Transcript Phylum Chordata - Chicagoland Jewish High School

Phylum Chordata
Chordate Cladogram
Mammals
Birds
Amphibians
Fishes
Nonvertebrate
chordates
Invertebrate ancestor
Reptiles
All chordates at sometime during their
life history have:
• a notochord: a dorsal supporting rod located
dorsally just below the nerve cord; it provides
support and is replaced by the vertebral column
in vertebrates
• a dorsal hollow nerve cord: a fluid-filled canal;
spinal cord is protected by vertebrae
• pharyngeal gill pouches: openings that
function in feeding, gas exchange, or both
Chordates that are not vertebrates
• Subphylum
Urochordata
• contains 1,250
species
Tunicates (Sea Squirts),
Larvae
• The larvae of tunicates resemble the ancestral
chordate.
• It has all three chordate characteristics and
looks like a tadpole.
• The free-swimming larva develops into a sessile,
filter-feeding adult.
Adult
• The adult has a thick-walled body sac and an
incurrent siphon and an excurrent siphon.
• Gill slits are the only chordate feature retained
by the adult form.
• In some tunicates, the adult form may have been
lost. These animals retained the larval form as
adults. Vertebrates may have evolved from
forms like these.
Subphylum Cephalochordata
Subphylum Cephalochordata
 23 species of lancelets are in the genus
Branchiostoma
 elongated, lance-shaped body resembles the
lancelet, a two-edged surgical knife
 inhabit shallow coastal waters; they lie partly buried
in sandy substrates and filter feed
 Lancelets retain the three chordate characteristics
as an adult
 notochord extends from head to tail
 segmented muscles and their
 dorsal hollow nerve cord
Vertebrate Chordates
• Subphylum
Vertebrata
• Animals with a
vertebra column.