CHORDATES and VERTEBRATES
Or you got a lot of nerve... or is it
backbone?
• The phylum Chordata includes three subphyla, the
vertebrates and two phyla of invertebrates, the
urochordates and the cephalochordates.
Fig. 34.1
FOUR CHARACTERISTICS
These chordate
characteristics are
a notochord; a dorsal,
hollow nerve cord;
pharyngeal slits;
and a muscular,
postanal tail.
Four anatomical features characterize
the phylum Chordata
• 1. The notochord, present in all chordate
embryos, is a longitudinal, flexible rod located
between the digestive tube and the nerve
cord.
• 2. The dorsal, hollow nerve cord develops in
the vertebrate embryo from a plate of
ectoderm that rolls into a tube dorsal to the
notochord.
• 3. Pharyngeal gill slits connect the pharynx,
just posterior to the mouth, to the outside of
the animal.
• 4. Most chordates have a muscular tail
extending posterior to the anus.
Assignment Chordate
1. Provide details for each of the four
anatomical features of the chordates.
2. Describe the two chordates that are
invertebrates
3. Describe the evolution of chordates
Vertebrates
• Neural crest, pronounced cephalization, a
vertebral column, and a closed circulatory
system characterize the subphylum
Vertebrata.
• Why are these four features important to
vertebrates?
Fig. 34.7
Finally
• At each evolutionary step describe the
changes to vertebrates to help explain the
diversification we see today.