PHYLUM CHORDATA

• Dorsal Notochord-long rod that supports the body-

becomes the vertebrae in most.

• Dorsal Nerve cord-becomes the central nervous system.

• Pharyngeal gill slits-openings in the throat for feeding &

breathing-becomes the Pharynx in humans.

• Tail-forms in embryos and extends past the anus.

Evolution of Fishes

� Primitive fishes lacked jaws and paired fins

� Ancestral jawless fish ruled the seas during Devonian Period: Age of Fishes

Evolution of Fishes

CLASS PISCES:

FISHES

CLASS PISCES

BECAUSE THERE

ARE 20,000 SPECIES

THERE ARE 3

SUBCLASSES

SUBCLASS

AGNATHA

(JAWLESS FISH)

CHONDRICHTHYES

(CARTILAGE)

OSTEICHTHYES

(BONY FISH)

SUBCLASS SUBCLASS

Jawless Fishes = Agnathans

� No true teeth/jaw

� Skeleton made of fibers/cartilage

� Cartilage-strong supporting tissue (softer/more flexible than bone)

� Lack true vertebrae (keep notochord as adults)

� ONLY VERTEBRATE PARASITES!

� 2 groups: Lampreys and Hagfishes

Lampreys � Parasites

� Sucker-like oral disks with teeth to grasp and suck tissues/flesh

Hagfishes

� Detritivores

� No eyes

� Toothed tongue

� Secrete slime

� 6 hearts

� Tie into knot

Hagfish

Cartilaginous Fishes =

Chondrichthyes � Sharks, Rays, Skates

� Cartilage skeleton (no bone)

� Sharks have thousands of teeth in rows

� Skates and Rays glide with wing-like pectoral fins (bottom-dwelling)

CARTILAGINOUS FISH

� 850 Species of Sharks, Rays, & Skates

� Skeleton is made of cartilage. S-shaped swimming/rigid fins.

� External Gill slits.

� Store oils & constant motion to stay afloat.

� Scales are small bony plates (at one time used as sandpaper).

RAYS & SKATES

� Flattened body for a bottom-

dwelling niche

� Spiracles & eyes on the

dorsal side.

� Mouth, nostrils & gill slits on

ventral side.

� Stingrays have a hollow barb.

� Manta ray grows to 18’.

SHARKS

� Close to 300 species.

� Largest fish in the world-Whale Shark.

� Can smell 1drop/blood

In 1 million parts/water.

� Lateral line detect

vibrations in the water

� Ampullae of Lorenzini

Sense changes in electrical

field.

WHALE SHARK

Bony Fishes = Osteichthyes

� Bone skeleton (hard, calcified tissue)

� Ray-Finned Fishes-fins formed from bony spines covered by thin layers of skin (largest group)

� Lobe-Finned Fishes-fleshy fins with bones

(some jointed like arms/legs)…ex. Lungfish & Coelacanth

Fish:

Anal fin

Eye

Mouth

Dorsal fin Caudal fin

Operculum (gill cover) Pelvic fin Pectoral fin

Lateral line Scales

•Aquatic Vertebrates

•Paired Fins

•Scales

•Gills

Feeding

� Herbivores, carnivores, parasites, filter feeders,

and detritivores

� Digestive tract:

mouth�esophagus�stomach�pyloric ceca�intestine�anus (solid waste)

� Enzymes added by liver and pancreas

Mouth

Esophagus Stomach

Pyloric cecum Liver

Pancreas

Intestine

Anus

Digestive System

Respiration

� Gills on sides of pharynx to exchange gases

� Gill Filaments-feathery structures with capillaries for gas exchange

� Gill Rakers-prevents prey from escaping through gills

� Gill Arches-support and protect gills

� Operculum-protective bony cover over gill openings

Gills

Lungfish

� Adaptation to oxygen-poor water

� Tube brings oxygen from air into fish’s

mouth to “LUNG”

Circulation

� Closed system

� 2 chambered heart

� Single loop: heart�gills�body (back to heart)

Fish Heart

� Sinus Venosus-sac that collects oxygen poor

blood from veins; sends blood to�Atrium-

large muscular chamber; sends it to�Ventricle-large muscular chamber that pumps blood; sends it to�Bulbus Arteriosus-muscular tube that

connects to�Aorta-large blood vessel that sends blood to gills

Sinus Venosus Atrium

Ventricle

Bulbus arteriosus

Fish Heart

Body muscle

circulation

Brain and head

circulation

Heart Digestive system circulation

Gills Circulation in a Fish

Excretion

� Eliminate nitrogenous waste as ammonia

(urine)

� Kidneys filter waste from blood

� Diffusion through gills Kidney

Brain

•Well-developed nervous system with brain

•Eyes with color vision

•Taste/Smell

•Lateral Line System- detect currents/vibrations in water (sense

nearby fishes)

Response/Nervous System

Olfactory Bulbs-smell (olfaction)

Cerebrum-smell (and voluntary

activities)

Optic Lobe-process info from

eyes

Cerebellum-coordinates body

movements

Medulla Oblongata-controls

internal organs

Olfactory bulb

Cerebrum

Optic lobe

Cerebellum

Medulla oblongata

Movement • Swim Bladder-internal gas filled organ to

adjust buoyancy in bony fish only

Movement continued…

� Contract paired sets of muscles

� Fins propel

� Dorsal/Ventral fins for stability (Dorsal/Anal)

� Paired fins for fine movements/turning (Pectoral/Pelvic)

� Caudal fin for speed

Reproduction

� External/Internal fertilization

� Oviparous-eggs (embryo) develop and hatch outside mom’s body; obtain food from egg yolk

� Ovoviviparous-eggs stay in mom’s body; obtain food from egg yolk; young are “born alive”

� Viviparous-embryos stay in mom’s body; obtain

food from mom; young are born alive

•Anadromous-live

in ocean but

migrate to fresh

water to breed; Ex.

Salmon

Migrations

• Catadromous- Breed

in the oceans but live

in freshwater

• Eels migrate to the

Sargasso Sea, they

spawn at depths of 300

meters and die when

done