Class Agnatha

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.
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
Key Innovations Bony Fish

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
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
Sharks and Rays

5-6
Sharks 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


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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)
Characteristics of Bony Fish

Characteristics for life on the reef and for life in
the open ocean:


5-8
lateral lines that detect water motion and
vibrations.
open ocean fish have a torpedo-like
streamlined 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 wall
Sacs help take in O2 and remove CO2
Must surface and gulp air (will drown if held under
water)
Ancestor to tetrapod??
