Chapter 29: Echinoderms and Invertebrate Chordates
Section 2: Invertebrate Chordates
Invertebrate Chordates

Phylum __________________________
o Fish, frogs, birds, snakes, dogs, cows, and humans

Most of the ____________________________ are vertebrates, which means they
have backbones, so they are placed in the subphylum Vertebrata

The invertebrate chordates are divided into two subphyla – __________________
___________________________________
What Is a Chordate?

Belong to phylum Chordata

Chordates are animals that are characterized by a ______________________,
a _________________________________________________, and
_____________________________________________________

All chordates display these three characteristics at some stage in their life
1st Characteristic

The ____________________________, is a long, flexible supporting rod that
runs through at least part of the body, usually along the dorsal surface just beneath
the nerve cord

In most vertebrates, the notochord is quickly replaced by the
_______________________
2nd Characteristic

The _____________________________________________________, runs along
the dorsal surface just above the notochord

In most chordates, the front end of this nerve cord develops into a
_________________________________

Nerves leave this cord at regular intervals along the length of the animal and
connect to _________________________________________________________
3rd Characteristic

_____________________________________, are paired structures in the
pharyngeal, or ____________________, region of the body

In ________________________ chordates the pharyngeal slits are
_______________________ that connect the pharyngeal cavity with the outside

Many invertebrates have gills of some sort in various places, but only chordates
have pharyngeal gills

In _____________________________ chordates that use lungs for respiration,
pharyngeal slits are present only for a ___________________________________
____________________________________

These slits soon _________________________ as the embryo develops

In chordates such as humans, pouches form in the pharyngeal region but never
open up to form slits

For this reason, some scientists regard pharyngeal pouches, not slits, as the “true”
chordate characteristic
Tunicates

Small marine chordates that eat ________________________ they filter from the
water

Get their name from a special body covering called the ____________________

Only the ______________________________________________ of tunicates
have a notochord and a dorsal nerve chord

When tunicate larvae mature, they undergo metamorphosis and become
___________________ adults that grow into colonies attached to a solid surface

Both larval tunicates and adults filter feed and breathe at the same time through a
pharyngeal basket pierced by gill slits
Lancelets

Small fishlike creatures that live in the sandy bottom of shallow tropical oceans

Have a _____________________________________

Have a mouth that opens into a long pharyngeal region with up to 100 pairs of
_____________________________

Feed by passing water through their _____________________, where food
particles are caught in a _______________________________

This mucus is swallowed into a digestive tract that starts at one end of the
pharynx and continues straight through the animal to the anus, near the tail

Have a simple, _______________________________________ that pumps blood
through vessels in a ________________________________________________

They show evidence of segmentation in the arrangement of their nerves and
muscles

Muscles are organized into V-shaped units that are paired on either side of the
body

Each muscle unit receives a branch from the ______________________________

Lancelets have no ______________

Their mouth is composed entirely of _________________________________

Also lack appendages and can move only by _____________________________
__________________________________________________________
How Invertebrate Chordates Fit into the World

It is important to remember that living vertebrates did not evolve from living
lancelets or tunicates

Both these subphyla have ___________________________________

However, similarities in structure and embryological development indicate that
vertebrates and invertebrate chordates evolved from _______________________
____________________________ many millions years ago