a history of fishes where did they come from?. a history of fishes 2 evolutionary history fish have...
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A History of Fishes
Where did they come from?
A History of Fishes 2
Evolutionary History
Fish have adapted to a wide range of environmental parameters• Temperatures -1.8°C - 40°C• pH 4 - 10
• O2 Concentrations 0 - Saturation
• Salinity 0 - 90• Depths 0 - 7000m
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
Evolutionary History
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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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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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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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Placoderms
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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
o Since cartilage does not readily fossilize not a very good fossil record
Characteristics
This group is important
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Chondrichthyes
Two distinct evolutionary lines• Elasmobranchii
oSharks, skates, and rays
• HolocephalioRatfishes and chimaeras
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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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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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Actinopterygii (Ray-fined fishes)
Chondrostei• Sturgeons, and
paddlefishes
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Actinopterygii (Ray-fined fishes)
Neopterygii• Remaining
23,000+bony fishes
Neopterygii
Osteichthyes Lineage
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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 - ratfishesElasmobranchii -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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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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Physical Properties of Water
Water is 800x denser than air!
Water is incompressible
Water is a universal solvent
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Have you hugged your Ichthyologist?
Ichthyology - study of fishes• Describing new taxa • Understanding evolutionary
relationshipsoTaxonomy and systematics
• Ecology, physiology, and behavior
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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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Species Names
Each spp. is assigned a unique two part scientific name• Longnose Dace Rhinichthys cataractae
(Valenciennes 1842)• Names are usually descriptive in some
wayoRhinichthys - nose-fishocataractae - the fast water in which it lives
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