BIOL 121 Lecture Notes - Lecture 34: Amnion, Saurischia, Mesozoic

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20 Mar 2017
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Amphibians were not able to colonize the drier terrestrial habitats because their skin was permeable to water loss. Lineage leading to amphibians: gills were lost due to a greater reliance on air-breathing. Lungs evolved as an adaptation to life in wetlands, but were also a preadaptation for life on land. so they needed to return to water to reproduce: The eggs are laid in water where they are fertilized externally. Aquatic tadpole larvae hatch out of the eggs. First reptiles appeared at end of carboniferous. Pelycosaur a permian member of the reptile group from which mammals evolved. Permian was cooler and dryer than the carboniferous. Prevents eggs from flattening out when laid on land. Within the egg there is a fluid-filled chamber called the amnion in which the embryo can develop. The ornithischia & saurischia constitute the dinosaurs ; birds are derived from the saurischia.

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