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:
  • Notochord
  • Dorsal, hollow nerve cord
  • 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:
  • No paired appendages (fins)
  • Some attach to host and feed off of host’s blood
  • Some eat dead fish or marine worms

2. Chondrichthyes

  • Chondr= Cartilage; -ichthyes= fish
  • Have a jaw and paired appendages (fins)
  • Subclasses:
  • Elasmobranchii (sharks, rays)
  • 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”
  • Egg in water
  • Mature life on land
  • Cold-blooded
  • Urodeles (salamander)
  • “tailed ones”
  • Anurans (frogs, toads)
  • “tail-less ones”
  • Metamorphosis- tadpole to frog
  • Apodans (caecilians)
  • “legless ones”
  • 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
  • Scales with keratin
  • Obtain all oxygen with lungs
  • Can lay amniotic eggs on land

6. Aves

  • Evolved from reptiles
  • Archaeopteryx- earliest bird (Jurassic Period)
  • Bird anatomy enhances flight
  • Hollow bones
  • Females have one ovary (reduces weight)
  • Have larger brain than reptile
  • Very acute vision
  • Endothermic (maintain own body temp)
  • 4 chambered heart supports high metabolism
  • Ratites- flightless birds
  • Carinates- birds that fly

7. Mammalia

  • Endothermic
  • Have hair and fat layer to maintain heat
  • Mothers have mammary glands to nourish babies
  • Embryo usually grows in uterus instead of egg
  • Monotremes
  • Mammals with eggs
  • platypuses
  • Marsupials
  • Mammals with pouches
  • Eutherian Mammals
  • Placental mammals