Chordates

Notochord

Flexible rod along dorsal side of chordates; becomes the vertebral column in vertebrates

Dorsal hollow nerve cord

Tubular nerve cord in chordates; becomes the spinal cord in vertebrates

Post-anal tail

Muscular tail extending past the anus in chordates

Pharyngeal gill slits/pouches

Openings in the pharynx of chordates

Ectothermic

Animal that lacks an internal mechanism for maintain temperature in a narrow range

Endothermic

Animal that maintains body temperature by generating heat internally

Endoskeleton

An internal skeleton; may be composed of cartilage or bone

Cranium

Part of the skull that encloses and protects the brain

Scales

Keratin-rich skin structures that reduce water loss

Tunicates

Marine filter feeders; gills used for feeding and gas exchange

Free-swimming larvae have chordate features

Sessile adults have gelatinous cellulose tunic

Vertebrates

Notochord is replaced by a vertebral column for support

Endoskeleton provides support and some protection

Brain is enclosed in a bony cranium

Sensory organs are concentrated in the head

Jawless fishes

- Hagfishes

- Lampreys

Most primitive vertebrates

Jawless; no limbs

Two-chambered heart

Ectothermic

Cartilaginous fishes

- Sharks

- Rays

- Skates

Skeleton is composed primarily of cartilage (except skull)

Paired appendages

Skin covered with placoid scales

Two-chambered heart

Ectothermic

Bony fishes

- Salmon

- Tuna

- Perch

- Seahorse

- Flounder

Skeleton is composed of bony tissues

Paired appendages

Operculum allows water movement over gills while fish is motionless

Swim bladder provides buoyancy

Two-chambered heart

Ectothermic

Amphibians

- Frogs

- Toads

- Salamanders

Live on land and water

Require abundant moisture

Water required for laying eggs (no shells)

Gas exchange occurs via gills, simple lungs, skin, or oral cavity lining

Three-chambered heart

Ectothermic

Non-avian reptiles

- Snakes

- Lizards

- Turtles

- Alligators and crocodiles

Dry, scaly skin conserves moisture

Internal fertilization with amniotic eggs with leathery shells

Spongy lungs for gas exchange

Most have a three-chambered heart

Ectothermic

Avian reptiles

- Birds

- Dinosaurs

Internal fertilization with amniotic eggs with calcium-rich shells

Complex lungs for gas exchange

Feathers (modified scales), pneumatic (hollow) bones

Wings and enlarged pectoral muscles for flight

Four-chambered heart

Endothermic

Mammals

- Primates

- Rodents

- Whales & dolphins

- Bats

- Cats & dogs

- Ungulates

Mammary glands for milk production

Hair (modified scales)

Highly developed nervous system

Complex lungs for gas exchange; muscular diaphragm

Internal fertilization; most develop via a placenta

Four-chambered heart

Endothermic

operculum

partially covers their gills to improve gas exchange

Phylum chordata

Notochord, hollow nerve chord, pharyngeal gill slits