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A. Characteristics of Chordata
 Notochord- a stiff rod that helps support the dorsal nerve cord and body of the
organism
 Pharyngeal Slits- an opening from the neck to the throat that helps separate food from
water and helps with gas exchange
 Dorsal Nerve Chord- lateral muscles/organs gets messages from the brain from the nerve
fibers that are attached to the brain
 Post-anal Tail- helps organism swim, tail goes past the anus
B. Urochordata (adult)
 Incurrent siphon- water enters
 Pharynx- water is filtered
 Stomach- receives food from the
water
 Excurrent Siphon- squirts out water
C. Urochordata (larva)
 Has:
o Notochord
o Dorsal, hollow nerve cord
o Post- anal tail
 This makes them part of the phylum chordata
D. Cephalochordata (lancelets)
 Swim thru the water using notochord muscles
 Each muscle segment is called a somite
E. Vertebrata
1. Agnatha
 Greek- “no jaws”
 lampreys and hagfish
 Characteristics:
o No paired appendages (fins)
o Some attach to host and feed off of host’s blood
o Some eat dead fish or marine worms
2. Chondrichthyes
 Chondr= Cartilage; -ichthyes= fish
 Have a jaw and paired appendages (fins)
 Subclasses:
o Elasmobranchii (sharks, rays)
o Chimaera (chimaeras)
 Lateral line system- detects vibrations in
the water
3. Osteichthyes
 Oste= Bone; ichthyes= fish
 Bone endoskeleton made with hard calcium phosphate
 Operculum- protective flap over the gills
 Swim bladder- sac filled with gas that controls the buoyancy of the fish
 Have better control in swimming than sharks
4. Amphibia
 First vertebrates on land (salamanders, frogs, caecilians)


Fins evolved into legs
“Double Life”
o Egg in water
o Mature life on land
 Cold-blooded
 Urodeles (salamander)
o “tailed ones”
 Anurans (frogs, toads)
o “tail-less ones”
o Metamorphosis- tadpole to frog
 Apodans (caecilians)
o “legless ones”
o Live in tropical areas and burrow into soil
5. Reptilia
 Amniotic egg allowed reptiles to reproduce without dependence on water
 Lizards, snakes, turtles, and crocodiles
 Use solar energy to control body temp (ectotherm)
 Adaptations for land
o Scales with keratin
o Obtain all oxygen with lungs
o Can lay amniotic eggs on land
6. Aves
 Evolved from reptiles
 Archaeopteryx- earliest bird (Jurassic Period)
 Bird anatomy enhances flight
o Hollow bones
o Females have one ovary (reduces weight)
o Have larger brain than reptile
o Very acute vision
 Endothermic (maintain own body temp)
 4 chambered heart
supports high metabolism
 Ratites- flightless birds
 Carinates- birds that fly
7. Mammalia
o Endothermic
o Have hair and fat layer to maintain heat
o Mothers have mammary glands to nourish babies
o Embryo usually grows in uterus instead of egg
o Monotremes
o Mammals with eggs
o platypuses
o Marsupials
o Mammals with pouches
o Eutherian Mammals
o Placental mammals