GEO 105 Week 9 Notes
GEO 105 Week 9 Notes GEO 105
C of C
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This 5 page Class Notes was uploaded by Samantha Pratt on Friday March 4, 2016. The Class Notes belongs to GEO 105 at College of Charleston taught by Egerton in Spring 2016. Since its upload, it has received 26 views. For similar materials see Earth History in Geology at College of Charleston.
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Date Created: 03/04/16
Week 9 Geology Notes From Fins to Feet Part 5 Transition on to land Devonian Period (start of next test) Devonian 419359 Tropical to temperate environments Glaciers possibly at poles Increase in co2 but drops in Devonian Increase in oxygen Because on increase in plants on land Still sea level high (not as high as Ordovician) LAND LIFE Plants First soil Global spread of plants First trees Seed bearing plants Late Devonian first forests (30ft tall trees) Anthropod diversity increases First Tetrapods (amphibians, reptiles, birds, mammals) Soil=roots Braided streams to meandering (deeper) streams because of vegetation Fish can move to waterways NEAR LAND LIFE Aquatic life expands into shallower habitats Marine and freshwater Abundant algae in shallow water environments = little shading, so dense algae=bottom waters mat of decomposing algae > anoxic bottom waters AQAUTIC LIFE Age of the Fish High diversity Placoderms dominating First ray finned and lobe finned fish Shark diversity and abundance increases Extensive reed system Osteichthyes: Bony fish Arose in late Silurian Two distinctive lineages: Actinopterygii “ray fin” and Sarcoterygii “lobe fin” Bones, paired fins, teeth Rayfin fishes: 25,000 plus, fins made of dermal bone, multiple paired fins, teeth fused to jaw bones Rotation of fins (base of humorous) Lobe finned fish: Few are alive today 2 extant species coelacanths 6 extant species lungfish Fish breathing: fish have nostrils for smelling not breathing most fish have gills only for breathing lungfish have both gills and lungs many fish have swim bladders today o homologous with lungs tadpoles have lungs and gills (developing lungs later on) LEAVING THE WATER Problems with living on land= Gravity, desiccation, respiration, reproduction, senses Why leave the water= Virtually all estuarine and shallow are fish predators (7 feet long and 1 feet long), Avoid getting eaten, protect eggs from being eaten, better able to breath Devonian estuarine vertebrate fauna Gaining traction: 385 mya > fish: fins, conical heads, no neck, scales Eusthenopteron: 385 mya, lobe finned fish, clear humerus, radius and ulna, clear femur, tibia, and fibula, earliest bone marrow, external and internal choana (nostrils), no neck, and short ribs Tiktallik: 375 mya, lobe finned fish, clear humeru, radius, and ulna, shoulder, elbows, and wrist joints, no fins, more like flippers, pelvis large with circular hipsocket (no sacrum), external and internal (choana) nostrils, reduced hymoandibular, first neck, longer ribs, expanded snout, flattened head, eyes on top, scales, no operculum 365 mya > amphibians: flattened heads, necks, four legs with digits Euromerica= Ecuador, plant species, warm Problems with living on land: o Gravity thickening of bones, development of more ridged vertebral column, more musculature o Desiccation scales to waterproof skin o Respiration gills to lungs o Reproduction eggs still require water o Senses smell (internal and external nostrils) o Hearing senses (hyomandibular > stapes) decent with modification Loss of operculum results freeing of back of the skull that becomes shoulder girdle Lungs and swim bladders homologous structures END OF DEVONIA EXTINCTION 20% families, 7080% species (375359ma) Prolonged marine biotic crisis extending 2025 million years Affected those in low latitude shallow marine environments most Marine didn’t do so well, insects and plants were fine Affected: PLACODERMS Causes (Devonian plant hypothesis): widespread black shale in shallow inland seas >organic rich sediment indicates anoxic environments o Plants using CO2 > storing carbon o Organic carbon being buried o Decrease in atmospheric CO2 o Water anoxia (when oxygen is low, bacteria turn to other elements for energy > sulfate, by product is hydrogen sulfide H2S) o Extensive soil formation: extensive mechanical and chemical weathering decrease in atmospheric CO2
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