BIOL2712 Study Guide - Final Guide: Magnetoreception, Endochondral Ossification, Cephalaspidomorphi
25 Jun 2018
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Fishes
What is a fish?
A gill-breathing ectothermic, aquatic vertebrate that possesses gills, fins and skin
that is usually covered with scales
oAll vertebrates that are not tetrapods (4 limbs with digits)
Around 30,000 living species
NOT a monophyletic group
oCommon ancestor with amphibians, reptiles and mammals
First Major Group of Fishes: Superclass Agnatha (paraphyletic)
Paraphyletic – developed from common ancestor
Agnatha (jawless fish) – all have cranium, but not vertebrae
Extinct Ostracoderms (armored jawless fish)
oAncestor of the jawed gnathostomes
Living hagfishes (scavenger)
oNo vertebrae
Living lampreys (parasites)
oRudimentary vertebrae
Slender eel like bodies with naked skin
Medial fins but no paired appendages
Second Major Group of Fishes: Superclass Gnathostomes
Jawed fish – all have cranium and vertebrae
Extinct Placoderms (armored)
Living Chondrichthytes (sharks, rays)
oUse cartilage and not bone for skeleton
Living Osteichthytes (bony fish)
oTwo lineages
Ray-finned fish
Lobe-finned fish
Agnatha: Class Myxini
Hagfishes
Jawless
Marine group with 65 species
Feeds on dead or dying fish, molluscs etc. (scavenger)
Tooth keratinized plates
Almost blind but keen sense of smell and touch
Lots of slime
Known to:
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oTie knots for leverage
oProduce slime in defense
Agnatha: Class Cephalaspidomorphi
Lampreys
Jawless
Marine and freshwater
41 species
Predatory/parasite with rasping mouthparts
Larval period
o3-7 years
Agnatha: Extinct Clades
Jawless, bottom suspension feeding vertebrate
oLarge pharangeal pumps
Ancestor of the bony fishes
oArmored with dermal bone
No intrenbal endochondral bone
oPaired pectoral appendages in some
Osteostraci
Extinct by end of Devoinia 360 mya
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From Agnatha to Gnathostome
From jawless to jawed, from eel-like to paired fins
The evolution of the jaw
oTime to leave the bottom and mud sucking
oJaws evolved from modifications of the supports for pharyngeal gill slits
oAppear fully formed in the fossil record
Late Silurian 420 mya
The evolution of paired fins
oIncreased maneuverability
oOpened up a three-dimensional niche for exploration
Gnathostomes: Early Jawed Fish
Bony armor
Devonian period: 400 mya
Complex reproductive system
oCopulation
oOviviparity
Embryos that develop inside eggs in the mother’s body until they’re
ready to hatch
Frogs
oViviparity
Live birth
No placental connection with the mother
Receive their nourishment from yolk
oMatrtrophy
Live birth in which animal is supplied with nourishment from the
mother
i.e. the placenta
Placoderms
oRuled the sea
oExtinct 350 mya
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
A gill-breathing ectothermic, aquatic vertebrate that possesses gills, fins and skin that is usually covered with scales: all vertebrates that are not tetrapods (4 limbs with digits) Not a monophyletic group: common ancestor with amphibians, reptiles and mammals. First major group of fishes: superclass agnatha (paraphyletic) Agnatha (jawless fish) all have cranium, but not vertebrae. Extinct ostracoderms (armored jawless fish: ancestor of the jawed gnathostomes. Jawed fish all have cranium and vertebrae. Living chondrichthytes (sharks, rays: use cartilage and not bone for skeleton. Feeds on dead or dying fish, molluscs etc. (scavenger) Almost blind but keen sense of smell and touch. Known to: tie knots for leverage, produce slime in defense. Jawless, bottom suspension feeding vertebrate: large pharangeal pumps. Ancestor of the bony fishes: armored with dermal bone. No intrenbal endochondral bone: paired pectoral appendages in some. From jawless to jawed, from eel-like to paired fins.
