• Animals that have a backbone are called vertebrates.

• Vertebrates belong to phylum chordata (called chordates)

• Vertebrates make up largest group of chordates

Chordates

•Two other groups of chordates are lancelets and tunicates

•Much simpler than vertebrates (no backbone or well developed head)

Chordate Characteristics

• 1) Have a tail (some only have a tail during embryo stage)

• 2) Hollow nerve cord —in vertebrates it is called spinal cord

• 3) Pharyngeal pouch —develop into gills or other body parts as embryo matures

• 4) Notocord —stiff but flexible rod that gives body support– In most vertebrates, embryo’s

notocord is replaced by a backbone

Vertebrate Characteristics

– Have a backbone (strong but flexible column of bones called vertebrae)

– Have well developed head protected by skull (made of bone or cartilage)

• Cartilage is tough material that flexible parts of ears and nose are made of

– Skeletons of vertebrate embryos are cartilage and harden into bone

Are Vertebrates Warm or Cold?

• Birds and mammals are endotherms (warm blooded)– Use energy

released by chemical reactions in the body to stay warm

• Fish, amphibians, and reptiles are ectotherms (cold blooded)

– Depend on their surroundings to stay warm

Fish Characteristics

• More than 25,000 species of fish

• All fishes share several characteristics:– (1) Born to swim

• use fins to steer, stop, and balance

• scales are bony structures that cover and protect body and lower friction

– (2) Making Sense of the World

• have senses of vision, hearing, and smell

• have a lateral line system (row of sense organs that detect water vibrations)

– (3)Underwater Breathing• use gills to breathe

(organ that removes oxygen from water)

• gills also remove carbon dioxide from the blood

– (4) Making More Fish

• most fish reproduce by external fertilization

• females lay eggs in water and male drops sperm on them

Kinds of Fishes

• Three classes of fishes still living today:– (1) Jawless fishes

• first fishes (have been around for half a billion years)

• Two kinds: hagfish and lampreys

• Smooth, slimy skin and round, jawless mouth

• No backbone, but does by a skull, brain, and eyes

Cartilaginous Fishes

– (2) Cartilaginous Fishes• skeleton never changes to

bone; stays cartilage• have fully functional jaws• strong swimmers and expert

predators• excellent senses of sight and

smell• to stay afloat, they store a lot

of oil in their liver, which helps them be buoyant

• Examples: skates, stingray, sharks

Bony Fishes– (3) Bony Fishes

• largest class of fish (95% of all fishes are bony fishes)

• very different from other fishes—skeleton made of bone and body covered by bony scales

• Unlike other fishes, they can rest in one place without swimming because they have a swim bladder (gas-filled sac that helps fish be more buoyant)

• Two main groups: ray-finned and lobe-finned– Ray finned:

eels, herrings, trout, minnows, perch

– Lobe finned: lungfishes

Hagfish: jawless

Shark: cartilaginous

Trout: bony

Stingray:

cartilaginous

Lungfish:

bony

Lamprey:

jawless