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Final Exam BIO1130 - Silurian and Devonian

Final Exam BIO1130 - Silurian and Devonian - Ordovician...

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Ordovician Survivors: - Molluscs o Shelled Cephalopods half folded in shells, living inside coiled shells o Bivalves: possessed by molluscs (two shells) o Gastropods: - Worms - Echinoderms: sessile ones will disappear more typical ones survive - Bryozoa - Arthropoda: o Trilobites (not as many as before) o Marine forms (Crustacea) - Sponges Silurian Period : - World has warmed up - Water levels increase - Huge amount of continental shelf mass surrounding the equator o Therefore primary productivity INCREASES - Age of Fishes and plants (invasion of land by plants) Crustacea : (major innovators of this time – develop to environment) - Make their appearance because trilobites disappear - Small organisms have the capacity to filter out shit - Form the basis of primary herbivores - Crabs, lobsters, shrimps (larger crustacea) Armoured Fishes: - Fish make there first appearance start of the Silurian and Devonian (Age of Fishes – - Covered in solid plates (protection) - Placoderms: Gnathostoma – vertebrates with jawed fish, also include the lineage Tetrapoda o Earliest vertebrates with jaws - Ostracoderm: o Heavily armoured body, jawless fish - Experimentation with vertebrate fish - Agnatha (Jawless Fishes) Lamprey or Hagfish o Gill Arches : evolved as supporting structures between the slits turned into respiratory surface o Has to constantly be moving and flow water in and out of mouth through gills (cannot pump water) o Hagfish & Lamprey (survivor still today) o Has no mechanism to close its jaw! o Rams into the ground with mouth open and ‘sucks’ everything in and filters the food out of the water The water goes out the holes in the back (early signs of gills) Gill Slits: ( distinguishes chordates from other deuterostomes) - Paired openings originating as exit holes for water that carried small food allows Evolution of the Jaw: - Jaw bones are modified gilled arches that originally held open gill slits allow for opening and closing of mouth - Arches become more and more ‘bendable’ to the point where the mouth can close - Chondrichthyes : ( cartilaginous fish sharks and rays) o First ones with jaws (sharks) – new feeding mechanism o Dorsal fins, pelvic girdle and fin, pectoral girdle and fin 3 because moves in 3D o Feeding : Teeth can clamp down and grasp stuff (not made for cutting just grasping and holding on) o Do not have the “big suits of armour” not armoured fish replaced by fish with scales o No way to ventilate their gills (no pumping of water) therefore they are constantly swimming to breathe
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