Phylum Chordata Phylum Chordata General Characteristics A

					         Phylum Chordata
       General Characteristics
A.   Have a notochord. What does this
B.   Have dorsal hollow nerve tube. What
     does this form?
C.   Have pharyngeal gill slits. What
     happens to these?
D.   Have tails at one point in their
Embryonic Comparison
II. Classification
  A. Subphylum Cephalochordata
    1. Lancelets
II. Classification
  B. Subphylum Urochordata
    1. Sea Squirts (Tunicates)
II. Classification
  C. Subphylum Hemichordata
    1. Acorn Worms
D. Subphylum Vertebrata
  1. Characteristics:
     a) Have a backbone (spinal column)
     b) Have endoskeleton made of calcium &
  2. Two major groups of vertebrates:
     ectotherms and endotherms.
IV. Ectothermic (Cold-blooded) Classes
A.   Class Agnatha (Jawless fish)
     1.Skeleton made of cartilage.
     2.No scales with tubular body.
     3.Lack paired appendages. e.g.
       lampreys and hagfish

B.   Class Chondrichthyes
     1. Skeleton made of cartilage,
        e.g. Rays, Skates and Sharks
     2. Lack gill covers (opercula)
        and swim bladders.
     3. Have placoid scales
C. Class Osteichthyes
  1. Skeleton is made of
     bone e.g. trout, bass,
     salmon, sole etc.
  2. Gills with opercula for
     protection and to
     move water over gills.
  3. Have cycloid scales.
  4. Most common fish
D. Class Amphibia (means “dual life”)

 1. Smooth skin and lack claws; e.g. frogs, toad,
 newts and salamanders.
 2. Evolved from fleshy-lobed fish (Coelocanth)
     E. Class Reptilia
E.    1. Dry (water proof), scaly skin with claws.
F.    2. Evolved from amphibians
G.    3. Snakes, lizards, turtles, crocodiles and alligators

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     V. Problems with transition to land
A.    Drying out.
B.    Too heavy. Why?
C.    Extreme temperature changes.
D.    Respiration - why don’t gills work on land?
E.    Reproduction
      How to get egg & sperm together?
      How do chordates prevent their eggs from drying
     VI. Adaptations to land
A.    Waterproof skin coverings; scales, feathers and fur.
B.    Appendages move more ventral as opposed to
      lateral placement.
C.    Lungs replaced gills
D.    Amniotic eggs with internal fertilization.
      -Evolved first in reptiles
D. Amniote Egg
     ** Water Tight but permeable to oxygen.
     1. Chorion - used for respiration
     2. Allantois - stores liquid wastes
      3. Amnion - filled with fluid for a cushion
     4. Yolk Sac - stores food (yolk)
     5. Embryo
             3                           2


VII. Endothermic (homeothermic) Classes

  A. What is the advantage of being homeothermic?
     1. Can live in cold environments or cold nights.
  B. What is the source of heat?
     1. Muscles contraction
  C. Which body systems must adapt to be
     A. Digestive system Why?
     a) Respiratory system Why?
     b) Circulatory system Why?
     c) Integumentary Why?
D.   Class Aves
      1. Body covered with feathers
      2. Have wings and beaks with no teeth.
      3. Have hollow bones
      4. All birds are oviparous.
      5. Evolved from reptiles-Archaeopteryx
E. Class Mammalia
A. Body covered with hair
B. Nurse young with mammary glands

C. Warm blooded

D. Give birth to live young

E. Evolved from reptiles.
VIII. Movement

 A.   Fish
      1. Fins used to stabilize and move fish through water
      2. Fish are streamlined to move easily through the water.
      3. Swim bladders filled with oil or gas to help fish float in
         the water.
              Movement (con’t)
B.    Amphibians, reptiles and mammals
     1. Most use four muscular limbs, to hop,
        walk and run on land.
         a) Limbs gradually moved from the
            side to under an animal.
     2. Snakes and legless lizards use large
        scales called scutes on ventral surface.
VIII. Movement (con’t)
   C.    Birds
         1.   Wings and feathers
         2.   What was the original function of feathers?

  Down                  Contour             Quill
              Movement (con’t)
C.    Birds
     3. Adaptations for flight
        a) Forearms modified into wings with
        b) Hollow bones with modified skeleton for
           muscle attachment and flight movement.
        c) Air sacs throughout make them less dense
           and ready supply of oxygen.
        d) Excretory wastes are crystalized combined
           with digestive waste. Why?
IX. Feeding
A.   Most have teeth and were the first
     animals to have a hinged jaw (except
     jawless fish).
B.   Types of food depend on the species:
     herbivores, carnivores, omnivores,
     parasites, and scavengers.
Hinged Jaw Evolution
X. Protection
A.   Flight, schooling, camouflage,
     poison, spines, teeth, etc.
B.   Scales
C.   Feathers, fur and fat help
XI. Digestion

A.   Highly specialized
     system with
     associated organs
     like the liver,
     pancreas, and
XII. Circulation
A.    Closed circulatory system with
      different hearts.
     1. Fish have a 2-chambered heart.
2. Amphibians most reptiles have a 3-
   chambered heart.
3. Birds and mammals have a four
   chambered heart.
4. What is the problem with a three
   chambered heart?
1. Birds & mammals have a 4-chambered heart.
     XIV. Respiration
A.   Fish use gills.
B.   Reptiles, birds
     and mammals
     use lungs.
C.   Amphibians use small lungs, but mostly
     through their skin.

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XV. Excretion
A.   All use kidneys
     1. Consisting of millions of nephrons.
     2. We will study the structure and function of a kidney
        when we study the human body..
B.   Problems with water balance:
     1. Marine fish have salt-removing structures in gills that
        actively transport salt out of them.
     2. Marine birds and reptiles secrete excess salt through
        specialized glands.
     3. Fresh water animals are more waterproof and more
        active kidneys.
Overall Excretory System
XVI. Nervous
A.   All have complex systems.
B.   Cerebral cortex increases from fish to
     1. This area is associated with higher
        functioning, so what does the above
        statement mean?
Brain evolution

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XVII. Reproduction
A.   Some are oviparous
     1. Lay eggs which hatch and develop outside of mother’s
B.   Some are ovoviviparous
     1. Eggs hatch inside mother and give birth to live young,
        but no nourishment provided by mother.
C.   Some are viviparous
     1. Bear live young, which are nourished by mother.