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Fish
Chordates
• 4 Characteristics
– Notochord
– Dorsal Nerve Chord
– Pharyngeal Pouches
– Post Anal Tail
Vertebrates
• 3 Characteristics
– Vertebrae (bones and/or cartilage protecting
the spinal chord)
– Cranium (skull protecting the brain)
– Endoskeleton (consisting of bone or cartilage)
Classification of Vertebrates
• 45,000 species (24,000 are fish)
• The live in all but the most extreme terrestrial
habitats
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Class Agnatha
Class Chondricthyes
Class Osteicthyes
Class Amphibia
Class Reptilia
Class Aves
Class Mammalia
Evolution
• 550 million years ago
• Fossil records indicate that jawless fish
are the oldest chordates
– they do not have fins but instead they are
covered with heavy boney scales and
skeletons of cartilage
• Origin of the Jaw
– about 440 million years ago
– Evolved from the 1st pair of gill arches
Agnatha
The jawless Fish
Lampreys and Hagfishes
• Live as scavengers and parasites
• Notochord serves as the main axial support
• Lampreys
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many lampreys live in fresh water
grow to 60cm in length and ½ kg in weight
soft bodied
lacks jaw, limb girdles, and ribs
simple specialized brain
seven gill slits
have caused extensive damage to lake trout
Chondrichthyes
The Cartilage Fishes
Chondrichtyes
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Least complex living vertebrates
Complete vertebral column
Movable jaws
Skeleton
Girdles
Fins
Includes sharks, skates, and rays
Sharks
• largest living fish
• skin is covered by rows of placoid scales
• each placoid has a backward-pointing
spine covered by enamel
• the jaws are lined with several rows of
razor-sharp teeth
– 6-20 rows, 20,000 teeth in a lifetime
Rays and Skates
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flattened bodies
large anterior paired fins
whip-like tails
rays – diamond or disk shaped bodies
skates – triangular bodies
may have a dorsal fin
most are under 1 meter long
swim with undulating motion
bottom dwellers – feed on mollusks and crustaceans
protect by burying themselves
stingrays have a tail with a venomous barbed spine
Osteichthyes
The Bony Fishes
Body Shape and Structures
• More than 20,000 species.
• Bodies divides into 3 sections.
– head
– trunk
– tail
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Streamlined bodies tapered at both ends.
Very fast swimmers.
Gills lie in large gill chamber.
Hard plate called operculum protects the gills.
Structure and Function of
Fins
• Paired fins are homologous to the limbs of other
vertebrates.
• Pectoral fins are homologous to arms. Pelvic are
homologous to the legs
• pectoral and pelvic fins are used for steering and
balance.
– single fins
• Caudal fin grows from the tail.
• Caudal fin’s movements help push the fish forward.
• Anterior and posterior dorsal fins help the fish stay
upright.
• Anal fin grows along the neckline.
Body Systems
Integument
• Scales are thin disks of bone that grow from
pockets of skin.
• Determine age by number of rings on scales.
• scales overlap like shingles.
• New scale material is visible as concentric rings.
• Lubricated by mucus secreted by glands.
• Counter-shading.
• Pigment in chromatophores is rearranged by
muscles in skin.
• The ability to change colors varies between
species, size, and age.
– ex. flounder.
Digestive and Excretory
• Diet for carnivorous fishes:
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earthworms
insects
Crayfish
Frogs
Fish
Large mouths
Small sharp teeth
Tongue fastened to the floor of the mouth.
taste buds line the tongue and the mouth.
kidneys lie above digestive tract that filter wastes
from the blood.
Digestive and Excretory
cont.
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Path of food
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Mouth
Esophagus
Stomach
Intestine
Anus
*Not along pathway (but still
involved in digestion)
1. Liver
2. Gall Bladder
3. Pancreas
4. Villi
Circulatory System
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A closed system
Blood is similar to other vertebrates.
Both red and white blood cells.
3 different vessels
– Arteries
– Capillaries (gas exchanged through walls)
– Veins
• Get nutrients from the intestine/transport wastes from
metabolism
• 2 chambered heart.
• Ventricle pumps blood though ventral aorta.
• Atrium receives the deoxy. Blood from body. It is the first
chamber of the heart.
Circulatory System cont.
• Path of blood:
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Ventricle
Conus Arteriosus
Gills
Aorta
Capillaries
Veins
Sinus venosus
Atrium
Immune System
• The immune system consists of those
organs, tissues, and cells that give an
organisms protection against infection and
invasion by foreign cells.
• Thymus gland
– Lies in throat region.
– made of lymphoid tissue.
Respiration
• Gills (3 parts)
• each gill consists of
an arch of bone called
gill arch.
• Oxygen used is
atmospheric oxygen
dissolved in water.
• Actual gas exchange
takes place in the
capillaries of the gill
filaments.
Air Bladder
• Air bladder is a thin-walled sac that lies
between the kidneys and digestive organs.
• Acts as a float.
• Filled with oxygen, nitrogen, and carbon
dioxide.
• The air bladder adjusts by either by losing
air to the blood or receiving more gas from
the blood.
Reproductive
• 2 Types
– Internal
– External
• Parts
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Ovaries
Testis
Sperm
Milt
Yolk
• Process is called
spawning.
Nervous
• Lobes
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Medulla Oblongata
Optic Lobe
Olfactory Lobe
Cerebrum
Cerebellum
Nerves
– Cranial
– Spinal
Fish Brain