Fishes

Section 30.1

Animal Classification

Animals

Invertebrates

Vertebrates

SpongesCnidariansWormsMollusksArthropodsEchinoderms

Ectotherms(cold-blooded)

Endotherms(warm-blooded)

AmphibiansReptiles

BirdsMammals

Fishes

Phylum Chordata

Classes of Fishes

Superclass Agnatha – jawless fish 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) Cartilaginous fishes

Sharks, skates and rays

Classes of Fishes

Class Osteichthyes (ahs tee IHK the ez) Bony fishes

Fishes Breathe Using Gills

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 Spawning – External fertilization in fishes

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

Fishes in the class Chondrichthyes and Ostheichthyes have paired fins

Fins – fan-shaped membranes that are used for balance, swimming, and steering

Paired Fins

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