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Evolution of Tetrapods and Amphibians

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Biology (Sci)
BIOL 111
Irene Gregory- Eaves

03/11/11 Ray finned fish: spiney/soft cartilaginous fins, most fish are these Lobed finned fish: lung fish/coelacanths - have bones in fins Coelacanth: thought to be extinct (65mya), most abundant around time of dinosaurs 1938: found at South African fish market 1998: 2 species found in Indonesia Lung fish: 6 species - Walk on lobe-fins - tetrapod motion/close relative - breath through gills/primitive lungs - used during drying out of environment - estivate in mud during droughts - make a mucus sac to sustain themselves Why move to land? - In Devonian = droughts (400mya) - low O2 in water due to warm water - Increased competition in water – crowding in small pools - New food resources on land (arthropods, plants) - No vertebrate predation Repercussions of moving to land: Repercussion Need Less moisture Must prevent desiccation – gas exchange requires a moist surface and diffusion of O , most require water for fertilization 2 and larval development Less dense media Needs stronger skeletal support, muscles, require more energy to move and better circulatory system More O Advantageous 21% vs >1%, gases diffuse 2 faster in air than water Temp less stable Body temperature will fluctuate more as water has a high specific heat, more energy required to maintain
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