Bio153_Lecture16_colonizingland_sv

Bio153_Lecture16_colonizingland_sv - Movement on to Land...

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Deuterostomes: Movement to Land Movement on to Land Acanthostega: one of the earliest tetrapods Ichthyostega Transition from Water to Land : Tetrapods Bony exoskeleton Jaws and teeth Limbs capable of moving on land Amniotic egg F irs t ve rteb ra te s t ca rtila g in o u fish es t fish w ith ex ten si v e b n t b y jaw t te trap d t am io Cambrian Ordovician Silurian Devonian Carboniferous Mississippian Pennsylvanian Permian Tetrapods: successful colonizers of terrestrial habitats Will we see more transitions from water to land? Why Colonize Land? Advantages : - oxygen - competition -predation -habitats -shelter Adaptations required : - air provides little support - large fluctuations in temperature – cycles of freezing, thawing, drying, flooding - both physiological and behavioral adaptations needed for terrestrial living Transition From Water to Land Adaptations for terrestrial living : Changes in: 1. skeletal system 2. gas exchange system 3. circulatory system 4. reproduction Transition From Water to Land Air - approximately 1000x less buoyant density than water - provides little support Changes in skeletal system : - strong vertebrae - movement- limbs -ribcage - pectoral girdle free from cranium - mobile neck
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Transition From Water to Land Changes in gas-exchange system : Oxygen – at least 20x more abundant in air – harder to extract oxygen from water - diffuses more rapidly in air than in water - in water, is temperature dependent - in air, is altitude dependent In water environment: gill filaments are oriented to the direction of water flow In terrestrial environment: respiratory exchange system must be moist, vascularized, protected Lungs of lobe-finned fishes – pharyngeal sac - gulp air; (adaptation to drought: when water gets stagnant, switches from gill- breathing to gulping air) Transition From Water to Land Changes in circulatory system : - fish: 2-chambered heart - blood is pumped to the gills to pick up oxygen - single circuit Transition From Water to Land Changes in circulatory system : tetrapods:
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This note was uploaded on 02/01/2012 for the course BIOLOGY 153 taught by Professor Dr.arts during the Fall '10 term at University of Toronto- Toronto.

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Bio153_Lecture16_colonizingland_sv - Movement on to Land...

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