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Fishes
Section 30.1
Animal Classification
Invertebrates
Sponges
Cnidarians
Worms
Mollusks
Arthropods
Echinoderms
Animals
Ectotherms
(cold-blooded)
Vertebrates
Fishes
Amphibians
Reptiles
Phylum Chordata
Endotherms
(warm-blooded)
Birds
Mammals
Classes of Fishes
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Superclass Agnatha – jawless fish
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Hagfish feed on dead or dying fishes
Lampreys use suckerlike mouths to suck out the
prey’s blood
Skeleton made of cartilage
Classes of Fishes
Classes of Fishes

Class Chondrichthyes (kahn DRIHK the ez)
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Cartilaginous fishes
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Sharks, skates and rays
Classes of Fishes

Class Osteichthyes (ahs tee IHK the ez)
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Bony fishes
Fishes Breathe Using Gills
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Fishes have gills made up of feathery gill
filaments that contain tiny blood vessels
Oxygen and carbon dioxide are exchanged
through the capillaries in the gill filaments
Two-Chambered Hearts

One chamber receives deoxygenated blood
from the body tissues, and the second
chamber pumps blood directly to the
capillaries of the gills
Two-Chambered Hearts


Atrium – receiving chamber of the heart
Ventricle – pumping chamber of the heart
Sexual Reproduction

External fertilization is common in most fishes
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Spawning – External fertilization in fishes
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Cod can produce as many as 9 million eggs, of which
only a small percentage survive
No parental involvement after spawning
Cartilaginous fishes undergo internal
fertilization
Paired Fins
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Fishes in the class Chondrichthyes and
Ostheichthyes have paired fins
Fins – fan-shaped membranes that are used
for balance, swimming, and steering
Paired Fins

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Dorsal – towards the
backbone
Pectoral – chest area
Pelvic – hip area
Anal
Caudal - tail
Developed Sensory Systems

Lateral line system – a line of fluid-filled
canals running along the sides of a fish that
enable it to detect movement and vibrations
in the water

Found in cartilaginous and bony fishes
Developed Sensory Systems


Fishes have eyes
Some fishes that live areas absent of light
may have reduced, almost non-functional
eyes
Blind cave fish (small, non-functioning eyes)
Developed Sensory Systems

Some fishes have an extremely sensitive
sense of smell

Sharks can follow a trail of blood through the
water for 300 feet
Scales


Scales – thin bony plates formed from the
skin
Scales can be toothlike, diamond-shaped,
cone-shaped, or round
Scales

Shark scales are similar to teeth found in
other vertebrates
Jaws

The advantage of jaws is that they enable an
animal to grasp and crush its prey with great
force
Jaws


Sharks have up to 20 rows of teeth that are
continually replaced (e.g. vending machine)
Their teeth point backwards to prevent prey
from escaping once caught
Vertebrae Provides Flexibility

Separate vertebrae are important for fish
locomotion which involves continuous flexing
of the backbone
Swim Bladder


Swim bladder – a thin-walled, internal sac
found just below the backbone in most bony
fishes
A swim bladder controls a fish’s depth by
regulating the amount of gas in the bladder
Swim Bladder


Some fishes remove gases through a special
duct that attaches the swim bladder to the
esophagus
Sharks don’t have swim bladders

Sharks maintain their buoyancy via fatty livers