Download Ch 17

1/11/11
I. Phylum Hemichordata
•  Characteristics
Chapter 17
Chordates
A. Class Enteropneusta
•  Marine worms range in size from 10-40
cm
•  Known as acorn worms
•  Dioecious with external fertilization
•  Larval stage called tornaria, which
eventually settle to the substrate and
grow into adult form
–  Marine animals with body divided into three
segments and true coelom
–  Ciliated pharyngeal slits
–  Open circulatory system
–  Complete digestive tract
–  Dorsal nerve cord
B. Class Pterobranchia
•  Small marine worms
that live inside
secreted tubes
•  Dioecious with
external fertilization
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II. 4 Chordate Characteristics
•  Notochord - supportive rod that runs the
length of the dorsal side of the body
•  Pharyngeal slits - allow water to pass from
the pharynx to the outside of the body
(sometimes modified as gills)
•  Tubular nerve cord - hollow nerve cord that
runs the length of the dorsal side (spinal cord)
•  Postanal tail - extends posteriorly from the
anus
A. Subphylum Urochordata
•  Tunicates, sea squirts
•  Attach to the substrate and move water thorugh the
body using oral siphons
•  Monoecious with external fertilization
•  Larva are tadpole like with all four chordate
characteristics
III. Phylum Chordata
•  Bilateral symmetry
•  Notochord, pharyngeal gill slits, dorsal
nerve cord, postanal tail
•  Endostyle or thyroid gland
•  Complete digestive tract
B. Subphylum
Cephalochordata
•  Lancelets
•  Small, tadpole like
animals with all four
chordate
characteristics
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Zoology Anatomical Terms
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Posterior
Anterior
Lateral
Medial
Distal
Ventral
Dorsal
The four Hallmarks
(characteristics) of Chordates
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Post Anal
Tail
Pharyngeal
Gills / Slits
Why?
Dorsal
Tubular
Nerve Cord
Support/
Nervous
Endoskeleto system/
n/ Muscle sensory
Attachment organ
Where?
Dorsally
Posterior
What?
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Notochord
Dorsally
Movement/ Respiration/
balance
filter
feeding
Anterior
and lateral
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