, amniotic membranes are still present. Most mammals do not lay eggs (except for monotremes). The shells of reptile eggs are leathery and require a moist environment. The shells of bird eggs are composed of calcium carbonate and are hard, but fragile. Although the shells of various amniotic species vary significantly, they all allow retention of water. This was a significant development that distinguished them from amphibians, which were restricted to moist environments due their shell-less eggs. The evolution of amniotic membranes meant that the embryos of amniotes were provided with their own aquatic environment, which led to less dependence on water for development and thus allowed the amniotes to branch out into drier environments. The amniotes âreptiles, birds, and mammalsâare distinguished from amphibians by their terrestrially adapted egg, which is protected by amniotic membranes. ![]()
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