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A History of Fishes Where did they come from?
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A History of Fishes 2 Evolutionary History Fish have adapted to a wide range of environmental parameters Temperatures-1.8°C - 40°C pH4 - 10 O 2 Concentrations0 - Saturation Salinity0 - 90 Depths0 - 7000m
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A History of Fishes 3 Diversity and Evolution The diversity of fishes reflects their long evolutionary history A major challenge to ichthyologists involves unraveling the evolutionary pathways of both extant (living) and extinct taxa
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Evolutionary History
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A History of Fishes 6 Ostracoderms Characteristics Lack of jaws, lack of paired fins, bony armor, and internal cartilaginous skeleton Modern day representatives of this group include the classes Pteraspidomorphi (hagfishes) and Cephalaspidomorphi (lampreys)
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A History of Fishes 7 Early Jawed fishes Jaws are probably the greatest advancement in vertebrae evolution This allowed for an explosion in diversity due to the different prey items that can be processed
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A History of Fishes 8 Placoderms Diverse group with a bizarre appearance Jaws, dermal body plates, internal skeleton, and paired fins Some were over 2 meters in size and possessed a craniovertebral joint (increased prey size)
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A History of Fishes 9 Placoderms
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A History of Fishes 10 Chondrichthyes Arose during the early Paleozoic and followed a very different line of evolution Cartilaginous fishes, 2 distinct lines of evolution, the connection between the two is poorly understood oSince cartilage does not readily fossilize not a very good fossil record Characteristics This group is important
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A History of Fishes 11 Chondrichthyes Two distinct evolutionary lines Elasmobranchii oSharks, skates, and rays Holocephali oRatfishes and chimaeras
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A History of Fishes 12 Sarcopterygii (Lobe-finned fishes) Present day lungfishes and coelacanths This group has paired fins which actually have muscle in the fin itself It is this class which is believed to have given rise to the amphibians
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A History of Fishes 13 Actinopterygii (Ray-fined fishes) The most successful of all the modern fishes Distinguished form sarcopterygians: triangular dorsal fin, paired fins without fleshy lobes, and ray finned As this class flourishes the previous groups decline or disappear, which may show possible ecological interactions
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A History of Fishes 14 Actinopterygii (Ray-fined fishes) Chondrostei Sturgeons, and paddlefishes
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A History of Fishes 15 Actinopterygii (Ray-fined fishes) Neopterygii Remaining 23,000+bony fishes
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Neopterygii Osteichthyes Lineage
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A History of Fishes 17 Evolutionary Review Ostracoderms - primitive jawless fishes No living representatives, possible relatives include hagfish and lamprey Placoderms - first jawed fishes No apparent descendants Chondrichthyes - cartilaginous fishes Holocephali - ratfishes Elasmobranchii -sharks, skates, & rays Osteichthyes - bony fishes Sarcopterygii - lobe-finned fishes Present day lungfishes and coelcanth Actinopterygii - ray-fined fishes Chondrostei - sturgeons & paddlefishes Neopterygii - remaining bony fishes
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A History of Fishes 18 Population Distributions By volume 97% of all water on earth is found in the worlds oceans 58% of all fish species are marine 41% are freshwater species 1% move between the two habitats Marine Habitat 13% of marine species associate in open water 78% live over the continental shelf
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A History of Fishes 19 Physical Properties of Water Water is 800x denser than air! Water is incompressible Water is a universal solvent
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A History of Fishes 20 Have you hugged your Ichthyologist? Ichthyology - study of fishes Describing new taxa Understanding evolutionary relationships oTaxonomy and systematics Ecology, physiology, and behavior
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A History of Fishes 21 Nomenclature The most frustrating aspect of ichthyology is the constant changing of scientific names These names change for several reasons: Changes are necessary as new information is discovered concerning evolutionary history
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A History of Fishes 22 Species Names Each spp. is assigned a unique two part scientific name Longnose Dace Rhinichthys cataractae (Valenciennes 1842) Names are usually descriptive in some way oRhinichthys - nose-fish ocataractae - the fast water in which it lives
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