1.  

2.  All bony fishes
 Familiar descendants of tetrapods
 Characterized by an air sac that can be secondarily lost
 Large units of dermal bone can be found on the head
and shoulder girdle
 The group is subdivided based on the structure of paired
appendages (fins)

3. Osteichthyans Elasmobranchs
Has cycloid scales. Has placoid scales
Presence of dermal No Bones in their
bone body
Operculum covers
the gills Gill Slits are exposed
(Naked)

4.  

5.  The Chondrichthyes
o cartilage, composed of chondrocytes suspended in a protein
matrix.
 Osteichthyes
o composed of cartilage and bone.

6.  Chondricthyes
o large scales called placoid scales
• Scales have a bone like base embedded in the skin and a backward
projecting enamel covered dentine spine.
 Osteichtyes
o Have cycloid or ctenoid scales.
• Cycloid scales are smooth, flat and round
• Ctenoid scales posses a comb-like extensions (ctenii)

10.  Chondricthyes
o Teeth are confined to the jaws and are embedded in the gums
 Osteichthyes
o Teeth are not confined to the jaws

11.  Chondrichtyes
o Remain buoyant by producing large amount of oil in their livers
 Osteichthyes
o They remain buoyant by filling their swim bladder with gas

12.  Chondrichthyes
o Cartilaginous fish can swim forward only
 Osteichthyes
o Can swim forward and backward

13.  

14.  

16. operculum

17.  An operculum (gill cover) is a flexible bony plate protects
the sensitive gills.

18. Branchiostegal membrane

19.  Membrane extending from the ventral edge of the
operculum in bony fishes to beneath the jaws.

20. mouth

21.  The mouth serves for taking in food; also for the
breathing current of water.
 It has a small mouth that does not extend to eye.
 They are toothless fish.

22. nostrils

23.  The nostrils of fish do not open into the back of the
mouth as do those of mammals, and are not, therefore,
for breathing.
 They lead into organs of smell which are as a rule, very
sensitive, so that a fish can detect the presence of food
in the water at considerable distances.

24. eyes

25.  Fish see through their eyes and can detect color.
 The eyes are rounder in fish than mammals because of
the refractive index of water and focus is achieved by
moving the lens in and out, not distorting it as in
mammals.

26.  

28.  Maneuverability (steering) and propulsion

29.  The main purpose of the dorsal fin is to stabilize the
animal against rolling and to assist in sudden turns.

30. o Stabilize the fish while swimming.

31.  The paired pectoral fins are located on each side,
usually just behind the operculum, and are
homologous to the forelimbs of tetrapods.
 It assists in maintaining depth as the fish swims.

32.  The paired pelvic or ventral fins are located ventrally
below the pectoral fins. They are homologous to the
hindlimbs of tetrapods. The pelvic fin assists the fish in
going up or down through the water, turning sharply,
and stopping quickly.

33.  The lateral line is a sense organ used to detect
movement and vibration (mechanoreceptors) in the
surrounding water. In most species, it consists of a line
of receptors running along each side of the fish.

34.  Scales serve as protection for the fish.
 Reduces drag during swimming.