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??