30-1 The Chordates
Slide
1 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
What Is a Chordate?
What Is a Chordate?
Members of the Phylum Chordata are called
chordates.
A chordate is an animal that has (for at least some
stage of its life) a dorsal, hollow nerve cord; a
notochord; pharyngeal pouches; and a tail that
extends beyond the anus.
Notochord
Muscle segments
Hollow nerve cord
Mouth
Tail
Anus
Slide
2 of 25
Pharyngeal pouches
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
What Is a Chordate?
The hollow nerve cord runs along the dorsal portion
of the body. Nerves branch from this cord at regular
intervals and connect to internal organs, muscles,
and sense organs.
The notochord is a long supporting rod that runs
through the body just below the nerve cord. Most
chordates only have a notochord as embryos.
Notochord
Hollow nerve cord
Slide
3 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
What Is a Chordate?
Pharyngeal pouches are paired structures in the
throat (pharynx) region.
In some chordates, slits develop to connect to the
outside of the body; these eventually develop gills.
Pharyngeal pouches
Slide
4 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
What Is a Chordate?
The tail can contain bone and muscle and is used for
swimming by many aquatic species.
Tail
Slide
5 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
What Is a Chordate?
Most Chordates Are Vertebrates
About 96% of all chordate species are vertebrates in
the Subphylum Vertebrata.
Most vertebrates have a vertebral column, or
backbone.
In vertebrates, the dorsal, hollow nerve cord is called
the spinal cord.
Slide
6 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
What Is a Chordate?
As a vertebrate embryo develops, the front end of the
spinal cord grows into a brain.
The backbone, which replaces the notochord, is made
of individual segments called vertebrae.
In addition to support, vertebrae enclose and protect
the spinal cord.
The backbone is part of the endoskeletal system.
Unlike an arthropod’s exoskeleton, the endoskeleton
grows as the animal grows, is not shed, and contains
living and nonliving material.
Slide
7 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
What Is a Chordate?
Phylogeny of Chordates: Evolutionary relationships
Sharks
& their
Jawless
relatives
fishes
Nonvertebrate
chordates
Bony
fishes
Reptiles Birds
Amphibians
Mammals
Invertebrate ancestor
Slide
8 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
Nonvertebrate Chordates
Nonvertebrate Chordates
The two groups of nonvertebrate chordates are
tunicates and lancelets.
Similarities in anatomy and embryological
development indicate that vertebrates and
nonvertebrate chordates evolved from a common
ancestor.
Both tunicates and lancelets are soft-bodied marine
organisms.
Slide
9 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
Nonvertebrate Chordates
Tunicates
Subphylum Urochordata (sea squirts)
The larval form of filter-feeding tunicates have all of
the chordate characteristics.
Slide
10 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
Nonvertebrate Chordates
Adult filter-feeding tunicates have neither a notochord
nor a tail.
Slide
11 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
Nonvertebrate Chordates
Lancelets
Subphylum Cephalochordata
Lancelets are small, fishlike creatures that live on
the ocean bottom.
An adult lancelet has a definite head region that
contains a mouth.
Slide
12 of 25
Copyright Pearson Prentice Hall
End Show
30-1 The Chordates
Nonvertebrate Chordates
As water passes through the pharynx, a sticky mucus
catches food particles.
They swallow the mucus into the digestive tract.
Lancelets use the pharynx for gas exchange and are
thin enough to exchange gases through their body
surface.
Lancelets have a closed circulatory system and do not
have a true heart.
Slide
13 of 25
Copyright Pearson Prentice Hall
End Show