Chapter 29 - Vertebrates

Notochord

Flexible, dorsal rod shaped structure that runs along the nerve cord

Develops into vertebrae

Dorsal hollow nerve cord

Develops from a plate of ectoderm that rolls into a neural tube located dorsal to the notochord

Develops into the central nervous system

Pharyngeal slits of clefts

Develop into gill supports in fish

Develops into parts of jaws, inner ear, and tonsils in tetrapods

Ancestral use was filter feeding and gas exchange

Post-anal tail

Multiple muscle segments

Undulating locomotion

Endostyle

Found in invertebrate chordates and larvae of modern lampreys

Considered to be an evolutionary precursor of the thyroid gland of vertebrates

Assists in filter feeding

Thyroid

Produces and secretes hormones in all vertebrates

Hormones regulate the body’s metabolic rate, growth, and development

Cephalochordate

All key chordate features in adults

Lancelets

Gas exchange occurs mainly across the external body surface

Urochordata

Swimming larvae has all key chordate features, but notochord, post anal tail, and dorsal nerve cord are absent in adults

Tunicates (“sea squirts”)

Suspension feeds with pharyngeal slits

Axial skeleton

Skull, vertebrae (backbone), ribs

Appendicular skeleton

Pectoral and pelvic area

Cyclostomes

Jawless vertebrates

Reduced vertebrae

Eel like bodies and no lateral fins

Hagfish

Marine scavengers

Cartilage skull, notochord for support and movement

Keratinous teeth aid feeding

Defensive slime

Lampreys

Jawless parasite on fish

Notochord and cartilaginous skeleton

Gnathostomes

Vertebrates with jaw derived from skeletal rods which supports gill slits

Usually have bony teeth

Chondrichthyes

Cartilaginous fish

Sharks, rays, skates

Bone minerals lost to reduce density

Buoyancy raised by liver oils and active swimming

Oviparous

Eggs laid and hatch outside the mother’s body; embryo develops within protective egg-case, fed by yolk

Viviparous

Young develop within the uterus, obtain nourishment prior to birth by nutrients from the mother’s blood through a yolk sac placenta, live birth

Ovoviviparous

Fertilized egg retained within mother; embryo fed by egg yolk, live birth

Osteichthyes

Bony fish

Includes both ray fin and lobe fin

Usually oviparous with external fertilization

Ray finned fishes

Thin fins modified for maneuvering, defense, etc.

Gas filled swim bladder for buoyancy

Most diverse group of all vertebrates

Lobe finned fish

Pelvic and pectoral fins supported with bones and muscles

Includes tetrapods

Tetrapods

Four limbs with wrist and digits

Head moves independent of body

Lung breathing as adults

Amphibia

Most basal extant tetrapod group

Gas exchange with air across moist skin and lungs

Positive pressure breathing

Amnion

Protects embryo within watery amniotic sac

Allantois

Waste disposal / gas exchange in amniotes

Chorion

Gas exchange in amniotes

Yolk sac

Delivers nutrients in amniotes

Anapsid

Skulls with no openings behind the eye

Synapsids

Skulls with one opening behind the eye

Mammals

Diapsids

Skulls with two openings behind the eye

Modern lizards, snakes, crocodiles, alligators, birds

Reptiles

Scaly skin with keratin and waxy lipids

Negative pressure breathing

Ectothermic

Use environment to warm body

Behavioral thermoregulation

All non bird reptiles

Endothermic

High metabolic rate warms body

Physiological thermoregulation

Birds and mammals

Mammals

Secrete milk for feeding young

Hair or fur

Monotremes

Egg laying mammals

Oviparous

Echidnas and platypus

Marsupials

With maternal pouch

Embryo starts growing in uterus with placenta

Eutherians

Placental mammals

Young more developed at birth

Viviparous

Primates

Related to arboreal life

Hands and feet adapted for grasping

Eyes forward and flat face

Anthropoids

Monkeys, apes, and humans

New World monkeys

Prehensile tails, arboreal

Old World monkeys

Tails can’t grasp

Mostly ground dwelling

Hominid

Any member of the family Hominidae

Includes living and extinct great apes, modern humans, orangutans, gorillas, chimpanzees, and bonobos

Hominin

The group consisting of modern humans, extinct human species and all out immediate ancestors