Chapter 34 – Vertebrates
Phylum Chordata
 Arrived in early Cambrian Period (530 mya)
 Evolution of limbs (360 mya) allowed them to move onto land
 ~52,000 vertebrates
 Chordate Characteristics
o Bilateral deuterostomes
o Alimentary Canal
o Closed Circulatory System
o Coelomates
o 4 Unique Traits
 Notochord
 Longitudinal, flexible rod b/w digestive tube & nerve cord
 Skeletal support for length of organism
o Most develop complex, jointed skeleton
 Humans = cartilaginous discs
 Dorsal Hollow Nerve Cord
 Made from a plate of ectoderm that rolls into a tube (dorsal)
 Develops into central nervous system
o Brain & spinal cord
 Pharyngeal Gill Slits
 Grooves (clefts) in pharynx
 Functions:
o Suspension-feeding for many invertebrates
o Gas exchange in vertebrates (NOT tetrapods)
o Humans (& tetrapods) = parts of ear, head, & neck
 Muscular, Post-Anal Tail
 Posterior to anus
 Has skeletal elements & muscles
 Propelling force in many aquatic species
 Tail is greatly reduced during embryonic development in others
o Human = Coccyx
Subphylum Cephalochordata
 Lancelets
 Invertebrate Marine suspension feeders
 Have all 4 chordate traits as adults
 1 Hox cluster
Subphylum Urochordata
 Tunicates (aka sea squirts)
 Filter feeders
 Have all 4 traits as a short-lived larva
 Adults draw in water thru incurrent siphon; filter food particles
 1 Hox cluster
Craniates (all groups below)
 Chordates w/ a head
o Brain, sense organs, skull
 Eyes, heart (2+ chambers), RBCs w/ hemoglobin, & kidneys
 2 Hox clusters
Class Myxini
 Hagfishes
 Cartilaginous skull & teeth-like projections
 No jaw or vertebrae
Subphylum Vertebrata (all groups below)
 Craniates w/ vertebrae around nerve cord
Class Petromyzontida – lamprey
 Jawless w/ teeth
 Cartilaginous skeleton (vertebrae)
Gnathostome (all groups below)
 Vertebrates w/ hinged jaws & teeth
o Skeletal support from gill slits?
 Enlarged forebrain (smell & sight)
 Hox duplication
Class Chondrichthyes
 Cartilaginous fish
 Sharks, skates, rays
 Cartilaginous skeleton w/ some calcium
 From a mineral ‘parent’
Osteichthyes (all groups below)
 Bony fish – endoskeleton ossified w/ calcium phosphate
 Class Actinopterygii – ray-finned fish
o Bass, trout, tuna, etc.
 Class Sarcoptergyii – lobe-finned fish
o Coelocanths (Actinistia)
o Lungfish (Dipnoi) – have lungs
Tetrapods (all groups below)
 4 limbs & feet w/ digits
 Ears detecting airborne sound
 Lungfish (Subclass Dipnoi) – developed legs under water & began coming out of water
 Class Amphibia – Toad, salamander, legless lizard
o 6,150 species in 3 orders
o Metamorphosis – aquatic larva to land adult
o External fertilization, moist skin for gas exchange (w/ lungs)
 Amniotes (all groups below)
o Have amniotic egg (extra- embryonic membranes)
o Amnion, chorion, yolk sac, & allantois
o Simulates water environment
o Class Reptilia – Lizards, snakes, crocs, turtles
 Breath air & have keratin scales
 Lay shelled eggs on land
 Ectothermic – body heat mainly from ‘outside’ (cold-blooded)
o Class Aves – Birds
 Descended from reptiles (Archaeopteryx)
 Egg-layer w/ feathers (keratin)
 Weight loss – no bladder, small gonads, toothless, hollow bones
 Endotherm – body heat thru metabolism (warm-blooded)
o Class Mammalia (5,300 species)
 Mammary glands produce milk
 Mothers nourish children
 Hair or fur (keratin)
 Larger brain relative to body size
 Differentiated teeth
 Middle ear bones
 Endotherms
 Mammal Types
 Monotremes – egg-layers
o Duck-billed platypus
 Marsupials – embryonic development finished inside pouch (marsupium)
o Kangaroo, opossum, koala
 Placental (eutherians) – baby develops inside mother; connected by placenta

Order Primates
 Dexterous hands & opposable thumbs
 Flat nails instead of claws
 Large brain, short jaw, flat face
 High parental care & complex social behavior
 Eyes front facing & set close
 Members
o Lemurs & Tarsiers
o New world monkeys – South America
o Old world monkeys - Africa; baboons, macaques, rhesus monkey
 No prehensile tail (no tree hanging)
o Apes – Gibbons, orangutans, gorillas, chimps, & humans
 No tail, long arms, short legs