Jan 03, 2016
Jawless fish. Living species include lampreys and hagfish.
Ostracoderms – armor plates of bony tissue
Placoderms – mineral hardened backbone and jaw
Significant because they may represent the ancestor of bony fish/sharks.
Class Agnatha
Key Innovations Bony Fish
Bone tissue with a vertebrae part of inner skeleton, paired with muscle
segments Jaws started trend towards more complex
sensory organs and nervous systems Paired fins
Gills – large surface area for water to diffuse into blood vessels
Don't function out of water Lungs – supplemented and then replaced gills
Increase effiency
Key Innovations Bony Fish
Characteristics of Cartilaginous Fish
Class Chondrichthyes includes sharks, rays and their close relatives. jawed fish, that lack a swim bladder, and
cartilaginous skeletons. 5-7 gill silts, stream lined body “conveyor belt” of teeth.
Modified scales
5 - 6
Sharks and RaysSharks and rays have other interesting
characteristics: lateral lines – lines of sensory hair along the
length of the body, detect water motion and vibrations.
electroreception – the ability to sense minute electricity created by muscles and nerves.
ampullae of Lorenzini - visible pits near their snouts used to detect the electrical current.
Osteichthyes
Ray-finned fish – flexible fin with support from skin and scales
Bony endoskeleton Swim bladder – exchanges gases with blood to
help with floatation (gulp air)
5 - 8
Characteristics of Bony Fish Characteristics for life on the reef and for life
in the open ocean:lateral lines that detect water motion and
vibrations.
open ocean fish have a torpedo-likestreamlined shape to minimizes drag and turbulence.
Lobe-Finned Coelacanths only surviving group Ventral fin are extensions of body with skeletal
support
Lungfish
Have gills and 1-2 small outpouching of gut wallSacs help take in O2 and remove CO2Must surface and gulp air (will drown if held under water)Ancestor to tetrapod??