Chapter 29: Echinoderms and Invertebrate Chordates

Chapter 29: Echinoderms and Invertebrate Chordates

Section 2: Invertebrate Chordates

Invertebrate Chordates

Phylum ______

oFish, 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