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Amphibians: diversity, life history, and declining populations



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PER Winter 2006 Notes for HH lect 4 2 14 06 Amphibians diversity life history and declining populations 1 The move to land lobe finned fish Compared to ray finned fish salmon tuna etc lobe fins have Reduced skeletal elements in their fore and hind fins Greater flexibility at what would become elbows and knees and More muscularization of proto limbs more power and control Most lobe fins including us also have choanae internal nostrils that open into the oral cavity which allow breathing through the nose Tetrapods Lost anal and dorsal fins Fully transformed remaining fins into muscularized limbs Dactyly evolution of digits Aquatic terrestrial habitat Why make the move to land What problems are caused by a move to land 2 Some diagnostic characters of modern amphibians Glandular skin that contains both mucous and poison glands but no epidermal structures Three chambered heart two atria one ventricle Cutaneous respiration most species also have lungs but the three chambered heart does not provide enough pressure to fully inflate the lungs so amphibian lungs aren t that efficient Complex inner ear anatomy the papilla amphibiorum a membrane that allows amphibians to hear acoustic signals of less than 1 000 Hz very low bass sounds Highly variable chromosome number genome size and ploidy Where Linneaus got it right and where he got it wrong 3a Major groups caecilians Gymnophiona Limbless burrowing tropical amphibians Circumtropical except Madagascar Adults are almost entirely subterranean and therefore mostly blind Internal fertilization plus some very interesting parental care and reproductive modes 3b The salamanders Caudata salamanders and newts which are just a small group of often aquatic salamanders within the family Salamandridae The only major group of amphibians with both tails and limbs Most diverse in SE U S adaptive radiation spread them to most of North America and some of Central America plus a few in Europe and east Asia while ancient landmass of Laurasia



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