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PHYLUM CHORDATA
“Our Phylum”
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Vertebrata
“Pre-Cambrian”
produced only
unicellular organisms
THE CAMBRIAN EXPLOSION
All major phyla including
Phylum Chordata
Geologic Time Scale
Origin of Species
(Chapter IX)
On the Imperfection of the Geologic Record
“There is another and allied difficulty, which is
much graver. I allude to the manner in which
numbers of species of the same group , suddenly
appear in the lowest known fossiliferous rocks.”
Darwin was aware …
Explosion led to as many as 100 phyla most
of which are extinct (32 extant phyla?)
CHORDATE EXAMPLES
“DUDES”Deuterostomes
Chordates are DEUTEROSTOMES
5 CHORDATE CHARACTERISTICS
1) Notochord – present in embryonic, larval or adult stages
Not Cartilage!!
Large fluid-filled cells
having turgor pressure
CELLS
of the notochord
Embryonic Salamander
Notochord Cells
Neural Tube
x.s.
l.s.
2) DORSAL TUBULAR NERVE CORD
CHORDATE CHARACTERISTICS continued …
Chick
Gastrulation
HIGHER Central Nervous Systems remain hollow
EXAMPLE: Human Brain
Contrast to Phylum Annelida:
Ventral & Solid
Nerve Cord
Earthworm
Embryos
During pharyngeal development,
outside ectoderm invaginates …
inside endoderm evaginates
SLIT formation?
3) PHARYNGEAL POUCHES & CLEFTS
FISH?
CHORDATE CHARACTERISTICS continued …
Gill Slits: Openings that connect the pharynx to the outside
Tetrapod Vertebrates
Pouches form … but slits don’t break through.
Pouches develop into …
middle ear cavity
eustachian tube
tonsils
parathyroid glands
CHORDATE CHARACTERISTICS continued …
4) POSTANAL TAIL (advance in locomotion)
anus
OUR TAIL
Post-anal Tail + Notochord (or Vertebral
Column) + Muscles + Fins =
Propulsive Power
5) ENDOSTYLE or THYROID GLAND
CHORDATE CHARACTERISTICS continued …
Strip of tissue on the floor of the pharynx – secretes sticky mucus that
traps food from “inhaled” water.
In vertebrates, the thyroid gland develops in place of the endostyle.
The vertebrate
Thyroid Gland
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Vertebrata
All Oceans
Most Depths
1600 species
Urochordates (tunicates)
http://www.flickr.com/photos/nuytsia_pix/3130748320/
(secretes mucus)
(lined with ciliated cells)
ODD?
Closed circulatory system … BUT …
- no distinction between arteries & veins
- no capillaries
- blood flows forward & back
ODD?
*super-high tissue concentrations
of vanadium & niobium
*tunic contains cellulose
Amphioxus
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Vertebrata
29 species
THE 5
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Vertebrata
the
Tunicates use gill slits for
feeding:
Water (w/food) enters
“mouth” & exits slits
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