Phylum: Chordata

1
Phylum Chordata

• Chapter 34

2
What you need to know!

• The 4 chordate characteristics.
• Adaptations that allowed animals to move onto
  land.
• Traits which distinguish each of the following
  groups Chondrichthyes, Osteichthyes, Amphibia,
  Reptilia, Birds, and Mammalia.
• How the 3 classes of mammals differ in their
  reproduction.

3
Characteristics of all Chordates

1. Notochord Longitudinal, flexible rod located
   between the digestive and the nerve cord
2. Nerve cord (dorsal, hollow) eventually develops
   into the brain and spinal cord (arthropods
   ventral)
3. Pharyngeal slits become modified for gas
   exchange, jaw support, and/or hearing
4. Muscular, postanal tail

4
Neurulation (Vertebrates)

• Neural Tube dorsal folding of the ectoderm
  forming a hollow nerve tube
• Neural Crest embryonic cells (mesoderm) near the
  neural tube that migrate throughout the body to
  form special bones like the jaw and cranium
• Animation
• http//learningobjects.wesleyan.edu/neurulation/an
  imation.php

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Macroevolutionary Trends
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Vertebrata

• Pronounced Cephalization concentration of
  sensory and neural equipment in the head
• Cranium (skull) encloses brain
• Endoskeleton notochord becomes cartilage or
  bone (vertebral column) enclosing the hollow
  nerve chord
• Bone is more advanced than cartilage
• Hinged Jaw
• Closed circulatory system with a ventral
  chambered heart

7
Land Adaptations

• Gills ? lungs
• Paired lobed fins ? legs (tetrapod)
• Amniotic Egg (shelled egg) several
  extraembryonic membranes that are not part of the
  embryo, but produced by embryonic tissue
• Amnion protects embryo, contains amniotic fluid
  for shock absorption
• Allantois forms extra sac for waste disposal
  and gas exchange
• Yolk Sac nutrient stockpile
• Chorion gas exchange

8
Amniotic Egg
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Major Divisions

• Fish
• Class Chondrichthyes flexible endoskeletons and
  jaws (i.e. shark and stingray)
• Class Osteichthyes (bony fish) most numerous
  vertebrates, boney endoskeleton, scales (i.e.
  trout and salmon)
• Class Amphibia gas exchange across skin (most
  use lungs), soft water-based eggs, larvae have
  two-chambered hearts, adults have three chambers
  (i.e. frogs and salamanders)
• Class Reptiles gas exchange in lungs,
  intercourse, amniotic egg, scales (keratin),
  ectothermic, three chambered heart (i.e. turtles,
  lizards, and alligators)

10
Major Divisions

• Birds (subdivision of reptiles) amniotic eggs,
  scales on legs, wings, feathers, endotherms, four
  chambered heart
• Class Mammalia milk from mammary glands, hair,
  endotherms, four chambered heart, large brains,
  teeth

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Mammalian Subdivisions

1. Monotremes egg laying mammals (i.e. platypuses
   and spiny anteaters)
2. Marsupials born early, complete embryonic
   development in a pouch (i.e. kangaroos and
   opossums)
3. Placental mammals (eutherians) long pregnancy,
   fetus develops in the uterus (i.e. dogs and
   humans)