1.
- extends through
length of the body as a simple skeleton
2. Dorsal, hollow
3. Pharyngeal
4. Muscular
 Tunicates
 Lancelets
 Fish
 Amphibians
 Reptiles
 Birds
 Mammals
 Tunicates
 “Tail Cords” – over 2,000 species
 Adults sessile
 Free swimming larvae; only larvae
have a 4 defining characteristics
 Lancelets
 “Head-Cords”
 tiny marine animals
 retain all 4 characteristics into adulthood
 Notochord, pharyngeal slits, dorsal hollow nerve cord, post
anal tail
 led to vertebrates
 Filter Feeders
 5 Classes
 1st vertebrates, aquatic
 Generally characterized by
scales, fins and pharyngeal
gills
 Exothermic (Ectothermic)
– no internal body
temperature regulation
Circulation
 closed circulatory system with a 2 chambered heart.
Reproduction
 reproduce through external fertilization - spawning
Jawless Fish
 Hagfish (Class Myxini) and Lampreys (Cephalaspidomorphi)
 Lack vertebrae (hagfish) or have incomplete vertebral column
(lamprey)
 Predators that attach to the side of a fish with modified mouth
 Have no scales
Class Chondrichthyes
 Cartilage fish
 Sharks, skate, rays and
sawfish
 Primitive Older fish
 Most have to swim to breathe
Bony Fish
 Ray finned fish (Class Actinopterygii )
- - most common fish
- have jaws and paired fins
- fins supported by rays fanning our
from central bone
 Lobe finned fish (Class Sarcopterygii)
- fins supported by central axis bone
- ancestors of amphibians
Walking Fish - Grunion
Class Amphibia
 Frogs and salemanders
 Aquatic as larvae, after metamorphosis, live on land as




adults.
Have moist skin with many glands
must be moist to breathe; respirate through skin
evolved from fish 360 mya
exothermic
Circulation
 Amphibians have a double-loop circulatory system
with three-chambered heart.
Reproduction
 Fertilization is external
 Shell-less eggs must be laid and fertilized in water
Class Reptilia
 Include 3 groups: snakes, turtles, crocodiles
 Fully adapted to life on land
 Amniotic egg
 scaly skin (prevents loss of moisture)
 Exothermic - regulate their body
temperatures by basking in the sun,
burrowing in the ground. Soaking in water
etc…
Circulation
 more efficient circulatory and respiratory systems
(lungs, 3 chambered heart).
Reproduction
 internal fertilization
 Lay fluid filled amniotic egg covered with a
protective shell
Class Aves
 Most are adapted for flight
 Covered with feathers
 hollow bones
 2 legs for walking, 2
modified for wings
 Birds are endothermic -
generate body heat
internally by their own
metabolism.
Circulation
4 chambered heart; allows for efficient delivery of O2
to cells.
Reproduction
 internal fertilization.
 incubate eggs and feed young
 have amniotic eggs (keeps eggs moist)
 Fossil evidence shows that birds evolved from the same
line as crocodiles and dinosaurs.
Class Mammalia
Characteristics:
 hair - insulation, camouflage,
sensory device, waterproofing,
signaling and defense
 mammary glands
 Endothermic
Circulation
4 Chambered heart
Require a constant supply of
nutrients and oxygen to maintain
homeostasis and metabolism
Keeping blood separate makes the
delivery of nutrients and oxygen
more efficient.
Reproduction
Internal fertilization
3 Types
1.
Monotremes - young develop in
shelled eggs;
Ex. spiny anteater and duck-billed
platypus
2. Marsupial - young leave mother’s
body to pouch before development is
complete.
Ex. kangaroo and opossum
3. Placental - young develop completely
within the uterus of the female
Ex. Human, whales, giraffe etc…